State of the Black Sea Whiting (Merlangius merlangus euxinus) (Nordmann, 1840) 1. Basic Identification Data Scientific name: Merlangius Common name: Whiting ISCAAP Group: 32 merlangus euxinus Geographical sub-area: 29 Stock assessment method: trawl survey, VIT and YPRLEN 2.1 Authors: Gheorghe RADU and Valodea MAXIMOV with consultancy for data from STECF/BS stock assessment working group Affiliation:National Institute for Marine Research and Development “Grigore Antipa” Constanta 2. Stock identification and biological information 2.1 Stock unit In the Black Sea, the whiting is one of the most abundant species among the demersal fishes. It does not undertake distant migrations, spawning mainly in the cold season within the whole habitat area. The whiting produces pelagic juveniles, which inhabit the upper 10-meter water layer for about a year. The adult whiting is cold-living, preferring temperatures 6-10º С. Fishes at the age less than 6 years are predominant in the whiting populations, the older year classes are found in catches individually. It occurs all along the shelf, dense commercial concentrations are formed by 1-3 year old fishes in the water down to 150 m depth, most often at 60-120 m depths (Radu G.&Radu E.,2008). Such concentrations on the shelf of Bulgaria, Georgia, Romania, the Russian Federation and Ukraine not do from every year, appearing at periods of 4-6 years - in the years of appearance of highly productive year classes. (Ivanov L. and Beverton R.J.H., 1985) Fig 2.1.1 Whiting migration routes in the Black Sea area (Radu G., 2003) Fig.2.1.2 Whiting migration routes in the Black Sea Romanian area The problem of units for whiting stocks in the Black Sea has not been settled yet. Fisheries experts from the Black Sea Commission specify the stock as shared that is although this fish does not make long migrations; its whole stock (or two different stocks – Eastern and Western) is exploited by each Black Sea country in their waters and for its adequate assessment the analysis of the regional data is required. So, the problem of quantity and location of whiting stock units in the Black Sea is not solved. At present whiting stocks belong to the groups of shared ones. 2.2 Growth and maturity The determination of the biologic parameters represents an important objective for the establishment of the demographic structure, the growth parameters, as well as other parameters required for the study of recruitment, mortality, effective and biomass, divided into age classes. In the Black Sea for the grounds with relatively slight fished off whiting population was characteristic of predominance of larger-sized fishes than in the grounds with wide shelf (Shlyakhov, 1983). In 1996 – 2005 in the grounds of intensive Turkish trawl fisheries one can observe tendency to reduction of mean length of fishes which became equal or even less than in Ukrainian waters. It is not quite typical and in our opinion it is the evidence of excessive intensity of fishery. Turkish scientists came to the same conclusion (Genç et al., 2002). In front the Bulgarian coast whiting catch length composition ranged between 50 and 230 mm and individual weight between 3.08–86.2 g. The highest percent belongs to the 115-120 mm group, followed by 135-140 mm and 155-160 mm. The length group 85- 90 mm, accounts around 6% of the whiting by-catch. The rest of the length groups are very weakly presented in the landings (Maximov et al., 2009). The analysis performed by (Raykov et al., 2008), show that highest value for L asymptotic of the whiting was calculated in Ukranian waters (39 cm) with the lowest growth rate (k = 0.106), accordingly. In Bulgarian and Romanian marine area the values are very similar and lower, as regards the asymptotic length (Radu G et al., 2006, 2010, 2011). Overall, in the last years, the whiting population on the Romanian littoral was homogenous, the length ranging between 40 and 230 mm/2.03–82.92 g, the dominant classes being those of 90-145 mm/5.50–23.84 g. The average body length was 107.45 mm, and the average weight 10.58g (Maximov et al., 2009), (Radu G et al., 2006, 2010, 2011). The analysis of age components during the entire Romanian fishing season emphasized the presence of individuals aged between 0;0+ to 5;5+ years, with a domination of individuals aged between 2;2+ years and 3;3+ years. Table 2.2.1 Maturity give and Natural mortality of whiting at Romanian littoral Age Maturity M Ogive 0 0.00 0.90 1 0.25 0.70 2 0.75 0.64 3 1.00 0.50 4 1.00 0.46 5 1.00 0.46 6 1.00 0.46 Table2-1: Maximum size, size at first maturity and size at recruitment at Romanian littoral in 2010- 2011 Somatic magnitude measured (LH, LC, etc)* Lt Units* cm Sex Fem Mal Both Unsexed Maximum size 27 22 27 Reproduction December-March observed season Size at first maturity Reproduction areas Depth bigger than 14.5 12.5 12.5 50m Recruitment size 4.5 Nursery areas Shelf Table2-2: Growth and length weight model parameters Sex Units female male both unsexed L∞ cm 31.65 K 0.16 Growth model t0 -1..344 Data source Romanian data Length weight a 0.0065 relationship b 3.0038 M (vector by M age length or age) 0.9 - 0 0.7 - 1 0.64 - 2 0.50 - 3 0.46 - 4 0.46 - 5 0.46 - 6 sex ratio 57% (% females/total) 7 1000 Female Male Total 900 6 800 5 700 600 4 500 % 3 400 No. individuals 2 300 200 1 100 0 0 45-50 55-60 65-70 75-80 85-90 95-100 105-110 115-120 125-130 135-140 145-150 155-160 165-170 175-180 185-190 195-200 Length class (mm) Fig.2.2.1 - Structure on length classes for whiting in 2011, total catches in Romanian area 5; 5+ years, 2% 4; 4+ years, 1% 0; 0+ years, 4% 3; 3+ years, 7% 1; 1+ years, 40% 2; 2+ years, 46% Fig.2.2.2 - Structure on age classes for whiting in 2011, total catches in Romanian area 3. Fisheries information 3.1 Description of the fleet 3.1.1 Table Romanian whiting catches in 2008-2011 Country Year Vessel Gear Mesh size Fishery GSA Species Catche Discards length range (t) (t) ROM 2008 VL2440 OTM 14D16 DEMF SA 29 WHG 22.844 0.115 ROM 2008 VL1824 OTM 14D16 DEMF SA 29 WHG 19.194 0 ROM 2008 VL1218 OTM 14D16 DEMF SA 29 WHG 3.092 0 ROM 2008 VL0612 FPN 14D16 MDPSP SA 29 WHG 9.95 0 ROM 2009 VL0612 FPN 14D16 MDPSP SA 29 WHG 0.874 38.635 ROM 2010 VL0612 FPN 14D16 MDPSP SA 29 WHG 10.45 10.405 ROM 2010 VL0006 FPN 14D16 MDPSP SA 29 WHG 0.759 1.419 ROM 2011 VL2440 OTM 14D16 MDPSP SA 29 WHG 0 9.005 ROM 2011 VL0612 FPN 14D16 MDPSP SA 29 WHG 0.095 17.396 ROM 2011 VL0006 FPN 14D16 MDPSP SA 29 WHG 0 0.65 3.3 Catches as used in the assessment 3.3.1 Catches as used in the assessment – 2011 data (N) Age BG GE RO RF TR UK TOTAL 0 1403 74931 508017 163536 14490272 281958 15520116 1 41179 739365 2111161 881924 142979132 1520559 148273321 2 29457 1943238 1300157 338752 375785127 584056 379980786 3 8617 551556 226080 55485 106660401 95664 107597803 4 2004 89344 50152 17522 17277419 30210 17466650 5 401 47583 3755 2920 9201629 5035 9261324 6 0 0 0 0 0 0 0 Total 83060 3446017 4199322 1460140 666393979 2517483 678100001 3.3.2 Catches as used in the assessment – average 2000-2011 data (N) Age BG GE RO RF TR UK TOTAL 0 99412 661806 2324152 4846045 208468058 596986 216996460 1 142215 710179 4361592 3960433 220753280 627938 230555637 2 63684 514948 1999136 1928853 178522751 339680 183369051 3 39695 156531 425444 667224 52440187 100176 53829256 4 16341 57286 82615 378395 17682739 33121 18250497 5 18900 27619 14355 165466 6633630 14377 6874347 6 96 2994 0 17949 1276243 2565 1299846 Total 380344 2131363 9207294 11964365 685776887 1714843 711175095 3.2 Historical trends In Bulgaria, Georgia, Romania, the Russian Federation and Ukraine whiting is very rarely the target species for fisheries and yielded as by-catch during trawl fisheries for other fish species or while non-selective fisheries with fixed nets in the coastal sea areas. Official statistics in all Black Sea countries does not reflect the true capture of whiting which is much higher than reported one. In 1996 – 2005 the total mean annual catch of whiting by Black Sea countries (except Turkey) according to the data of official statistics submitted to FAO was less than 0.6 thousand tons. It should be noted that with target trawl fisheries for sprat and other fishes whiting is by-caught in larger quantities that it is specified in official reports of the countries. Thus in the waters of Ukraine during sprat fisheries with midwinter trawls in 1996 – 2002 whiting by-catch was assessed in the range of 0.65 – 1.8 thousand tons (Shlyakhov, Charova, 2003). Sprat catches with small by-catches quantity of whiting are sometimes not registered and they are recorded in statistics as sprat. Recording is made in case of increased by-catches (more than 10-20%). This situation is common in the waters of Bulgaria, Georgia, Romania and the Russian Federation.