Journal of The School of Marine Science and Technology,Vol.8 No.2
Abundance estimation of Sergestid shrimp Sergia lucens of 1998-2007
year classes in Suruga Bay
Takuya SAKUMA, Atsushi FUKUI, Tatsuya HOSHO and Itsuro UOTANI
Abstract
Stock abundances of 1998-2007 year classes of Sergestid shrimp in Suruga Bay were estimated by virtual
population analysis using the length frequency and catch data. The number (N1) and biomass (B1) at recruit of each
year class were estimated to be 46.1-119.2 (mean ± SD 82.6± 23.7) x 108 individuals and 801-2,577 (1,888± 585)
t, respectively. The numbers at recruit (N1) were about 1/40-1/3 of 1961-1965 year classes. The reproduction rate
(N1/N4 and B1/B4, where N4 and B4 indicate the number and biomass, respectively, of the previous year class) were
correlated with the average water temperatures during the spawning season, the rates tended to increase as the
average water temperatures become higher during the spawning season. Accordingly, the water temperatures
affected the survivals of the eggs and larvae. The poor catches of the autumn fishing of 2004 year resulted from the
following causes: (1) delayed recruit of age 0 cohort (2004 year class) due to large-meander of the Kuroshio path
and (2) smaller abundance of age 1 cohort (2003 year class).