Variations in Egg Production Rates by Pseudocalanus Spp. In a Subarctic Alaskan Bay During the Onset of Feeding by Larval Fish

Weekly estimates of female abundance and daily egg production rates were made for Pseudocalanusspp. during 1987 and 1988 in Auke Bay, southeastern Alaska. The sampling, which included measurements in primary production, was done during April and May when larval fish initiate feeding on copepod nauplii. The objective of the study was to examine the relative importance of female abundance and daily egg production rates for Pseudocalanus spp. in determining production of nauplii during the study period. In both years primary production rates exceeded 500 mg C·m―2·d―1. At this level of primary production Pseudocalanus spp. should not have been food-limited in either year. The average egg production rates per individual female during the 2 years were identical: 2.6 eggs·female―1· d―1. The average populations of female Pseudocalanus were 4,765 and 7,656 individuals·m―2 in 1987 and 1988, respectively. The larger populations of female Pseudocalanus spp. in 1988 resulted in higher overall egg production and better feeding conditions for larval fish. Thus, during the period when larval pollock began feeding on nauplii, female copepod abundance was more important than temporal differences in egg production rates in determining production of nauplii. A complete understanding of the copepod-larval fish relationship in Auke Bay will require explanation of the causes for interannual variability in abundance of adult female Pseudocalanus spp.