Pollock Stock Status2018 Stock Status of Alaska (Walleye) Pollock in the Russian waters
1. West Bering Sea Zone (east of 174° E) and Chukotka Zone
The value of total allowable catch (TAC) was significantly varying in the West Bering Sea Zone (east of 174° E) during several last years. Pollock stock biomass and abundance in the Russian EEZ was estimated at 396.98 kt and 2.28 billion individuals, respectively, according to trawling-acoustic survey data. According to bottom trawling survey data, pollock stock biomass and abundance was estimated at 1.07 million tons and 2.19 billion individuals respectively. In the pelagic zone of this region, the junior-age pollock stock was dominated by individuals born in 2013 (74.2%) and 2011–2012 (13.8%) and the adult pollock stock was dominated by 2010 year-class (3.13%). In the near-bottom zone, junior-age pollock individuals born in 2014 (52.4%), 2013 (11.5%) and 2012 (7.2%) dominated, while the adult pollock stock was dominated by individuals born in 2009 (6%) and 2011 (4.9%). In 2016, total pollock stock biomass in the eastern part of the Bering Sea, as based on trawling-acoustic and bottom trawling survey data, reduced by 18.34% in comparison with 2014 (from 10.91 million tons down to 8.91 million tons). Total abundance in 2016 (19.28 billion individuals) reduced even more significantly from 2014 (28.9 billion individuals) – by 33.3% Thus, the abundance and biomass of East Bering Sea pollock significantly reduced during 2014–2016, and this reduction acquires features of a sustained trend. According to our estimates, spawning stock biomass as of early 2018 will decrease to 1,690 kt. A justifiable TAC value for 2018 should be 396.4 kt (with expected further reduction in the following years). Based on multi-year mean data of pollock migrations from West Bering Sea Zone to Chukotka Zone (1.35% in biomass terms), pollock TAC in 2018 will be 5.4 kt in Chukotka Zone and 391.0 kt in West Bering Sea Zone (east of 174° E).
2. West Bering Sea Zone (west of 174° E), Karaginskaya Subzone
Pollock fishery in the western part of the Bering Sea within Karaginskaya Subzone and West Bering Sea Zone (west of 174° E) is focused on the West Bering Sea stock. According to established practices, recommended yield for West Bering Sea pollock is determined first for the whole stock and then is divided into two parts – Karaginskaya Subzone and Zone 61.01 (west of 174° E). West Bering Sea pollock resources are currently exploited using two fishing methods – trawl fishery and Danish seine fishery. During last ten years, trawl fishery accounted for 50.1% in Karaginskaya Subzone and for 93.4% in West Bering Sea Zone (west of 174° E). The year-to-year dynamic of the age composition of West Bering Sea pollock in last ten years showed that it has undergone noticeable changes caused by alternation of year-classes of varying strength. In the period under consideration, only individuals born in 2001 may be classified as a strong year-class which contributed to fishable stock growth by 2007. After that, only medium abundance (2002, 2006 and 2013) and low abundance (2003–2005, 2007–2013) cohorts were observed which resulted in reduction of pollock resources. Due to lack of any significant recruitment in recent years, it can be expected that pollock stock will continue to decline in the coming years. Using cohort-based procedures, we estimated the pollock stock for two years ahead. As of early 2018, total stock biomass will somewhat grow and amount to 364.8 kt, and spawning stock biomass will amount to 205.7 kt. Pollock TAC in 2018 will be 8.9 kt in Karaginskaya Subzone and 1.8 kt in West Bering Sea Zone in the water area to the west of 174° E.
3. Petropavlovsk-Commander Subzone, North Kuril (Pacific) Zone
Fishing vessels equipped with Danish seines traditionally account for the bulk of pollock catches (68.4%) in Petropavlovsk-Commander Subzone. As for North Kuril Zone, pollock is harvested here mostly by trawls (82.7% of total catch on average). Age composition estimates showed that in 2016 individuals belonging to the relatively strong year-class of 2011 dominated in Petropavlovsk-Commander Subzone and North Kuril Zone in abundance terms – 21.8% and 23.7% respectively. In general, East Kamchatka pollock of this age cohort accounted for 22.9% versus the multi-year mean of 18.8% for 5-year-old individuals. The second-largest group in occurrence terms was the 2010 year-class (16.3%). Upon analyzing the multi-year dynamic of its age composition, it should be stressed that, after two consecutive strong year-classes of East Kamchatka pollock born in 2000–2001 and the 2003 strong year-class contributing to stock growth after 2005, only medium or low abundant cohorts were registered. As a result, the resources of this grouping have been declining since 2011. Therefore, the bulk of spawning stock biomass in 2017–2018 will be individuals born in 2011, while individuals born in 2013 will just start joining the adult portion of pollock stock, so it can be expected to stay at the level of 2016. According to model-based estimations, total and spawning stock biomass in 2016 was 1,611.7 and 1,018.7 kt respectively. With consideration for mean zone-to-zone pollock yield distribution in last 5 years, the ratio of its recommended yield should be as follows: Petropavlovsk-Commander Subzone – 44.7% and North Kuril Zone – 55.3%. Thus, pollock TAC in 2018 will be 87.2 kt in Petropavlovsk-Commander Subzone and 107.8 kt in North Kuril Zone.
4. South Kuril Zone
According to results of a trawling survey, total abundance and biomass of South Kuril pollock in summer of 2016 was 2.751 billion individuals and 461.5 kt respectively. Of this amount, 2.704 billion individuals and 431.8 kt was registered on the Pacific side of South Kuril Islands. Respective figures for the Sea of Okhotsk side were 47 million individuals and 29.7 kt. The bulk of pollock biomass (97%) was registered off the ocean coast of Iturup Island. The estimated value of the fishable pollock stock in South Kuril Zone for 2018 will be 397.8 kt which is 15% less than had been earlier predicted for 2017 (469 kt with a TAC of 110.7 kt). Proceeding from the expected fishable stock biomass of pollock in South Kuril Zone in 2018, its TAC will be 93.9 kt.
5. Sea of Okhotsk Zone, North Sea of Okhotsk Subzone, West Kamchatka Subzone and Kamchatka-Kuril Subzone
Integrated survey results showed that, based on acoustic method, echo-integration assessments of the pollock stock in the Sea of Okhotsk in the spring of 2016 were 29.3 billion individuals and 7.3 million tons (without East Sakhalin). Pollock biomass was estimated at 3.0 million tons in West Kamchatka waters, 0.349 million tons in Shelikhov Gulf and 3.9 million tons in the North Sea of Okhotsk area. According to trawl survey data for the spring of 2016, pollock abundance and biomass in the Sea of Okhotsk was 46.1 billion individuals and 11.1 million tons respectively. Spawning stock was estimated at 11.8 billion individuals and 6.4 million tons, with the abundance and biomass of immature individuals being 34.3 billion individuals and 4.7 million tons respectively. According to model-based estimations, total and spawning stock biomass of pollock in the northern part of the Sea of Okhotsk as of early 2016 was 9.79 and 6.04 million tons respectively. Using cohort-based approaches, pollock stock was estimated for two years ahead. It is expected that, as of early 2018, total stock biomass will somewhat grow compared with 2017 and reach 10.22 million tons, while spawning stock biomass will amount to 6.56 million tons. Based on practical experiences of recent years, TAC distribution between subzones in 2018 will be as follows: North Sea of Okhotsk Subzone – 348 kt, West Kamchatka Subzone – 348 kt, and Kamchatka-Kuril Subzone – 270.7 kt.
6. Sea of Okhotsk Zone, East Sakhalin Subzone
Experts estimate that Northeast Sakhalin pollock stock was growing during 2007–2012. In 2015, pollock spawning intensity, abundance and biomass data were at a relatively high level off Northeast Sakhalin. It is forecasted that pollock fishable stock biomass off Northeast Sakhalin in 2018 will be 469.2 kt. In general, this estimate is evidence of rather high level of pollock stock condition. In line with the “precautionary approach” and existing Harvest Control Rule (HCR), optimal take may be 22.8% for the predicted biomass of 469.2 kt. Pollock TAC in 2018 will be 107.2 kt.
7. Primorye Subzone
With consideration for total mortality, as of early 2018 the abundance of pollock at the age of 3–12 years will go down to 182.5 million individuals but, as the strong 2014 year-class will start joining the fishable stock, the abundance of commercial-size individuals and their biomass will grow to 95 million individuals and 45 kt respectively. The fishable stock will consist of 4-year-old individuals at 46.8%, the 2013 year-class will be within 26.0% and the 2012 year-class will account for 20.2%. According to trawl survey data, pollock abundance and biomass in Primorye Subzone was 337.4 million individuals and 72.5 kt respectively, of which 61.3 million and 19.7 kt was registered in western areas of the Tatar Strait north of Cape Zolotoy. The TAC of pollock living in the northwestern part of the Sea of Japan between the Peter the Great Bay and Cape Yuzhny (51°40′ N) will be 10.5 kt in 2018. Pollock take in the waters of Khabarovsk Region will be about 0.5 kt and that in the area south of Cape Zolotoy will be 10.0 kt.
8. West Sakhalin Subzone
It is expected that the fishable stock biomass (3 to 11 years of age) will be 21.2 kt in 2018. The bulk of biomass of catches to be harvested in 2018 will be 7-9-year-old individuals which will collectively account for 81.9% of total catch. Recommended TAC for West Sakhalin Subzone in 2018 will be 1.6 kt.
Source: Status of fisheries resources. The forecast total catch of aquatic bioresources in the Far Eastern Fishery Region in 2018. – Vladivostok: TINRO-Center, 2018. – 389 p.