Stock Assessment Form Demersal Species
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Stock Assessment Form version 0.9 (Adapted to the data of Ukraine, which does not use GFCM standards) Stock Assessment Form Demersal species 2012-2013 Catches, population parameters, natural mortality and length composition as well the date trawl surveys picked dogfish in Ukrainian sector of the Black Sea were presented. Status of the stock is rated as “Depleted” Stock Assessment Form version 0.9 Stock assessment form for Picked dogfish 1 Basic Identification Data .............................................................................................................. 2 2 Stock identification and biological information ........................................................................... 2 2.1 Stock units ............................................................................................................................. 3 2.2 Growth and maturity ............................................................................................................. 3 3 Fisheries information ................................................................................................................... 6 3.1 Description of the fleet .......................................................................................................... 6 3.2 Historical trends .................................................................................................................... 8 3.3 Management regulations ...................................................................................................... 9 3.4 Reference points .................................................................................................................. 14 4 Fisheries independent information ........................................................................................... 15 4.1 Trawl surveys ....................................................................................................................... 15 5 Ecological information ............................................................................................................... 18 5.1 Protected species potentially affected by the fisheries ...................................................... 18 5.2 Environmental indexes ........................................................................................................ 18 6 Stock Assessment ....................................................................................................................... 18 7 Stock predictions ........................................................................................................................ 19 8 Draft scientific advice ................................................................................................................. 19 References………………………………………..………………………………………………………………………………….19 1 1 Basic Identification Data Scientific name: Common name: ISCAAP Group: Squalus acanthias Linnaeus, Picked dogfish 38 1758 Geographical sub-area: GSA 29 Country Ukraine Stock assessment method: indirect Author: Vladyslav SHLYAKHOV, YugNIRO, Ukraine Affiliation: none 2 Stock identification and biological information Picked dogfish belongs to long-living and viviparous fish; therefore reproduction process includes copulation and birth of fries. The picked dogfish population includes 19-20 year-classes and among commercial fish species of the Black Sea this species is inferior only to sturgeons in duration of lifespan (Commercial fisheries description…, 1988; Kirnosova, 1993; Shlyakhov, Daskalov, 2009). In Ukrainian waters of the Black Sea picked dogfish undertakes seasonal migrations. In autumn feeding migrations are aimed at the grounds of the formation of the wintering concentrations of anchovy and horse mackerel in the vicinity of the Crimean shelf. Reproductive migrations picked dogfish take place towards the coastal shallows with two peaks of intensity – in spring and autumn. The autumn migration for reproduction covers more individuals usually. The major grounds for reproduction of picked dogfish in the Ukrainian waters are located in Karkinitsky Bay, in front of Kerch Strait and in Feodosia Bay. Near the coasts of Ukraine the intense spawning season is in March-May. Two peaks of birth of juveniles can be distinguished – spring period (April-May) and summer-autumn (August- September). To give birth of juveniles the females approach the coastal zone in depth 10 – 30 m (Maklakova, Taranenko, 1974). At this time males keep separately from females in depth 30 – 50 m. The birth of picked dogfish juveniles takes place at the temperature of water 12 – 18°С. 2 During wintering the densest concentrations of picked dogfish are observed, where picked dogfish feeds intensively. In the northwestern Black Sea in the waters of Ukraine and Romania in depth from 70-80 m down to 100-120 m abundant wintering concentrations of picked dogfish are observed, where they are located on the grounds of whiting and sprat concentrations (Kirnosova, Lushnicova, 1990). 2.1 Stock units According to the previous research belonging to the USSR period, existence of existence of single population is indicated for the Black Sea (Svetovidov, 1964; Maklakova, Taranenko, 1974). All regional stock assessment picked dogfish made assuming / confidence in the existence of a single population (Prodanov et al, 1997; Daskalov et al, 2012; Sampson et al, 2013). 2.2 Growth and maturity Picked dogfish is a major demersal predator, reaching the Black Sea the length of 150 cm. According to investigations conducted in former USSR waters, Kirnosova, (1993) found that the picked dogfish maximum age is 20 years Age and length, at which 50% of individuals are mature, are 10.49 years and 87.57 cm for males and 11.99 years and 102.97 cm for females, respectively. According to A. Probatov (1957) in North-Eastern part of the Black Sea the size at first maturity picked dogfish occurs 13-17 year old: at 100-110 cm length for males and 110-115 cm for females. In conformity with Ukrainian data, maturity comes earlier - at the age of 9 to 14 years at a length of 80-90 cm (Table 2.2.1-2.2.2). 3 Table 2.2 -1: Maximum size, size at first maturity and size at recruitment of the Black Sea turbot (NE-stock, East Ukrainian waters) Somatic magnitude measured – SL, cm* Unit*** Sex Fem Mal Both Unsexed 1 Maximum size observed Reproduction April-May (historical) season (copulation and 140 125 birth of juvenile); August-September (birth of juvenile) Size at first maturity Reproduction Black Sea, Cape 100 80 areas ** Takil – Cape Meganom Recruitment size Nursery areas** Black Sea, Cape Takil – Cape Sarych 85** North-Western part of the Black Sea *Standard length. **Min catch’ size. ***Main part of areas in Ukrainian waters. Table 2.2 -2: The maturity ogive (average) of picked dogfish for 1971-2012 is the following: Age Year 1-8 9 10 11 12 13 14 15 16 17 18 19 1971-2012 0.00 0.10 0.25 0.45 0.55 0.75 0.95 1.00 1.00 1.00 1.00 1.00 . Natural mortality parameters picked dogfish according to YugNIRO’ investigations (Kirnosova, 1990) are: M Method Male Female “Integral” Beverton-Holt (1957) 0.20 0.15 Tyurin (1962) 0.21 0.16 Gulin (1971) 0.23 0.20 4 Table 2.2 -3: Growth and length (SL, cm) weight model parameters of the Black Sea picked dogfish (Ukrainian waters) Sex Unit* female male both Unsexed L∞ 303 272 282 K 0.026 0.029 0.027 Growth model t0 -3.32 -3.84 -3.668 Data source Kirnosova, 1990; Sampson et al, 2013 a 0.0000064 0.00000158 0.0000024 Length weight (2002-2011) relationship b 2.9593 3.2590 3.1690 (2002-2011) M 0.11 (vector by length or age) 0.114÷0.135 sex ratio (% females/total) 50.0% 5 Table 2.2 -4: Natural mortality picked dogfish vector by age (after Kirnosova, 1990) Age M female male male+female 1 0,69 0,67 0,68 2 0,46 0,38 0,42 3 0,30 0,3 0,30 4 0,24 0,23 0,24 5 0,22 0,18 0,20 6 0,12 0,15 0,14 7 0,11 0,13 0,12 8 0,10 0,1 0,10 9 0,10 0,09 0,09 10 0,09 0,05 0,07 11 0,07 0,03 0,05 12 0,06 0,11 0,09 13 0,04 0,28 0,16 14 0,02 0,95 0,49 15 0,14 2,88 1,51 16 0,42 - 0,42 17 0,60 - 0,60 18 0,92 - 0,92 19 2,84 - 2,84 Av.weight 0,17 0,22 0,20 3 Fisheries information In Ukraine, fisheries activities data are collected by Basin fisheries inspections under the umbrella of the State Agency of Fisheries of Ukraine. Ukrainian classification of fishing vessels is very different from the International Classification of ships. Statistics (official) for most components of fishing effort (number of fishing days by fishing gear, the number of trips to fish, catch per unit effort, etc.) is either missing or incomplete, or strongly distorted. For harvesting of picked dogfish in the Black Sea are used types of gears: gill nets (target fishery and by-catch), hook gears (target fishery), trawls (by-catch),. Information on their actual dislocations and the actually used amount of gear to get very difficult as it is officially reported missing. For this reason, we included the fisheries information, except appropriate tables from “Stock Assessment Form version 0.9’, to the additional tables. 3.1 Description of the fleet Picked dogfish is an object of both industrial, and small-scale (artisanal) gill nets fishery. A common classification of fisheries in the Black Sea fishing vessels imply its division into small-size 6 vessels (bot, bajda, boat, yawl, etc.), small-tonnage vessels (SCHS, MRST, MRTK, PTR, RS, etc.) (Commercial fisheries description, 1988; Shlyakhov et al, 2006). Small- size vessels, i.e. vessels without stationary engine or with a low-power engine, not part of Classification Association. They are used for operations