Laboratory study of the effect of light on the emergence behaviour of eight species of commercially important adult penaeid prawns

Abstract

The emergence behaviour of eight species of commercial prawns (between 25.0 and 30.0 mm carapace length) was studied in the laboratory. All except Penaeus merguiensis were nocturnal: they emerged from the substratum in the evening when the light was dimmed and buried themselves in the morning, usually before dawn. P. merguiensis generally remained on the substratum during the day. The species can be grouped on the basis of their behaviour: the first group (P. plebejus and P. latisulcatus) was most sensitive to light, the second group (P. semisulcatus, Metapenaeus ensis, P. esculentus, M. endeavouri and M. bennettae) was less sensitive to light, and the third (P. merguiensis) was least sensitive to light. To find out what triggered emergence, two species (P. esculentus and P. plebejus) were exposed to different rates of light dimming at dusk. Both species responded to absolute light intensity, but the response of P. plebejus was affected by the rate of change of light intensity. The different responses of the species to different light intensities explains some of the differences in catchability in a multi-species prawn fishery.