ONTOGENIC DEVELOPMENT OF DIGESTIVE ENZYME-ACTIVITIES IN LARVAL WALLEYE POLLOCK, THERAGRA-CHALCOGRAMMA

Activities of digestive enzymes trypsin, amylase and lipase in laborat ory-reared walleye pollock, Theragra chalcogramma, were measured from hatching to Day 39 (just before notochord flexion) in 1993. All measur ements were conducted individually or semi-individually (groups of two larvae of the same standard length). Close relationships between dige stive enzyme activities and morphological development of digestive org ans were observed. Activities of trypsin and lipase were low during th e transition period from endogenous to exogenous energy. Amylase activ ity was constant with large variance during the same period. Specific enzyme activities of trypsin and amylase indicated high values with la rge variance during the early period. All three enzyme activities incr eased with age after the transition period, and the specific enzyme ac tivities became constant. The existence of two types of lipase was sug gested. One lipase showed a peak of specific activity at Day 4 and mig ht be related to yolk-sac absorption. The activity of the other lipase increased with age after Day 14 and might be related to digestion of prey lipid. Our results suggest that digestive enzymes included in foo d organisms supplement larval pollock digestive enzymes.