Results of spawning salmon monitoring in Sakhalin in 2010
Every year SakhNIRO scientists monitor dynamics of pink and chum salmon catches and their biological indices in main fishing and reproduction areas. In 2010 stock surveys covered all the salmon fishing areas in Sakhalin and South Kuriles. According to the decision of the Commission on Regulation of Anadromous Fisheries, regular data collection has been organized from 17 (out of more than 400) fishing seines. Besides, as part of cooperation with the fishermen samples have also been collected on other coastal sites.
In the season 2010 scientists have analyzed more than 8000 pinks and 4500 chums from marine fixed seines and stock registration barriers in the river mouths. The scientists have monitored the sex structure of the stock, fish length and weight and absolute fertility of females. Such data analysis in combination with catch dynamics helps estimate the time periods of runs and ratio of various fish groups in catches which are of the greatest importance for online regulation of salmon fishery.
In particular, in the southwest Sakhalin the rise of local stock of pink salmon from the Sea of Japan has encouraged a shift of main catches to earlier period and record strong runs into the rivers. Actual catches exceeded the most optimistic forecasts 4.2 times, the forecasts based on calculations with the use of maximum recruitment rate. The scientists continued observations of fish runs even in the period of introduction of the temporary fishery ban and that enabled them to raise the recommended catch of potential pink salmon catch.
In the waters of East Sakhalin, judging by the catch dynamics, emergence of large size males and change of sex structure, the migration runs of pink salmon have been dominated by late form of the species. Taking into account the above mentioned data the scientists have developed comparably precise forecasts on fish runs, according to which the preliminary recommended potential salmon harvest for East Sakhalin of 42,400 tonnes has been increased by 13,000 tonnes.
In the South Kuriles the bulk of the pink salmon catches (namely more than 90%) originates from Iturup. As to the stock level, the forecast has turned true with 28,700 tonnes harvested out of the recommended 29,600 tonnes, while the shift of catches to later time periods have even exceeded the expectations: due to a dramatic decline in runs of younger pink salmon the fishery actually began only in first ten days of August with running fish being of late form.
In general, despite the weak even year, the salmon fishery has been a success with the fleets based on the islands catching more than 100,000 tonnes of pink and chum salmons.