Factors affecting the fisheries and the stock
Mackerel is mainly exploited in a directed fishery for human consumption. This fishery tends to target bigger fish and there is evidence that this causes discarding of smaller, less marketable fish.
In June 2009, an agreement was concluded between contracting parties to the Coastal States on mackerel banning highgrading, discarding, and slipping from pelagic fisheries targeting mackerel, horse mackerel, and herring beginning in January 2010.Regulations and their effects
During 1998–2008, management aimed at attaining a fishing mortality for mackerel in the range of 0.15–0.2. The realized fishing mortality during this period ranged between 0.22 to 0.45. The current assessment shows reductions in fishing mortality and increases in biomass from 2003 onwards.
Prior to the late 1960s, spawning biomass of North Sea mackerel was estimated to be above 3 million tonnes. Due to overexploitation, recruitment has failed since 1969 leading to a marked decline in the stock size. The measures advised by ICES have been aimed at protecting the North Sea spawning component and promoting stock recovery. The North Sea spawning component has increased since 1999, but continued protection is needed as the abundance remains low.
The closure of the mackerel fishery in Divisions IVb,c and IIIa throughout the whole year is designed to protect the North Sea component in this area, and also protect juvenile Western mackerel which are numerous, particularly in Division IVb,c during the second half of the year. Unfortunately, the closure has resulted in increased discards of mackerel in the non-directed fisheries (especially horse mackerel fisheries) in these areas as vessels are currently permitted to take only 10% of their catch as mackerel bycatch. As estimates of mackerel bycatch are not available, the reported landings of mackerel in Divisions IIIa and IVb,c from 1997 onwards underestimate catches because they do not include discarded bycatch.
The advised fishery closure of Division IVa during the first half of the year is based on the perception that the Western mackerel enter the North Sea in July/August, and stay there until December before migrating back to their spawning areas. Updated observations in the late 1990s suggest that this return migration actually begins in mid- to late February. This is believed to result in large-scale misreporting from the northern part of the North Sea (Division IVa) to Division VIa. As a consequence, ICES recommended that the closure for Division IVa be extended to the 15th
of February (This is incorrectly stated as 1 February in the 2002 ICES Advice). This was adopted for the 1999/2000 fishing season onwards. However, misreporting from Division IVa to VIa continues to occur. Changes in fishing technology and fishing patterns
In recent years significant catches have been taken in Icelandic waters, an area where almost no catches have been previously reported. In 2008 and 2009, catches in this area constituted approximately 18% of the total catch.
In the southern part of the distribution area, Atlantic mackerel (Scomber scombrus
) can be caught together with Spanish mackerel (Scomber colias
). In recent years, catches of Spanish mackerel have increased. The catch in 2005 was the highest since 1982. Catches of both species are landed separately. ICES advice applies to Atlantic mackerel only.Impacts of environment on the fish stock
Survey data and catch information suggest distributional changes of both juveniles and adult mackerel. This indicates an expansion of mackerel further west and less north compared to previous years, illustrating the interannual dynamics of a fast moving species. The distribution pattern coincided with considerably warmer surface waters in 2009 than in earlier years in both the western part of the Norwegian Sea and in the northern part of the Icelandic zone. Together with temperature, feeding opportunities seem to affect the distribution of the mackerel stock. Other factorsStock components:
ICES currently uses the term “Mackerel in Northeast Atlantic” to define the mackerel present in the area extending from ICES Division IXa in the south to Division IIa in the north, including mackerel in the North Sea and Division IIIa. The spawning areas of mackerel are widely spread, and only the stock in the North Sea is sufficiently distinct to be clearly identified as a separate spawning component. Tagging experiments have demonstrated that after spawning, fish from Southern and Western areas migrate to feed in the Norwegian Sea and the North Sea during the second half of the year. In the North Sea they mix with the North Sea component. Since it is currently impossible to allocate catches to the stocks previously considered by ICES, for practical reasons all mackerel in the Northeast Atlantic are considered to comprise a single stock (i.e. the mackerel in the Northeast Atlantic stock).
Catches cannot be allocated specifically to spawning area components on biological grounds but by convention, catches from the Southern and Western components are separated according to the areas in which these are taken.
To keep track of the development of spawning biomass in the different spawning areas, mackerel in the Northeast Atlantic stock are divided into three area c
omponents: the Western Spawning Component, the North Sea Spawning Component,
and the Southern Spawning Component:
|Mackerel in Northeast Atlantic
|Distributed and fished in ICES Subareas and Divisions IIa, IIIa, IV, V, VI, VII, VIII, and IXa.
||VI, VII, VIIIa,b,d,e.
The Western Component is defined as mackerel spawning in the western area (ICES Divisions and Subareas VI, VII, and VIII a,b,d,e). This component currently accounts for 76% of the entire Northeast Atlantic stock. Similarly, the Southern Component is defined as mackerel spawning in the southern area (ICES Divisions VIIIc and IXa). Although the North Sea component has been at an extremely low level since the early 1970s, ICES considers that the North Sea Component still exists as a discrete unit. This component spawns in the North Sea and Skagerrak (ICES Subarea IV and Division IIIaN). Current knowledge of the state of the spawning components is summarised below.Western Component:
The catches of this component were low in the 1960s, but increased to more than 800 000 t in 1993. The main catches are taken in directed fisheries by purse-seiners and mid-water trawlers. Large catches of the western component are taken in the northern North Sea and in the Norwegian Sea. The 1996 catch was reduced by about 200 000 t compared with 1995, because of a reduction in the TAC. The catches since 1998 have been stable. The SSB of the Western Component declined in the 1970s from above 3.0 million t to 2.2 million t in 1994, but increased to 2.7 million t in 1999. A separate assessment for this stock component is no longer required, as a recent extension of the time-series of mackerel in the Northeast Atlantic data now allows the estimation of the mean recruitment from 1972 onwards. Estimates of the spawning-stock biomass, derived from egg surveys, indicate a decrease of 14% between 1998 and 2001 and a 6% decrease from 2001 to the 2004 survey. The results from 2007 indicated a 5% increased from 2004 to 2007. North Sea Component:
Very large catches were taken in the 1960s in the purse-seine fishery, reaching a maximum of about 1 milliont in 1967. The component subsequently collapsed and catches declined to less than 100 000 t in the late 1970s. Catches during the last five years are assumed to be about 10 000 t. The 2002 and 2005 triennial egg surveys in the North Sea both indicate similar egg production, but in 2008 egg production decreased by about 40%.Southern Component:
Mackerel is a target species for the hand line fleet during the spawning season in Division VIIIc, during which about one-third of the total catches are taken. Mackerel are also taken as a bycatch in other fleets. The highest catches (87%) from the Southern Component are taken in the first half of the year, mainly from Division VIIIc, and consist of adult fish. In the second half of the year catches consist of juveniles and are mainly taken in Division IXa. Catches from the Southern Component increased from about 20 000 t in the early 1990s to 44 000 t in 1998, and were close to 50 000 t in 2002. Estimates of the spawning-stock biomass, derived from egg surveys, are highly variable, and give average estimates of around 16-20% of the combined mackerel in the Northeast Atlantic stock (1995–2007).
MethodologyScientific basisData and methods
This assessment is based on catch numbers-at-age for the period 1972–2008 and triennial egg survey estimates of SSB from 1992 to 2007. In the past, estimates of total mortality have been similar to those obtained from tag-recapture studies.
Some sampling for discards has been carried out since 2000 and a formal requirement was initiated in the EU in 2002. Estimating proportions of catch discarded and slipped is problematic in pelagic fisheries due to high variability in discard and slipping practices. In some fleets no sampling for discards is carried out. Recently, information on these practices has been improving; discards from sampled fleets (Scotland, the Netherlands, and Germany) in 2008 amounted to 27000 tonnes.
Recruit surveys provide information on the distribution of young mackerel, but are subject to high variability and have not proved useful in estimating year-class strength.Information from the fishing industry
The fishing industry has informed ICES that in all the EU fishing fleets targeting mackerel, large quantities of juvenile and adult mackerel continue to be seen on the fishing grounds, as reported last year. This is not confined to one area or to one member state’s fleet. In addition, the abundance of mackerel in the entire distribution area is creating major problems with unwanted bycatches for some fleets not targeting mackerel. Furthermore, the industry has observed that the distribution seems to have changed in a westerly direction, giving more catches of larger fish in the earlier part of the season than usual. Stakeholders are actively seeking mechanisms that would allow inclusion of fishing industry information into the assessment process and are involved in a number of pilot projects in this regard.Uncertainties in assessment and forecast
Due to the shortage of fishery-independent data, the absence of age-disaggregated information for the spawning-stock index and the uncertainty in the magnitude of catches, SSB estimates are uncertain, but fishing mortality and the trend in SSB are better estimated.
The estimated catch for 2009 used in the forecast is uncertain due to additional catches in excess of the TAC that cannot be quantified precisely at present.
Some information on the level of discards is available and was included in the assessment, but the number of fleets sampled is not sufficient to capture the full scale of discarding. Comparison with previous assessment and advice
The perception of the stock based on the assessment results is very similar to last year's assessment. The basis of the advice this year is the precautionary management plan given above. , Faroe Islands, and the EU agreed to the plan in 2008, but it has not been agreed to by all of the participants in the fishery. Previous advice was based on a management plan agreed by , Faroe Islands, and the EU in 1999.
Overall Assessment Results
|Figure 184.108.40.206. Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components). Summary of stock assessment: landings, fishing mortality, recruitment, and SSB. |
|Figure 220.127.116.11. Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components). Stock - recruitment plot, yield per recruit analysis, and PA plot. |
Table 18.104.22.168a. Table 22.214.171.124b.
|Figure 126.96.36.199. Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components). Comparison of current assessment with previous assessments (solid blue line – Limit reference points; dashed blue line – precautionary reference points; and green lines management plan biomass trigger and upper and low limits). |
Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components). Catches by country 1988-2008 (cont.) (data submitted by Working Group members).
Table 188.8.131.52. Table 184.108.40.206.
|Germany, Fed. Rep.
|Germany, Dem. Rep.
|USSR (Russia from 1990)
Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components). Summary of stock assessment.
|* Geometric mean of recruitment series (1972–2006).
Yield and spawning biomass per Recruit.
||1.67 million t
||2.3 million t
||Trigger reference point used in the precautionary management plan given above
||Flim * 0.55 (CV 36%)
Between 0.20 and 0.22
> 2.2 million t
|Precautionary management plan given above
|unchanged since 2008
F-reference points (2009):
|Average last 3 years
is not well defined.
Projection Outlook for 2010.
Basis: Catch(2009) = 830 (rounded from 832) (TAC plus discards plus 70 TAC overshoot plus 112 TAC set by Iceland plus 36 new unilateral Norway and Faroe Islands declared quota and minus 18 that the UK and Ireland have agreed not to fish); F(2009) = 0.31; R08 = GM 72–06 = 3859 million; SSB(2009) = 2591.
||F(2010 & 2011)
|Implied change in catch1
||Implied change in TAC2
|Roll over TAC
||F(management plan upper bound) 0.22
||F(management plan mid point) 0.21
||F(management plan lower bound) 0.20
||+20% TAC (management plan upper bound)
||-20% TAC (management plan lower bound)
Weights in ‘000 t.
1Catches in 2010 relative to estimated catches in 2009
2 Catches in 2010 relative to TAC 2009
Scenarios in italics are not considered consistent with the management plan.
Scientific AdviceSingle-stock exploitation boundariesICES advises that total catches in 2010 should be between 527 000 tonnes and 572 000 tonnes. Exploitation boundaries in relation to existing management plans
The precautionary management plan described above for Northeast Atlantic mackerel (F between 0.20 and 0.22) implies catches between 527000t and 572000 t in 2010. The SSB is expected to remain stable in 2011 for a catch in this range. Exploitation boundaries in relation to precautionary considerations
ICES advises that the existing measures to protect the North Sea spawning component remain in place. These are:
- There should be no fishing for mackerel in Divisions IIIa and IVb,c at any time of the year;
- There should be no fishing for mackerel in Division IVa during the period 15 February–31 July;
- The 30 cm minimum landing size at present in force in Subarea IV should be maintained.
Mackerel in the Northeast Atlantic. Single-stock exploitation boundaries (advice), management, and catch data for the combined area.
|Predicted catch corresp. to advice|
|1987||Given by stock component|| ||442||616||11||655|
|1988||Given by stock component|| ||610||622||36||680|
|1989||Given by stock component|| ||532||576||7||590|
|1990||Given by stock component|| ||562||580||16||628|
|1991||Given by stock component|| ||612||609||31||668|
|1992||Given by stock component|| ||707||729||25||760|
|1993||Given by stock component|| ||767||784||18||825|
|1994||Given by stock component|| ||837||794||5||821|
|1995||Given by stock component|| ||645||729||8||756|
|1996||Significant reduction in F||-||452||509||11||564|
|1997||Significant reduction in F||-||470||517||19||570|
|1998||F between 0.15 and 0.2||498||549||627||8||667|
|1999||F of 0.15 consistent with PA ||437||562||585||n/a||640|
|2005||F=0.15 to 0.20||[320–420]||422||447||20||543|
|2006||F=0.15 to 0.20||[373–487]||444||3186||18||473|
|2007||F=0.15 to 0.20||[390–509]||502||558||8||579|
|2008||F=0.15 to 0.20||[349–456]||458||420||27||611|
|2009||F=0.15 to 0.20||[443–578]||6057|| || || |
|2010||harvest control rule||[527-572]|| || || || |
Weights in ‘000 t.
1Data on discards and slipping from only two fleets.
2Landings and discards from Divisions and Subareas IIa, IIIa, IV, V, VI, VII, VIII, and IXa.
3All areas except some catches in international waters in Subarea II.
4Catches updated in 2003 with revisions from SGDRAMA in 2002.
5 Updated with ICES FishStats data.
7 Does not includes the unilateral Norway/Faroe Islands TAC first declared in 2009 and Icelandic TAC.
Mackerel in the Northeast Atlantic. Single-stock exploitation boundaries (advice), management, and catch data for Western component.
|Predicted catch corresp. to advice|
|1987||SSB = 1.5 mill. t; TAC||380||405||11||633|
|1988||F = F0.1; TAC; closed area; landing size||430||573||36||656|
|1989||Halt SSB decline; TAC||355||495||7||571|
|1990||TAC; F = F0.1||480||525||16||606|
|1991||TAC; F = F0.1||500||575||31||647|
|1992||TAC for both 1992 and 1993||670||670||25||742|
|1993||TAC for both 1992 and 1993||670||730||18||805|
|1994||No long-term gains in increased F||8313||800||5||796|
|1995||20% reduction in F||530||608||8||728|
|1996||No separate advice||-||422||11||529|
|1997||No separate advice||-||416||19||529|
|1998||No separate advice||-||514||8||623|
|1999||No separate advice||-||520||0||597|
|2000||No separate advice||-||573||2||703|
|2001||No separate advice||-||630||1||694|
|2002||No separate advice||-||642||24||723|
|2003||No separate advice||-||548||9||644|
|2004||No separate advice||-||500||11||615|
|2005||No separate advice||-||397||20||494|
|2006||No separate advice||-||4185||17||420|
|2007||No separate advice||-||472||8||519|
|2008||No separate advice||-||431||27||551|
|2009||No separate advice||-||569|| || |
|2010||No separate advice||-|| || || |
Weights in ‘000 t.
1TAC for mackerel taken in all Divisions and Subareas VI, VII, VIIIa,b,d, Vb, IIa, IIIa, and IVa.
2Landings and discards of Western component; includes some catches of North Sea component.
3Catch at status quo F.
4Catches updated in 2003 with revisions from SGDRAMA in 2002.
5Revised from previous year (was 392).
Mackerel in the Northeast Atlantic. Single-stock exploitation boundaries (advice), management, and catch data for North Sea component.
|Predicted catch corresp. to advice1|
|1987||Lowest practical level||LPL||55||3|
|1988||Closed areas and seasons; min. landing size; bycatch regulations||LPL||55||6|
|1989||Closed areas and seasons; min. landing size; bycatch regulations||LPL||49.2||7|
|1990||Closed areas and seasons; min. landing size; bycatch regulations||LPL||45.2||10|
|1991||Closed areas and seasons; min. landing size; bycatch regulations||LPL||65.5||-4|
|1992||Closed areas and seasons; min. landing size; bycatch regulations||LPL||76.3||-4|
|1993||Maximum protection; closed areas and seasons; min landing size||LPL||83.1||-4|
|1994||Maximum protection; closed areas and seasons; min landing size||LPL||95.7||-4|
|1995||Maximum protection; closed areas and seasons; min landing size||LPL||76.3||-4|
|1996||Maximum protection; closed areas and seasons; min landing size||LPL||52.8||-4|
|1997||Maximum protection; closed areas and seasons; min landing size||LPL||52.8||-4|
|1998||Maximum protection; closed areas and seasons; min landing size||LPL||62.5||-4|
|1999||Maximum protection; closed areas and seasons; min landing size||LPL||62.5||-4|
|2000||Maximum protection; closed areas and seasons; min landing size||LPL||69.7||-4|
|2001||Maximum protection; closed areas and seasons; min landing size||LPL||71.4||-4|
|2002||Maximum protection; closed areas and seasons; min landing size||LPL||72.9||-4|
|2003||Maximum protection; closed areas and seasons; min landing size||LPL||62.5||-4|
|2004||Maximum protection; closed areas and seasons; min landing size||LPL||57.7||-4|
|2005||Maximum protection; closed areas and seasons; min landing size||LPL||44.9||-4|
|2006||Maximum protection; closed areas and seasons; min landing size||LPL||47.1||-4|
|2007||Maximum protection; closed areas and seasons; min landing size||LPL||53.1||-4|
|2008||Maximum protection; closed areas and seasons; min landing size||LPL||48.6||-4|
|2009||Maximum protection; closed areas and seasons; min landing size||LPL||62||-4|
|2010||Maximum protection; closed areas and seasons; min landing size||LPL|| || |
Weights in ‘000 t.
1Subarea IV and Division IIIa.
2TAC for Subarea IV, Divisions IIIa, IIIb,c,d (EU zone), and Division IIa (EU zone).
3Estimated landings of North Sea component.
LPL = Lowest Practical Level.
Mackerel in the Northeast Atlantic. Single-stock exploitation boundaries (advice), management, and catch data for Southern component.
|Predicted catch corresp. to advice|
|1987||Reduce juvenile exploitation||-||36.57||22|
|1988||Reduce juvenile exploitation||-||36.57||25|
|1990||Reduce juvenile exploitation||-||36.57||21|
|1991||Reduce juvenile exploitation||-||36.57||21|
|1996||No separate advice||-||30.00||34|
|1997||No separate advice||-||30.00||41|
|1998||No separate advice||-||35.00||44|
|1999||No separate advice||-||35.00||44|
|2000||No separate advice||-||39.20||36|
|2001||No separate advice||-||40.18||43|
|2002||No separate advice||-||41.10||50|
|2003||No separate advice||-||35.00||26|
|2004||No separate advice||-||32.31||35|
|2005||No separate advice||-||24.87||50|
|2006||No separate advice||-||26.18||53|
|2007||No separate advice||-||29.61||63|
|2008||No separate advice||-||27.01||60|
|2009||No separate advice||-||35.83|| |
|2010||No separate advice|| || || |
Weights in ‘000 t.
1Division VIIIc, Subareas IX and X, and CECAF Division 34.1.1 (EU waters only).
2Catches updated in 2003 with revisions from SGDRAMA in 2002.
Management unit: Yes
ICES evaluated the following management plan for mackerel in the Northeast Atlantic:
Fishing mortality F = 0.22* SSB/2 200 000
- For the purpose of this long-term management plan, “SSB” means the estimate according to ICES of the spawning stock biomass at spawning time in the year in which the TAC applies, taking account of the expected catch.
- When the SSB is above 2 200 000 tonnes, the TAC shall be fixed according to the expected landings, as advised by ICES, on fishing the stock consistent with a fishing mortality rate in the range of 0.20 to 0.22 for appropriate age groups as defined by ICES.
- When the SSB is lower than 2 200 000 tonnes, the TAC shall be fixed according to the expected landings as advised by ICES, on fishing the stock at a fishing mortality rate determined by the following:
- Notwithstanding paragraph 2, the TAC shall not be changed by more than 20% from one year to the next, including from 2009 to 2010.
- In the event that the ICES estimate of SSB is less than 1 670 000 tonnes, the Parties shall decide on a TAC which is less than that arising from the application of paragraphs 2 to 4.
- The Parties may decide on a TAC that is lower than that determined by paragraphs 2 to 4.
- The Parties shall, as appropriate, review and revise these management measures and strategies on the basis of any new advice provided by ICES.
ICES concluded that the plan is precautionary under the assumption that the TAC equals the total removals from the stock. The plan was agreed by Norway, Faroe Islands and the EU in October 2008.
Management AdviceManagement considerations
Catches in 2007 and 2008 have been considerably in excess of the ICES’ advice. The absence of effective international agreements on the exploitation of the stock (between all nations involved in the fishery) is a cause of concern and prevents control of the exploitation rate of the stock. According to the short-term forecast, the total estimated catch in 2009 results in an estimated fishing mortality of 0.31, which is above that stipulated in the management plan (it should be noted that this F would be lower without the significant additional catches in excess of the TAC). The 2010 TAC advice given above should apply to all areas fished.
The spawning stock biomass (SSB) has increased from a low of 1.8 million tonnes in 2002 to around 2.5 million tonnes in 2008, a level similar to that seen in the 1990s. Figure 220.127.116.11. indicates the current estimated stock level and recent stock development.
Available information indicates that the distribution of the spawning area and feeding areas of mackerel have expanded in recent years. Mackerel has been commercially fished in areas where it was previously not fished, particularly in the Icelandic EEZ.
An evaluation of unaccounted mortality in the mackerel fishery (Simmonds, 2007) suggested that both biomass and removals were significantly greater than those estimated using the standard assessment model. These analyses also suggested that the historic estimates of fishing mortality provided by the standard assessment are not affected by unaccounted mortality. These conclusions need further investigation. The results from the stock assessment provide the best estimates of biomass for mackerel in the Northeast Atlantic.Management plan evaluations
In June 2008 ICES provided advice in response to a European Commission (EC) request on evaluation of management plan for mackerel in the Northeast Atlantic (Section 18.104.22.168 ICES, 2008). A number of precautionary harvest rules were presented to stakeholders, for both medium-term expectations and short term catch options. A management plan based on these options was agreed in October 2008.
Biological State and Trend
|Spawning biomass in relation to precautionary limits
||Fishing mortality in relation to precautionary limits
||Fishing mortality in relation to high long term yield
||Fishing mortality in relation to target fishing mortality
|Full reproductive capacity
Based on the most recent estimate of SSB (in 2009), ICES classifies this stock as having full reproductive capacity. Based on the most recent estimates of fishing mortality (in 2008), ICES classifies the stock as being harvested at increased risk.
Fishing mortality in 2008 is estimated to be just above Fpa
. SSB has increased by 47% since 2002 and is currently estimated to be above Bpa
. The 2002 year class is the highest on record. Subsequent year classes are estimated to be about average. There is insufficient information to confirm the sizes of the 2007 and 2008 year classes.
Source of information
ICES. 2009. Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.