Acceptability of complex microencapsulated diets by striped bass ( Morone saxatilis) larvae

Abstract

The acceptability of two microencapsulated diets (casein-walled complex microcapsules, CWC, and CWC containing water and lipid soluble fractions of Artemia, MCWC) by striped bass larvae, from 7 to 21 days posthatching (DPH), was tested. These two microencapsulated diets were fed to striped bass larvae exclusively (CWC or MCWC alone, 1.1 mg/larva/day) or as partial replacement of live food, Artemia nauplii (two nauplii/ml+MCWC, 1.1 mg/larva/day). Controls were unfed larvae and larvae fed with a full ration of Artemia (five nauplii/ml) or 40% ration of Artemia (two nauplii/ml). The ingestion {(number of larvae with food items in the gut÷total number of larvae examined)×100%} of CWC and MCWC by larvae were 42% and 75%, respectively at 7 DPH, while the ingestion in groups fed with full, or 40% ration Artemia, and fed 40% Artemia plus MCWC were nearly 100% (96%–98%). On 14 DPH, the ingestion by the larvae fed CWC and MCWC increased markedly, reaching 100%. The survival of the larvae fed solely CWC and MCWC were 44% and 54% respectively, lower than the two controls fed full or 40% ration of Artemia and the group fed MCWC+40% Artemia. The survival of the later three groups ranged from 72 to 78%. All the unfed larvae died by 19 DPH. The larvae fed a full ration of Artemia had the highest mean wet weight and total length. Supplementing the group fed 40% ration Artemia with MCWC slightly improved the growth of the larvae compared to the nonsupplemented group. At the end of the experiment, larvae in that group had significantly greater wet weight gain and total length than the nonsupplemented group. The results of this study revealed that a complex-protein walled capsule is readily ingested by striped bass larvae at first feeding. Potentially, the complex-protein microencapsulated diet containing Artemia extracts can be used as partial replacement of live food. However, to achieve such a goal, study is needed to improve its nutritional quality and digestibility, in particular.