Digestive Enzyme Activities in Striped Bass from First Feeding through Larva Development

Abstract

Growth and activities of the digestive enzymes trypsin, chymotrypsin, carboxypeptidase A, α-amylase, and pepsin in striped bass Morone saxatilis were measured from the day before the fish first accepted food (day 4) to near the end of larva development (day 32). Fish were fed either live brine shrimp nauplii Artemia sp. (BSN), heat-killed BSN, or a prepared diet designed to be nutritionally complete with satisfactory physical and palatability properties. The larvae consumed the prepared diet but did not grow and all larvae fed this diet died soon after day 16. Larvae fed live or heat-killed BSN grew satisfactorily but growth of fish fed live BSN was faster (P < 0.05). With the exception of pepsin, which was not found until day 16, all of the measured enzymes were present in the digestive tract at the time of first feeding and activities of these enzymes were 25 to 60% of those at day 32, For the first 12 d, specific activity of the enzymes was not influenced by growth or diet. Near day 16, enzyme activities decreased for all diet groups but after day 16 enzyme activities increased with growth rate. These results suggest that lack of growth by fish fed the prepared diet was caused not by inactivity of digestive enzymes but possibly by deficiency of growth factors supplied in living or heat-killed BSN.