Long-term mean biomass and dominant fish species in the bottom and near-bottom biotopes of Peter the Great Bay

Biomass and species composition of demersal fish in the bottom biotopes of Peter the Great Bay (Japan Sea) are considered on the data of 2428 trawl catches in 36 surveys conducted by Pacific Res. Inst. of Fisheries and Oceanography (TINRO) in 1978–2009. The most common 20 species are ranked, as the basis of ichthyocenoses, by areas of the bay. The long-term mean total biomass of fish in the bay is estimated as 75,500 t. Arabesque greenling Pleurogrammus azonus, japanese flounder Pseudopleuronectes yokohamae and saffron cod Eleginus gracilis are distinguished by the highest mean biomass. Mean density of fish distribution varied from 6.2 to 19.4 t/km2. It was the highest in the middle Ussuri Bay (13.95 t/km2; mean fish biomass in the area 18,230 t) and in the estuarine areas. Besides, the data on long-term mean biomass of benthos collected in the same trawl surveys and zooplankton sampled in 117 plankton surveys in 1988–2013 are presented.

The dynamics of the liver weight and liver indices in the course of gonad maturation of gadid species on Eastern Kamchatka

Longterm data on the liver weight, hepatosomatic (HSI) and gonadosomatic (GSI) indices of walleye pollock, Pacific cod and saffron cod are analyzed on Eastern Kamchatka in seasonal aspect and in the course of gonad maturation. Individual values of the indices extensively vary and depend on the fish body length, season and stage of gonad maturity. The dynamics of the HSI is agree to the dynamics of the GSI during the year and depending on gonad maturity. The maximum values of the HSI are typical for walleye pollock and Pacific cod individuals with the gonads of the III stage of maturity. The maximum values of the index in saffron cod are found in mature individuals with immature gonads. The minimum values are demonstrated by the fish with the gonads at the stage of final spawning or of post-spawning recovery. During the annual reproduction cycle males and females of walleye pollock and cod realize different scenarios of spending and accumulating liver fat. Whereas the maximum HSI is observed in the fish with the gonads at the III maturity stage, the minimum values in males are typical for individuals with smelting gonads, and in females – on finishing the spawn. That can be connected to possible feeding for the individual. Liver weight and liver index can increase in males just shortly after finishing spawning, in females that is found only at the stage of post-spawning recovery.

Some peculiarities of saffron cod Eleginus gracilis (Tilesius) biology and distribution on South-East Kamchatka

Analysis of Danish seine catches from the coastal waters of South-East Kamchatka has revealed all seasonal distribution of saffron cod connected to the sites of the continental sandbanks influenced by aquatic vortexes with increased benthic biomass, where the catches could reach 2.5 t/fishing operation. Based on the data of the trawl and Danish seine surveying, the stock abundance, the occurence frequency, the catches of saffron cod and the contribution into the total catch in the area mentioned increased in the fall-winter period, but could not be characterized as significant. In the period of the research (2003–2018) the Danish seine catches of saffron cod varied as 1–189 t, averaged 31.8 t. The fish in the Danish seine catches had the body length from 11 to 56 cm and the body weight from 20 to 750 г. The mean length and weight of saffron cod in summer was 30.8 cm and 241.7 g and in winter – 31.2 cm and 301.6 g respectively. Occurrence of independent reproductive groups of saffron cod in the coastal bays and on the shelf of South-East Kamchatka can be suggested based on the data of stock abundance distribution, differences in the size composition and the time of maturity.

The catch dynamics of main commercial fish species in the Far East seas

The materials on the retrospective and current catch of marine fish species in the Far Eastern region are presented. In the Far Eastern seas, from 3.0 to 3.4 million tons of LMR are captured, constituting more than 2/3 of the total Russian catch. In 2019, the catch of commercial fishes, for which the TAC is set, amounted to 2.3 million tons. The catch structure is dominated by walleye Pollock (75%), herring (11%), cod (6%), and flounder (3 %), saffron cod (2.5%). The catch of non-quota species in the region amounted to 354.6 thousand tons. The most important species in the 2019 were Japanese sardine (37%), herring (35%), mackerel (10%), gobies (8%), flounder (5%) and rays (2%). The analysis of the current state of the resource base in the Far Eastern region shows good prospects for national fishery.

Spread of seafish invasions in the northen sea of okhotsk as a factor of human infection

The results of the analysis are presented in the comparative aspect of the long-term - 1989 - 2021. - dynamics of infection of commercial fish with parasites common to humans and animals, and determination of their role in the spread of invasions among the population of the region. During this period, in marine fish – herring Clupea pallasii Valenciennes, 1847 (Clupeiformes: Clupeidae), saffron cod Eleginus gracilis, flounder Acanthopsetta nadeshnyi and smelt Osmerus mordax dentex Steindachner, 1870 – 5 types of helminthes potentially dangerous for humans have been identified, which can cause such dangerous diseases like anisacidosis, diphyllobothriasis and corynosomiasis. All fish species show high rates of invasion. Herring is infested by 97.4%, saffron cod - 55.2%, flounder - 67.5%, smelt - 58.4%. Ichthyopathological examinations isolated Anisakis simplex, Pseudoterranova decipiens, Pyramicocephalus phocarum, Diphyllobothrium sobolevi, Corynosoma strumosum. Individuals with combined invasion were registered: saffron cod Anisakis simplex, Pyramicocephalus phocarum, Corynosoma strumosum; smelt Anisakis simplex (Pseudoterranova decipiens), Diphyllobothrium sobolevi, Corynosoma strumosum. The most dangerous for humans are flounder and smelt due to the localization of helminths in the muscles.

Coastal fishes in the northwestern Okhotsk Sea (westward from 147o E): fishery and prospects of its development

Fishery at the northwestern Okhotsk Sea coast is analyzed for the period from 2000 to 2019. Pacific herring, saffron cod, pacific cod, capelin, flounders (Limanda aspera, Pleuronectes quadrituberculatus and Platichthys stellatus), and smelts (Hypomesus japonicus and Osmerus mordax) are landed in this area. The spawning herring prevails (95.2 %) in the catch. Almost all spawning herring is caught at the coast of Khabarovsky Krai. Taking into account the area of spawning grounds for herring in the lagoons of the coasta, withdrawal of this species could be increased, though actually it was decreased in the last two decades in 1.8 times, and since 2012 the herring fishery is continued in Okhotsk District only. The fishing strategy changed: offshore harvesting with stationary nets transformed to combined using of stationary and casting nets and expanded to the rivers. The catches delivery changed, as well: the herring catches are processed mostly ashore since 2008. Withdrawal of saffron cod fluctuated from 1.9 % to 186.5 % of the total available catch (TAC) volume for this species, with rapid growth in the last 5 years; its main fishing grounds shifted from the waters of Nikolayevsk District to the waters of Tugur-Chumikan District. Landings of smelt grew since 2009, too: annual catches of rainbow smelt increased from 72.2 t, on average, in 2009–2014 to 119.4 t in the last 5 years (up to 90 % of this volume was caught in Tugur-Chumikan District); landing of japanese smelt grows even faster and now exceeds 50 % of TAC. The stock of capelin was exploited weakly, annual catches of this species changed from 0.7 % to 23.3 % of TAC. Stationary and casting nets were the only fishing gears used for the capelin fishery in 2000s, but recently midwater trawls are also used. Catches of flounders had a growth tendency, though they were rather low and never exceeded 50 % of the recommended volumes. Dynamics of the pacific cod landings became positive when fishermen started to use small boats for this fishery, its annual catches increased in 2014–2019 from 69.7 to 84.8 t, the withdrawal rate achieved 9.3 % of TAC. Available fish resources in the northwestern Okhotsk Sea and technical equipment of local enterprises provide strong potential of fishery industry in this area.