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How they looked at the ODE

Head of the TINRO Pollock and Herring Laboratory - about the projections of the pollock population for the next ten years

Taking the traditional six-month respite, the Far East fishermen are systematically preparing for the “B” season of white pollock fishing, which will take place from October to December 2020. What methods are used to assess the commercial stocks of the most widespread species of the North Pacific Ocean, is there a shift in the timing of fish arrival, and what predictions about the size of the pollock population for the next ten years does science give, said the head of the pollock and herring laboratory of the Pacific branch of the Federal State Budgetary Scientific Institution "VNIRO" (TINRO), candidate biological sciences Evgeny Ovsyannikov.

How they looked at the ODE
Photo: provided by the press service of VNIRO

- Evgeny Evgenievich, how do you estimate the size of the pollock population in the region in 2020?

- Due to its high ecological plasticity and biological features, such as high fertility, earlier puberty, rapid growth and a wide range of nutrition, pollock is a dominant in the ecosystems of the Far Eastern seas. The largest populations live in the Okhotsk and Bering Seas. With a high level of abundance, in the 1980s its resources in each of these seas reached almost 20 million tons, which ensured its catch in Russian waters of more than 2,5 million tons. Today, the state of pollock populations in these two seas is estimated to be above average, and Russian fishermen catch about 1,4 million tons, or more than 80% of the total pollock catch in Russia.

Considering the high commercial importance, detailed studies of pollock have been carried out at TINRO for almost 40 years. At the initial stages, ichthyoplankton and trawl surveys were carried out, not only in order to assess the stocks of the species, but also to understand its life cycle - to determine the spawning areas where pelagic eggs, larvae, juveniles, accumulations of adults, areas to which the pollock migration to feeding, the spectrum of its nutrition and food supply, etc. As a result, by now the ecology of the pollock has been studied quite well, methods of work have been developed to assess and monitor its stocks, and comprehensive research expeditions are being conducted. In these studies, the state of pollock stocks is assessed by three independent methods: trawl, ichthyoplankton and trawl-acoustic. The number and biomass of all types of aquatic biological resources found in the catches is also estimated, work is being done to study the nutrition of pollock and other species, and oceanological research is being conducted. In the Sea of ​​Okhotsk, we conduct such studies annually, and in the northwestern part of the Bering Sea - once every two years.

- What does the latest research in this area show? Is it appropriate to talk about a deficit?

- Research on pollock in the Sea of ​​Okhotsk, carried out in spawning grounds in April-May 2020 at the R / V Professor Kaganovsky, shows that over the past year, the biomass of pollock in the area has slightly increased. The increase was due to the weight growth of fish of the productive generations of 2013-2014 and the average harvest of 2015-2016. The number of generations in 2017-2019 is assessed as low. This means that starting from 2023-2024 in the Sea of ​​Okhotsk, a decrease in the commercial stock of pollock may begin, and the catch volumes will have to be reduced. Considering that during this period the share of productive and medium-yielding generations will still be quite high among commercial fish, we expect that the decline will be smooth.

It is not yet possible to predict the development of the situation with a margin for a longer period. It is necessary to conduct research in the coming years and pay special attention to the emergence of generations with different levels of productivity. If medium and high-yielding generations begin to appear, then the stock will remain at the average level, and if the series of lean generations continues, the stock will decrease.

- What about the Bering Sea?

- Our research in the northwestern part of the Bering Sea (Navarinsky District) this year is scheduled for late summer and early autumn, when specialized fishing is taking place in the area. The specificity of the Navarino region is that two populations of pollock are caught here - the West Bering Sea and the East Bering Sea. The second population predominates just in late August and early September, when we study the migration volumes of pollock from the eastern part of the Bering Sea and the value of the mixed stock in the season of maximum abundance. We also use the results of American studies to assess the stocks of pollock in the area of ​​Cape Navarin. Our staff is taking part in the trawl acoustic surveys of the Alaska Fisheries Research Center (AFSC) in the eastern Bering Sea.

As I have already mentioned, the state of pollock stocks in the Bering Sea is now estimated to be above average. At the same time, the volume of the stock in Russian waters depends not only on the total stock in the Bering Sea, but also on the climatic and oceanological conditions and the state of the food supply. When our waters are warming, the amount of plankton (euphausiids and large copepods) available for pollock feeding increases, and with this the number of migrants entering our waters. We have seen this situation in recent years. In May, there is a rapid seasonal warming of the waters, and pollock begins to approach the area of ​​Cape Navarin earlier than the average multiyear period, forming dense feeding accumulations on which the fishing fleet operates.

Our employees collect information on fishing vessels, and we see that the pollock is actively feeding. During the summer period, feeding stocks of pollock gradually move along the Koryak coast to Anadyr Bay. Due to a decrease in the reserves of food plankton in our waters, the reverse migration begins in September, which is also somewhat earlier than usual. In the coming years, we expect that a gradual cooling will begin in the northwestern part of the sea. At the same time, the number of generations in 2012-2015 is estimated as average, and the young generation of 2017-2018 has a significant number. Therefore, we can expect that there will not be a decrease in the approaches of pollock to our waters, and here it will be possible, as now, to catch about 400 thousand tons of this species. But it should be borne in mind that with a high probability the timing of pollock approaches will shift to the average annual, i.e. fishing can begin in the first half of June.

- What methods of catching pollock are most effective in the Okhotsk and Bering Seas?

- Specialized pollock fishing in our waters is carried out by pelagic trawls. In the Far East basin, this type of fishery accounts for more than 95% of the pollock catch. The remaining volumes are caught as by-catch by snur breeders in the fishery for bottom food items and in the longline fishery for cod. Specialized fishing for pollock with bottom trawls is prohibited under the Fishing Rules.

Pollock catching with pelagic trawls is a rather gentle type of fishing: with the help of acoustic devices, pollock accumulations are found in the water column, and then they are fished. Modern equipment makes it possible to determine not only the density and location of shoals, but also the expected size composition of catches and to understand what type of aquatic biological resources forms them. Therefore, in this type of fishery, the composition of by-catch of other fish species is usually very low, at the level of 1-2% of the weight of the catch, and only the by-catch of herring in some areas can reach 20-40%. Also note that pollock trawling is carried out in the water column and does not harm benthic communities.

- Tell us about the scientific and economic justification of measures to regulate the pollock trawl fishery in the Pacific seas.

- There is a complex, multi-level system of regulation of the pollock fishery, the main task of which is the conservation and sustainable use of its resources while minimizing the impact of fishing on ecosystems. This system assumes the implementation of complex research expeditions aimed at assessing the stocks of pollock, its biocenological environment, environmental conditions and food resources. Scientific observers monitor the pollock fishery. To assess the state of reserves, assessment methods are used, obtained from the data of research trawl, ichthyoplankton, acoustic surveys; estimates calculated using mathematical modeling methods based on data from field statistics and materials collected by scientific observers.

For the Fishing Rules, points have been developed, the main task of which is to minimize the impact of pollock fishing, both on the main species and on the ecosystem as a whole. For example, there are restrictions on fishing gear, areas and timing of fishing. The parameters of fishing gear allowed for fishing, the amount of by-catch of juvenile pollock, the amount of by-catch of other species of aquatic biological resources, etc., have also been established. and passing the State Ecological Expertise.

The existing system of pollock fishery management in Russia meets the modern requirements for fisheries, which, for example, is confirmed by the international environmental certification by the pollock trawl fishery in the Sea of ​​Okhotsk in accordance with the standards of the Marine Stewardship Council (MSC).

- What, according to your forecasts, will the fishing industry be guided by in the coming years? What areas are worth investing in, what to be ready for?

- In the next five to ten years, pollock will continue to be an important commercial species for Far Eastern fishermen. Unlike species such as saury, ivasi sardine and mackerel, the catch volumes of which depend on their approaches to our waters, pollock lives mainly in Russian waters. As the dominant species in the ecosystems of the Okhotsk and Bering Seas, according to our forecasts, in the coming years, it can provide about 1,7-2 million tons of catch in the whole basin. With regard to the use of these resources, it is necessary to increase the supply of pollock to the domestic market and pay special attention to its deep processing at sea and at coastal enterprises. Among the population, using the media, it is necessary to conduct an active advertising campaign about the benefits of wild white fish and pollock in particular. In catering establishments, you can hold pollock food festivals and arrange fish days. We have a good opportunity to use this self-reproducing and environmentally friendly resource for public health.
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