Feeding resumption, morphological changes and mortality during starvation in Japanese flounder larvae

Abstract

Japanese flounder Paralichthys olivaceus larvae established first feeding 3 days after hatching (DAH) at c. 17° C. Non‐fed fish reached irreversible starvation at age 5 DAH. Non‐fed fish showed similar feeding rate and feeding intensity as the fed fish when they were provided with prey before 5 DAH, after which the starved larvae did not feed even when prey became available. None of the six morphological measurements examined (total length, body height, eye height, head height, gut height and myotome height) showed significant differences between the non‐fed and fed larvae until 5 DAH. Normal development continued only in the fed group, and the non‐fed larvae showed reverse growth or body collapse after 5 DAH. Owing to the shrinkage and collapse at the top of head due to starvation, head height could be a sensitive indicator of starvation in Japanese flounder larvae. In the fed treatments, high mortality occurred from first feeding (3 DAH) to irreversible starvation (5 DAH), accounting for about two‐thirds to three‐quarters of the overall mortality (46–52%) throughout the experiments. This mortality was not prey density or larval density dependent. Mortality during the same period in the non‐fed larvae accounted for about a third of the overall mortality (100%).