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EPO Tunas and billfishes fishery
Fishery  Fact Sheet
Fishery report 2020
EPO Tunas and billfishes fishery
Fact Sheet Citation  
Tunas and billfishes in the Eastern Pacific Ocean
Owned byInter-American Tropical Tuna Commission (IATTC) – more>>

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Overview: The eastern Pacific Ocean (EPO) fishery for tunas and tuna-like species is a fully developed international industrial fishery that has been managed by the IATTC since 1950. Until about 1960, fishing for tunas in the EPO was dominated by pole-and-line vessels operating in coastal regions and in the vicinity of offshore islands and banks. By 2012, fewer than five of these vessels remained in the fishery. By 1961 the EPO fishery was dominated by purse seine vessels, which by 2012 numbered more than 200. Longline fisheries expanded from the western Pacific into the EPO during the 1950s, and by about 1965 operated throughout the EPO. The IATTC has adopted a vessel registry and has in place restrictions on catch and on vessels and fishing capacity operating in the EPO.Catch of the tropical tunas, bigeye, skipjack, and yellowfin, in the EPO has ranged from about 500,000 to 830,000 t since 2000, averaging about 560,000 t per year since 2007.

Location of EPO Tunas and billfishes fishery
 

Geographic reference:  EPO
Spatial Scale: Regional
Reference year: 2019
Approach: Fishery Management Unit

Jurisdictional framework
Management Body/Authority(ies): Inter-American Tropical Tuna Commission (IATTC)
Mandate: Scientific Advice; Management
Area of Competence: IATTC area of competence
Maritime Area: High seas
Maritime Area: National waters

Harvested Resource
Target Species: Yellowfin tuna; Skipjack tuna; Bigeye tuna …  
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Associated Species: Pacific bluefin tuna; Striped marlin; Swordfish
Fishery Area: East Pacific Ocean

Fishery Indicators
Catch
Effort

Harvested Resource
Type of production system: Industrial   

Fishery Area
Climatic zone: Polar; Temperate; Tropical.   Horizontal distribution: Oceanic.   Vertical distribution: Pelagic.  

Geo References

This document summarizes the catches and effort of the fisheries for species covered by the IATTC’s Antigua Convention (“tunas and tuna-like species and other species of fish taken by vessels fishing for tunas and tuna-like species”) in the eastern Pacific Ocean (EPO) in 2019. The most important of these species are the scombrids (family Scombridae), which include tunas, bonitos, seerfishes, and some mackerels.

Almost all the catches in the EPO are made by the purse-seine and longline fleets; pole-and-line vessels, and various artisanal and recreational fisheries, account for a small percentage of the total catches. The IATTC staff compiles catch data for all fishing gears, including trolls, harpoons, and gillnets.

Detailed catch data are available for the purse-seine fishery, which takes over 90% of the total reported catches; the data for the other fisheries are incomplete. Purse-seine data for 2018 and 2019, and 2017-2019 data for longlines and other gears, are preliminary.

Access to the fisheries is regulated by Resolution C-02-03, which allows only vessels on the IATTC Regional Vessel Register to fish for tunas in the EPO. Vessels are authorized to fish by their respective flag governments, and only duly authorized vessels are included in the Register. The Register lists, in addition to a vessel’s name and flag, its fishing gear, dimensions, carrying capacity, date of construction, ownership, home port, and other characteristics. However, this requirement has not been applied to the thousands of small artisanal vessels, called pangas, that are known to catch tunas, among other species, in coastal waters of the EPO, but data on their numbers, effort, and catches are incomplete or unavailable. A pilot program, focused on sharks, to collect data on these fisheries in Central America has been completed (SAC-11-14), and a long-term sampling program is scheduled to commence in 2020.

The IATTC staff has collected and compiled data on the longline fisheries since 1952, on catches of yellowfin and skipjack since 1954, bluefin since 1973, and bigeye since 1975. The data in this report, which are as accurate and complete as possible, are derived from various sources, including vessel logbooks, on-board observer data, unloading records provided by canners and other processors, export and import records, reports from governments and other entities, and the IATTC species and size composition sampling program.

All weights of catches and discards are in metric tons (t). In the tables, 0 means no effort, or a catch of less than 0.5 t; - means no data collected; * means data missing or not available.
Resources Exploited
The principal species of tunas caught are:
Albacore - Northern Pacific
Bigeye tuna - Eastern Pacific (EPO)
Skipjack tuna - Eastern Pacific
Yellowfin tuna - Eastern Pacific
The principal species of tunas caught are the three tropical tuna species (yellowfin, skipjack, and bigeye), followed by the temperate tunas (albacore, and lesser catches of Pacific bluefin); other scombrids, such as bonitos and wahoo, are also caught.

There are important fisheries for dorado, sharks, and other species and groups that interact with the tuna fisheries in the EPO and are thus within the IATTC’s remit. This document therefore also covers other species such as billfishes (swordfish, marlins, shortbill spearfish, and sailfish), carangids (yellowtail, rainbow runner, and jack mackerel), dorado, elasmobranchs (sharks, rays, and skates), and other fishes.
Fleet segment

THE FLEETS

The purse-seine and pole-and-line fleets
The IATTC Regional Vessel Register contains detailed records of all purse-seine vessels that are authorized to fish for tunas in the EPO. However, only vessels that fished for yellowfin, skipjack, bigeye, and/or Pacific bluefin tuna in the EPO in 2019 are included in the following description of the purse-seine fleet.

The IATTC uses well volume, in cubic meters (m3), to measure the carrying capacity of purse-seine vessels. Reliable well volume data are available for almost all purse-seine vessels; the well volume of vessels lacking such data is calculated by applying a conversion factor to their capacity in tons shown in (Table A-10); (Figure 2).
Figure 2:  Carrying capacity, in cubic meters of well volume, of the purse-seine and pole-and-line fleets in the EPO, 1961-2019

The 2018 and preliminary 2019 data for numbers and total well volumes of purse-seine vessels that fished for tunas in the EPO are shown in (
Flag Gear Well (m3) Total
    <401 401-800 801-1300 1301-1800 >1800 No. Vol. (m3)
    Number    
COL PS 2 2 7 3 - 14 14,860
ECU PS 38 31 22 10 12 113 91,658
EU(ESP) PS - - - - 2 2 4,120
MEX PS 5 4 21 23 - 53 62,659
NIC PS - - 3 2 1 6 9,066
PAN PS - 2 5 5 4 16 22,361
PER PS 5 4 - - - 9 4,175
SLV PS - - - 1 2 3 6,202
USA PS 14 - 3 8 6 31 28,201
VEN PS - - 6 6 2 14 20,364
Grand total PS 64 43 67 58 29 261  
Well volume (m3)
Grand total PS 15,930 26,297 73,246 88,505 59,688   263,666
: none



) and (
Flag Gear Well volume (m3) Total
    <401 401-800 801-1300 1301-1800 >1800 No. Vol. (m3)
    Number    
COL PS 2 2 7 3 - 14 14,860
ECU PS 38 33 22 9 12 114 91,057
EU(ESP) PS - - - - 2 2 4,120
MEX PS 5 2 21 23 - 51 61,146
NIC PS - - 3 2 1 6 9,066
PAN PS - 2 5 6 4 17 23,719
PER PS 6 5 - - - 11 4,767
SLV PS - - - 1 2 3 6,202
USA PS 11 - 3 9 6 29 30,367
VEN PS - - 7 6 1 14 19,781
Grand total PS 62 44 68 59 28 261  
Well volume (m3)
Grand total PS 16,015 26,070 75,928 88,886 58,186   265,085
: none



). During 2019, the fleet was dominated by Ecuadorian and Mexican vessels, with about 34% and 23%, respectively, of the total well volume; they were followed by the United States (11%), Panama (9%), Venezuela (7%), Colombia (6%), Nicaragua (3%), El Salvador (2%), Peru (2%) and the European Union (Spain) (2%). The sum of the percentages may not add up to 100% due to rounding.

The cumulative capacity at sea during 2019 is compared to those of the previous five years in Figure 3.
Figure 3:  Carrying capacity, in cubic meters of well volume, of the purse-seine and pole-and-line fleets in the EPO, 1961-2019

The monthly average, minimum, and maximum total well Volumes At Sea (VAS), in thousands of cubic meters, of purse-seine and pole-and-line vessels that fished for tunas in the EPO during 2009-2018, and the 2019 values, are shown in (Table A-12). The monthly values are averages of the VAS estimated at weekly intervals by the IATTC staff. The average VAS values for 2009-2018 and 2019 were slightly over 141 thousand m3 (60% of total capacity) and about 146 thousand m3 (55% of total capacity), respectively.

Other fleets of the EPO

Information on other types of vessels that are authorized to fish in the EPO is available in the IATTC’s Regional Vessel Register. In some cases, particularly for large longline vessels, the Register contains information for vessels authorized to fish not only in the EPO, but also in other oceans, and which may not have fished in the EPO during 2019, or ever.
Catch
Since 1993 all Class-6, purse-seine vessels with carrying capacities greater than 363 metric tons (t), carry observers who collect detailed data on catches, both retained and discarded at sea. Estimates of the total amount of the catch that is landed (hereafter the “retained catch”) are based principally on data collected during vessel unloadings.

Longline vessels, particularly the larger ones, fish primarily for bigeye, yellowfin, albacore, and swordfish. Data on the retained catches of most of the larger longline vessels are obtained from the vessels’ flag governments; data for smaller longliners, artisanal vessels, and other vessels that fish for species covered by the Antigua Convention are incomplete or unavailable, but some are obtained from vessel logbooks, or from governments or governmental reports.

Data for the western and central Pacific Ocean (WCPO) are taken from the Tuna Fishery Yearbook for 2018, published by the Western and Central Pacific Fisheries Commission (WCPFC).

This report summarizes data from all the above sources. The estimated total catches of tropical tunas (yellowfin, skipjack, and bigeye) in the entire Pacific Ocean from all sources mentioned above are shown in (Table A-1), and are discussed further in the sections below.

Estimates of the annual retained and discarded catches of tunas and other species taken by tuna-fishing vessels in the EPO during 1990-2019 are shown in (



Table A-2a), (Table A-2b) and (Table A-2c). The catches of tropical tunas during 1990-2019, by flag, are shown in (Table A-3a), (Table A-3b), (Table A-3c), (

Table A-3d), (Table A-3e), and the purse-seine catches and landings of tunas during 2018-2019 are summarized by flag in (Table A-4a), ( Table A-4b).

Catches by species

Yellowfin tuna

The annual catches of yellowfin during 1989-2018 are shown in (Table A-1), and Figure B-1.
Figure B-1:  Total catches (retained catches plus discards) for the purse-seine fisheries, by set type (DEL, NOA, OBJ), and retained catches for the longline (LL) and other (OTR) fisheries, of yellowfin tuna in the eastern Pacific Ocean, 1975-2019. The purse-seine catches are adjusted to the species composition estimate obtained from sampling the catches. The 2019 data are preliminary.

The 2019 EPO catch of 228 thousand t is 8% less than the average of 248 thousand t for the previous 5-year period (2014-2018). In the WCPO, the catches of yellowfin reached a record high of 692 thousand t in 2017.

The annual retained catches of yellowfin in the EPO, by gear, during 1990-2019 are shown in Table A-2a. Over the most recent 15-year period (2004-2018), the annual retained purse-seine and pole-and-line catches have fluctuated around an average of 224 thousand t (range: 167 to 274 thousand t). The preliminary estimate of the retained catch in 2019, 228 thousand t, is 5% less than that of 2018, but 2% greater than the 2004-2018 average. On average, about 0.5% (range: 0.1 to 1.1%) of the total purse-seine catch of yellowfin was discarded at sea during 2004-2018 (Table A-2a). During 1990-2004, annual longline catches in the EPO averaged about 23 thousand t (range: 12 to 35 thousand t), or about 8% of the total retained catches of yellowfin. They then declined sharply, to an annual average of 10 thousand t (range: 8 to 13 thousand t), or about 4% of the total retained catches, during 2005-2018. Catches by other fisheries (recreational, gillnet, troll, artisanal, etc.), whether incidental or targeted, are shown in Table A-2a, under “Other gears” (OTR); during 2005-2018 they averaged about 2 thousand t.

Skipjack tuna

The annual catches of skipjack during 1990-2019 are shown in (Table A-1). Most of the catch is taken in the WCPO. Most of the catch is taken in the WCPO. Prior to 1998, WCPO catches averaged about 900 thousand t; subsequently, they increased steadily, from 1.2 million t to an all-time high of 2 million t in 2014. In the EPO, the greatest catches occurred between 2003 and 2019, ranging from 153 to 350 thousand t, the record catch in 2019.

The annual retained catches of skipjack in the EPO by purse-seine and pole-and-line vessels during 1990-2019 are shown in (Table A-2a). During 2004-2018 the annual retained purse-seine and pole-and-line catch averaged 267 thousand t (range: 147 to 338 thousand t). The preliminary estimate of the retained catch in 2019, 347 thousand t, is 30% greater than the 15-year average for 2004-2018.

Discards of skipjack at sea decreased each year during the period, from 8% in 2004 to a low of less than 1% in 2018, averaging about 2% of the total catch of the species.

Catches of skipjack in the EPO by longlines and other gears are negligible as shown in Table A-2a.

Bigeye tuna

The annual catches of bigeye during 1990-2019 are shown in (Table A-1). Overall, the catches in both the EPO and WCPO have increased, but with considerable fluctuations. In the WCPO they averaged more than 77 thousand t during the late 1970s, decreased during the early 1980s, and then increased steadily to 119 thousand t in 1992; they jumped to 168 thousand t in 1998, and reached a high of 180 thousand t in 2004, since when they have fluctuated between 123 and 156 thousand t. In the EPO, the average catch during 1990-2019 was 105 thousand t, with a low of 83 thousand t in 1993 and a high of 149 thousand t in 2000.

The annual retained catches of bigeye in the EPO by purse-seine and pole-and-line vessels during 1990-2019 are shown in Table A-2a. The introduction of fish-aggregating devices (FADs), placed in the water by fishers to attract tunas, in 1993 led to a sudden and dramatic increase in the purse-seine catches. Prior to 1993, the annual retained purse-seine catch of bigeye in the EPO was about 5 thousand t by 1994 it was 35 thousand t, and in 1996 was over 60 thousand t. During 1997-2018 it has fluctuated between 44 and 95 thousand t; the preliminary estimate for 2019 is 71 thousand t. (Table A-2a). During 2000-2019 the percentage of the purse-seine catch of bigeye discarded at sea has steadily decreased, from 5% in 2000 to less than 1% in 2014, averaging about 1.7%.

Before the expansion of the FAD fishery, longliners caught almost all the bigeye in the EPO, averaging 88 thousand t annually during 1985-1992. Since 1993, the annual average catch has declined by 50%, to 44 thousand t, and the preliminary estimate for 2019 is less than 25 thousand t.

Small amounts of bigeye are caught in the EPO by other gears, as shown in Table A-2a.





Bluefin tuna

The 1990-2018 average EPO retained catch is 3.6 thousand t (range: 400 t to 9.9 thousand t); the preliminary estimate for 2019 is 2.5 thousand t (Table A-2a).

The catches of Pacific bluefin in the entire Pacific Ocean, by flag and gear, as reported by the vessels’ flag governments to the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC), are shown in (Table A-5a).

Catches of Pacific bluefin by recreational gear in the EPO are reported in numbers of individual fish caught, whereas all other gears report catches in weight; they are therefore converted to tons for inclusion in the EPO catch totals. The original catch data for 1990-2019, in numbers of fish, are presented in (Table A-5b).

Albacore tuna

Data provided by the relevant CPCs on catches of albacore in the EPO, by gear and area (north and south of the equator), are shown in (Table A-6). The catches of albacore in the EPO, by gear, are shown in (Table A-2a). A portion of the albacore catch is taken by troll vessels, included under “Other gears” (OTR) in Table A-2a

Other tunas and tuna-like species

While yellowfin, skipjack, and bigeye tunas comprise the great majority of the retained purse-seine catches in the EPO, other tunas and tuna-like species, such as black skipjack, bonito, wahoo, and frigate and bullet tunas, contribute to the overall harvest. The estimated annual retained and discarded catches of these species during 1990-2019 are shown in Table A-2a. The catches reported in the “unidentified tunas” (TUN) category in Table A-2a contain some catches reported by species (frigate or bullet tunas) along with the unidentified tunas. The total retained catch of these other species by the purse-seine fishery in 2019 was 12.2 thousand t, more than the 2004-2018 average of 8.0 thousand t (range: 1 to 19 thousand t) as shown in (Table A-2a). Black skipjack are also caught by other gears in the EPO, mostly by coastal artisanal fisheries. Bonitos are also caught by artisanal fisheries, and have been reported as catch by longline vessels in some years.

Billfishes

Catch data for billfishes (swordfish, blue marlin, black marlin, striped marlin, shortbill spearfish, and sailfish) are shown in (Table A-2b).

Swordfish are caught in the EPO with large-scale and artisanal longlines, gillnets, harpoons, and occasionally with recreational gear. During 1999-2013 the longline catch of swordfish averaged 15 thousand t, but during 2014-2016 this increased by about 50%, to over 23 thousand t, possibly due to increased abundance of swordfish, increased effort directed toward the species, increased reporting, or a combination of all of these.

Other billfishes are caught with large-scale and artisanal longlines and recreational gear. The average annual longline catches of blue marlin and striped marlin during 2004-2018 were about 3.3 thousand and 1.8 thousand t, respectively. Smaller amounts of other billfishes are taken by longline.

Little information is available on the recreational catches of billfishes, but, the retained catches are believed to be substantially less than the commercial catches for all species, due to catch-and-release practices.

Billfishes are caught incidentally in the purse-seine fisheries, which during 2003-2017 accounted for about 1% of the total catch of billfishes in the EPO. Prior to 2011, they were all classified as discarded dead; however, the growing rate of retention of such bycatches made it important to reflect this in the data, and since 2011 retained catch and discards are reported separately in Table A-2b.

Other species

Data on the purse-seine catches and discards of carangids (yellowtail, rainbow runner, jack mackerel), dorado, elasmobranchs (sharks, rays, and skates), and other fishes caught in the EPO are shown in (Table A-2c).

The purse-seine data are from three different sources: estimates of retained and discarded catches by Class-6 vessels recorded by on-board observers, who cover all trips by such vessels; reported retained and discarded catch for Class-5 vessels, but only for the very small proportion of their trips covered by observers; and catches recorded in the logbooks of Class 1-5 vessels, which include only retained catches, not discards. The data for Class 1-5 vessels have not been raised to the total effort of the fleet, so they are considered minimum estimates only. The data for 2018-2019 are preliminary.

In previous reports, much of the catch of elasmobranchs was allocated to ‘other gears’ (OTR) in Table A-2c. However, it has been determined that many of these catches from 2006 onward were in fact made with longlines, and in this report they have been transferred to the correct column (LL) in the table.

Dorado are unloaded mainly in ports in Central and South America. The reported catches of dorado have declined, from a high of 71 thousand t in 2009 to 15 thousand t in 2016.

Distributions of the catches of tunas

Purse-seine catches

The average annual distributions of purse-seine catches, by set type, of tropical tunas (yellowfin, skipjack, and bigeye) in the EPO during 2014-2018 are shown in Figures A-1a, A-2a, and A-3a,
Figure A-1a:


Figure A-2a: Average annual distributions of the purse-seine catches of skipjack, by set type, 2014-2018. The sizes of the circles are proportional to the amounts of skipjack caught in those 5° by 5° areas.


Figure A-3a: Average annual distributions of the purse-seine catches of bigeye, by set type, 2014-2018. The sizes of the circles are proportional to the amounts of bigeye caught in those 5° by 5° areas.

respectively, and preliminary estimates for 2019 are shown in Figures A-1b, A-2b, and A-3b.
Figure A-1b: Annual distributions of the purse-seine catches of yellowfin, by set type, 2019. The sizes of the circles are proportional to the amounts of yellowfin caught in those 5° by 5° areas.
Figure A-2b: Annual distributions of the purse-seine catches of skipjack, by set type, 2019. The sizes of the circles are proportional to the amounts of skipjack caught in those 5° by 5° areas.


Figure A-3b: Annual distributions of the purse-seine catches of bigeye, by set type, 2019. The sizes of the circles are proportional to the amounts of bigeye caught in those 5° by 5° areas.

Most of the yellowfin catches in 2019 were taken in sets associated with dolphins, in three main areas: south of Mexico from 125°W to 145°W, north and east from the Galapagos Islands to the coast, and offshore west of 120°W. As in 2018, larger-than-normal catches of yellowfin were taken in dolphin sets far offshore around the equator. Lesser amounts were taken in floating-object sets throughout the EPO south of 10°N, with a singular concentration around 150°W and the equator (Figure A-1b).
Figure A-1b: Annual distributions of the purse-seine catches of yellowfin, by set type, 2019. The sizes of the circles are proportional to the amounts of yellowfin caught in those 5° by 5° areas.



The skipjack catches in the EPO in 2019 closely matched the previous 5-year average, in both total catches and in 2019 were more evenly distributed throughout the EPO than in previous years, with most of the catch taken in floating-object sets throughout the EPO. Catches around the Galapagos Islands decreased from 2018, while catches near the coast of Peru increased, due to higher catches in unassociated sets (Figure A-2b).
Figure A-2b: Annual distributions of the purse-seine catches of skipjack, by set type, 2019. The sizes of the circles are proportional to the amounts of skipjack caught in those 5° by 5° areas.



Bigeye are not often caught north of about 7°N in the EPO, and almost all of the 2019 catches were taken in sets on FADs. More of the catch was taken far offshore than in previous years, concentrated mainly west of 120°W just north of the equator (Figure A-3b).
Figure A-3b: Annual distributions of the purse-seine catches of bigeye, by set type, 2019. The sizes of the circles are proportional to the amounts of bigeye caught in those 5° by 5° areas.

Longline catches

Since 2009, the IATTC has received tuna catch and effort data from Belize, China, France (French Polynesia), Japan, the Republic of Korea, Panama, Chinese Taipei, the United States, and Vanuatu. Albacore, bigeye and yellowfin tunas make up the majority of the catches by most of these vessels. The distributions of the catches of bigeye and yellowfin in the Pacific Ocean by Chinese, Japanese, Korean, and Chinese Taipei longline vessels during 2014-2018 are shown in Figure A-4.
Figure A-4: Distributions of the average annual catches of bigeye and yellowfin tunas in the Pacific Ocean, in metric tons, by Chinese, Japanese, Korean, and Chinese Taipei longline vessels, 2014-2018. The sizes of the circles are proportional to the amounts of bigeye and yellowfin caught in those 5° by 5° areas.

Size compositions of the catches of tunas

Purse-seine, pole-and-line, and recreational fisheries

Length-frequency samples are the basic source of data used for estimating the size and age compositions of the various species of fish in the landings. This information is necessary to obtain age-structured estimates of the populations for various purposes, including the integrated modeling that the staff uses to assess the status of the stocks which is found in the Stock Assessment Reports . The results of such studies have been described in several IATTC Bulletins, in its Annual Reports for 1954-2002, and in its Stock Assessment Reports.

Length-frequency samples are obtained from the catches of purse-seine vessels in the EPO by IATTC personnel at ports of landing in Ecuador, Mexico, Panama, and Venezuela.

The methods for sampling the catches of tunas are described in the IATTC Annual Report for 2000 and in IATTC Stock Assessment Reports 2 and 4.

Historical long-term time series of size-composition data for yellowfin and bigeye are available in the Stock Assessment Reports, and average length stock status indicators (SSIs) are available for yellowfin, bigeye and skipjack (SAC-11-05). In this report, data on the size composition of the catches during 2014-2019 are presented (Figures A-6 to A-8), with two sets of length-frequency histograms for each species: the first shows the data for 2019 by stratum (gear type, set type, and area), and the second the combined data for each year of the 2014-2019 period (Figure A-6), (Figure A-7) and (Figure A-8).
Figure A-6a: Estimated size compositions of the yellowfin caught in the EPO during 2019 for each fishery designated in Figure A-5. The value at the top of each panel is the average weight of the fish in the samples.




Figure A-6b: Estimated size compositions of the yellowfin caught by purse-seine and pole-and-line vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight of the fish in the samples.


Figure A-7a: Estimated size compositions of the skipjack caught in the EPO during 2019 for each fishery designated in Figure A-5. The value at the top of each panel is the average weight of the fish in the samples.




Figure A-7b: Estimated size compositions of the skipjack caught by purse-seine and pole-and-line vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight of the fish in the samples.


Figure A-8a: Estimated size compositions of the bigeye caught in the EPO during 2019 for each fishery designated in Figure A-5. The value at the top of each panel is the average weight.


Figure A-8b: Estimated size compositions of the bigeye caught by purse-seine vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight.

For stock assessments of yellowfin, nine purse-seine fisheries (four associated with floating objects (OBJ), three associated with dolphins (DEL), and two unassociated (NOA)) and one pole-and-line (LP) fishery, which includes all 13 sampling areas) are defined (Figure A-5).



Of the 971 wells sampled during 2019, 728 contained yellowfin. The estimated size compositions of the fish caught are shown in Figure A-6a
Figure A-6a: Estimated size compositions of the yellowfin caught in the EPO during 2019 for each fishery designated in Figure A-5. The value at the top of each panel is the average weight of the fish in the samples.

Most of the yellowfin catch was taken in the DEL fisheries during the first half of the year, with smaller amounts taken in the NOA-N fishery in the second quarter and in the OBJ fisheries throughout the year. The largest yellowfin (>120 cm) were caught in the DEL-N fishery throughout the year, and in the NOA-N fishery. Smaller yellowfin (<60 cm) were taken in the OBJ fishery, primarily in the second, third and fourth quarters.

The estimated size compositions of the yellowfin caught by all fisheries combined during 2014-2019 are shown in Figure A-6b.
Figure A-6b: Estimated size compositions of the yellowfin caught by purse-seine and pole-and-line vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight of the fish in the samples.

The average weight of the yellowfin in 2019, 8.1 kg, continued the increase from previous years, and the size distribution also showed a trend toward larger fish, with the greatest quantity around the 140 cm length interval.

For stock assessments of skipjack, seven purse-seine (four OBJ, two NOA, one DEL) and one LP fishery are defined (Figure A-5).

The last two include all 13 sampling areas. Of the 971 wells sampled, 668 contained skipjack. The estimated size compositions of the fish caught during 2019 are shown in Figure A-7a.
Figure A-7a: The purse-seine fisheries defined by the IATTC staff for analyses of yellowfin, skipjack, and bigeye in the EPO. The thin lines indicate the boundaries of the 13 length-frequency sampling areas, and the bold lines the boundaries of the fisheries.

Most of the skipjack catch was taken in the OBJ fisheries in the second, third and fourth quarters, and in the NOA-S fishery in the first and second quarters. Large skipjack (65-80 cm) were caught in the NOA-N fishery in the second quarter, close to 150°W between the equator and 10°N, the smallest (<40 cm) were caught primarily in the OBJ-N and OBJ-S fisheries in the second and fourth quarters

Most of the 2017 skipjack catch was taken in the Northern and Southern floating-object fisheries throughout the year, and in the Equatorial and Inshore floating-object fisheries, and the Southern unassociated fishery, in the first and second quarters. The smallest skipjack, less than 45 cm, were caught in the Northern and Southern floating-object fisheries in the third and fourth quarters (Figure A-2b).
Figure A-2b: Annual distributions of the purse-seine catches of skipjack, by set type, 2019. The sizes of the circles are proportional to the amounts of skipjack caught in those 5° by 5° areas.

The estimated size compositions of the skipjack caught by all fisheries combined during 2014-2019 are shown in Figure A-7b.


Figure A-7b: Annual distributions of the purse-seine catches of skipjack, by set type, 2019. The sizes of the circles are proportional to the amounts of skipjack caught in those 5° by 5° areas.

The average weight of skipjack in 2019 (2.0 kg) was consistent with previous years (1.8-2.2 kg).

For stock assessments of bigeye, six purse-seine (four OBJ, one NOA, one DEL) and one LP fishery are defined (Figure A-5);


Figure A-5: The purse-seine fisheries defined by the IATTC staff for analyses of yellowfin, skipjack, and bigeye in the EPO. The thin lines indicate the boundaries of the 13 length-frequency sampling areas, and the bold lines the boundaries of the fisheries.



all except the OBJ fisheries include all 13 sampling areas. Of the 971 wells sampled, 202 contained bigeye. The estimated size compositions of the fish caught during 2019 are shown in Figure A-8a.
Figure A-8a: Estimated size compositions of the bigeye caught in the EPO during 2019 for each fishery designated in Figure A-5. The value at the top of each panel is the average weight.



Most of the 2019 catch of bigeye was taken in the OBJ-N and OBJ-S fisheries throughout the year, with lesser amounts caught in the OBJ-E fishery.

The estimated size compositions of bigeye caught by all fisheries combined during 2014-2019 are shown in Figure A-8b.


Figure A-8b: Estimated size compositions of the bigeye caught by purse-seine vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight.

The average weight of bigeye in 2019 (5.0 kg) was slightly higher than the previous four years (4.7-4.9 kg), but lower than the 2014 average of 5.6 kg. As in previous years, most of the bigeye caught was in the 40-80 cm range.

Pacific bluefin are caught by purse-seine and recreational gears off California and Baja California, historically from about 23°N to 35°N, but only between 28°N and 32°N in recent years. Also, the purse-seine fishing season has started earlier than previously: in 2019, bluefin were first caught in February, and the fishery was closed in March, when the annual catch limit was reached. Most of the catch is transported live to grow-out pens near the coast of Mexico. Mexico’s National Fisheries Institute (INAPESCA) provided length-composition data for purse-seine catches during 2014-2019 (Figure A-9).


Figure A-9: Estimated size compositions of the bigeye caught by purse-seine vessels in the EPO during 2014-2019. The value at the top of each panel is the average weight.

The average weight for 2019 calculated from these length data, 42.3 kg, was lower than for 2017 and 2018 (55.4 and 55.7 kg, respectively), due to a sharp reduction in fish larger than 120 cm, but higher than for 2014-2016 (25.6-33.5 kg).



Longline fishery

The size compositions of yellowfin and bigeye caught by the Japanese longline fleet (commercial and training vessels) in the EPO during 2014-2018 are shown in Figure A-10 and Figure A-11.




Figure A-10: Estimated size compositions of the catches of yellowfin by the Japanese longline fleet in the EPO, 2014-2018. The size distribution has been standardized as a proportion of the total number of measured tuna in each size range. The value at the top of each panel is the average weight. Source: Fisheries Agency of Japan.
Figure A-11: Estimated size compositions of the catches of bigeye by the Japanese longline fleet in the EPO, 2014-2018. The size distribution has been standardized as a proportion of the total number of measured tuna in each size range. The value at the top of each panel is the average weight. Source: Fisheries Agency of Japan.

The average annual weight during that period ranged from 35.1 to 61.0 kg for yellowfin, and from 60.7 kg to 66.2 kg for bigeye.



Catches of tunas and bonitos, by flag and gear

The annual retained catches of tunas in the EPO during 1990-2019 by flag and gear, are shown in (Table A-3a). and, (

Table A-3b). and, (

Table A-3c). and, (Table A-3d). and, (

Table A-3e).



The purse-seine catches of tunas in 2018 and 2019, by flag and species, are summarized in (Table A-4a).

Of the nearly 653 thousand t of tunas caught in 2019, 46% were caught by Ecuadorian vessels, and 20% by Mexican vessels. Other countries with significant catches included Panama (10%), Colombia (7%), Venezuela (5%), United States (5%), Nicaragua (3%) and Peru (2%). The purse-seine landings of tunas in 2018 and 2019, by species and country of landing, are summarized in (Table A-4b).

. Of the more than 622 thousand t of tunas landed in the EPO in 2019, 64% were landed in Ecuadorian ports, and 21% in Mexican ports. Other countries with landings of tunas in the EPO included Colombia (3%), Peru (4%) and the United States (2%).


Effort
Purse-seine
Estimates of the numbers of purse-seine sets of each type (associated with dolphins (DEL), associated with floating objects (OBJ), and unassociated (NOA)) in the EPO during 2004-2019, and the retained catches from those sets, are shown in (Table A-7) and in Figure 1.
Figure 1: Purse-seine catches of tunas, by species and set type, 2004-2019

In Figure 1 the catch data for 2004-2019 incorporate previously unavailable data, and are thus different from the corresponding data presented in previous publications.

The estimates for vessels ≤363 t carrying capacity were calculated from logbook data in the IATTC statistical data base, and those for vessels >363 t carrying capacity were calculated from the observer data bases of the IATTC, Colombia, Ecuador, the European Union, Mexico, Nicaragua, Panama, the United States, and Venezuela.

Since the introduction of artificial fish-aggregating devices (FADs) in the mid-1990s, they have become predominant in the floating-object fishery, and now account for an estimated 98% of all floating-object sets by Class-6 vessels (Table A-8).

Longline
The reported nominal fishing effort (in thousands of hooks) by longline vessels in the EPO, and their catches of the predominant tuna species, are shown in (Table A-9).
Ecosystem Assessment
 
INTRODUCTION

Over the past two decades, the scope of management of many fisheries worldwide has broadened to take into account the impacts of fishing on non-target species in particular, and the ecosystem generally. This ecosystem approach to fisheries management (EAFM) is important for maintaining the integrity and productivity of ecosystems while maximizing the utilization of commercially-important fisheries resources, but also ecosystem services that provide social, cultural and economic benefits to human society.



EAFM was first formalized in the 1995 FAO Code of Conduct for Responsible Fisheries, which stipulates that “States and users of living aquatic resources should conserve aquatic ecosystems” and that “management measures should not only ensure the conservation of target species, but also of species belonging to the same ecosystem or associated with or dependent upon the target species”. In 2001, the Reykjavik Declaration on Responsible Fisheries in the Marine Ecosystem elaborated these principles with a commitment to incorporate an ecosystem approach into fisheries management.



The IATTC’s Antigua Convention, which entered into force in 2010, is consistent with these instruments and principles. Article VII (f) establishes that one of the functions of the IATTC is to “adopt, as necessary, conservation and management measures and recommendations for species belonging to the same ecosystem and that are affected by fishing for, or dependent on or associated with, the fish stocks covered by this Convention, with a view to maintaining or restoring populations of such species above levels at which their reproduction may become seriously threatened”. Prior to that, the 1999 Agreement on the International Dolphin Conservation Program (AIDCP) introduced ecosystem considerations into the management of the tuna fisheries in the EPO. Consequently, for over twenty years the IATTC has been aware of ecosystem issues, and has moved towards EAFM in many of its management decisions (e.g. SAC-10 INF-B). Within the framework of the Strategic Science Plan (SSP), the IATTC staff is conducting novel and innovative ecological research aimed at obtaining the data and developing the practical tools required to implement EAFM in the tuna fisheries of the EPO. Current and planned ecosystem-related work by the staff is summarized in the SSP (IATTC-93-06a) and the Staff Activities and Research report (SAC-11-01).



Determining the ecological sustainability of EPO tuna fisheries is a significant challenge, given the wide range of species with differing life histories with which those fisheries interact. While relatively good information is available for catches of tunas and billfishes across the entire fishery, this is not the case for most bycatch species (see section 2). Furthermore, environmental processes that operate on a variety of time scales (e.g. El Niño-Southern Oscillation, Pacific Decadal Oscillation, ocean warming, anoxia and acidification) can influence the distribution, abundance and availability of species to different degrees, which in turn affects their potential to be impacted by tuna fisheries.



Biological reference points, based on estimates of fishing mortality, spawning stock biomass, recruitment, and other biological parameters, have been used for traditional single-species management of target species, but the reliable catch and/or biological data required for determining such reference points, or alternative performance measures, are unavailable for most non-target species. Similarly, given the complexity of marine ecosystems, there is no single indicator that can completely represent their structure and internal dynamics and thus be used to monitor and detect the impacts of fishing and the environment.



The staff has presented an Ecosystem Considerations report for many years, but this report is significantly different from its predecessors, in content, structure, and purpose. Its primary purpose is to complement the annual report on the fishery (SAC-11-03) with information on non-target species and on the effect of the fishery on the ecosystem, and to describe how ecosystem research can contribute to management advice and the decision-making process. It also describes some important advances in research related to assessing ecological impacts of fishing and the environment on the EPO ecosystem.



DATA SOURCES

In this report, catches of bycatch species were obtained from observer data for the large-vessel purse-seine fishery with a carrying capacity > 363 t, while gross annual removals by the longline fishery were obtained from data reported to the IATTC. Purse-seine data were available through 2019, with data from the last 2 years considered preliminary as of March 2020. Longline data were available through 2018 as the deadline for data reporting for the previous year occurs after the 2019 SAC meeting. Each data source is described in detail below.



Purse-Seine

Data from the purse-seine fishery are compiled from 3 data sources: 1) IATTC and National Program observer data, 2) vessel logbook data extracted by staff at the Commission’s field offices in Latin American tuna ports, and 3) cannery data. The observer data from the large-vessel fishery are the most comprehensive in terms of bycatch species. Observers of the IATTC and the various National Programs provide detailed bycatch data by species, catch, disposition and effort for the exact fishing position (i.e., the latitude and longitude of the purse-seine set). Both the logbook and cannery datasets contain very limited data on bycatch species as captains and crew of the vessels who record the logbook data are primarily focused on reporting aspects of the commercially important tuna species. The logbook data, like the purse seine, includes the exact fishing position, but limited effort data are recorded with only one entry per day. The cannery (or “unloading”) data do not have an exact fishing position but rather a grouped position (e.g., the eastern Pacific or western Pacific Ocean). These data contain bycatch species only if they were retained in a purse-seine well during the fishing operation.

Because the smaller (Class 1-5) purse-seine vessels are not required to carry observers, logbook records and the port sampling program are the primary data sources for these vessels. As such, the data are limited and contain little or no information on interactions with bycatch species. Some detailed operational data are available from a recent voluntary scheme in Ecuador in which several smaller vessels carried observers, from a small number of Class-5 vessels that have been required to carry observers for limited periods under the AIDCP, and a current IATTC pilot project trialing the efficacy of electronic monitoring methodologies (SAC-11-10). An analysis is planned to evaluate whether such voluntary data may be representative of the fleet as a whole and therefore included in future iterations of this report.

Therefore, in this report we focus on the comprehensive observer dataset from large purse-seine vessels to provide catch data for bycatch species. Under the AIDCP program, an observer is placed on a large purse-seine vessel prior to each trip. The bycatch data provided by the observers is used to estimate total catches, by set type (i.e. floating objects (OBJ), unassociated tunas (NOA), and dolphins (DEL)). The numbers of sets of each type made in the EPO during 2004–2019 are shown in Table A-7 of Document SAC-11-03.



Despite the observer requirement, some sets are known to have taken place, based on logbooks and other sources, but were not observed. For example, at the start of bycatch data collection in 1993, about 46% of sets were observed, increasing to 70% in 1994. From 1994 to 2008, the average percent of sets observed was around 80%. From 2009 onwards, nearly 100% of sets were observed. Catch-per-day data for both target and non-target bycatch species are extrapolated to account for such instances.



Longline

The considerable variability in reporting formats of longline data has hindered the staff’s ability to estimate EPO-wide catches for bycatch species (SAC-08-07b, SAC-08-07d, SAC-08-07e). Bycatch data for longline fisheries reported here were obtained using data of gross annual removals (i.e. the total annual catch by species estimated by each CPC reported to the IATTC in summarized form). This is the same data source used to compile annual longline estimates for principal tuna and tuna-like species in SAC-11-03. Because there is uncertainty in whether the IATTC is receiving all bycatch data from the longline fishery of each CPC, these data are considered incomplete, or “sample data”, and are therefore regarded as minimum annual reported catch estimates for 1993–2018. A staff-wide collaboration is underway to revise the data provision Resolution C-03-05 to improve the quality of data collection, reporting, and analysis to align with IATTC’s responsibilities set forth in the Antigua Convention and the SSP.

During this process, the staff were able to determine that the longline catches of sharks, reported by CPCs were several times higher than previously reported catches for the longline fishery. A review of the data revealed that a high proportion of shark catches were assigned to “other gears” in the staff’s annual Fishery Status Reports since 2006 but were in fact taken by longline. Therefore, the resulting transfer of catch data from “other gears” to “longline” significantly increased the longline catches of sharks from 2006 onwards (see Table A2c in SAC-11-03).



Longline data reporting has been improving since the adoption of Resolution C-19-08. The staff is receiving detailed set-by-set operational level observer data for some CPCs, although the current mandated observer coverage of 5% of the total number of hooks or “effective days fishing” continues to be significantly lower than the 20% coverage recommended by the staff, the Working Group on Bycatch, and the Scientific Advisory Committee. As of August 2020, the staff had received longline observer data from eight CPCs (Chinese Taipei, Ecuador, Japan, Korea, Mexico, the United States, and the EU (Portugal) and EU (Spain)), and exploratory analyses of the data were initiated to identify how representative they are of the activities of the total fleet. The results of these analyses will be presented to the SAC in 2021. As longline data reporting continues to improve, IATTC staff will seek to provide estimates of longline catches in the EPO based on observer data.



FISHERY INTERACTIONS WITH SPECIES GROUPS TUNAS AND BILFISHES

Data on catches of the principal species of tunas and bonitos of the genera Thunnus, Katsuwonis, Euthynnus, and Sarda, and of billfishes in the Istiophoridae and Xiphiidae families, are reported in Document SAC-11-03. The staff has developed stock assessments and/or stock status indicators (SSIs) for bigeye (SAC-11-06, SAC-11-05), yellowfin (SAC-11-07, SAC-11-05), and skipjack (SAC-11-05) tunas and has collaborated in the assessments of Pacific bluefin and albacore tunas led by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC).

Marine mammals

Marine mammals, especially spotted dolphins (Stenella attenuata), spinner dolphins (S. longirostris), and common dolphins (Delphinus delphis), are frequently found associated with yellowfin tuna in the EPO. Purse-seine fishers commonly set their nets around herds of dolphins and the associated schools of yellowfin tuna, and then release the dolphins while retaining the tunas. The incidental mortality of dolphins was high during the early years of the fishery, but declined dramatically in the early 1990s, and has remained at low levels since then (Figure L-1).
Figure L-1: Incidental dolphin mortalities, in numbers of animals, by purse-seine vessels, 1993–2019.

Marine mammals have not been reported in the longline data, although with new observer data, estimates may be able to be provided in future

Sea turtles

Sea turtles are occasionally caught in the purse-seine fishery in the EPO, usually when associated with floating objects that are encircled, although they are sometimes also caught by happenstance in sets on unassociated tunas or tunas associated with dolphins. They can also become entangled in the webbing under fish-aggregating devices (FADs) and drown, or be injured or killed by fishing gear.



Sea turtle mortalities and interactions recorded by observers on large purse-seine vessels, by set type, during 1993–2019. Interactions were defined from observer information recorded as fate on the dedicated turtle form as: entangled, released unharmed, light injuries, escaped from net, observed but not involved in the set and other/unknown. The olive ridley turtle (Lepidochelys olivacea) is, by far, the species of sea turtle most frequently caught, with a total of 19,104 interactions and 874 mortalities during 1993-2019, but only 368 interactions and 1 mortality in 2019 as shown in Figure L-2 and (Table L-1).
Figure L-2: Sea turtle a) mortalities and b) interactions, in numbers of animals, for large purse-seine vessels, 1993–2019, by set type (dolphin (DEL), unassociated (NOA), floating object (OBJ)).

In 2019, in 110 reported interactions with eastern Pacific green turtles, 70 with loggerheads, 9 with hawksbills, and none with leatherback turtles, only one mortality was recorded, of an unidentified turtle.



In the longline fishery, sea turtles are caught when they swallow a baited hook, are accidentally hooked, or drown after becoming entangled in the mainline, floatlines or branchlines and cannot reach the surface to breathe. They are also caught in coastal pelagic and bottom-set gillnet fisheries, where they become enmeshed in the net or entangled in the floatlines or headrope. Although very few data on incidental mortality of turtles due to longline and gillnet fishing are available, the mortality rates in the EPO industrial longline fishery are likely to be lowest in “deep” sets (around 200-300 m) targeting bigeye tuna, and highest in “shallow” sets (<150 m) for albacore and swordfish. There is also a sizeable fleet of artisanal longline and gillnet fleets from coastal nations that are known to catch sea turtles, but limited data are available.

Data on sea turtle interactions and mortalities in the longline fishery have not been available (SAC-08-07b), although they are expected to improve with the submission of operational-level observer data for longline vessels >20 m beginning in 2019 pursuant to Resolution C-19-08. Recalling the observer coverage for longline vessels is only 5%, compared to 100% of observed trips in the large-vessel purse-seine fishery, the observer data provided in national reports for 2019 (SAC-11-INF-A(a-j)) include 115 turtle interactions, of which eight (7%) resulted in mortalities. The reported interactions/mortalities by species were loggerhead (39/1), green (31/0), olive ridley (29/4), leatherback (13/2), and Kemp’s ridley (1/1), plus unidentified sea turtles (2/0). The staff hopes to use the new operational observer data submissions required under C-19-08 to report the first total longline fleet catch estimate for sea turtle species in 2021.

Various IATTC resolutions, most recently C-19-04, have been intended to mitigate fishing impacts on sea turtles and establish safe handling and release procedures for sea turtles caught by purse-seine and longline gears.

A vulnerability assessment was conducted for the eastern Pacific stock of leatherback turtles for 2018, using the Ecological Assessment of Sustainable Impacts of Fisheries (EASI-Fish) approach (see section 5) and a document has been prepared for the meeting of the Bycatch Working Group (BYC-10 INF-B). In brief, the status of the stock was determined to be “most vulnerable” in 2018, while scenario modelling showed that the implementation of improved handling and release practices by the longline fleet would reduce post-release mortality to the extent that the population might be considered “least vulnerable”.



Seabirds

There are approximately 100 species of seabirds in the tropical EPO. Some of them associate with epipelagic predators, such as fishes (especially tunas) and marine mammals, near the ocean surface; for some, feeding opportunities are dependent on the presence of tuna schools feeding near the surface. Some seabirds, especially albatrosses and petrels, are caught on baited hooks in pelagic longline fisheries.



The IATTC has adopted one resolution on seabirds (C-11-02); also, the Agreement on the Conservation of Albatrosses and Petrels (ACAP) and BirdLife International have updated their maps of seabird distribution in the EPO, and have recommended guidelines for seabird identification, reporting, handling, and mitigation measures (SAC-05 INF-E, SAC-07-INF-C(d), SAC-08-INF-D(a), SAC-08-INF-D(b), BYC-08 INF J(b)). Additionally, ACAP has reported on the conservation status of albatrosses and large petrels (SAC-08-INF-D(c); BYC-08 INF J(a)).



As with sea turtles, data on seabird interactions and mortalities in the longline fishery have been unavailable (SAC-08-07b), although they are expected to improve with the submission of operational-level observer data for longline vessels >20 m beginning in 2019. The observer data available in national reports for 2019 (SAC-11 INF-A(a-j)) include seven interactions with unidentified seabirds, all recorded as dead, and one black-footed albatross (Phoebastria nigripes), released alive. The staff hopes to report the first total longline fleet catch estimate for seabird species in 2021 using the operational observer data.



Sharks

Sharks are caught as bycatch or targeted catch in EPO tuna longline and purse-seine fisheries as well as multi-species and multi-gear fisheries of the coastal nations.

Stock assessments or stock status indicators (SSIs) are available for only four shark species in the EPO: silky (Carcharhinus falciformis) (Lennert-Cody et al. 2018; BYC-10 INF-A), blue (Prionace glauca) (ISC Shark Working Group), shortfin mako (Isurus oxyrinchus) (ISC Shark Working Group), and common thresher (Alopias vulpinus) (NMFS). As part of the FAO Common Oceans Tuna Project, Pacific-wide assessments of the porbeagle shark (Lamna nasus) in the southern hemisphere (Clarke 2017) and the bigeye thresher shark (Alopias superciliosus) (Fu et al. 2018) were completed in 2017, and for the silky shark (Clarke 2018a) in 2018, as well as a risk assessment for the Indo-Pacific whale shark population (Clarke 2018b) also in 2018. Whale shark interactions with the tuna purse-seine fishery in the EPO are summarized in Document BYC-08 INF-A. The impacts of tuna fisheries on the stocks of other shark species, not previously mentioned, in the EPO are unknown.

Catches (t) of sharks in the large-vessel purse-seine fishery (1993–2019) and minimum reported catch estimates by longline fisheries (1993–2018) are provided in (

Table L-3).

while catches of the most frequently caught species, are shown in Figure L-3.
Figure L-3: Estimated purse-seine (top panel) and longline (bottom panel) catches in metric tons (t) of key species of sharks in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Longline catches are minimum reported gross-annual removals that may have been estimated using a mixture of different weight metrics.



Total longline catch estimates for 2019 were not available at the time of this report and reporting of many shark species began in 2006. The silky shark (family Carcharhinidae) is the species of shark most commonly caught in the purse-seine fishery with annual catches averaging 559 t—primarily from sets on floating objects (Figure L-3)—and being 430 t in 2019. In contrast, minimum reported annual catch in the longline sample data for 2006–2018 averaged 11,813 t and was 15,072 t in 2018.

Catches (t) of sharks in the large-vessel purse-seine fishery (1993–2019) and minimum reported catch estimates by longline fisheries (1993–2018) are provided in Table L-3, while catches of the most frequently caught species, discussed below, are shown in Figure L-3. Total longline catch estimates for 2019 were not available at the time of this report and reporting of many shark species began in 2006. The silky shark (family Carcharhinidae) is the species of shark most commonly caught in the purse-seine fishery with annual catches averaging 559 t—primarily from sets on floating objects (Figure L-3)—and being 430 t in 2019. In contrast, minimum reported annual catch in the longline sample data for 2006–2018 averaged 11,813 t and was 15,072 t in 2018.

Annual catch for the oceanic whitetip shark (Carcharhinidae) in the purse-seine fishery averaged 61 t (also primarily from sets on floating objects) and was 5 t in 2019. The minimum reported annual catch in the longline fishery averaged 79 t and was 19 t in 2018. Catches of oceanic whitetip have declined in the purse-seine fishery since the early 2000s, while catches have been variable in the longline fishery (Figure L-3).
Figure L-3: Estimated purse-seine (top panel) and longline (bottom panel) catches in metric tons (t) of key species of sharks in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Longline catches are minimum reported gross-annual removals that may have been estimated using a mixture of different weight metrics.



Minimum annual reported catch of blue shark in the longline fishery averaged 5,382 t and was 12,064 t in 2018. By contrast, the annual catch in the purse-seine fishery averaged only 1.9 t, with 1 t caught in 2019.

Other important species of sharks caught in the purse-seine and longline fisheries include the smooth hammerhead (Sphyrna zygaena), the pelagic thresher (Alopias pelagicus), and mako sharks (Isurus spp.) shown in (Table L-3).

Catch estimates for the smooth hammerhead shark in the purse-seine fishery averaged 22 t (primarily caught in floating-object sets) and was 18 t in 2019, while in the longline fishery minimum annual reported catch averaged 496 t (2006–2018) and was 851 t in 2018. In contrast, the pelagic thresher was caught primarily in unassociated tuna school sets in the purse-seine fishery with estimated annual catch averaging 4.8 t and was 2 t in 2019 (Figure L-3).
Figure L-3: Estimated purse-seine (top panel) and longline (bottom panel) catches in metric tons (t) of key species of sharks in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Longline catches are minimum reported gross-annual removals that may have been estimated using a mixture of different weight metrics.

Minimum annual reported catch of the pelagic thresher in the longline fishery averaged 1,042 t and was 464 in 2018. Catch estimates for the mako sharks in the purse-seine fishery were lower than the aforementioned shark species averaging 2.6 t and was 1 t in 2019. However, in the longline fishery the minimum annual reported catch averaged 1,263 t and was 2,882 t in 2018.

The small-scale artisanal longline fisheries of the coastal CPCs target sharks, tunas, billfishes and dorado (Coryphaena hippurus), and some of these vessels are similar to industrial longline fisheries in that they operate in areas beyond national jurisdictions (Martínez-Ortiz et al. 2015). However, essential shark data from these longline fisheries are often lacking, and therefore conventional stock assessments and/or stock status indicators cannot be produced (see data challenges outlined in SAC-07-06b(iii)). An ongoing project is being undertaken to improve data collection on sharks, particularly for Central America, for the longline fleet through funding from the Food and Agriculture Organization of the United Nations (FAO) and the Global Environmental Facility (GEF) under the framework of the ABNJ Common Oceans program (SAC-07-06b(ii), SAC-07-06b(iii)). A one-year pilot study was completed in 2019, collecting shark-fishery data and developing and testing sampling designs for a long-term sampling program for the shark fisheries throughout Central America (Phase 2 of the project). A progress report on the FAO-GEF ABNJ project has been prepared (SAC-11-13). Data obtained from this project may be included in future iterations of the Ecosystem Considerations report to provide improved catch estimates for sharks by the various longline fleets.



Rays

Estimated annual catches of manta rays (Mobulidae) and stingrays (Dasyatidae) by the large-vessel purse-seine (1993–2019) and minimum reported annual catches by longline (1993–2018) fisheries are provided in (
Table L-4 Estimated purse-seine catches by set type in metric tons (t) of rays for size-class 6 vessels with a carrying capacity >363 t (1993–2019) and minimum reported longline (LL) catches of rays (gross-annual removals in t) (1993–2018, *data not available). Purse-seine set types: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Species highlighted bold are discussed in main text. Data for 2019 are considered preliminary. “Other rays” include Chilean torpedo (Torpedo tremens), Pacific cownose (Rhinoptera steindachneri), and unidentified eagle rays (Myliobatidae).
  Mobulidae
  Mobula thurstoni, smoothtail manta Mobula mobular,
spinetail manta
Mobula munkiana,
munk's devil ray
Mobula tarapacana,
chilean devil ray
Mobula birostris,
giant manta
  Purse seine LL Purse seine LL Purse seine LL Purse seine LL Purse seine LL
Year OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL
1993 - - - - - - - - - - - - - - - - - - - -
1994 - <1 - - - - - - - - - - - - - - <1 - - -
1995 - - - - - - - - - - - - - - - - - <1 - -
1996 - - - - - - - - - - - - - - - - - - - -
1997 - - - - - - - - - - - - - - - - - <1 - -
1998 - <1 - - - - - - - - - - - - - - 3 19 <1 -
1999 - <1 <1 - - - - - - - - - - - - - 5 10 <1 -
2000 1 4 3 - - - - - - - - - - - - - <1 5 <1 -
2001 <1 7 2 - <1 <1 1 - - - <1 - <1 - - - 1 3 <1 -
2002 <1 17 2 - <1 <1 7 - <1 <1 <1 - <1 1 <1 - 1 4 1 -
2003 <1 25 5 - <1 4 <1 - <1 <1 <1 - - - <1 - <1 6 <1 -
2004 <1 15 3 - <1 2 4 - - <1 <1 - <1 2 <1 - 1 3 4 -
2005 <1 3 6 - 1 9 8 - - <1 <1 - <1 4 7 - 3 14 21 -
2006 <1 18 2 - 2 36 14 - - 2 <1 - <1 6 3 - 10 16 128 -
2007 <1 2 4 - 3 12 11 - <1 <1 <1 - 2 4 2 - <1 11 4 -
2008 <1 5 2 - 2 18 5 - <1 3 <1 - <1 24 3 - 2 32 10 -
2009 <1 1 3 - 1 4 20 - <1 1 <1 6 <1 <1 8 - <1 5 3 -
2010 2 5 5 - 2 26 25 - <1 1 <1 118 <1 1 8 - 1 29 <1 -
2011 <1 14 <1 - 1 5 10 - <1 1 <1 - <1 3 7 - 3 4 <1 -
2012 <1 38 1 - 4 20 3 - <1 1 <1 - <1 7 1 - 3 24 7 -
2013 <1 6 2 - 1 9 5 - <1 1 <1 - <1 3 1 - <1 10 13 -
2014 <1 <1 3 - 16 6 5 - <1 <1 <1 - <1 <1 <1 - <1 4 - -
2015 <1 2 3 - 3 1 24 - <1 <1 1 - 1 2 6 - <1 10 <1 -
2016 <1 <1 5 - <1 2 9 - <1 2 2 - 1 2 2 - 4 18 2 -
2017 <1 <1 1 - 3 1 1 - <1 <1 <1 - <1 - <1 - 5 33 <1 -
2018 <1 1 <1 - 3 4 4 - <1 - <1 - 1 <1 <1 - 5 4 <1 -
2019 <1 5 <1 - 2 12 4 - <1 - <1 - 3 <1 1 - <1 5 3 -
Total 11 172 53 - 45 170 160 - 2 15 9 124 16 64 53 - 51 272 201 -
  Mobulidae Dasyatidae Other rays All rays
  Mobulidae spp.,
mobulid rays, nei
Pteroplatytrygon violacea,
pelagic stingray
Dasyatidae spp.,
stingrays, nei
Other rays
  Purse seine LL Purse seine LL Purse seine LL Purse seine   Purse seine LL
Year OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL
1993 9 213 27 - <1 5 <1 - - - - - - - - - 9 219 27 -
1994 3 73 19 - <1 4 <1 - - - - - - - - - 3 77 20 -
1995 3 29 30 - <1 <1 <1 - - - - - - - - - 3 30 30 -
1996 4 73 16 - <1 <1 <1 - - - - - - - - - 4 74 16 -
1997 5 41 17 - <1 <1 3 - - - - - - - - - 5 42 20 -
1998 5 228 18 - <1 <1 <1 - - 3 - - <1 <1 - - 7 251 20 -
1999 8 84 16 - <1 1 <1 - - - - - - - - - 13 96 17 -
2000 2 94 23 - <1 <1 <1 - - - - - - - - - 4 104 27 -
2001 3 20 23 - <1 <1 <1 - - - - - - - - - 5 30 27 -
2002 2 69 37 - <1 <1 <1 - <1 - - - - - - - 6 92 48 -
2003 9 61 37 - <1 25 <1 - - - - - - - - - 11 121 44 -
2004 4 46 19 - <1 <1 <1 - <1 5 <1 - - - - - 6 75 31 -
2005 2 19 11 - <1 <1 <1 - <1 <1 <1 - - 31 - - 8 80 53 -
2006 3 23 14 - <1 <1 <1 - <1 12 <1 - - - 3 - 16 115 166 -
2007 2 12 12 - <1 <1 <1 - <1 3 <1 2 - <1 - - 8 44 35 2
2008 3 10 5 - <1 <1 <1 - <1 <1 <1 2 - - - - 8 93 27 2
2009 2 7 15 - <1 <1 <1 - <1 <1 1 8 - - - - 6 19 50 13
2010 7 20 17 - <1 <1 2 - <1 - <1 3 - 20 - - 13 103 58 121
2011 1 11 5 - <1 <1 <1 - <1 <1 <1 <1 - <1 - - 7 40 25 <1
2012 1 10 3 - <1 <1 <1 - <1 <1 <1 - <1 <1 <1 - 9 100 16 -
2013 <1 6 6 - <1 <1 <1 - <1 <1 <1 - - - 1 - 5 36 28 -
2014 1 4 1 - <1 <1 <1 - <1 <1 <1 - - - - - 20 17 11 -
2015 1 4 9 - <1 <1 <1 - <1 <1 1 1 - - - - 7 20 46 1
2016 3 12 11 - <1 <1 <1 - <1 - <1 - - - - - 10 37 32 -
2017 7 20 6 - <1 <1 <1 - <1 <1 <1 - - - <1 - 18 56 11 -
2018 6 5 6 - <1 <1 <1 - <1 <1 <1 - - - - - 17 15 12 -
2019 4 16 8 - <1 <1 <1 - <1 <1 <1 - - <1 <1 - 11 40 18 -
Total 100 1,210 411 - 9 41 16 - 3 27 6 16 0 52 5 - 238 2,024 914 140



).



while catches of key species are shown in (Figure L-4).








Figure L-4: Estimated purse-seine catches in metric tons (t) of key species of rays in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL).

These rays are primarily caught by the purse-seine fishery, with low catches reported only for the munk’s devil ray (2009: 6 t, 2010: 118 t) and Dasyatidae spp. (16 t over a 6-year period), with half the catches made in 2007 by the longline fishery as shown in Table L-4.

The giant manta had the largest average catches in the purse-seine fishery (19.4 t), followed by the spinetail (13.9 t), and smoothtail (8.7 t) mobulid rays. Catches of these species in 2019 were 8, 19, and 5 t, respectively. Catches of the pelagic stingray were low, averaging only 2.5 t and being 2 t in 2019 (
Table L-4 Estimated purse-seine catches by set type in metric tons (t) of rays for size-class 6 vessels with a carrying capacity >363 t (1993–2019) and minimum reported longline (LL) catches of rays (gross-annual removals in t) (1993–2018, *data not available). Purse-seine set types: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Species highlighted bold are discussed in main text. Data for 2019 are considered preliminary. “Other rays” include Chilean torpedo (Torpedo tremens), Pacific cownose (Rhinoptera steindachneri), and unidentified eagle rays (Myliobatidae).
  Mobulidae
  Mobula thurstoni, smoothtail manta Mobula mobular,
spinetail manta
Mobula munkiana,
munk's devil ray
Mobula tarapacana,
chilean devil ray
Mobula birostris,
giant manta
  Purse seine LL Purse seine LL Purse seine LL Purse seine LL Purse seine LL
Year OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL
1993 - - - - - - - - - - - - - - - - - - - -
1994 - <1 - - - - - - - - - - - - - - <1 - - -
1995 - - - - - - - - - - - - - - - - - <1 - -
1996 - - - - - - - - - - - - - - - - - - - -
1997 - - - - - - - - - - - - - - - - - <1 - -
1998 - <1 - - - - - - - - - - - - - - 3 19 <1 -
1999 - <1 <1 - - - - - - - - - - - - - 5 10 <1 -
2000 1 4 3 - - - - - - - - - - - - - <1 5 <1 -
2001 <1 7 2 - <1 <1 1 - - - <1 - <1 - - - 1 3 <1 -
2002 <1 17 2 - <1 <1 7 - <1 <1 <1 - <1 1 <1 - 1 4 1 -
2003 <1 25 5 - <1 4 <1 - <1 <1 <1 - - - <1 - <1 6 <1 -
2004 <1 15 3 - <1 2 4 - - <1 <1 - <1 2 <1 - 1 3 4 -
2005 <1 3 6 - 1 9 8 - - <1 <1 - <1 4 7 - 3 14 21 -
2006 <1 18 2 - 2 36 14 - - 2 <1 - <1 6 3 - 10 16 128 -
2007 <1 2 4 - 3 12 11 - <1 <1 <1 - 2 4 2 - <1 11 4 -
2008 <1 5 2 - 2 18 5 - <1 3 <1 - <1 24 3 - 2 32 10 -
2009 <1 1 3 - 1 4 20 - <1 1 <1 6 <1 <1 8 - <1 5 3 -
2010 2 5 5 - 2 26 25 - <1 1 <1 118 <1 1 8 - 1 29 <1 -
2011 <1 14 <1 - 1 5 10 - <1 1 <1 - <1 3 7 - 3 4 <1 -
2012 <1 38 1 - 4 20 3 - <1 1 <1 - <1 7 1 - 3 24 7 -
2013 <1 6 2 - 1 9 5 - <1 1 <1 - <1 3 1 - <1 10 13 -
2014 <1 <1 3 - 16 6 5 - <1 <1 <1 - <1 <1 <1 - <1 4 - -
2015 <1 2 3 - 3 1 24 - <1 <1 1 - 1 2 6 - <1 10 <1 -
2016 <1 <1 5 - <1 2 9 - <1 2 2 - 1 2 2 - 4 18 2 -
2017 <1 <1 1 - 3 1 1 - <1 <1 <1 - <1 - <1 - 5 33 <1 -
2018 <1 1 <1 - 3 4 4 - <1 - <1 - 1 <1 <1 - 5 4 <1 -
2019 <1 5 <1 - 2 12 4 - <1 - <1 - 3 <1 1 - <1 5 3 -
Total 11 172 53 - 45 170 160 - 2 15 9 124 16 64 53 - 51 272 201 -
  Mobulidae Dasyatidae Other rays All rays
  Mobulidae spp.,
mobulid rays, nei
Pteroplatytrygon violacea,
pelagic stingray
Dasyatidae spp.,
stingrays, nei
Other rays
  Purse seine LL Purse seine LL Purse seine LL Purse seine   Purse seine LL
Year OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL OBJ NOA DEL LL
1993 9 213 27 - <1 5 <1 - - - - - - - - - 9 219 27 -
1994 3 73 19 - <1 4 <1 - - - - - - - - - 3 77 20 -
1995 3 29 30 - <1 <1 <1 - - - - - - - - - 3 30 30 -
1996 4 73 16 - <1 <1 <1 - - - - - - - - - 4 74 16 -
1997 5 41 17 - <1 <1 3 - - - - - - - - - 5 42 20 -
1998 5 228 18 - <1 <1 <1 - - 3 - - <1 <1 - - 7 251 20 -
1999 8 84 16 - <1 1 <1 - - - - - - - - - 13 96 17 -
2000 2 94 23 - <1 <1 <1 - - - - - - - - - 4 104 27 -
2001 3 20 23 - <1 <1 <1 - - - - - - - - - 5 30 27 -
2002 2 69 37 - <1 <1 <1 - <1 - - - - - - - 6 92 48 -
2003 9 61 37 - <1 25 <1 - - - - - - - - - 11 121 44 -
2004 4 46 19 - <1 <1 <1 - <1 5 <1 - - - - - 6 75 31 -
2005 2 19 11 - <1 <1 <1 - <1 <1 <1 - - 31 - - 8 80 53 -
2006 3 23 14 - <1 <1 <1 - <1 12 <1 - - - 3 - 16 115 166 -
2007 2 12 12 - <1 <1 <1 - <1 3 <1 2 - <1 - - 8 44 35 2
2008 3 10 5 - <1 <1 <1 - <1 <1 <1 2 - - - - 8 93 27 2
2009 2 7 15 - <1 <1 <1 - <1 <1 1 8 - - - - 6 19 50 13
2010 7 20 17 - <1 <1 2 - <1 - <1 3 - 20 - - 13 103 58 121
2011 1 11 5 - <1 <1 <1 - <1 <1 <1 <1 - <1 - - 7 40 25 <1
2012 1 10 3 - <1 <1 <1 - <1 <1 <1 - <1 <1 <1 - 9 100 16 -
2013 <1 6 6 - <1 <1 <1 - <1 <1 <1 - - - 1 - 5 36 28 -
2014 1 4 1 - <1 <1 <1 - <1 <1 <1 - - - - - 20 17 11 -
2015 1 4 9 - <1 <1 <1 - <1 <1 1 1 - - - - 7 20 46 1
2016 3 12 11 - <1 <1 <1 - <1 - <1 - - - - - 10 37 32 -
2017 7 20 6 - <1 <1 <1 - <1 <1 <1 - - - <1 - 18 56 11 -
2018 6 5 6 - <1 <1 <1 - <1 <1 <1 - - - - - 17 15 12 -
2019 4 16 8 - <1 <1 <1 - <1 <1 <1 - - <1 <1 - 11 40 18 -
Total 100 1,210 411 - 9 41 16 - 3 27 6 16 0 52 5 - 238 2,024 914 140



).



Although catches of these rays can be variable by set type, they have been highest in unassociated sets, followed by dolphin sets, and lowest in floating-object sets (Figure L-4).
Figure L-4: Estimated purse-seine catches in metric tons (t) of key species of rays in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL).



Other large fishes

Large pelagic fishes caught by the large-vessel purse-seine, primarily on floating-object sets, (1993–2019) and longline (1993–2018) fisheries are shown in Table L-5, with time series of catches of key species presented in Figure L-5. The most commonly-caught pelagic fishes in both fisheries is dorado (Coryphaenidae) with the estimated average annual catch for the purse-seine fishery being 1,309 t (1,237 t in 2019) and the minimum reported annual catch for the longline fishery averaging 5,997 t (3,499 t in 2018). Dorado is also one of the most important species caught in the artisanal fisheries of the coastal nations of the EPO (SAC-07-06a(i)). Recommendations for potential reference points and harvest control rules for dorado in the EPO can be found in document SAC-10-11.

Other key species caught by the purse-seine fishery include wahoo (Scombridae) and rainbow runner (Carangidae). Wahoo had an estimated average annual catch of 386 t, although catches have declined from a peak of 1,025 t in 2001 to 202 t in 2019 (Figure L-5).
Figure L-5: Estimated purse-seine and longline catches in metric tons (t) of key species of large fishes in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL). Longline catches are minimum reported gross-annual removals.

Minimum reported annual catch of wahoo by the longline fishery have averaged 149 t and was 313 t in 2018. No catches of rainbow runner have been reported by the longline fishery. However, in the purse-seine fishery estimated average annual catches of rainbow runner have been 48 t, peaking in 2007 at 158 t and declining thereafter to 21 t in 2019 (Figure L-5).







Pelagic fishes commonly reported by the longline fishery include opah (Lampridae), snake mackerels (Gempylidae) and pomfrets (Bramidae). Minimum reported annual catches for these species averaged 324 t, 182 t, and 49 t, respectively. Catches of all these species have increased after the mid-2000s as shown in Figure L-5.

For the most recent year (2018), there were 1,024 t, 227 t, and 125 t of opah, snake mackerels, and pomfrets reported, respectively (Table L-5).



Forage species

A large number of taxa occupying the middle trophic levels in the EPO ecosystem—generically referred to as “forage” species—play a key role in providing a trophic link between primary producers at the base of the food web and the upper-trophic-level predators, such as tunas and billfishes. Some small forage fishes are incidentally caught in the EPO by purse-seine vessels on the high seas, mostly in sets on floating objects, and by coastal artisanal fisheries, but are generally discarded at sea. Catches of these species are presented in (Table L-6).

And for the large-vessel purse-seine fishery, with the majority of catches coming from floating object sets. with key species as identified by catch data presented in (Figure L-6)
Figure L-6: Estimated purse-seine catches in metric tons (t) of key species of small fishes in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL).

Bullet and frigate tunas (Scombridae) are by far the most commonly reported forage species with estimated annual catches averaging 1,075 t from 1993–2019. However, their catches have declined from 1,922 in 2005 to 276 t in 2019 (Figure L-6).
Figure L-6: Estimated purse-seine catches in metric tons (t) of key species of small fishes in the eastern Pacific Ocean. Purse seine catches are provided for size-class 6 vessels with a carrying capacity >363 t (1993–2019) by set type: floating object (OBJ), unassociated tuna schools (NOA) and dolphins (DEL).

Triggerfishes (Balistidae) and filefishes (Monacanthidae) are the second most commonly reported forage group with annual estimated catches averaging 268 t and totaling 58 t in 2019. Catches for this group peaked in 2004 at 914 t but have otherwise been variable. Annual catches of sea chubs (Kyphosidae) have averaged 15 t, which began to increase after 2002 but have steadily decreased to <1 t in 2019. Lastly, annual catches of the various species in the category ‘epipelagic forage fishes’ averaged 4.2 t with 13 t estimated to be caught in 2019.

PHYSICAL ENVIRONMENT*

Environmental conditions affect marine ecosystems, the dynamics and catchability of target and bycatch species, and the activities of fishers, and physical factors can have important effects on the distribution and abundance of marine species. The following summary of the physical environment covers: 1) short- and long-term environmental indicators, and 2) environmental conditions and their effect on the fishery during the previous year, in this case, 2019.

The ocean environment changes on a variety of time scales, from seasonal to inter-annual, decadal, and longer. Longer-term climate-induced changes, typically decadal (at intervals of 10–30 years) and characterized by relatively stable average conditions and patterns in physical and biological variables, are called “regimes”. However, the dominant source of variability in the upper layers of the EPO is the El Niño-Southern Oscillation (ENSO), an irregular fluctuation involving the entire tropical Pacific Ocean and the world’s atmosphere (Fiedler 2002). El Niño events occur at two- to seven-year intervals, and are characterized by weaker trade winds, deeper thermoclines, and higher sea- surface temperatures (SSTs) in the equatorial EPO. El Niño’s opposite phase, commonly called La Niña, is characterized by stronger trade winds, shallower thermoclines, and lower SSTs. The changes in the biogeochemical environment caused by ENSO have an impact on the biological productivity, feeding, and reproduction of fishes, seabirds, and marine mammals (Fiedler 2002).

ENSO is thought to cause considerable variability in the availability for capture of commercially-important tunas and billfishes in the EPO (Bayliff 1989). For example, the shallow thermocline during a La Niña event can increase purse-seine catch rates for tunas by compressing the preferred thermal habitat of small tunas near the sea surface, while the deeper thermocline during an El Niño event likely makes tunas less vulnerable to capture, and thus reduces catch rates. Furthermore, warmer- or cooler-than-average SSTs can also cause the fish to move to more favorable habitats, which may also affect catch rates as fishers expend more effort on locating the fish.

Recruitment of tropical tunas in the EPO may also be affected by ENSO events. For example, strong La Niña events in 2007–2008 may have been partly responsible for the subsequent lower recruitment of bigeye tuna, while the largest recruitments corresponded to the extreme El Niño events in 1982–1983 and 1998 (SAC-09-05). Yellowfin recruitment was also low in 2007, but high during 2015–2016, after the extreme El Niño event in 2014–2016 (SAC-09-06).



The Climate Diagnostics Bulletin of the US National Weather Service reported that in 2019 anomalies—defined in the Bulletin as a departure from the monthly mean—in oceanic and atmospheric characteristics (surface and sub-surface temperatures, thermocline depth, wind, convection, etc.) were indicative of El Niño conditions during January-June and ENSO-neutral conditions during July-December.

Indices of variability in such conditions are commonly used to monitor the direction and magnitude of ENSO events in the Pacific Ocean. In this report, the Oceanic Niño Index (ONI), used by the US National Oceanic and Atmospheric Administration (NOAA) as the primary indicator of warm El Niño and cool La Niña conditions within the Niño 3.4 region in the east-central tropical Pacific Ocean (Dahlman 2016) (Figure L-7), is used to characterize inter-annual variability in SST anomalies. The ONI is a measure of El Niño defined by NOAA as “a phenomenon in the equatorial Pacific Ocean characterized by a five consecutive 3-month running mean of SST anomalies in the Niño 3.4 region that is above (below) the threshold of +0.5°C (-0.5°C).” The ONI categorizes ENSO events from “extreme” to “weak” (Figure L-7).
Figure L-7: El Niño regions used as indicators of El Niño Southern Oscillation (ENSO) events in the Pacific Ocean (top panel), and the Oceanic Niño Index (ONI) used to monitor ENSO conditions in Niño region 3.4 from 5°N to 5°S and 120°W to 170°W (bottom panel). Time series shows the running 3-month mean ONI values from the start of the IATTC observer program through December 2019. ONI data obtained from: http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

For example, the “extreme” El Niño event in 1997–1998 was followed by a “very strong” La Niña event in 1998–2000. “Strong” La Niña events were also observed in 2007–2008 and 2010–2011. The highest ONI values (>2.5) were recorded during the 2015–2016 El Niño event, while moderate-weak El Niño conditions persisted in 2019.



The Pacific Decadal Oscillation index is used to describe longer-term fluctuations in the Pacific Ocean, and has also been used to explain, for example, the influence of environmental drivers on the vulnerability of silky sharks to fisheries in the EPO (Lennert-Cody et al. 2018). (PDO; Figure L-8)
Figure L-8: Monthly values of the Pacific Decadal Oscillation (PDO) Index, January 1993-December 2019. PDO data obtained from: https://www.ncdc.noaa.gov/teleconnections/pdo/data.csv

The PDO—a long-lived El Niño-like pattern of Pacific climate variability, with events persisting 20–30 years—tracks large-scale interdecadal patterns of environmental and biotic changes, primarily in the North Pacific Ocean (Mantua 1997), with secondary patterns observed in the tropical Pacific, the opposite of ENSO (Hare and Mantua 2000). As with ENSO, PDO phases are classified as “warm” or “cool”. PDO values peaked at 2.79 in August 1997 and at 2.62 in April 2016, both of which coincided with the extreme El Niño events indicated by the ONI. During 2019, PDO conditions were primarily cool.



SPatio-temportal exploration of environmental conditions

A time series of SST and CHL-a in the eastern tropical Pacific (ETP) from 5°N to 5°S—the same latitudinal band used in the ONI—was explored to show the variability in these variables across space and time using time-longitude Hovmöller diagrams. The SST time series show mean monthly values from 1993–2019, while that for CHL-a concentrations covers data for 2003–2019 due to data availability (Figure L-9).
Figure L-9: Time-longitude Hovmöller diagram with data averaged across the tropical eastern Pacific Ocean from 5°N to 5°S for mean monthly SST for January 1993–January 2020 (top panel) (https://www.esrl.noaa.gov/psd/) and mean monthly chlorophyll-a concentration for January 2003–January 2020 (bottom panel) (https://coastwatch.pfeg.noaa.gov/erddap/info/erdMH1chlamday/index.html)



The SST plot clearly shows the extension of warmer waters during the extreme El Niño events of 1997–1998 and 2015–2016 and cooler waters during the strong La Niña events in 1999–2000, 2007–2008 and 2010–2011 across the ETP.

The CHL-a plot shown in Figure L-9, although the pattern is less clear than the SST plot, shows an increase in CHL-a concentrations following the strong La Niña events in 2007–2008 and 2010–2011, likely due to increases in nutrient availability. Because large interannual variability was not observed with the CHL-a time series, SST may be a more important driver of any observed changes in catches.



Environmental conditions and distribution of catches

The availability of fish. And thus catches. Are strongly related to environmental conditions and processes, particularly in pelagic waters (Fiedler and Lavín 2017; Chassot et al. 2011). ENSO conditions are influenced by many oceanic and atmospheric factors, but both SST and chlorophyll-a (CHL-a) levels (an indicator of primary productivity biomass) are known to be good explanatory variables to describe and predict the habitat and distributions of oceanic animals (Hobday and Hartog 2014).



Quarterly mean SSTs and CHL-a concentrations, respectively, to: 1) provide a general indication of seasonal variability, and 2) overlay the distribution of tropical tuna catches, as a first step, to illustrate the potential influence of environmental conditions on catches across the EPO during 2019. In future, staff plan to incorporate the catch distribution of bycatch species and apply sophisticated models to better describe relationships between environment and catches as shown in Figure L-10 and Figure L-11.
Figure L-10: Mean sea surface temperature (SST) for each quarter during 2019 with catches of tropical tunas overlaid. SST data obtained from NOAA NMFS SWFSC ERD on March 5, 2020, “Multi-scale Ultra-high Resolution (MUR) SST Analysis fv04.1, Global, 0.01°, 2002–present, Monthly”, https://coastwatch.pfeg.noaa.gov/erddap/info/jplMURSST41mday/index.html.


Figure L-11: Mean log chlorophyll-a concentration (in mg m3) for each quarter during 2019 with catches of tropical tunas overlaid. Chlorophyll data obtained from NOAA CoastWatch on February 19, 2020, “Chlorophyll, NOAA, VIIRS, Science Quality, Global, Level 3, 2012-present, Monthly”, NOAA NMFS SWFSC ERD, https://coastwatch.pfeg.noaa.gov/erddap/info/nesdisVHNSQchlaMonthly/index.html.

Cooler waters occurred off northern Mexico and the southwestern United States around 30°N and extended westwards during quarters 1 (January–March) and 2 (April–June), and off South America, predominantly around 5°S to 100°W, in quarters 3 (July–September) and 4 (October–December). Warmer waters developed off Central America and extended westwards during quarters 2 and 3. A secondary warm pool was observed in the southwestern EPO (0–20°S, 130°–150°W) all year long, but waters were warmer and larger in area in this region during quarters 1 and 2 compared to 3 and 4.



CHL-a concentrations were higher along the equator and the coast of the Americas year-round. The oligotrophic (an area of low productivity, nutrients, and surface chlorophyll, often referred to as an “oceanic desert”) South Pacific Gyre—located between around 20°–40°S—present in quarter 1 retracted in quarters 2 and 3 but returned in quarter 4.



During quarters 1 and 2, skipjack predominated in the catches in the cooler waters (~25°C) off the coast of South America, where CHL-a concentration was high. During quarter 3, a large portion of the tuna catches consisted of skipjack along a warm-water front (25–~28°C) slightly north of the equator from the coast of South America to about 120°W, also a region of high CHL-a concentration, and these persisted through quarter 4, although with greater catches east of 100°W. A secondary concentration of catches occurred west of 130°W, close to the western boundary of the EPO.



During quarter 1 most of the catch along the equator from about 110°W to 140°W consisted of yellowfin, while skipjack and bigeye constituted an increased proportion of catches during quarters 2–4.

IDENTIFICATION OF SPECIES AT RISK

The primary goal of EAFM is to ensure the long-term sustainability of all species impacted—directly or indirectly—by fishing. However, this is a significant challenge for fisheries that interact with many non-target species with diverse life histories, for which reliable catch and biological data for single-species assessments are lacking.

An alternative for such data-limited situations, reflected in Goal L of the SSP, are Ecological Risk Assessments (ERAs), vulnerability assessments that are designed to identify and prioritize at-risk species for data collection, research and management.



‘Vulnerability’ is defined as the potential for the productivity of a stock to be diminished by the direct and indirect impacts of fishing activities. The IATTC staff has applied qualitative assessments, using Productivity-Susceptibility Analysis (PSA) to estimate the relative vulnerability of data-limited, non-target species caught in the EPO by large (Class-6) purse-seine vessels (Duffy et al. 2019) and by the longline fishery (SAC-08-07d).



Because PSA is unable to quantitatively estimate the cumulative effects of multiple fisheries on data-poor bycatch species, a new approach—Ecological Assessment of Sustainable Impacts of Fisheries (EASI-Fish)—was developed by the IATTC staff in 2018 (SAC-09-12) to overcome this issue. This flexible, spatially-explicit method uses a smaller set of parameters than PSA to first produce a proxy for the fishing mortality rate (F) of each species, based on the ‘volumetric overlap’ of each fishery on the geographic distribution of these species. The estimate of F is then used in length-structured per-recruit models to assess the vulnerability of each species using conventional biological reference points (e.g. (F(MSY)), (F(0.1))).

EASI-Fish was successfully applied to 24 species representing a range of life histories, including tunas, billfishes, tuna-like species, elasmobranchs, sea turtles and cetaceans caught in EPO tuna fisheries as a ‘proof of concept’ in 2018 (SAC-09-12). It was subsequently used to assess the vulnerability status of the spinetail devil ray (Mobula mobular), caught by all industrial tuna fisheries in the EPO (BYC-09-01), and the EPO stock of the critically-endangered leatherback turtle (Dermochelys coriacea) (BYC-10 INF-B). Therefore, EASI-Fish will be used in future to assess the vulnerability of all species groups (e.g., elasmobranchs, sea turtles, teleosts) impacted by EPO tuna fisheries.





ECOSYSTEM DYNAMICS

Although vulnerability assessments (e.g. EASI-Fish) are useful for assessing the ecological impacts of fishing by assessing the populations of individual species, ecosystem models are required to detect changes in the structure and internal dynamics of an ecosystem. These models are generally data- and labor-intensive to construct, and consequently, few fisheries worldwide have access to a reliable ecosystem model to guide conservation and management measures. These models require a good understanding of ecosystem components and the direction and magnitude of the trophic flows between them, which require detailed ecological studies involving stomach contents and/or stable isotope studies. Purposefully, IATTC staff have had a long history of undertaking such trophic studies, beginning from the experimental determination of consumption estimates of yellowfin tuna at the IATTC’s Achotines laboratory in the 1980s, to more recent analyses of stomach content and chemical indicators of a range of top-level predators.



In 2003, the IATTC staff compiled the trophic data to complete the development of a model of the pelagic ecosystem in the tropical EPO (IATTC Bulletin, Vol. 22, No. 3)—named “ETP7”—to explore how fishing and climate variation might affect target species (e.g. tunas), byproduct species (e.g. wahoo, dorado), elasmobranchs (e.g. sharks), forage groups (e.g. flyingfishes, squids) and species of conservation importance (e.g. sea turtles, cetaceans). A simplified food-web diagram, with approximate trophic levels (TLs), from the model is shown in Figure L-12.


Figure L-12: Simplified food-web diagram of the pelagic ecosystem in the tropical EPO. The numbers inside the boxes indicate the approximate trophic level of each group.

The model was calibrated to time series of biomass and catch data for a number of target species for 1961–1998. There have been significant improvements in data collection programs in the EPO since 1998, that has allowed the model to be updated with these new data up to 2018 (ETP8).



Ecological Indicators

Since 2017, ETP8 has been used in the Ecosystem Considerations report to provide annual values for six ecological indicators that, together, can identify changes in the structure and internal dynamics of the ETP ecosystem. These indicators are: mean trophic level of the catch (TL(c)), the Marine Trophic Index (MTI), the Fishing in Balance (FIB) index, Shannon’ index, and the mean trophic level of the modelled community for trophic levels 2.0–3.25 (TL(2.0)), ≥3.25–4.0 (TL(3.5)), and >4.0 (TL(4.0)). A full description of these indicators is provided in SAC-10-14. Additionally, simulations using ETP8 were conducted to assess potential impacts of the FAD fishery on the structure of the ecosystem (SAC-10-15).



An update assessment of the ETP8 model was not undertaken in 2020 due to a significant change in how the IATTC staff have reclassified the catch data submitted by the CPCs for “other gears” into longline and other gear types following an internal review of the data. This resulted in a dramatic increase in reported longline catches of high trophic level predators (sharks), which can have a strong influence on ecosystem dynamics. Although catch estimates are now finalized for 2019 the staff is now tasked to assign species-specific catch to the relevant functional groups in the ETP8 model, and then rebalance and recalibrate the model to provide an updated ecosystem status for 2019 at SAC-12 in 2021.



The most recent report on ecological indicators undertaken in 2019 (SAC-10-14) showed that values for TLc and MTI increased from 4.65 and 4.67 in 1970 to 4.69 and 4.70 in 1991, respectively, as the purse-seine fishing effort on FADs increased significantly (Figure L-13).



TL(c) continued to decrease to a low of 4.65 in 1997, due to the rapid expansion of the fishery from 1993 where there was increasing catches in the intervening period of high trophic level bycatch species that tend to aggregate around floating objects (e.g. sharks, billfish, wahoo and dorado). This expansion is seen in the FIB index that exceeds zero during the same period, and also a change in the evenness of biomass of the community indicated by Shannon’s index. By the early 2000s, TLc, MTI, and Shannon’s index all show a gradual decline, while the FIB gradually increased further from zero to its peak in 2017 at 0.66 as shown in Figure L-13.

Both TL(c) and MTI reached their lowest historic levels of 4.64 and 4.65 in 2017, respectively. Since its peak in 1991, TLc declined by 0.05 of a trophic level in the subsequent 27 years, or 0.02 trophic levels per decade.



The above indicators generally describe the change in the exploited components of the ecosystem, whereas community biomass indicators describe changes in the structure of the ecosystem once biomass has been removed due to fishing. The biomass of the TLMC4.0 community was at one of its highest values (4.449) in 1993 but has continued to decline to 4.443 in 2017 (Figure L-13).





As a result of changes in predation pressure on lower trophic levels, between 1993 and 2017 the biomass of the TLMC3.25 community increased from 3.800 to 3.803, while interestingly, the biomass of the TL(MC2.0) community also increased from 3.306 to 3.308.



Together, these indicators show that the ecosystem structure has likely changed over the 50-year analysis period. However, these changes, even if they are a direct result of fishing, do not appear to be currently ecologically detrimental, but the patterns of changes, particularly in the mean trophic level of the communities, certainly warrant the continuation, and possible expansion, of monitoring programs for fisheries in the EPO.


Management
Management unit: Yes

Jurisdictional framework
Management Body/Authority(ies): Inter-American Tropical Tuna Commission (IATTC)
Mandate: Scientific Advice; Management.  
Area of Competence: IATTC area of competence
Maritime Area: High seas; National waters.  
Management Advice
It is unlikely, in the near future at least, that there will be stock assessments for most of the bycatch species. Therefore, the IATTC must continue to undertake ecological research that can provide managers with reliable information to guide the development of science-based conservation and management measures, where required, to ensure the IATTC continues to fulfil its responsibilities under the Antigua Convention and the objectives of the IATTC’s 5-year SSP. The priority research areas that have been identified by the scientific staff that require further development are detailed below:



Following the development of the EASI-Fish approach, analysis of the full suite of over 100 impacted bycatch species will be conducted in stages, by taxonomic group, beginning in 2021. The priority of groups to be assessed will likely be elasmobranchs, teleosts, turtles and cetaceans.



A shortcoming of the ETP8 ecosystem model, from which the ecological indicators are derived, is that its structure is based on stomach content data from fish collected in 1992–1994. Given the significant environmental changes that have been observed in the EPO over the past decade, there is a critical need to collect updated trophic information. There have been proposals made by the staff in 2018, 2019 and 2020 to establish an ecological monitoring program to collect stomach content data to update the ecosystem model.



A second limitation of the ETP8 model is that it describes only the tropical component of the EPO ecosystem, and results cannot be reliably extrapolated to other regions of the EPO. Therefore, after updated diet information is collected, future work will aim to develop a spatially-explicit model that covers the entire EPO and calibrate the model with available time series of catches, ideally for species representing different trophic levels, and effort data for key fisheries in the EPO.

Environmental variables can have a profound influence on the catches of target and bycatch species, as has been shown previously by IATTC staff and now undertaken annually in this report. However, the staff’s research to investigate the impact of environmental conditions on the fishery could be greatly improved with the availability of high-resolution operational level data for the longline fishery. Although IATTC Members and CPCs are now required to submit operational level observer data to the IATTC that covers at least 5% of their fleets, future work is required to assess the representativeness of these data for future environmental analyses.
Source of Information
 
Inter-American Tropical Tuna Commission (IATTC)  “"Report on tuna fishery, stocks, and ecosystem in the Eastern Pacific Ocean in 2019. Inter-American Tropical Tuna Commission." Fishery Status Report. IATTC 2020.” 2020 Click to openIATTC-95-05_The fishery and status of the stocks 2019
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