Relationship of the Greenland Halibut Stocks in the Okhotsk Sea With Environmental Factors

Abstract

Dynamics of the greenland halibut biomass in the fishery districts of the Okhotsk Sea (or subzones) is considered. The biomass variation in the East-Sakhalin subzone has a significant (p < 0.05) negative correlation with the number of 3+ fish in other subzones, with the time lag of 3 years (r = –0.53) and 4 years (r = –0.49), that is interpreted as alternative distribution of the halibut recruitment from the common spawning area either to this district or other ones. From other hand, the recruits abundance in other districts is significantly and positively associated (r = 0.52, p < 0.05) with the index of zonal atmosphere transfer in January and with the index of meridional atmosphere transfer in March of the years of hatching. The recruitment dependence on the spawning stock could be explained by Beaverton-Holt equation with the residuals significantly and positively (r = 0.64, p = 0.03) related with the Arctic Oscillation index. Transport of the eggs, larvae and juveniles of greenland halibut from the spawning grounds at western Kamchatka to the western Okhotsk Sea is considered as the mechanism of its recruitment distribution between the districts in relation with atmospheric indices. The transport was simulated for 1993–2017 using the circulation model JCOPE2 as the movement of 250,000 artificial passive particles, imitating eggs and larvae, with water flows at the depth 40–50 m where their main aggregations are supposed. The particles were released in the area at western Kamchatka where the maximal concentration of spawning females occurred. Number of the particles reached the sections off eastern Sakhalin and their arrival times were computed, their pathways were tracked. The portion of particles released in December and reached northern Sakhalin within 150 days changed in significant positive correlation (r = 0.44, p < 0.05) with dynamics of the halibut stock in the East-Sakhalin subzone, with the time lag 6 years. Even closer correlation (r = 0.94, p < 0.05) could be found for the optimum income of the particles released in October or November in the general additive model of the stock. Using the model results for the recent years, the greenland halibut stock decreasing in the East-Sakhalin subzone is forecasted for the next 6 years.