Pollock Stock Status

Walleye Pollock Stock Status in 2015  

67.01. Chukotka zone 
61.01 Western Bering Sea zone (to the east from 174°00'E)
At present time, the assessment of total allowable catch in the Russian part of the Bering Sea is done separately for two regions which correspond to the two stock units: in the western part (Olutorsky Bay, Karaginsky Bay and the adjacent water near Koryak coastal area up to 174°00'E) and in the north-western part (region to the east from 174°00'E up to separation line). During summer season, small aggregations of walleye pollock also occur in Chukotka zone. In 2008, the TAC for walleye pollock has not been established in that region and this species was caught as a by-catch only.
  
According to the data from acoustic-trawl and bottom trawl surveys in the Bering Sea during summer-fall season of 2015, the abundance and biomass of the Eastern Bering Sea walleye pollock are above the average due to the abundant generations in 2008 and 2012 and the generation with the average abundance in 2009-2011 and in 2013-2014.
  
Based on the data from the acoustic-trawl surveys in the Russian zone in 2015, the walleye pollock biomass is 396 980 metric tons and its abundance is 2,280M individuals. The pelagic fish was mostly represented by 2011-2014 generations. According to the data from the bottom trawl survey, the biomass of walleye pollock was 1.07M metric tons and the abundance was 2,190M individuals. The immature walleye pollock of 2013 and 2014 generations has predominated at near-bottom layer (11.6 % and 52.4 %, respectively).
  
In the Russian zone during summer season of 2015, the walleye pollock of 2013 and 2011-2012 generations has prevailed among young pelagic fish (74.2 % and 13.8 %, respectively); 2010 generation was predominant among mature fish (3.13 %). The young walleye pollock of 2014, 2013, and 2012 generations has predominated at near-bottom layer (52.4 %, 11.5 %, and 7.2 %, respectively); 2009 and 2011 generations were predominant among mature fish (6.0 % and 4.9 %, respectively).
  
The biomass of walleye pollock in near-bottom layer at the eastern part of the sea in 2015 was 6.39M metric tons; the abundance was 10,980M individuals. The immature fish of 2008-2011 generations has predominated at near-bottom layer.

As the main target indicator for biomass in 2015, the biomass estimate of spawning stock was obtained based on the stochastic forecast calculations as 1,750K metric tons, which corresponds to the maximum sustainable yield and is corrected for uncertainty in its estimates to upward direction. As the marginal limit for biomass, the minimal biomass value of spawning stock was assessed based on the retrospective observations, and is equal to 830K metric tons.

Based on the average long-term data on the extent of fish distribution from the Western Bering Sea zone to Chukotka zone, its TAC is set to 1.35 % of the total biomass value.

61.01. Western Bering Sea zone (to the west from 174°00'E)
61.02. East Kamchatka zone
61.02.1 Karaginskaya subzone
After the depressive stock condition in 1990s up to early 2000s, the western Bering Sea population of walleye pollock has increased due to the ban on specialized fishing of walleye pollock in Karaginskaya subzone. The stock growth has been confirmed both by direct stock assessment and by stock evaluation based on theoretical fishery models. However, it was a short-term increase. The results of the last trawling surveys in 2012-2013 and the model calculations have showed that the rates of walleye pollock stock reduction after 2007 were much higher than it was previously thought, that is explained by the absence of abundant or average-number generations in recent years and by the increased fishing pressure.

According to the model estimates, in the beginning of 2015 the overall stock of western Bering Sea walleye pollock was 285.9K metric tons, and the spawning stock was 146.3K metric tons. 

61.02.2. Petropavlovsk-Commandorskaya subzone 
61.03. North Kuril zone
The biomass estimate for overall stock in the beginning of 2015 was 1,791.4K metric tons and for spawning stock it was 1,088.3K metric tons. At present time, there is a slight stock increase due to the emergence of 2011 generation with elevated abundance.

61.04. South Kuril zone
According to the results of trawl survey at the Pacific side of southern Kuril Islands, 9.8 billion individuals and 411.6K tons of walleye pollock have been assessed in 2015. The abundance of yearlings was 8.4 billion individuals that corresponds to high level of productivity among generations. From the Sea of Okhotsk side of Kuril Islands, including Iturup Island, the abundance of walleye pollock in Prostor Gulf was 1.2 billion individuals and the biomass was 259.4K metric tons. The biomass at Kunashir Strait was 25.4K metric tons. In general, the overall stock of walleye pollock near South Kuril Islands was assessed as 11.1 billion individuals and 696K metric tons. The 45 % increase of total biomass estimate for walleye pollock, compared to the previous year, is mainly due to the favorable ice condition around South Kuril Islands in spring 2015 that allowed to conduct research surveys in the entire standard region.

61.05. The Sea of Okhotsk zone
61.05.1. North Sea of Okhotsk subzone
61.05.2. West Kamchatka subzone 
61.05.4. Kamchatka-Kuril subzone
According to acoustic method with echo-integration technology, in the spring season of 2015 the abundance of walleye pollock at the North Sea of Okhotsk was 25.1 billion individuals and its biomass was 8.3M metric tons. According to ichthyoplankton method, the abundance and the biomass of walleye pollock were estimated as 26.828 billion individuals and 8.296M metric tons, respectively. Within that amount, 11.327 billion individuals and 6.069M metric tons were walleye pollock producers, 15.501 billion individuals and 2.228M metric tons were immature fish. The biomass estimate for walleye pollock from the northern part of the Sea of Okhotsk in 2015 was obtained by ichthyoplankton method – 8.056M metric tons. According to trawl survey, the abundance of walleye pollock in the Sea of Okhotsk was 43.3 billion individuals and its biomass was 11.864M metric tons. The spawning stock was estimated as 18.1 billion individuals and 8.504M metric tons. 38.5 % of producer biomass has been observed near Western Kamchatka, 1.6 % in Shelikhov Bay, and 59.9 % in the North Sea of Okhotsk region.

In the spring of 2015, the individuals of abundant 2011 generation have predominated in the age-size structure of walleye pollock from the North Sea of Okhotsk at the age of 4 years; they constituted 26.5 % of overall of walleye pollock abundance. The commercial stock was represented mainly by the fish of 40-55 cm in length, among which 6-years and 7-years old individuals were predominant, and 8-years old individuals were also noticeable. Based on the research data from 2015, the age-size structure of walleye pollock in the Sea of Okhotsk can be characterized as good.
  
The decrease of walleye pollock resources has stopped in 2015, the stocks stabilized on the level above the annual average, and it is possible that there will be some small growth of this assemblage starting from 2016-2017.

The model estimate for the overall stock of walleye pollock at the age of 2-20 years was 9.53M metric tons and the spawning stock was 6.13M metric tons in the beginning of 2015. The biomass of spawning stock is growing in the last few years and this trend will remain in the nearest future.

61.05.3. East Sakhalin subzone
In the research surveys of 2015, the walleye pollock was represented by individuals at the age of 2-3 to 13-15 years. At the same time, four age classes were dominated both during spawning and feeding periods – individuals at the age of 5 to 8 years, i.e. 2007-2010 generations. In 2015, almost all fish of 2009 generation has been included into spawning and commercial stocks and showed significant age structure. In 2015, the biomass of walleye pollock living near the north-eastern Sakhalin remained fairly high. The biomass of mature fish in 2015 was 632K metric tons and the overall biomass was 738K metric tons. According to the egg surveys in 2015, the biomass of producers was estimated as 313.3K metric tons based on the average biomass, equal to 0.6 kg. Thus, the direct assessments (egg and trawl surveys) of walleye pollock living off the coast of East Sakhalin suggest that its current resources remained at a sufficiently high level, close to adjusted forecast estimate (the commercial stock biomass for 2015 was predicted based on the modeling results – 489K metric tons).

61.06. The Sea of Japan zone
61.06.1. Primorye subzone
The walleye pollock stock for 2015 in Primorye subzone, to the south of Golden Cape, could be no less than 32.56K metric tons or 647.16M individuals, with taking into account its pelagic component. Given the facts that 0.614K metric tons (or 0.826M individuals) have been already caught before the beginning of trawl survey, that the abundance of walleye pollock in the nearshore of Primorsky region was more than 647.98M individuals (33.172K metric tons), at the same time its biomass in the north-western part of Tatar Straight (to the north of Golden Cape) could be less than 10K metric tons and the abundance could be less than 33.141M individuals.

Thus, the overall biomass of walleye pollock at Primorye subzone in the beginning of 2015 was about 43.2K metric tons, the stock was 681.124M individuals, and the biomass of the commercial stock was 26.3K metric tons. The obtained stock estimate values are 2 times lower than the average for 2001-2014.

61.06.2. West Sakhalin subzone
The survey in 2015 was held in the whole area of Tatar Straight; the overall biomass of walleye pollock was 24.6K metric tons and the commercial stock biomass was 22.3K metric tons. In 2006-2015, the level of walleye pollock resources near the western Sakhalin coast has been increased that was caused by the introduction of abundant generations to the commercial segment of a stock, especially 2006 generation. At the same time, no extraordinary dominant generations were observed in the age structure of the commercial stock of 2015.
   
Walleye pollock stock estimates for the fishery zones in the Far Eastern Fishery Region in 2015 and the TAC advice for 2015-2016

Zone / subzone

Overall stock biomass in 2015,

000 mt

Commercial stock biomass in 2015,

000 mt

TAC advice for 2015/2016,

000 mt

67.01 – Chukotka zone

7856,980*

1750,000**

5,500/6,200

61.01 – the Western Bering Sea zone (to the east of 174°0'E)

430,000/455,800

61.01 – the Western Bering Sea zone (to the west of 174°0'E)

285,900

146,300

0,000/0,000

61.02.1 – Karaginskaya subzone

11,500/7,400

61.02.2 – Petropavlovsk-Commander subzone

1791,400

1088,300

83,100/88,600

61.03 – North Kuril zone

103,200/109,500

61.04 – South Kuril zone

696,000

196,707

106,700/89,300

61.05 – the Sea of Okhotsk zone

61.05.1 – the North Sea of Okhotsk subzone

9530,000

6130,000

325,400/348,000

61.05.2 –  West Kamchatka subzone

325,200/348,000

61.05.4 – Kamchatka Kuril subzone

253,200/270,700

61.05.3 – East Sakhalin subzone

738,000

489,000

103,000/107,000

61.06 – the Sea of Japan zone

61.06.1 – Primorye subzone

43,200

26,300

4,580/4,420

61.06.2 – West Sakhalin subzone

24,600

22,300

3,200/2,100

Total for all areas

20966,08

9848,907

1754,580/1837,020

Source: Status of fisheries resources. The forecast total catch of aquatic bioresources in the Far Eastern Fishery Region in 2016 (short version). – Vladivostok: TINRO-Center, 2016. – 389 p. (In Russian)

References: 

TAC allocation for 2016. Decree of the Ministry of Agriculture #465 of 07.10.2015

Aqua biological resources of Russian fisheries in 2015. FFA website