Temporal variation of seasonality of egg production and the spawning biomass of Pacific anchovy, Engraulis japonicus, in the southern waters of Korea in 1983–1994
Abstract:Embryonic mortality, egg production and the spawning stock biomass of Pacific anchovy, Engraulis japonicus, off Southern Korea during 1983–1994, and their biological response to oceanographic features in spring and summer, were analysed. The instantaneous mortality rate (IMR) of embryonic stages decreased in spring and increased in summer, with a range of 0.33–1.23 day–1 in spring and 0.78–1.69 day–1 in summer. Egg production in summer was three times that during spring and production was low in the late 1980s. Mean lengths of yolk-sac larvae and adult females were greater in spring than in summer, whereas spawning fraction and spawning stock ratio (spawning biomass:adult biomass) were lower in spring than summer. Estimated mean spawning stock biomass ranged from 141 × 103 to 380 × 103 MT in spring and from 221 × 103 to 557 × 103 MT in summer. Statistically, the seasonal and long-term trends of embryonic mortality, egg production and spawning stock biomass of Pacific anchovy can be explained largely by spring warming, summer cooling and by less abundant zooplankton in the late 1980s.
Document Type: Research Article
Affiliations: 1: National Fisheries Research and Development Institute, #408–1 Shirang-Ri, Kijang-Up, Kijang-Kun, Pusan 619–902, Korea 2: South-west Fisheries Science Center, PO Box 271, La Jolla CA 92037, USA
Publication date: 2001-09-01