Relation of growth to ingestion for larvae of Atlantic herring Clupea harengus and other fish

Larvae of Atlantic herring Clupea harengus were reared on wild plankton and Artemia salina nauplii in the laboratory at 7 to 9OC for 95 d. Between ages of 20 and 38 d, larvae were fed only Artemia nauplii and the specific rates of ingestion and growth were measured and compared. Relations of rate and efficiency of growth to ingestion were similar in terms of carbon and nitrogen. Growth was linearly related to ingestion (r2 = 0.89, n = 9). Starved larvae lost mass at a specific rate of 0.03 d-I (3 % d l ) until death at 14 d. A specific ingestion rate of 0.04 d 1 was required to balance defecation and metabolism. Gross growth efficiency (growth ratehngestion rate) rose from -1.2 at a low ingestion rate (0.015 d l ) to 0.4 at the greatest observed ingestion rate (0.11 d ' ) . Condition factor (dry weight length3) was significantly related to both ingestion rate and length (r2 = 0.69, n = 20). These results, combined with those for other fish larvae, indicate an asymptotic relation between rates of growth and ingestion such that gross growth efficiency is maximal (0.4) at intermediate ingestion rate. Fish larvae surviving in the sea appear to maximize their ingestion rate and thus grow rapidly but with a reduced efficiency.