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.

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 TL_c 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, TL_c, 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, TL_c 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 TL_MC3.25 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.