Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan .3. Paracalanus sp.

Population dynamics and production of the calanoid copepod Paracalanus sp. were studied from November 1986 to November 1987 in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan. This species was perennial, with a large abundance peak in June/July and small peaks in September/October and November/December. During a year of investigation, 15 generations could be detected. For each generation, the mean population egg production rate and the mean daily midstage abundance from NIII to CV were determined to obtain a survival curve from egg to CV. The mortality was extremely high during the early life stages: on average only 7.1% of the eggs produced might survive into NIII. This high mortality might be caused by predation by sympatric omnivorous copepods, in addition to sinking loss of eggs from the water column. The biomass of Paracalanus sp. showed marked seasonal variations largely in parallel with numerical abundance. The instantaneous growth rate of each developmental stage increased exponentially with temperature up to 20 degrees C, above which the rate was constant. The annual integrated production rate was 734 mg C m(-3) yr(-1) or 5.5 g C m(-2) yr(-1).