Feeding of Plaice (Pleuronectes Platessa L.) and COD (Gadus Morhua L.) Larvae

Abstract

Phytoplankton could be a necessary source of nourishment for young cod larvae, since in an initial investigation the guts of 6 out of a sample of 15 Lofoten cod larvae, just beyond the yolk-sac stage, contained Peridinium pellucidum and Coscinodiscus sp. Because of lack of cultivated phytoplankton, Chlamydomonas sp., Saccharomyces cerevisiae and trout food were given to plaice and cod larvae by means of Anemia nauplii pre-fed on this nutrient. Of the successfully reared plaice, a high proportion (97%) were normally pigmented when given pre-fed nauplii. A few hundred 3 months old surviving cod larvae, measuring about 12 mm died when being separated from Anemia nauplii in the tanks.

To avoid harmful cleaning operations, plaice and cod larvae were given freeze-dried food particles (10–200 μ), based on (1) Calanus finmarchicus, (2) non-fertilized and (3) 5 days incubated cod eggs. Surplus particles were expected to dissolve and disappear. None of the food types were as clearly visible in water as granules of yolk of hardboiled hen egg, which at initial feeding were taken by 95% of cod larvae in 90 minutes. Types (1) and (2), taken by 40 and 27% of the larvae respectively, formed deposits in the tanks. Type (3), almost invisible in water and possibly not taken regularly, formed no deposits. The stale deposits were eaten by the larvae. This fact could be one reason why no cod larvae survived unfed larvae longer than 24 days.