The assessment(s) Data used (and not used): Catch data Surveys - PDF document

� The assessment(s) � Data used (and not used): ◦ Catch data ◦ Surveys � Biological reference points David Miller � The 2010 assessment Wageningen IMARES � Potential issues/uncertainties in the assessment � Way forward? � WGWIDE examines 3 models: � Catch values are provided to ICES by the member nations fishing the stock ◦ TISVPA: separable selection (>1994) ◦ XSA: non3separable 3 assumes perfect catch data � Estimates are considered to be reliable ◦ SMS SMS SMS: Stochastic Multi3species Model (separable) SMS ���������� � � All analytical age3structured assessments Constant selection pattern for the 2 periods: catch 1981–1999,1999–2009 ◦ Ages 1310+ (age 10 is a plusgroup) First age with age independent 8 catchability � No benchmark assessment Age groups with the same variance 1, 2, 3–6, 7–10 ◦ Based on previous evaluations and comparisons, SMS has been chosen as the final assessment for the last 5 years Current survey plan Proposed plan for 2011 � International Blue Whiting Spawning Stock Survey International Blue Whiting Spawning Stock Survey International Blue Whiting Spawning Stock Survey International Blue Whiting Spawning Stock Survey Cruise tracks 63.0° � Norway, Russia, the Faroe Islands and the EU 63 62.0° 62 � Spawning grounds west of the British Isles 61.0° 61 � March3April (peak of spawning) 60 60.0° 59 200m 59.0° 58 500m 58.0° 1000m 57 ��������������������������� 2004'2010 57.0° Latitude Faroes ������������������������������� 56 56.0° �������� Netherlands 55 55.0° Ireland First age with age independent 5 54 catchability 54.0° Norway 53 Russia Age groups with the same variance 3–8, min std 0.4 53.0° 52 52.0° 51 50 51.0° 49 50.0° -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 -20° -19° -18° -17° -16° -15° -14° -13° -12° -11° -10° -9° -8° - 7° -6° -5° -4° -3° -2° -1° Longitude Celtic Explorer G.O. Sars Tridens Vimus Magnus Heinason

� International Ecosystem Survey in the Nordic International Ecosystem Survey in the Nordic International Ecosystem Survey in the Nordic International Ecosystem Survey in the Nordic � Primary source of information about the current Seas Seas state of the stock Seas Seas � EU, Norway, the Faroe Islands and Russia � Covers a large area ◦ Not always well standardised � Barents Sea, north & central Norwegian Sea ◦ Limited time and southwestern Norwegian Sea (Faroese ◦ Migrations occur during the survey and Icelandic Zones) ◦ Weather conditions often unfavourable � May � Short time series ◦ ‘catchability’ estimates still variable ���������������������������������� 2000'2010 ��������������� , �������� ◦ In a transition phase, should stabilise in the future First age with age independent 2 catchability Age groups with the same variance � 1,2 Trawls Stations � Blue Whiting is not the primry target of the survey � Generally small and loose registrations of blue whiting � Used as an index of recruitment (incoming year3class strength) � Norway � Norway, some years in co3ordination with � Spawning grounds west of the British Isles Russia � Precursor for IBWSSS � Barents Sea � 199132006 � late January‐early March ◦ 200432006 incorporated in IBWSSS � Only used in forecast Only used in forecast Only used in forecast Only used in forecast ◦ 2007 onwards: Norwegian contribution to IBWSSS ◦ Coverage on edge of the distribution area changed ◦ Considered first reliable indication of year3class �������������������������� 1993–2003 strength (recruitment) ������ , �������� First age with age independent 5 catchability Age groups with the same variance � 3–4, 5–6, 7–8

� NOT USED IN THE CURRENT ASSESSMENT NOT USED IN THE CURRENT ASSESSMENT NOT USED IN THE CURRENT ASSESSMENT NOT USED IN THE CURRENT ASSESSMENT � Spanish pair trawls CPUE ◦ 198332003 � Only representative for a small part of the ◦ Discontinued because fleet only represents a small stock: part of the landings in a small part of the ◦ Spanish bottom trawl survey distribution area ◦ Portuguese bottom trawl survey � Norwegian CPUE � Patchy temporal coverage / not updated: ◦ 198232003 ◦ Norwegian Sea summer survey (1981–2001, 2005–2007) ◦ Not updated ◦ Faroes plateau spring bottom trawl survey (1996–2008) ◦ Not considered representative of the development ◦ Faroes plateau autumn bottom trawl survey (1994–2008) of the stock Type Name Year range Age range Variable from year to year � History : Yes/No Caton Catch in tonnes 1981 – 2009 1'10 Yes ◦ SGPA 1998: Canum Catch at age in 1981 ' 2009 1'10 Yes � Blim = 1.5 million t (~lowest observed at the time) numbers � Flim=Floss=0.32 Weca Weight at age in the 1981 – 2009 1'10 Yes commercial catch � Bpa (2.25 Mt) and Fpa (0.21) arbitrarily calculated up from these West Weight at age of the 1981 – 2009 1'10 Yes � Simulations suggested in absence of clear stock3recruit spawning stock at relationship spawning time. Mprop Proportion of natural 1981 – 2009 1'10 No mortality before ◦ ACFM 1998 spawning � Fpa=0.32 (avg. F, no apparent neg. effects on rec.) Fprop Proportion of fishing 1981 ' 2009 1'10 No mortality before � Flim raised to 0.51 spawning Matprop Proportion mature 1981 ' 2009 1'10 No ◦ SGPRP 2003: at age Natmor Natural mortality 1981 ' 2009 1'10 No � Bloss=1.2 Mt, similar to current Blim, assessments still unstable Tuning data: – no change Type Name Year range Age range Tuning fleet 1 Norwegian Acoustic Survey 1991'2003 3'8 Tuning fleet 2 International Ecosystem Survey 2000 ' 2010 1'2 Tuning fleet 3 International Spawning Stock Survey 2004 ' 2010 3'8 � History: � History: ◦ ACFM 2006 ◦ MP simulation evaluation 2008 � Using Bpa as a trigger expected to lead to a >5% risk � high risk of stock collapse for F > 0.3 of SSB dropping below Blim � F0.1=0.18, low risk to stock � Suggests Bpa should be higher � Current BRPs: ◦ WKREF 2007 � In the period of low recruitment there seems to be no Reference Point B ��� � B �� F ��� � F �� sign of reduced recruitment at low SSB Value 1.5 mill t 2.25 mill t 0.51 yr '1 0.32 yr '1 � In the period of high recruitment no apparent trend in Basis B ���� Blim*exp(1.645* σ) F ���� F ��� With σ = 0.25 recruitment over the range of biomass � May be no need for different B lim values in different productivity regimes

� WGWIDE – assessment working group on widely distributed and highly migratory stocks � Vigo, Spain � Aug/Sep 2010 � Participants include scientists from almost all countries fishing the stock Catch proportion at age for Blue whiting al 10 Area 8 6 age 4 Season 2 1980 1985 1990 1995 2000 2005 2010 year Planned Realised � Deviations from pre3agreed survey plan: ◦ Temporal: Russian component 2 weeks late 63 � Excluded from survey (risk of ‘double counting’) 62 61 ◦ Spatial: Dutch component incomplete due to poor 60 weather 59 � Gap in area coverage occurred in an area of concentrated 58 fishing effort and thus likely to have contained a high but 57 un3 un un un 3quantified 3 3 quantified biomass quantified quantified Latitude 56 � Interpolated (estimated) from surrounding surveyed areas 55 54 � WGNAPES considered the revised estimate to 53 52 be robust and recommended WGWIDE to use 51 these values 50 49 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 Longitude Celtic Explorer G.O. Sars Tridens Vimus Magnus Heinason

2009 2010 � 2010 mean acoustic density the lowest observed since 2004 62° ◦ 50% decrease in stock biomass compared to the 2009 survey 60° sA - values 58° 0 - 100 100 - 500 500 - 1000 1000 - 141000 56° 54° 52° 50° 20° 16° 12° 8° 4° 0° 4° � Largest coordinated coverage in the # International Norweigian Sea Norwegian Sea and surrounding waters in ecosystem survey 2000-2009 # Effort and catch numbers summer ever age 1 age 2 48927 3133 #2000 � Small and loose registrations of blue whiting 85772 25110 #2001 15251 46656 #2002 � Generally colder in the Norwegian Sea, but 35688 21487 #2003 49254 22086 #2004 extremely warm Atlantic water masses in the 54660 19904 #2005 southern and southwestern part of Iceland 570 18300 #2006 21 552 #2007 29 75 #2008 0 14 #2009 0 0 #2010 � Close agreement in 3 models: Recruitment (age 1 yr) Fishing mortality 70 0.7 60 0.6 SMS 50 0.5 Recruits, *10^9 TISVPA 40 XSA 0.4 F 3-7 30 0.3 20 0.2 10 0.1 0 0 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Spawning stock biomass 8 7 6 SSB (million t) 5 4 3 2 1 0 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007