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Results of the Sea of Okhotsk pollock fishing season A-2020 Unofficial translation of KamchatNIRO publication. Original article is availible at KamchatNIRO website in Russian. From January 1 to April 9, 2020 in the northern part of the Sea of Okhotsk within the North Okhotsk Sea (61.05.1), West Kamchatka (61.05.2) and Kamchatka-Kuril (61.05.4) subzones, one of the largest domestic fishery took place - Sea of Okhotsk target pollock fishery.

Specialists of the Far Eastern branches of the Federal State Budgetary Scientific Institution "VNIRO", and the Kamchatka branch ("KamchatNIRO") in particular, traditionally took an active role in its information support and monitoring. From the very first days of the fishery, observers from the institutes worked on the fishing vessels. By the joint efforts of specialists from the Far Eastern branches, data have been collected in all the main areas of the pollock fishery. A huge array of fishery and biostatistical information has yet to be processed and thoroughly analyzed, however, some of the main results can be summed up now.

According to modern concepts, in the northern part of the Sea of Okhotsk within the boundaries of subzones 61.05.1, 61.05.2, 61.05.4, as well as in the open waters of the sea, a single group of pollock lives with a complex intrapopulation structure.

Throughout the history of pollock fishing in the northern part of the Sea of Okhotsk, the record catch in these fishing areas, equal to 1,925 thousand tons, was recorded in 1997. Due to a sharp decline in stocks, by 2004 it decreased by more than 5 times. Since 2005, the catch has increased and in 2010 reached 990 thousand tons. Due to a decrease in the resources of the North Sea of Okhotsk pollock since 2011, the total TAC decreased, and the catch also decreased, respectively. Since 2015, TAC and catch have increased and in 2016 amounted to 966.7 and 942.7 thousand tons, respectively. In 2017–2018 with the same TAC, the catch amounted, respectively, to 943.2 thousand tons (97.6% of TAC) and 945.4 thousand tons (97.8% of TAC). In 2019, 941.3 thousand tons of pollock (97.6% of TAC) were harvested in the northern part of the Sea of Okhotsk. In 2020, total TAC for North Sea of Okhotsk pollock was set at 1,064.0 kt, of which: North Sea of Okhotsk Subzone — 383.0 kt, West Kamchatka Subzone — 383.0 kt, Kamchatka-Kuril Subzone — 298.0 kt. With consideration for the benefits of unification of West Kamchatka and Kamchatka-Kuril subzones in 2010–2019, scientists recommended, same as in previous years, extend this practice to the 2020 season as well.

By data of Vessel Daily Reports (VDR) contained in the Fishery Monitoring System (FMS), pollock catch by pelagic trawls in a commercial fishing mode in the Rissian EEZ (target pollock fishery) by all ships totaled about 889.5 kt by April 10, 2020 (Table 1) which is more than a year before (817.2 kt). Another 25.0 kt (23.8 kt in 2019) was harvested by other fisheries, primarily the Danish seine fishery off West Kamchatka.

Table 1. Pollock TAC, yield and percentage of TAC use by fishing areas in the northern part of the

Sea of Okhotsk in January – early April 2020

Subzone TAC, kt

Ship-days in target trawl

fishery

Number of hauls in target

fishery

Total yield, kt Share of

TAC, % trawls all fishing gear

types 61.05.1 383.0 2,810 7,622 338.013 338.812 88.5 61.05.2 383.0 2,642 6,914 303.927 313.988

84.4 61.05.4 298.0 2,958 7,615 247.565 261.168 Total 1064.0 8,410 22,151 889.505 913.968 85.9

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Total catch in the unified Subzones 61.05.2 and 61.05.4 in January – March 2020, harvested by all fishing gear types, was 575.2 kt or nearly 51.7 kt more than in the preceding year. Total pollock catch in the Season A of 2020 was 914.0 kt (85.9% of TAC) compared with 841.1 kt (87.2% of TAC) during the same period in 2019.

In January 2020, same as in 2019, pollock fishing activities were concentrated in Kamchatka-Kuril subzone (Fig. 1–2). Monthly catch in this subzone was about 115.0 kt (130.6 kt in last year). The number of operating ships was up to 60 on some days. Mean daily catch was 3.7 kt and mean catch per ship was 80.3 tons. Fishing intensity in West Kamchatka Subzone was low till mid-January but abruptly grew in this month’s latter half as fishery began in the area between 54th and 56th parallels and in the mouth of Shelikhov Bay. Up to 61 ships operated simultaneously in the subzone in this month. Mean daily catch of all ships in this month was 2.2 kt, mean catch per ship was 85.3 tons and total catch was 67.8 kt. For comparison, as little as 0.7 kt was harvested in the same period of last year in Subzone 61.05.2. In the North Sea of Okhotsk Subzone, pollock was harvested in small quantities as by-catch in herring fishery till mid-January, and its target fishery was launched in the month’s latter half in the area northeast of the polygon occupied by neutral waters. Total monthly catch was 14.1 kt (26.0 kt in preceding year). Up to 16 ships operated in that period. Mean daily catch by all ships per month was 0.5 kt and catch per ship was 43.5 tons.

A total of up to 106 ships of various types operated in pollock fishery in the northern part of the Sea of Okhotsk in January. Total catch amounted to 196.9 kt (157.3 kt in preceding year), mean daily catch by the whole flotilla’s ships was 6.352 kt and mean catch per ship was 87.4 tons.

Fig 1. Dynamic of daily yield (A), number of ships (B) and mean catches per ship (C) in the northern part of the Sea of Okhotsk in January – first 10-day period of April 2019 (left) and 2020 (right)

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2019 January 2020 January

2019 February 2020 February

2019 March 2020 March

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2019 1–9 April 2020 1–9 April

Fig 2. Fleet distribution in pollock fishery in the northern part of the Sea of Okhotsk in January – early April 2019 (left) and 2020 (right) (circles – large-tonnage fleet (trawls), blue triangles –

medium-tonnage fleet (trawls), green diamonds – all ships (Danish seines))

In February, the focus of pollock fishery gradually moved to West Kamchatka Subzone (see Fig. 1–2). Monthly catch here was about 132.3 kt of pollock. A similar situation was observed in last year but catch was larger – about 150.2 kt. Up to 58 ships operated simultaneously in Subzone 61.05.2 in February 2020. Mean daily catch by all ships grew to 4.6 kt and mean catch per ship grew to 122.3 tons. The key fishing site was the area adjacent to the 57th parallel and Shelikhov Bay. The second-largest area in total yield terms in February was Kamchatka-Kuril Subzone. Monthly catch in this area was about 113.1 kt of pollock (71.7 kt in preceding year). Up to 71 ships operated simultaneously in the subzone. Mean daily catch was 3.9 kt and mean catch per ship was 73.2 tons. Pollock fishing areas almost did not change in this month. Pollock catch in February in the North Sea of Okhotsk Subzone more than doubled on the preceding month (34.2 kt). Yield in the same period of last year was considerably lower and amounted to some 10.8 kt. Up to 32 ships operated simultaneously. Total daily catch by all ships was 1.223 kt and mean catch per ship was 74.7 tons.

Pollock yield in February 2020 totaled 279.6 kt which is considerably more than in January and in last year’s February (232.7 kt). The number of catchers grew to 119 ships. Mean daily catch increased to 9.641 kt and mean catch per ship grew to 92.3 tons.

Same as a year ago, the focus of pollock fishery in March 2020 was in the North Sea of Okhotsk Subzone (see Fig. 1–2). Yield was gradually rising from 3.9 kt in the month’s beginning to 10.2 kt in its end and totaled 194.3 kt (versus 207.1 kt in same period of 2019). On some days, up to 86 ships operated simultaneously in the subzone. Mean daily catch by all ships in this month was 6.3 kt and mean catch per ship was 124.1 tons. Key fishing areas were northeastern slopes of TINRO Depression and Near-Tauy area. In West Kamchatka Subzone, pollock harvesting intensity somewhat decreased on the preceding month. Total monthly catch was 113.9 kt which is roughly equal to this figure in the same period of last year (112.4 kt). Fleet number was up to 63 ships. Mean daily catch by the whole flotilla reduced to 3.7 kt and mean catch per ship reduced to 112.4 tons. In Kamchatka-Kuril Subzone, same as in the preceding year, fishing intensity decreased times in March. Total catch was about 33.1 kt (33.4 kt in last year). Up to 55 ships of various types operated simultaneously. Mean daily catch by all ships dropped to 1.2 kt and mean catch per ship dropped to 61.4 tons.

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Traditionally, March is the most productive month in pollock fishery in the northern part of the Sea of Okhotsk. Fishing fleets operate on dense pre-spawning fish aggregations migrating to their breeding areas. This year was no exception. Monthly catch was 341.3 kt which somewhat less than in last year (352.9 kt). The number of catchers was 119 ships. Mean daily yield and mean catch per ship increased up to 11.0 kt and 105.6 tons, respectively, in comparison with the preceding month.

During April 1–9, 2020, pollock catch in the North Sea of Okhotsk Subzone totaled 96.1 kt which is roughly equal to last year’s result (98.2 kt) (see Fig. 1–2). Fleet number was up to 86 ships. Mean daily catch was 10.678 kt and mean daily catch per ship was 145.1 tons.

In general, daily pollock catch by all vessels in the northern part of the Sea of Okhotsk during the 2020 fishing season was gradually growing, as more catchers became engaged and more fishing operations were performed: from 0.6 kt in early January to 7.6 kt in mid-January (see Fig. 1). Then, daily catch reduced to 2.9 kt by January 26 and abruptly grew to 10.6 kt by month’s end. It remained roughly on the same level till late February – approx. 9.4 kt. Then this parameter was gradually increasing and reached its maximum of 13.9 kt on March 26. Then daily catch was gradually declining and amounted to some 10.0 kt by the end of the fishing season. Mean daily catch per fishing season was 9.1 kt (8.5 kt in last year) and mean catch per ship was 99.6 tons (84.2 tons in last year).

In summary, this year’s fishing season can be assessed as successful in terms of total yield and daily catches. January and February were more productive months in comparison with last year.

It is commonly known that success of any fishing season, in particular, in pollock fisheries, depends first of all on existing fishing conditions which are governed, above all, by stock condition.

Along with stock condition, fishing conditions are determined by many other factors. The most important ones in the Sea of Okhotsk, which is similar to Arctic seas in terms of severe winter conditions, are meteorological and ice conditions, and year-specific thermal conditions. Effects of meteorological conditions on operations of the whole fleet, particularly medium- and small-tonnage vessels, are obvious. Frequent storms directly interfere with normal operations of vessels, lead to down time and influence fish distribution. In particular, search for fish aggregations after storms normally takes more effort.

Temperature conditions directly affect ice formation processes and, secondly, essentially influence formation of stable fishable aggregations, rate of gamete maturity and, consequently, Effects of the amount of ice cover on fishing conditions are also quite obvious, with small- and medium-tonnage fleets more exposed to this factor. In addition to above said factors, fishing conditions also depend on the qualitative (size and sex) composition of fish in particular areas and in particular periods.

Other factors which do not influence fishing conditions directly but determine particular vessel’s and whole flotilla’s daily catches may include this vessel’s product range, total vessel number and composition of the flotilla, its technical capability, and many other factors. We will discuss below in more detail some of the above-mentioned factors which had effects on the past fishing season.

According to model-based estimates, total stock and spawning stock biomass of pollock older than two years in the northern part of the Sea of Okhotsk as of early 2019 was 9.3 and 6.7 million tons respectively (Fig. 3). Briefly characterizing pollock stock dynamics by results of model-based estimates, we would like to note that growth of its spawning stock biomass was observed during 2000–2018. This is explained by appearance of two consecutive strong year classes (2004 and 2005) and medium-strength year classes (born in 2000, 2002 and 2006) in the first half of 2000s, and appearance of a strong year class (2011) and two medium-strength

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classes (2013 and 2014) in early 2010s (Fig. 4.6.4). 2015 and 2016 year classes, initially assessed as having medium strength, are estimated as being below their multi-year mean according to new data. In this connection, a trend to spawning stock biomass reduction emerged in 2019. However, stock continues remaining at a high level which is considerably higher than its biomass target reference point.

Given that the assumed two-year-olds’ average abundance over last 10 years is 9.5 billion individuals, total pollock stock will grow to 9.7 million tons in 2020 due to full addition of medium-strength cohorts of 2013–2014 to its fishable stock biomass, while its spawning stock biomass, on the contrary, will somewhat decrease and amount to approx. 6.4 million tons.

Fig. 3. Year-to-year dynamic of North Sea of Okhotsk pollock total (A) and spawning (B) stock

biomass and percentiles of bootstrap distribution of its estimates

Meteorological situation in January and February 2020 was characterized by two depression centers, one southeast of Kamchatka and another over Alaska Bay (Fig. 4). On the

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one hand, cyclonic activities in January were less intensive than usually, evidence of which is positive anomalies of near-ground pressure in the distribution area of the Aleutian Low (Depression). In February, on the contrary, a negative pressure anomaly was observed in the area of cyclone positioning. On the other hand, the position of one of the depression’s local centers was inducing increased wind loads on the surface of the northeastern part of the Sea of Okhotsk which was located in the rear of deep cyclones.

Fig. 4. Mean monthly field of near-ground atmospheric pressure (left) and its anomalies (right)

in January, February and March 2020

In March, meteorological situation drastically changed, and the crest of the quasi-stationary Hawaii (North Pacific) anticyclone became anomalously developed and shifted the trajectory of cyclones to the Sea of Okhotsk. This situation resulted in inflow of warm air masses to fishing areas and strengthening of southerly winds.

Fig. 5 shows an intra-seasonal dynamic of mean daily values of near-water wind speeds and wave height for the northeastern part of the Sea of Okhotsk. As seen in this Figure, the observed occurrence of high wind speeds and associated high waves was somewhat lower in the winter of 2020 than in 2019; however, it is in this year that the most extreme situation was registered in the beginning of the second 10-day period of March. On March 12, mean daily

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wave height exceeded 5.5 m and was remaining at 3 meters during several following days. Mean wind speed was varying from 12 to 15 m/s and wind gusts were reaching a storm force during this period. As a consequence, the whole flotilla was staying in a storm mode on March 12–14 in Kamchatka-Kuril Subzone and no pollock catch was recorded. Another period of weather, adverse for fishing, was January 25–26 when wind speed was 15–16 m/s and wave height was 4–4.5 m. For instance, 45 ships operated off Southwest Kamchatka on January 24 and harvested some 3.4 kt of pollock. Only 31 ships operated on the next day and harvested some 1.4 kt of pollock, and virtually all ships in this area switched to a storm mode on January 26, with catch dropping to a minimum. Mean wind speed during the season was 8.9 m/s in 2019 and 8.7 m/s in 2020, and mean wave height was 1.88 and 1.95 m respectively.

In summary, meteorological conditions in the northeastern part of the Sea of Okhotsk in the winter of 2020 compared with 2019 were, in general, characterized by somewhat lower wind loads on the sea surface. But, in terms of wave height and extreme wind speed values, intra-seasonal periods more adverse for fishing were observed in the winter of 2020.

Fig. 5. Intra-seasonal (January – early April) variations of mean daily values of wave height (a)

and wind speed (b) in the northeastern part of the Sea of Okhotsk in 2019 and 2020

During the season, ice conditions in the northeastern part of the Sea of Okhotsk were characterized by ice formation rates close to their multi-year mean values; however, the amount of ice cover was lower relative to its normal amount and in comparison with 2019 data (Fig. 6). Within the northeastern part of the Sea of Okhotsk, continuous ice occupied primarily this area’s north including Shelikhov Bay. Virtually no fast ice was observed along West Kamchatka shores. A seasonal peak of ice cover development occurred in the first ten-day period of March when its square area accounted for 49% of the Northeast Sea of Okhotsk total area, which was roughly 5% less than normal coverage. As cyclones more frequently arrived in the Sea of Okhotsk, ice cover has started intensively breaking up since mid-March and in the first ten-day period of April its relative square area was already 32%. For comparison, in 2019 the amount of ice cover reached its maximum of 60% in the first ten-day period of March and stayed at this level for an unusually long time — till late March – early April.

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Fig. 6. Variation of the amount of ice cover in the northeastern part of the Sea of Okhotsk in winter of 2019 and 2020 and its average for 1996–2018

Mean value of the amount of ice cover for February – March (normally this is a period of

maximum ice cover development) was 44% which is 6% less than its normal value and 10% less than in 2019 (Fig. 7).

Fig. 7. Year-to-year variation of mean amount of ice cover in February–March in the

northeastern part of the Sea of Okhotsk during 1995–2020

Therefore, ice conditions in the northeastern part of the Sea of Okhotsk during the pollock fishing season of 2020 were more favorable in comparison with 2019 and had no critical influence on fishing conditions. Key fishing areas were accessible for fishing fleet.

According to Fig. 8 showing mean monthly fields of sea surface temperature (SST) and its anomalies (aSST) in January – March 2020, maximum SST values were traditionally observed in a meridional strip extending at some distance from West Kamchatka and associated with the area of incoming relatively warm transformed oceanic waters carried by the West Kamchatka Current. Minimum SST values were registered near shore along West Kamchatka as well as in the north and west of the area under consideration – locations of intensive ice formation processes.

As for SST anomaly distribution, some locations in the area’s northern part were characterized in January by increased temperatures exceeding normal values by up to 1.0°C. This was particularly noticeable near the northwestern shore of Kamchatka and in vicinity of the Kashevarov Bank. In the area’s southern part, on the contrary, negative deviations from

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multi-year means dominated. In February, temperature conditions came back to normal and were close to their normal values, slightly deviating both to negative and positive side. An exclusion was some locations in the area’s seaward southwestern part near ice cover edge and near southwest coast of Kamchatka where more considerable negative SST anomalies were observed. In March, positive deviations from normal values noticeably dominated in the whole ice-free area, with maximum values observed in the southern part of the area under consideration.

Fig. 8. Distribution of sea surface temperature (SST) and its anomalies (aSST) in the northeastern part of the Sea of Okhotsk in January, February and March 2020

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Surface temperature variability, averaged for the northeastern part of the Sea of Okhotsk, was characterized by gradually decreasing values during calendar winter months, with a minimum in late February – early March, which is generally a normal pattern for its intra-seasonal dynamic (Fig. 9). We would like to note, against the background of winter cooling down processes, somewhat decreased rates in early January associated with higher cyclonic activities. Then, till February inclusive, cooling down rates were higher compared with their multi-year means, evidence of which was a reduction of positive values of the SST anomaly in this period and dominance of its negative values in February. After its seasonal minimum, temperature started rising more intensively than usual, which was caused, above all, by arrival of a number of warm cyclones to the Sea of Okhotsk.

Fig. 9. Intra-seasonal variation of sea surface temperature (SST) and its anomaly (aSST) in the northeastern part of the Sea of Okhotsk during December 2019 – first 10 days of April 2020

Mean SST value in January – March 2020 was -0.06°C which is 0.32°C above its multi-year

mean (Fig. 10). This is the second-highest value over the last five winters following 2019 when January and February were anomalously warm.

Fig. 10. Year-to-year variation of mean sea surface temperature in January – March in the

northeastern part of the Sea of Okhotsk in 1982–2020

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Upon summarizing hydrological and meteorological conditions and their potential effects on pollock fishery in the northeastern part of the Sea of Okhotsk, we can draw the following conclusions. In temperature terms, the winter of 2020 was warmer than usual but colder than in 2019 when unusually high surface temperatures were observed in January and February. The amount of ice cover in 2020 was by approx. 5% smaller than normal, while in 2019 it slightly exceeded its multi-year mean which is explained, first of all, by cold and icy March. The most unfavorable fishing conditions in terms of wind speed and wave height occurred on January 24–25 and March 12–15 when mean daily wind speed was 12–16 m/s and mean daily wave height was 3–5 m with an absolute maximum of 5.6 m (March 12). In comparison with 2019, mean wind speed over the season was lower and wave height, on the contrary, higher.

According to information of KamchatNIRO observers, fish length in target pollock trawl fishery in January 2020 in Kamchatka-Kuril Subzone – key fishing area in this month – varied from 28 to 60 cm, with individuals of 39–43 cm size groups dominating (53.9%) (Fig. 11). Percentage of individuals shorter than the commercial length of 35 cm (37 cm according to Smitt) averaged at 11.3%.

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Fig. 11 Pollock size distribution in commercial trawl catches in January – April 2020 in the

northern part of the Sea of Okhotsk

In West Kamchatka Subzone, fish length in January varied from 21 to 61 cm and the bulk of catches was composed of individuals 38–42 cm long (57.3%). One month later, pollock size distribution in trawl catches in Subzones 61.05.2 and 61.05.4 did not show any noticeable changes. Individuals of the same size groups were dominating. In Subzone 61.05.1, pollock 29–58 cm long was found in catches in February and individuals of size groups 37–42 cm dominated (68.4%).

Pollock length in Danish seine catches off West Kamchatka in January varied from 34 to 71 cm and catches were dominated by individuals 43–46 cm long (44.2%) with their mean length and mean weight being 45.1 cm and 0.622 kg. Mean by-catch of juveniles was 2% (Fig. 12).

Fig. 12. Pollock size distribution in Danish seiner catches in January – February 2020 in the

northern part of the Sea of Okhotsk

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Combination of the factors mentioned above affected on fishing situation and allowed to increase both maximum and average catches per unit of effort (ship day) for individual subzones, months and, in general, for the fishing season comparing to the last year. In 2019 the average catch per ship-day for the whole fishing season and for all vessels was 84.2 tons, then in 2020 it was 99.6 tons.

Additionally, the efficiency of the pollock fishery was investigated for vessels providing the maximum contribution to the total catch - BMRT of the Pulkovsky Meridian type (BATM), which operated with the most common trawl system (pelagic trawl, model 154/1120 m, project 342 EKB). It can be seen that compared with 2018–2019 catches both per day and per trawling operation increased, while the number of fishing efforts, on the contrary, decreased (Table 2).

Table 2. Multuyear dynamics of fishing efforts and average catch per effort by BATM-type trawlers during target pollock fishery (January-April) in the Sea of Okhotsk

Trawl fishery Catch, t Number of

vessel-days Number of operations

Catch per vessel/-day, t

Catch per operation, t

Mid-water trawl fishery BATM-trawler, pelagic trawl, model 154/1120 m, project 342 EKB

2016 118050 905 2511 130,4 47,0 2017 138323 1068 2987 129,5 46,3 2018 156806 1361 3628 115,2 43,2 2019 154320 1396 3872 110,5 39,9 2020 149886 1187 3401 126,3 44,1

In total, 127 ships of various types operated in the target trawl fishery during the 2020

fishing season which is the smallest number over last 10 years. As a consequence, total number of ship-days in this year was considerably smaller than in last year – 8,417 and 9,034 respectively. Despite this and primarily due to larger catches per effort, pollock yield in Season A of 2020 significantly surpassed yield in the same period of last year.

Table 3. Number of vessels engaged into target pollock fishery in the Sea of Okhotsk in season A 2011-2020

Small trawler Average trawler Large trawler Super trawlers Total 2011 — 75 77 9 161 2012 1 66 80 9 156 2013 1 56 80 9 146 2014 — 49 77 7 133 2015 — 52 71 8 131 2016 — 63 71 7 141 2017 — 65 73 7 145 2018 — 59 75 7 141 2019 — 54 74 8 136 2020 — 54 66 7 127

Summary By data of Vessel Daily Reports (VDR) contained in the FMS, pollock catch by pelagic

trawls in a commercial fishing mode in the RF EEZ (target fishery) by all ships of the flotilla totaled about 889.5 kt by April 10, 2020 (Table 1) which is more than a year before (817.2 kt). Another 25.0 kt (23.8 kt in 2019) was harvested by other fisheries, primarily the Danish seine

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fishery off West Kamchatka. Total catch in the unified Subzones 61.05.2 and 61.05.4 in January – March 2020, harvested by all fishing gear types, was 575.2 kt or nearly 51.7 kt more than in the preceding year. Total pollock catch in the Season A of 2020 was 914.0 kt (85.9% of TAC) compared with 841.1 kt (87.2% of TAC) during the same period in 2019.

In general, daily pollock catch by all vessels in the northern part of the Sea of Okhotsk during the 2020 fishing season was gradually growing, as more catchers became engaged and more fishing operations were performed: from 0.6 kt in early January to 7.6 kt in mid-January (see Fig. 4.2.1). Then, daily catch reduced to 2.9 kt by January 26 and abruptly grew to 10.6 kt by month’s end. It remained roughly on the same level till late February – approx. 9.4 kt. Then this parameter was gradually increasing and reached its maximum of 13.9 kt on March 26. Then daily catch was gradually declining and amounted to some 10.0 kt by the end of the fishing season.

Mean daily catch per fishing season was 9.1 kt (8.5 kt in last year) and mean catch per ship was 99.6 tons (84.2 tons in last year).

In total, 127 ships of various types operated in the target trawl fishery during the 2020 fishing season which is the smallest number over last 10 years. As a consequence, total number of ship-days in this year was considerably smaller than in last year – 8,417 and 9,034 respectively. Despite this and primarily due to larger catches per effort, pollock yield in Season A of 2020 significantly surpassed yield in the same period of last year.

In summary, this year’s fishing season can be assessed as successful in terms of total yield and daily catches. January and February were more productive months in comparison with last year.

The pollock stock in the northern part of the Sea of Okhotsk is currently at a high level which is confirmed by fishery results. Given that the assumed two-year-olds’ average abundance over last 10 years is 9.5 billion individuals, total pollock stock will grow to 9.7 million tons in 2020 due to full addition of medium-strength cohorts of 2013–2014 to its fishable stock biomass, while its spawning stock biomass, on the contrary, will somewhat decrease and amount to approx. 6.4 million tons.

In temperature terms, the winter of 2020 was warmer than usual but colder than in 2019 when unusually high surface temperatures were observed in January and February. The amount of ice cover in 2020 was by approx. 5% smaller than normal, while in 2019 it slightly exceeded its multi-year mean, which is explained, first of all, by cold and icy March. The most unfavorable fishing conditions in terms of wind speed and wave height occurred on January 24–25 and March 12–15 when mean daily wind speed was 12–16 m/s and mean daily wave height was 3–5 m with an absolute maximum of 5.6 m (March 12). In comparison with 2019, in the winter of 2020 mean wind speed over the season was lower and wave height, on the contrary, higher.

From the viewpoint of qualitative composition of pollock catches in the northern part of the Sea of Okhotsk, fishing conditions were generally favorable. The bulk of catches consisted of individuals 37–41 cm long belonging to medium-strength year classes of 2013–2014. Same as in last year’s fishing season, increased by-catch of pollock juveniles was observed in occasional hauls in some areas and, first of all, in the area in vicinity of the 57th parallel.

The observers of VNIRO’s Far Eastern branches have collected a large volume of fishing and biological information which is still to be processed and thoroughly analyzed. These data will be used for assessments of current and future status of the North Sea of Okhotsk pollock stock and for estimations of TAC for 2022.