STATE OF SETTLEMENTS, RESOURCES AND FISHERY OF GRAY MUSSEL CRENOMYTILUS GRAYANUS AT THE COAST OF PRIMORSKY REGION (JAPAN SEA)

Abstract

Current state of the mussel Crenomytilus grayanus stock in the coastal waters of Primorsky Region (Japan Sea) is considered on the base of diving surveys conducted in 2007–2018. Data on spatial distribution and abundance of the mussel were collected at the depths up to 20 m using hydrobiological methods of scuba diving, the transects were arranged taking into account the historical data on distribution of commercial bivalves. Total biomass and abundance of the mussel were calculated using the Voronoi diagrams (Thiessen polygons). In total, the data were analyzed for 3023 stations located along the entire coast of Primorye from the Tumannaya/ Tumen River mouth to Cape Zolotoy; 3263 mussels were sampled, weighted and measured. The material was processed statistically and cartographically, the average biomass and distribution density were estimated for the mussel settlements. State of the mussel population is evaluated as stable, in general: the portion of mollusks with non-commercial size exceeds 50 % in majority of settlements that indicates active natural reproduction. Comparison of these new results with the data of the 1960s, 1970s, and 1990s shows that those mussel settlements, which were not exposed to intensive fishery, preserve their spatial structure and abundance for a long time. Commercial stock of the mussel in Peter the Great Bay is estimated as 32.6 . 10 3 t that is in 1.8 times higher than the previous assessment made in the 1970s, possibly because of more detailed survey. In the area from Cape Povorotny to Cape Zolotoy, the commercial stock of Gray mussel is estimated as 1.1 . 10 3 t. Thus, more than 96 % of this species resource is concentrated in Peter the Great Bay. Good long-term prospects for C. grayanus fishery in the coastal waters of Primorye are concluded.