State of the Black Sea Whiting (Merlangius merlangus euxinus) (Nordmann, 1840)

1. Basic Identification Data Scientific name: Merlangius

merlangus euxinus

Common name: Whiting ISCAAP Group: 32

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 Ogive

M

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 observed

27 22 27 Reproduction season

December-March

Size at first maturity 14.5 12.5 12.5

Reproduction areas Depth bigger than

50m

Recruitment size 4.5 Nursery areas Shelf

Table2-2: Growth and length weight model parameters

Sex

Units female male both unsexed

Growth model

L∞ cm 31.65

K 0.16

t0 -1..344

Data source Romanian data

Length weight relationship

a 0.0065

b 3.0038

M (vector by length or age)

M age

0.9 - 0

0.7 - 1

0.64 - 2

0.50 - 3

0.46 - 4

0.46 - 5

0.46 - 6

sex ratio (% females/total)

57%

0

1

2

3

4

5

6

7

45-5

0

55-6

0

65-7

0

75-8

0

85-9

0

95-1

00

105-

110

115-

120

125-

130

135-

140

145-

150

155-

160

165-

170

175-

180

185-

190

195-

200

Length class (mm)

%

0

100

200

300

400

500

600

700

800

900

1000

No

. in

div

idu

als

Female Male Total

Fig.2.2.1 - Structure on length classes for whiting in 2011, total catches in Romanian area

4; 4+ years, 1%

5; 5+ years, 2%

2; 2+ years, 46%

3; 3+ years, 7%

0; 0+ years, 4%

1; 1+ years, 40%

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

length

Gear Mesh size

range

Fishery GSA Species Catche

(t)

Discards

(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. Turkey is the only country in the region, where the annual target trawling fisheries for this fish is conducted. In 1996 – 2005 its annual catches varied from 6 thousand tons to 19 thousand tons, making on average 10.8 thousand tons. As compared with 1989 – 1995, when mean annual catch of whiting was equal to 17.6 thousand tons, the tendency towards reduction of both its catches and CPUE is observed. Also, the whiting represents a complementary catch of the Romanian and Bulgarian fishermen. The level of fishing productivity is different from year to year, depending on the fishing effort (number of boats, nets, effective fishing days) and on the evolution of the hydro-climatic conditions and the anthropogenic factors (Radu G et al., 2006, 2010, 2011). Table 3.2 Whiting catches in the Black Sea area (BSC2011, BS stock assessment working group, 2011,2012)

Year Bulgaria Georgia Romania Russian Federation

Turkey Ukraine Total

1988 - 5 1009 736 28263 1482 31495

1989 - 5 2738 7 19283 579 22612

1990 - - 2653 235 16259 87 19234

1991 - - 59 - 18956 24 19039

1992 - 70 1357 - 17923 . 19350

1993 - 172 599 16 17844 5 18636

1994 - 187 432 125 15084 64 15892

1995 - 146 327 91 17562 17 18143

1996 - 223 372 11 20326 3 20935

1997 - 58 441 10 12725 29 13263

1998 - 53 640 119 11863 55 12730

1999 - 41 272 184 12459 18 12974

2000 9 37 275 341 15343 20 16025

2001 8 32 306 642 7781 18 8787

2002 16 37 85 656 7775 9 8578

2003 13 45 113 93 7062 21 7347

2004 2 29 118 55 7243 43 7490

2005 3 30 92 78 6637 30 6870

2006 2 37 113 60 7797 15 8024

2007 16 41 118 22 11232 64 11493

2008 0 15 92 96 10986 9 11198

2009 2 15 40 52 8979 17 9105

2010 15 15 24 23 11894 17 11988

2011 1 42 27 21 8122 36 8249

3.3 Management regulations Not considering in details the similarity and differences of various measures of Black Sea whiting fisheries in various countries it should be noted that fishing in Turkey is conducted without limitation of annual catch or the fishing efforts. The mesh size of bottom trawls is designed to catch whiting being 40 mm and minimum commercial size 13.0 cm (TL). By the ruling of General Directorate of Fisheries in 2010, the use of monofilament strings was prohibited. Trawling is permitted only in the season between September and April, in the open areas outside the 3 miles zone from the coast. “Regulations of the Commercial Fisheries in the Black Sea Basin” currently in force in Ukraine have determined the following requirements: minimum commercial size of whiting – 12 cm (SL); the allowable by-catch of its juveniles – not more than 20% of total biomass of catch during non-target trawl fisheries and not more 30% by counting during the target fisheries with trawls (with mesh size not less than 12 mm). The annual regulation of whiting fisheries includes determination of the limits for whiting’s harvesting on the basis of its stock value and TAC. In Romania are not special regulations for whiting (Radu, 2011, Radu &Nicolaev, 2010).

3.4 Reference points

Reference Points

F YPR SSB/R TSB/R

F-zero 0 0 19.20354 25.28113

F0.1 0.352 3.318282 7.154227 11.49944

F-max 0.525 3.480953 4.676611 8.440517

F at 50% of MSP

0.24 2.914306 9.618898 14.42066

Mean F = 0.479 for the period 2000-2011 Mean F = 0.375 for 2011 4 Fisheries independent information 4.1 Swept area method 4.1.1 Brief description of the chosen method and assumptions used In the Romanian waters was used the bottom trawl 22/27-34 with horizontal opening of 13m. The average speed of the vessel was of 2.3-2.5 knots, the trawling time was standardized at 60 minutes. Have been registered the following elements: geographical coordinates for trawling points, water depth (m), the average trawling speed (knots), time of trawling, total catch and structure on species. For every trawling was taken one random sample for small size species and for big species like turbot and dog-fish each specimens were registered and measured. Having data regarding horizontal opening of the trawl, trawling speed and time have been calculated the surveyed area, catch per surveyed area, extrapolated catch per square Nm for each species and biomass.

4.1.2 Spatial distribution of the resources

1 2

Fig 4.1.2.1 Distribution of the whiting agglomerations at Romanian littoral in spring 2009 and 2010

1 2

Fig 4.1.2.2 Distribution of the whiting agglomerations at Romanian littoral in autumn 2009 and 2010

Fig 4.1.2.3 The distribution of the whiting agglomerations in demersal trawl survey, in spring and autumn 2011, Romanian area

4.1.3 Historical trends Table 4.1.3.1 The biomass whiting agglomerations (t) in the Romanian waters

Year 2009 2010 2011

Spring 11,853 7,410 26,171

Autumn 4,921 20,948 16,307

Along Georgian coasts after the disintegration of the USSR whiting biomass assessments were not made, but on the basis of monitoring the scientists from this country make conclusion that in the period from the early 1990s until the mid-2000s the whiting abundance as well as of other bottom fishes increase (Komakhidze, Diasamidze, Guchmanidze, 2003). In Romanian waters in 1996 – 2010 whiting remained the most abundant among bottom fishes although its mean annual catch reduced as much as four times as compared with 1989 – 1995. Partially it was caused by reduction of fishing efforts as compared with previous period (Nicolaev et al., 2003). The stock biomass was assessed 4,900-26,000 tons by swept area method (bottom trawl surveys) (Radu G.,2011). In the Russian sector of the Black Sea trawl survey show that stocks of whiting and other Gadidae (Gaidrosparus mediterraneus) are estimated about 7.6 – 8 thousand tons and the annual TAC for whiting averages 2 thousand tons (Volovik, Agapov, 2003). Along the Turkish coasts the total trawlable biomass of whiting in local areas were estimated by A. İşmen (2003). In 1992 the highest biomass between Sinop and Sarp (eastern Black Sea), which is an area, closed to trawl fishing – 30 thousand tons. In 1990 the biomass of whiting between Sinop and İğneada (western Black Sea) was estimated within the range of 1.1 – 1.7 thousand tons. Even if for the period of 1996 – 2005 similar direct assessments of whiting biomass were made, they were not published. In 1992 – 1995 in the waters of Ukraine whiting biomass changed from 43 up to 70 thousand tons, on average 54 thousand tons, and for the subsequent decade – from 40 up

to 68 thousand tons, on average 52 thousand tons (Shlyakhov, Charova, 2006). These data testify rather high inter-annual fluctuations but rather stable average level of whiting biomass in the specified areas where whiting specialized fisheries is almost absent and trawling fisheries are not conducted on the grounds with the densest whiting distribution. By this reason the most realistic assessments of the stock abundance seem to be estimates according to the data of trawl surveys or surveys produced on the basis of analysis of fisheries with obligatory correction for unregistered catch. With the exception of last year's estimates of the Black Sea EWG STECF, for last 15 years only one regional research was undertaken (Prodanov et al., 1997) that made possible to produce assessments of abundance and biomass of whiting in the Black Sea by VPA method for the period of 1971 – 1993 on the basis of analysis of regional biological and fishing data. According to Bulgarian scientists (Prodanov and Bradova, 2003), whiting biomass in the western part of the Black Sea excluding the western Turkish coastal waters in 1997 was assessed by VPA as 121 thousand tons, which was comparable with the long-term mean after decline in 1990 – 1991. / Prodanov K, Bradova, N. (2003).

5 Ecological information 5.1 Protected species potentially affected by the fisheries

5.2 Environmental indexes

6 Stock assessment 6.1 Name of Model VIT and YPR-LEN 3.1 We used the VIT program for estimation of abundance and fishing mortality and YPR-LEN (NOAA Fisheries Toolbox Version 3.1) for obtaining the reference points for dogfish in the Black Sea. The program VIT is conceived for the analysis of fisheries where the available information is limited. VIT is designed for the analysis of marine populations, exploited by one or several gears, based on single species' catch data (structured by age or size). The main assumption underlying the model is that of steady state, because the program works with pseudo-cohorts and it is therefore not suitable for historical data series. The program uses the catch data and ancillary parameters for rebuilding the population of the species and the mortality vectors affecting it by means of Virtual Population Analysis (VPA). Once the virtual population has been rebuilt, an analysis of the fishery can be carried out with the aid of several tools: Comprehensive VPA results, Yield-per-Recruit analysis based on the fishing mortality vector, analysis of sensitivity to parameter values and transition analysis. The latter permits non-equilibrium analysis of how a shift in exploitation regime is reflected in the fisheries. All these tools can be applied to specific studies of competition among fishing gears.

6.1.1 Model assumptions The VIT software was applied to assess population parameters based on pseudocohort analyses of average 2000-2011 data and 2011 data. In both variants the main share in total catch was represented by Turkey. The two scenarios were run with the following parameters: L∞ = 31.65 cm

k = 0.23

t0 = -1.193

a = 0.0065

b = 3.004

M = 0.462

6.1.2 Scripts

6.1.3 Results Table 6.1.3.1 Summary results for 2000-2011 data

Summary data Whiting 2000-2011 (Program VIT)

--- Total BG Ge RO RF TR UK Catch mean age 1.647 1.858 1.631 1.505 1.440 1.647 1.480

Catch mean length 14.639 15.231 14.563 14.275 13.794 14.639 14.033

Mean F 0.479 0.000 0.000 0.000 0.000 0.479 0.000

Global F 0.196 0.000 0.000 0.000 0.000 0.196 0.000

Total catch 1.690309E+12

5.629209E+05

1.617674E+07

2.665925E+08

4.489039E+08

1.689568E+12

9.322960E+06

Catch/D% 33.110 0.000 0.000 0.010 0.010 33.090 0.000

Catch/B% 35.090 0.000 0.000 0.010 0.010 35.070 0.000

B/R SSB/R Y/R Y/R BG Y/R GE Y/R RO Y/R RF Y/R TR Y/R UK

14.096 5.777 4.946 0.000 0.000 0.001 0.001 4.943 0.000

Current Stock Mean Age

0.944

Current Stock Critical Age

1.000

Virgin Stock Critical Age

3.000

Current Stock Mean Length

11.918

Current Stock Critical Length

12.537

Virgin Stock Critical Length

19.585

Number of recruits, R 3.417782E+11

Mean Biomass, Bmean

4.817628E+12

Spawning Stock Biomass, SSB

1.974550E+12

Biomass Balance, D 5.105508E+12

Natural death/D 66.890

Bmax/Bmean 34.010

Turnover, D/Bmean 105.980

Table 6.1.3.2 Summary results for 2011 data

Summary data for whiting BS2011

--- Total BG GE RO RF TR UK

Catch mean age 2.400 2.053 2.400 1.754 1.662 2.400 1.662

Catch mean length 17.529 16.370 17.529 15.283 14.970 17.529 14.970

Mean F 0.375 0.000 0.000 0.000 0.000 0.375 0.000

Global F 0.115 0.000 0.000 0.000 0.000 0.115 0.000

Total catch 2.484779E+12

2.607062E+04

6.667983E+07

6.843335E+07

7.882953E+06

2.484614E+12

2.285812E+07

Catch/D% 29.210 0.000 0.000 0.000 0.000 29.210 0.000

Catch/B% 28.960 0.000 0.000 0.000 0.000 28.950 0.000

B/R SSB/R Y/R Y/R BG Y/R GE Y/R RO Y/R RF Y/R TR Y/R UK

16.333 6.979 4.730 0.000 0.000 0.000 0.000 4.729 0.000

Current Stock Mean Age

1.002

Current Stock Critical Age

2.000

Virgin Stock Critical Age

3.000

Current Stock Mean Length

12.161

Current Stock Critical Length

16.464

Virgin Stock Critical Length

19.585

Number of recruits, R

5.253635E+11

Mean Biomass, Bmean

8.580992E+12

Spawning Stock Biomass, SSB

3.666680E+12

Biomass Balance, D

8.505808E+12

Natural death/D 70.790

Bmax/Bmean 32.820

Turnover, D/Bmean 99.120

Table6.1.3.3 Reference points for Black Sea whiting 2011

Reference Points

F YPR SSB/R TSB/R

F-zero 0 0 19.20354 25.28113

F0.1 0.352 3.318282 7.154227 11.49944

F-max 0.525 3.480953 4.676611 8.440517

F at 50% of MSP

0.24 2.914306 9.618898 14.42066

Mean F = 0.479 for the period 2000-2011 Mean F = 0.375 for 2011

Fig. 6.1.3.1 Fishing mortality related with Y/R and SSB/R

Fig. 6.1.3.2 Fishing mortality related with Catch Numbers

Fig. 6.1.3.3 Fishing mortality related with Y/R

Fig. 6.1.3.4 Fishing mortality related with Spawn numbers

Fig. 6.1.3.5 Fishing mortality related with %MSP

6.2 Robustness analysis

6.3 Assessment quality

7 Stock predictions 7.1 Short term predictions As the estimated F =0.375 exceeds Fmsy= 0.352,we classify the stock of whiting in the Black Sea as being exploited unsustainably. Given that this is not a highly migratory species we may conclude that the resident population is more exploited in the southern part (Turkish waters) than in the rest of the Black Sea - an effect that has been demonstrated by Prodanov et al. (1997) who performed separate VPA analyses of the western/northern and eastern/southern components of the whiting stock. If we consider the recommendation of the EWG 12-16 as FMSY ≤ 0.4, the two results obtained by me Fc (2011) = 0.375 and Fc (2000-20011) = 0.479 oscillate around of the value of Fmsy = 0.4. We can consider that the stock is fully exploited.

7.2 Medium term predictions

7.3 Long term predictions

8 Draft scientific advice Gaps that need to be addressed in the near future include: Several gaps were identified such as: limitations in performing of scientific surveys,

insufficient training in assessment methods, lack of harmonisation in data collection and age reading, insufficient knowledge of stock units, and lack of monitoring programs for assessing the IUU and discards. Management advice and recommendations - Recommends to organise workshop(s) for inter-calibration of age readings between different laboratories and scientists in the region, and harmonisation of the frameworks and methods of sampling of commercial fisheries and scientific surveys. - Reducing fishing mortality; - Regional management measures.

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