Advice June, revised September 2010

Transcription

1 .. Advice June, revised September ECOREGION STOCK Celtic Sea and West of Scotland Sole in Division VIIa (Irish Sea) Advice summary for Management Objective (s) Landings in Transition to an MSY approach Less than 9 t with caution at low stock size Cautiously avoid impaired recruitment Zero and a management plan should be (Precautionary Approach) developed Cautiously avoid impaired recruitment and achieve other objective(s) n/a of a management plan (e.g., catch stability) Stock status Fishing mortality F MSY Above Above Above F PA /F lim Between Between Below Spawning Stock Biomass (SSB) 8 9 SSB in t 7 9 MSY B trigger Below Below Below B PA /B lim Below Below Below.... Fishing Mortality (ages -7) Landings Recruitment (age ) Landings in t Recruitment in millions Fishing Mortality Flim Fpa 8 Spawning Stock Biomass Blim Bpa. FMSY MSYBtrigger F(ages -7).. SSB in t Figure... Sole in Division VIIa. Summary of stock assessment (weights in t). Top right: SSB and F over the years. SSB has continuously declined since to low levels and reached its lowest level in 8. The large reduction of F in recent years reflects the reduction in fishing effort. Recent recruitment levels have been lower than earlier in the timeseries, with the last five years of recruitment being the lowest in this series. Management plans No specific management objectives are known to ICES. In light of the EU policy paper on fisheries management (7 May, COM() ) this stock is classified under category which implies a TAC in of t. 7 ICES Advice, Book

2 The fisheries Sole are predominantly caught by beam trawl fisheries. Sole is caught in a mixed fishery with other flatfish as well as gadoids. Information from observer trips indicates that the discarding of sole is between and 8% in number. Catch by fleet Not available Effects of the fisheries on the ecosystem Although discard rates of sole are low in these fisheries, discard rates of other (commercial and non-commercial) species can be considerable. Beam trawling, especially using chain-mat gear, is known to have a significant impact on the benthic communities, although less so on soft substrates and in areas which have been historically exploited by this fishing method. Quality considerations Given the low stock size, predictions become more dependent on the assumed incoming recruitment. % Of the predicted landings in and % of the predicted SSB in are based on the assumed geometric mean recruitment. SSB (' tonnes) Fishing mortality: -7 Recruitment. Age: Millions Figure... Sole in Division VIIa (Irish Sea). Historical assessment results (final year recruitment estimates included). Scientific basis Assessment type Input data Discards and bycatch Indicators Other information Working group report Age analytical assessment (XSA) survey indices (UK(BTS-Q) and UK(BTS-Q)) Not included in the assessment None None WGCSE ICES Advice, Book 7

3 .. Supporting Information June, revised September ECOREGION STOCK Celtic Sea and West of Scotland Sole in Division VIIa (Irish Sea) Reference points Type Value Technical basis MSY MSY B trigger t Default to value of B pa Approach F MSY. Provisional proxy based on stochastic simulations assuming a Ricker S/R relationship (range..) B lim t B lim = B loss The lowest observed spawning stock, followed by an increase in SSB. Precautionary Approach B pa t B pa ~ B lim *.. The minimum SSB required ensuring a high probability of maintaining SSB above its lowest observed value, taking into account the uncertainty of assessments. F lim. F lim = F loss. Although poorly defined, there is evidence that fishing mortality in excess of. has led to a general stock decline and is only sustainable during periods of above-average recruitment. F pa. This F is considered to have a high probability of avoiding F lim. (unchanged since: ) Yield and spawning biomass per Recruit F-reference points (): Fish Mort Yield/R SSB/R Ages -7 Average last years..9. F max * F F med * Not well defined Outlook for Basis: F() = F sq = mean(f7 9) rescaled to F9 =.8; R() = RCT = (thousands); Landings() = 9 t; SSB() = 7 t Rationale Landings %SSB %TAC Basis F() SSB() () change ) Change ) MSY framework Fmsy*SSB()/B trigger.9 % -% ICES MSY transition 9 Transition. 8% -% EU MSY transition EU transition. 8 7% +% Precautionary approach B pa. 7 % -% EU Policy paper Cat.. % -% Zero catch F=. 7 % -% F () *.7. % -% Status quo F () * % % F ().8 % % F () *..9 % % Weights in tonnes. ) SSB relative to SSB. ) Landings relative to TAC. MSY approach Following the ICES MSY framework implies fishing mortality to be reduced to.9 (% lower than F MSY because SSB is % below MSY B trigger ), resulting in landings of less than t in. This is expected to lead SSB of t in. Following the transition scheme towards the ICES MSY framework implies fishing mortality of (.8*F () ) + (.*(F MSY *.) =. for. This results in landings of 9 t in. This is expected to lead to an SSB of in. 7 ICES Advice, Book

4 The EU transition scheme without extra reduction on account of low SSB implies a target F of.. This results in landings of t in. This is expected to lead to an SSB of 8 t in. PA approach Given the low SSB and low recruitment since, it is not possible to identify any non-zero catch which would be compatible with the precautionary approach. ICES recommends a closure of the fishery in and a recovery plan should be developed and implemented as a prerequisite to reopening the fishery. Policy paper In light of the EU policy paper on fisheries management (7 May, COM() ) this stock is classified under category because the stock is outside safe biological limits. The resulting TAC is derived from a % reduction from the assumed fishing mortality in. The resulting TAC would be t. Additional considerations Regulations and their effects Technical measures in force are minimum mesh sizes and minimum landing size ( cm). Changes in fishing technology and fishing patterns Beam trawl effort has decline by 7% between and 9. This is consistent with the F reductions estimated in the assessment. Fishing behaviour has changed in response to high fuel prices. There has been a switch by Irish trawlers to reduce gear size in some cases by as much as %. There is also evidence of larger vessels switching from twin-rigging back to single rigging to reduce fuel consumption. The m+ range vessels are now working at around % of their total power in a bid to reduce fuel costs. This implies a reduction in catch rates, and may also effect the length distribution of the catches. Comparison with previous assessment and advice Trends in SSB and fishing mortality are consistent with last year s assessment. F values for 8 have been revised upwards by %, and SSB in 9 has been revised downwards by 8%. Last year s advice was based on the precautionary approach. The basis for the advice is the same as last year but extended by MSY considerations. Sources ICES.. Report of the Working Group on the Celtic Seas Ecoregion (WGCSE), May, Copenhagen, Denmark. ICES CM /ACOM:. ICES Advice, Book 7

5 Yield/R (dashed line) Yield and Spawning Stock Biomass per Recruit Fishing Mortality (ages -7) SSB/R (line) Recruitment (age ) in millions Stock - Recruitment Blim Bpa MSYBtrigger 7 8 SSB in t Figure... Sole in Division VIIa (Irish Sea). Stock-recruitment plot and yield per recruit analysis. Table... Sole in Division VIIa (Irish Sea). Advice, management and landings. Year ICES Advice Predicted catch corresp. to advice Agreed TAC Official landings ICES Landings 987 No increase in F % of F(8); TAC % of F(87); TAC < Interim advice % of F(89); TAC No long-term gains in increased F F = F(9) ~ 9 t No long-term gains in increased F % reduction in F % reduction in F % reduction in F % reduction in F Reduce F below F pa Reduce F below F pa < Reduce F below F pa <.9... Keep F below F pa <.... Keep F below F pa <.... Maintain SSB above B pa < F<F pa < Recent catch levels ( ) < Maintain SSB above B pa Zero catch Zero catch and recovery plan... Zero catch and recovery plan. See scenarios - Weights in t. ) Catch at status quo F. ) Not including misreporting. ) Revised in 99 to.. 7 ICES Advice, Book

6 Table... Sole in Division VIIa (Irish Sea) in tonnes as officially reported to ICES, and working group estimates of the landings. Last year s landings are preliminary. Year Belgium France Ireland Netherlands UK (E+W) UK (Isle of Man) UK (N. Ireland) UK (Scotland) Officially reported Unallocated Total used by WG TAC < n/a. n/a n/a n/a onwards: N. Ireland included with England & Wales ICES Advice, Book 77

7 Table... Sole in Division VIIa. Summary of stock assessment. Year Recruitment SSB Landings Mean F Age Ages 7 thousands tonnes tonnes * Average * RCT estimate 78 ICES Advice, Book