Effect of stocking density and algal concentration on production parameters of calanoid copepod Acartia bilobata

Abstract

The present study investigated the effect of initial adult stocking densities and algal concentrations on production parameters of calanoid copepod, Acartia bilobata. Experiments were in triplicate with seven initial stocking densities (125, 250, 500, 1000, 2000, 4000, and 8000 adult copepods L−1) fed at three different concentrations (0.5, 1 and 5 ×105 cells mL−1) of Isochrysis galbana. Various production parameters; egg and nauplii production, egg hatching success, adult survival, and sex ratio were estimated. Individual egg production (IEP) increased from day one to five in all the groups irrespective of stocking densities and algal concentrations. IEP decreased significantly (p < 0.05) on day 1 from 9.61 ± 0.79–0.17 ± 0.05 eggs female−1day−1, and on day 5 from 13.44 ± 2.94–2.99 ± 0.58 eggs female−1day−1 with increase in stocking density from 125 to 8000 adult copepods L−1 respectively; however, an increase was noted as algal concentration increased. Total accumulated egg production increased upto the density of 1000 adults L−1, with 33945.02 ± 1556.43 eggs L−1 at highest algal concentration, and thereafter declined at higher densities. Synergistic effect of stocking density and algal concentration significantly impacted 16 and 24 h hatching success. Copepod adult survival decreased significantly from 71% to 78% (125 adult copepods L−1) to 2–10% (8000 adult copepods L−1) with increase in stocking density. It is concluded that moderate stocking density of 1000 adults L−1 with highest algal concentration (5 × 105 cells mL−1) is optimum for higher reproductive performance (egg production and hatching success) of A. bilobata. Present study provides baseline information for A. bilobata commercial mass production for use in hatcheries.