Dynamics of stock for yesso scallop Mizuhopecten yessoensis (Jay, 1856) in the northwestern Tatar Strait from the beginning of its fishery to nowadays

Abstract

Settlements of yesso scallop Mizuhopecten yessoensis in the northwestern Tatar Strait (within the waters of Khabarovsk Region) are considered on the data of scuba (< 20 m depth) and dredge (> 20 m depth) surveys conducted in 2001–2018. To 2018, only two settlements remain in this area from 9–12 ones in 2010–2014; both remained settlements have no commercial value. Trend to decreasing of the settlements density is shown: the mean density was 3.0 ind./m2 in 2001, 0.20 ind./m2 in 2010, and 0.0005 ind./m2 in 2018. Commercially valuable scallops with the shell height > 120 mm prevailed in the settlements (86–100 %), whereas juveniles were rare or absent (1.6 %, on average) in all years of surveys. CPUE decreased from 200 kg/diver/hour in 2001–2003 to 10 kg/diver/hour in 2018. These changes are obviously reasoned by overexploitation of the population using dredging and scuba gathering. Total commercial stock of yesso scallop dropped to the minimal value in 2018: 200 t, that was in 4.5 times lower than the established limit. Thus, 5 years ban is established for M. yessoensis landing in the area.