Body size and egg production in the marine copepod Acartia hudsonica during a winter‐spring diatom bloom in Narragansett Bay

Abstract

Seasonal changes in size and egg production in the copepod Acartia hudsonica were investigated during the 1984 winter–spring bloom in Narragansett. Bay. Possible food limitation was investigated through comparisons of short‐term weight change and egg production rate in copepods incubated in ambient Narragansett Bay water and in bay water enriched with cultured algae. A preliminary experiment showed that egg production responded in <24 h to a change in food availability at 4°C—the coldest experimental temperature. Food was not limiting in February–April, but mild food limitation developed in May–June, affecting body weight more than egg production. These results contrast with strong food limitation of the summer dominant, Acartia tonsa. Empirical regressions describe relationships between A. hudsonica length and weight, and egg production in relation to temperature, weight, and field Chl a.A separate study suggested that A. hudsonica adults were dominated by changing age groups during the winter–spring period. Present results indicate that the adult age distribution affects mean body weight, condition factor, and egg production rate, especially in April and May when the autumn‐hatched, overwintering copepods are being replaced by newly matured, winter–spring hatched adults.