6.3.26 Advice June 2014 ECOREGION STOCK North Sea Sole in Division IIIa and Subdivisions 22 24 (Skagerrak, Kattegat, and the Belts) Advice for 2015 ICES advises on the basis of the MSY approach that catches in 2015 should be no more than 211 tonnes. If discard rates do not change from last year (2013), this implies landings of no more than 205 tonnes. Stock status MSY (FMSY) Precautionary approach (Fpa,Flim) MSY (Btrigger) Precautionary approach (Bpa,Blim) F (Fishing Mortality) 2011 2012 2013 Above target Harvested sustainably SSB (Spawning-Stock Biomass) 2012 2013 2014 Below trigger Reduced reproductive capacity Figure 6.3.26.1 Sole in Division IIIa and Subdivisions 22 24. Summary of stock assessment (weights in tonnes). 95% confidence limits indicated for recruitment, fishing mortality, and spawning-stock biomass. Predicted values are shaded. Top right: SSB and F over the years. SSB has decreased since 2006 and is below B lim since 2013. Fishing mortality has been relatively stable and above F MSY since 2005. The last strong year class was the 2000 year class; since then recruitment has decreased to a historical low.. Management plans No specific management objectives are known to ICES. ICES Advice 2014, Book 6 1
Biology Sole is a nocturnal predator and therefore more susceptible to capture by fisheries at night than in daytime. Sole is a long lived flatfish species. The main spawning takes place in the second quarter in coastal areas close to the nurseries. The main diet of sole consists of worms and small soft-shelled bivalves. As for many other flatfish species sole has a sexual dimorphism, i.e. females reach older ages and bigger sizes than males. The fisheries Sole is taken in a mixed trawl fishery with Nephrops, plaice, and cod, the main season being in autumn winter. In addition there is a directed gillnet fishery for sole, mainly in Skagerrak in spring and summer. Catch distribution Total catch (2013): 342 t, where 332 t were official/estimated landings (44% demersal trawl), 56% gillnets), and 10 t discards. Quality considerations Sampling of landings is complicated by the low total landings which are dispersed spatially. This affects the quality of the input data, including the weight-at-age. Historically, the assessment has overestimated SSB and underestimated fishing mortality. Discard rates in recent years are around 2% in weight and not included in the assessment but this does not impact the quality of the assessment. The main indicator of recruitment, the cooperative Fishermen DTU Aqua sole survey, ceased in 2011 and this has deteriorated the quality of the assessment and advice. The lack of the survey and the use of commercial cpue data only with changes in gear regulations in the fishery (cod avoidance) make the estimation of the recent year classes more uncertain. The reinstatement of the survey would likely improve the accuracy of the assessment and the advice. Figure 6.3.26.2 Sole in Division IIIa and Subdivisions 22 24. Historical assessment results (final year recruitment estimates included). Scientific basis Stock data category 1 (ICES, 2014a) Assessment type Age-based analytical stochastic assessment (SAM). Input data Commercial catches (international landings, ages and length frequencies from catch sampling), one survey index (Fishermen DTU Aqua 2004 2011),three commercial indices (trawlers 12 20 m, 90 104 mm (1994 present), private logbook gillnetters (1994 2007), private logbook trawlers (1987 2008)); fixed maturity; and fixed natural mortality (0.1) for all age groups. Discards and bycatch Used to provide advice, but not included in the assessment. Discard information available since 2000, average discard rates 2010-2013 from main fleets are 2%. Indicators None. Other information Stock benchmarked in 2010 (WKFLAT 2010; ICES, 2010). Reference points benchmarked in 2014 (WKMSYREF2, ICES, 2014b). Working group Baltic Fisheries Assessment Working Group (WGBFAS). 2 ICES Advice 2014 Book 6
6.3.26 Supporting information June 2014 ECOREGION STOCK North Sea Sole in Division IIIa and Subdivisions 22 24 (Skagerrak, Kattegat, and the Belts) Reference points Type Value Technical basis MSY MSY B trigger 2000 t. Lowest observed SSB, excluding low SSBs in 1984 1985 (ICES, 2010). Approach F MSY 0.32 Equilibrium scenarios constrained by prob(ssb<b lim)<5% w. stochastic recruitment (WKMSYREF2, ICES, 2014b). B lim 1200 t. B loss and segmented regression (WKMSYREF2 2014, ICES, 2014b). Precautionary B pa 2000 t B lim e 1.645σ, σ=0.30 (WKMSYREF2 2014, ICES, 2014b). Approach F lim 0.92 F lim replacement line. Consistent with B lim (WKMSYREF2 2014, ICES, 2014b). F pa 0.49 B pa replacement line. Consistent with B pa and F lim (WKMSYREF2 2014, ICES, 2014b). (Last changed in: 2014). Outlook for 2015 Basis: F 2014 = mean F (2011 2013) = 0.389; SSB (2015) = 1232; R (age 2 in 2014) = GM (1994 2013) = 2.476 millions; landings (2014) = 329 t. Rationale Catches (2015) a) Landings (2015) Basis F (2015) SSB (2016) %SSB change b) %TAC change c) MSY 211 205 F MSY SSB 2015/MSY B trigger 0.20 1590 +29% -42% approach Precautionary 0 0 SSB 2016 >B pa 0.00 1790 +46% -100% approach Zero catch 0 0 F=0 0.00 1790 +46% -100% Other options 201 195 F 2014 0.5 0.19 1600 +30% -45% 373 362 F 2014 0.39 1430 +16% +3% 310 301 F MSY 0.32 1490 +21% -15% 310 301 15% TAC (F 2014 1.32) 0.32 1490 +21% -15% 363 353 No change in TAC 0.38 1440 +17% 0% (F 2014 1.6) 417 405 15% TAC (F 2014 1.92) 0.44 1380 +12% +15% 454 440 F pa (F 2014 1.26) 0.49 1350 +9% +25% Weights in tonnes. a) Catches are calculated based on landings and 3% discard rate (in weight), the same as 2013 discard rate. b) SSB 2016 relative to SSB 2015. c) Landings 2015 relative to TAC 2014. MSY approach Following the ICES MSY approach implies fishing mortality to be reduced to 0.20(lower than F MSY because SSB in the beginning of 2015 is 38% below MSY B trigger), which implies catches of no more than 211tonnes in 2015. If discards rates do not change from last year (2013), this implies landings of no more than 205 tonnes. This is expected to lead to an SSB of 1590 tonnes in 2016. Precautionary approach Even a zero catch in 2015 is not expected to result in SSB reaching B pa in 2016. ICES Advice 2014, Book 6 3
Additional considerations Management considerations New fishing and biomass reference points were defined in 2014 (ICES, 2014b) and adopted for the stock (see text table above). F MSY (0.32) was estimated lower than the previous estimate (0.38). The cod stock in the Kattegat is depleted and any bycatches of cod in the mixed fishery for sole should be avoided. The assessment of short-term stock dynamics is highly dependent on having an estimate of recruitment that used to be provided by the cooperative Fishermen DTU Aqua sole survey for sole. Re-instating the survey would improve the assessment and the forecast.. Changes in fishing technology and fishing patterns The SELTRA trawl was introduced in 2011 to protect cod. This trawl is likely less efficient on sole compared to previous trawl types; catch rates of sole are therefore expected to decrease with the SELTRA trawl. In 2013 a SELTRA trawl was introduced in Skagerrak. Also changes in the regulations for the protection of cod in the Nephrops fishery, with the introduction of a sorting grid system in the trawls since 2004, may have resulted in smaller bycatch of sole. These changes in regulations that likely have caused a significant change in selectivity for the smaller sole were not taken into account by the assessment model. Spatial and temporal fishing area closures were implemented in the Kattegat in January 2009 to reduce fishing mortality on cod. Although most of these areas are outside the main fishing areas for sole, the closures may influence the effort distribution on sole, and effects on the sole stock are unclear. Regulations and their effects The management area includes Division IIIa plus the Belts (Subdivisions 22 24). Danish vessel quota shares cover the whole management area and there is therefore no incentive to misreport sole between Division IIIa and the Belts. Data and methods The stochastic analytical assessment (SAM) includes cpue data from three commercial tuning series (reference fleets) and one scientific survey series along with catch-at-age information. However, only one commercial tuning fleet is available since 2012; the two remaining commercial fleets ceased in 2007 and 2008 and the survey ceased in 2011. Discard data are not included in the assessment, but used to provide advice on catches. Sampling of landings is complicated by the small total landings which are dispersed spatially. This affects the quality of the input data. Uncertainties in assessment and forecast The discontinuation of cooperative Fishermen DTU Aqua sole survey in 2012 increased the assessment uncertainty especially with regard to recruitment estimations. The survey was the only source for recruitment observations. Landings port information does not provide reliable information for recruitment estimation, due to significant change in selectivity. Comparison of the basis of previous assessment and advice The basis for the assessment has not changed from last year. The basis for the advice this year is the same as last year: the MSY approach. 4 ICES Advice 2014 Book 6
Sources ICES. 2010. Report of the Benchmark Workshop on Flatfish (WKFLAT), 25 February 4 March 2010, Copenhagen, Denmark. ICES CM 2010/ACOM:37. 270 pp. ICES. 2013. Report of the Baltic Fisheries Assessment Working Group (WGBFAS), 10 17 April 2013, Copenhagen, Denmark. ICES CM 2013/ACOM:10. ICES. 2014a. Advice basis. In Report of the ICES Advisory Committee, 2014. ICES Advice 2014, Book 1, Section 1.2. ICES. 2014b. Report of the Workshop to consider reference points for all stocks (WKMSYREF2), 8-10 January 2014, ICES Headquarters, Copenhagen, Denmark. ICES CM 2014/ACOM:47. 91 pp. ICES. 2014c. Report of the Baltic Fisheries Assessment Working Group (WGBFAS), 3-10 April 2014, Copenhagen, Denmark. ICES CM 2014/ACOM:10. Figure 6.3.26.3 Sole in Division IIIa and Subdivisions 22 24. Stock recruitment (left) and yield-per-recruit analysis plot (right). The vertical lines represent biological reference points. ICES Advice 2014, Book 6 5
Table 6.3.26.1 Sole in Division IIIa and Subdivisions 22 24. ICES advice, management, and landings. Year ICES Advice Predicted catch corresp. to advice Predicted landings corresp. to advice Weights in thousand tonnes. a) TAC applies to Division IIIa and the EC waters of Divisions IIIb and IIIc, d. b) Landings include Division IIIa and Subdivisions 22 24. c) Discard estimates not available for all year. d) Uncertain. e) No more than 461 t in Division IIIa. f) Discard assumed to be negligible. Agreed TAC a ICES landings b ICES discards c 1987 - - - 0.85 0.72-1988 - - - 0.95 0.71-1989 TAC - < 0.8 0.80 0.82-1990 Precautionary TAC - 0.6 0.50 1.05-1991 TAC - 1.0 1.00 - d - 1992 TAC - 1.0 1.40 - d - 1993 TAC at recent catch levels - 1.0 1.60 - d - 1994 No advice due to uncertain catches - - 2.10 1.20-1995 No advice - - 2.25 1.30-1996 No advice - - 2.25 1.10-1997 No advice - - 2.25 0.81-1998 No advice - - 1.80 0.61-1999 No increase in F - 0.8 1.35 0.64-2000 No increase in F - 0.65 0.95 0.65 0.169 2001 No increase in F - 0.7 0.70 0.48-2002 F below F pa - 0.5 0.50 0.86 0.010 2003 F below F pa - 0.3 0.35 0.62 0.043 2004 F below F pa - 0.5 0.52 0.82-2005 No increase in F - 0.85 0.90 0.99-2006 F below F pa - 0.82 0.90 0.84-2007 Limit catches to 2002 2005 average - 0.74 0.90 0.63-2008 F below F pa - 0.97 0.94 0.66-2009 F below F pa - 0.80 0.80 0.64-2010 F below F pa - 0.62 0.70 0.54 0.014 2011 See scenarios - - 0.84 0.55 0.008 2012 MSY framework - 0.61 0.61 e 0.36 0.011 2013 MSY framework - 0.56 0.59 0.32 0.010 2014 MSY approach 0.353 0.353 f 0.35 2015 MSY approach 0.211 0.205 6 ICES Advice 2014 Book 6
Table 6.3.26.2 Sole in Division IIIa and Subdivisions 22 24. Official landings (tonnes) and ICES corrections. For Sweden there is no information available between 1962 and 1974. Year Denmark Sweden Germany Belgium Netherlands Working Group Kattegat Skagerrak Belts Skag+Kat Kat+Belts Skagerrak Skagerrak Corrections 1952 156 51 59 1953 159 48 42 1954 177 43 34 1955 152 36 35 1956 168 30 57 1957 265 29 53 1958 226 35 56 1959 222 30 44 1960 294 24 83 1961 339 30 61 1962 356 58 1963 338 27 1964 376 45 1965 324 50 1966 312 20 1967 429 26 1968 290 16 1969 261 7 1970 158 25 1971 242 32 9 1972 327 31 12 1973 260 52 13 1974 388 39 9 1975 381 55 16 16 9-9 1976 367 34 11 21 2 155-155 1977 400 91 13 8 1 276-276 1978 336 141 9 9 141-141 1979 301 57 8 6 1 84-84 1980 228 73 9 12 2 5-5 1981 199 59 7 16 1 1982 147 52 4 8 1 1-1 1983 180 70 11 15 31-31 1984 235 76 13 13 54-54 1985 275 102 19 1 + 132-132 1986 456 158 26 1 2 109-109 1987 564 137 19 2 70-70 1988 540 138 24 4 1989 578 217 21 7 1 1990 464 128 29 2 427 1991 1 746 216 38 + 11 1992 856 372 54 12 1993 1016 355 68 9-9 1994 890 296 12 4-4 1995 850 382 65 6-6 1996 784 203 57 612-597 1997 560 200 52 2 1998 367 145 90 3 1999 431 158 45 3 2000 399 320 13 34 11-132 2 645 2001 1 249 286 21 25-103 2 478 2002 3 360 177 18 15 11 281 862 2003 3 195 77 17 11 17 301 618 2004 3 249 109 40 16 18 392 824 2005 3 531 132 118 30 34 Norway 145 990 2006 521 114 107 38 43 9 4 836 2007 366 81 93 45 39 9 0 633 2008 361 102 113 34 35 7 3 655 2009 325 103 145 37 27 4 641 2010 273 61 125 46 26 3 3 538 2011 271 127 65 53 33 3 552 2012 154 140 28 30 0 6 0 358 2013 153 78 33 54 9 6 0 332 1 Considerable non-reporting assumed for the period 1991 1993. 2 Catches from Skagerrak were reduced by these amounts because of misreporting from the North Sea. The subtracted amount has been added to the North Sea sole catches. Total landings for these years in Division IIIa have been reduced by the amount of misreporting. 3 Assuming misreporting rates at 50%, 100%, 100%, and 20% in 2002 2005, respectively. Total 266 249 254 223 255 347 317 296 401 430 414 365 421 374 332 455 306 268 183 283 370 325 436 468 435 513 495 373 324 282 212 276 337 397 643 722 706 824 1050 1011 1294 1439 1198 1297 1059 814 605 637 ICES Advice 2014, Book 6 7
Table 6.3.26.3 Sole in Division IIIa and Subdivisions 22 24. Summary of stock assessment (weights in tonnes). Estimated recruitment (age 2, in thousands), spawning-stock biomass (SSB), and median fishing mortality for ages 4 to 8 (Mean F Ages 4 8). Low = lower limit and High = higher limit of 95% confidence interval. Year Recruitment High Low SSB High Low Landings Mean F High Low Age 2 (tonnes) (tonnes) Ages 4-8 (thousands) 1984 2594 4934 1364 933 1200 725 337 0.405 0.543 0.303 1985 4470 7745 2580 1000 1308 765 397 0.367 0.497 0.271 1986 3947 6593 2363 1919 2473 1488 643 0.393 0.509 0.303 1987 3887 6171 2448 2019 2481 1642 722 0.437 0.554 0.345 1988 3959 6273 2499 2045 2501 1673 706 0.421 0.532 0.333 1989 5413 8576 3416 2038 2465 1685 824 0.444 0.555 0.356 1990 7293 11753 4526 2626 3191 2160 1050 0.437 0.545 0.351 1991 6607 10426 4187 3114 3789 2559 1011 0.49 0.605 0.397 1992 7569 12291 4661 3880 4678 3218 1294 0.545 0.687 0.432 1993 5459 8650 3446 3812 4645 3128 1439 0.56 0.71 0.442 1994 2652 4264 1650 3733 4422 3151 1198 0.517 0.632 0.423 1995 3176 4963 2032 3473 4089 2950 1297 0.523 0.646 0.424 1996 2182 3409 1397 2968 3484 2528 1059 0.473 0.576 0.388 1997 1216 2054 720 2455 2891 2084 814 0.443 0.542 0.362 1998 3104 4850 1987 1719 2037 1451 605 0.42 0.517 0.342 1999 3413 5357 2175 2287 2743 1907 638 0.388 0.477 0.316 2000 2453 3868 1555 2175 2607 1815 646 0.365 0.45 0.297 2001 3526 5471 2273 1958 2337 1641 476 0.323 0.411 0.254 2002 5758 9655 3434 2611 3151 2163 862 0.349 0.433 0.281 2003 3070 4887 1929 2884 3447 2414 619 0.34 0.432 0.268 2004 3445 5255 2258 3046 3619 2565 824 0.373 0.465 0.299 2005 2855 4320 1887 3492 4179 2918 990 0.403 0.503 0.323 2006 2392 3617 1582 2935 3497 2462 836 0.401 0.499 0.322 2007 2542 3867 1671 2024 2390 1714 633 0.399 0.497 0.32 2008 2884 4492 1852 1634 1958 1364 655 0.434 0.555 0.339 2009 2736 4529 1653 1885 2296 1548 641 0.382 0.483 0.301 2010 2222 3648 1354 1615 1982 1315 538 0.393 0.499 0.309 2011 1701 2810 1030 1578 1953 1275 552 0.366 0.472 0.284 2012 1165 2179 623 1441 1782 1165 358 0.387 0.506 0.296 2013 1001 2551 393 1037 1314 819 332 0.413 0.56 0.305 2014 2476 a) 1072 Average 3457 5649 2165 2303 2830 1943 767 0.42 0.53 0.333 a) Geometric mean (1994 2013). 8 ICES Advice 2014 Book 6