Some biological aspects of cod larvae (Gadus morhua L.)

Abstract

The development of functional larval stages is described in relation to different yolk sac\nstages. Morphological and histological work has been done concomitantly with the observation\non the larval feeding behaviour. Larvae were fed different sizes of phytoplankters and nauplii\nof Artemia salina. Cod larvae proved to avoid small flaggelates but were active feeders on bigger\nsized phytoplankters. The problem concerning the influence of phytoplankters on the first\nfeeding cod larvae is discussed. Cod larvae were shown to be a visual feeder on nauplii and the\nlight intensity threshold was between 0.1-0.4 lux.\n The point of no return (PNR) is tentatively determined, and the cod larval condition at that\nstage is compared to larval groups from the enclosure experiment (ELLERTSEN et al., 1979b) \nwhich had experienced different feeding conditions. The following characters were found \nsuitable for determining the condition of first feeding cod larvae: the size of the yolk sac, larval\nstandard length, dry weight, height of the myotome, the differentiation of the swim bladder\nand the alimentary tract.