The behaviour, growth, and survival of witch flounder and yellowtail flounder larvae in relation to prey availability

Rabe, Jessica (1999) The behaviour, growth, and survival of witch flounder and yellowtail flounder larvae in relation to prey availability. Masters thesis, Memorial University of Newfoundland.

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Abstract

Laboratory experiments were conducted to examine the effects of varying prey availability on the behaviour, growth, and survival of larval witch flounder (Glyptocephalus cynoglossus) and yellowtail flounder (Pleuronectes ferrugineus). The performance of larvae in relation to prey availability can provide insight into larval behavioural ecology, highlight factors that promote survival at sea, and aid in construction of appropriate feeding strategies during larviculture. In the first study, witch flounder larvae were exposed to a range of prey densities (250-16000 prey per liter) and their behaviour was recorded during feeding trials. Larvae were also reared at a range of prey densities (2000-8000 prey per liter) and their growth and survival were monitored. The foraging behaviour of witch flounder was not as affected by variation in prey availability as are other species. Larvae appear to have low prey requirements as they exhibit low foraging activity. Growth and survival of witch flounder in culture is relatively robust to changes in prey availability. The ability to forage when prey is more or less abundant may be a response to the extended larval period of this species. In the second study, yellowtail flounder larvae were reared at a constant high prey density (8000 prey per liter) and fed at high prey density at different feeding frequencies (1,2, and 4 per day). Larval behaviour, growth and survival were monitored. The consumption rate of larvae was highest in the treatments fed 1 and 2 times per day. Growth and survival of larvae fed 2 and 4 times per day were similar to that of larvae fed continuously. It is concluded that two feedings per day at high prey density is adequate for the culture of yellowtail flounder. Pulse feeding may be an efficient strategy for larval rearing.

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