Feeding at different illumination levels in larvae of three marine teleost species: cod, Gadus morhua L., plaice, Pleuronectes platessa L., and turbot, Scophthalmus maximus (L.)

Abstract

Abstract. Optimal illumination levels for feeding vary in different fish larvae according to feeding strategy, prey type and habitat. Determining optimal illumination conditions is important in aquaculture, as illumination seems to be the dominating factor affecting the distribution of many pelagic fish larvae. Cod, Gadus morhua L., plaice, Pleuronectes platessa L., and turbot, Scophthalmus maximus (L.), have all been considered for aquaculture, and have different vertical positioning strategies. Three parallel groups of larvae of each of these species were exposed to planktonic feed organisms at seven illumination levels ranging from darkness to 10 800 lux. The number of ingested organisms was counted. Cod had maximal feed uptake at 1·0 lux, and higher uptake at 0·1 lux than at 87 lux. Plaice reached a threshold level at 87 lux, and turbot at 860 lux. Cod larvae, which are slowly searching dusk/ dawn predators, preferred very low illumination levels. Plaice larvae, being constant swimmers with a vertically orientated behaviour, fed equally well over a wide illumination range. The near-surface-feeding turbot larvae preferred high illumination levels.