Dynamics of exploited populations of the calanoid copepod, Acartia tsuensis

Abstract

Cultures of the marine calanoid copepod, Acartia tsuensis, grown in 24-m 3 outdoor tanks and 25-l containers in the laboratory, were harvested at exploitation rates of 0 to 50% of the total population per day. The results showed that when chlorophyll a concentration is maintained at about 10 μg/l, the copepod can withstand an exploitation rate of up to 30%/day, forming cohorts and repeating its life cycle to yield a daily harvest of about 30 μg (dry)/l. The ability of A. tsuensis to resist a declining population under high rates of exploitation is considered to be related to some or all of the following mechanisms which will be at work under low population densities: (1) decrease of mortality; (2) decline of predation on nauplii by copepodids; (3) accelerated recruitment to spawning age owing to accelerated growth; (4) increase of fecundity not associated with increase in body size of adult females; (5) increase of fecundity due to increase in body size of adult females. The present study seems to verify the suitability of A. tsuensis as an organism for mass culturing as a food of marine fish larvae and juveniles.