Rearing cohorts of Calanus finmarchicus (Gunnerus) in mesocosms

Abstract

Cohort development and nutritional conditions of Calanus finmarchicus were studied in experimental seawater mesocosms in a Norwegian fjord. Artificially added cohorts developed from early naupliar stages to copepodite stage IV in 41–43 days at ambient temperature increasing from 4.3 to 6.8°C. A natural stock of C. finmarchicus, initially dominated by early copepodite stages, developed to CV, males and females. Total storage lipid increased exponentially until CV. Individual body carbon weight increased sigmoidally with age. Relationship of body carbon weight (W, μg) to prosome length (L, μm) determined for copepodites and adults (W=2.6×10−10L3.45, r2=0.92) showed a higher weight than from in situ studies. This investigation demonstrates (i) that cohorts of C. finmarchicus can be reared successfully in mesocosms, (ii) a good nutritional state of copepods in terms of body carbon content and lipid reserves, and (iii) that part of the final CV moulted to both males and females.