Seasonal changes in feeding rate, digestive enzyme activity, and assimilation efficiency of Calanus pacificus

Abstract

ABSTRACT. The feeding behavior of the marine calanoid copepod Calanus pacificus was investigated during the winter/spring transition in Puget Sound, Washington. USA. Maximum ingestion rate (I,,,), maximum clearance rate (F,,,,), and digestive enzyme activity were determined during spring and fall 1982, and the same measures plus assimilation efficiency were determined during spring 1984. Maximal feeding rates and digestive enzyme activity increased concurrently with the onset of the spring bloom in 1982. In 1984 feeding rates and digestive enzyme activity were already fully developed at the start of the sampling period, apparently due to an unusually early bloom in Puget Sound. Once developed, digestive enzyme activlty remained high even during periods when maxinlal feeding rates were deching. Assimilation efficiencies also were found to be relatively constant during the 1984 sampling. tion