Morphological changes during growth and starvation of larval cod ( Gadus morhua L.) and flounder ( Platichthysflesus L.)

Abstract

The larvae of cod ( Gadus morhua L.) and flounder ( Platichthys flesus L.) were reared and morphological observations made to assess the changes in nutritional status during growth and starvation. The survival time was 16 days for starved cod larvae maintained at 6.9 ± 0.4 ( sd) °C and 13 days for starved flounder larvae at 9.5 ± 0.8 ° C. Increase in total length of starving cod and flounder surviving on their endogenous yolk reserves were 0.051 mm · day −1 and 0.112 mm · day −1 respectively. When fed on rotifers the growth rates were 0.083 mm · day −1 for cod over a 32-day period and 0.174 mm · day −1for flounder over 34-day period post-hatching. The changes in body, yolk-sac, gut and myotome height were measured every second day in both starving and fed larvae and related to the point-of-no-return (PNR, when 50% of the larvae, although still alive, are no longer strong enough to feed). The ratios of gut height: myotome height, of eye: head height and of total length: body height, as well as the pectoral angle (the angle of the ventral surface of the body at the insertion of the pectoral fin), could all be used to assess the state of starvation of the larvae. Shrinkage in formalin averaged 8–12%.