FEEDING RHYTHMS AND FOOD OF PENAEUS-JAPONICUS BATE (CRUSTACEA, PENAEIDAE) IN SALT-MARSH PONDS - ROLE OF HALOPHILIC ENTOMOFAUNA

The feeding habits of Penaeus japonicus in aestival, semi-extensive cultivation, were studied in salt marsh ponds of the French Atlantic Coast. A bi-monthly sampling programme was carried out over 3 months: on each occasion, samples were taken hourly over a 24-h period and the stomach contents of a total of 1191 shrimps were analysed. A shift from continuous to nocturnal feeding occurred during the second month of the rearing period (i.e. between 74 and 97 days after metamorphosis). In semi-extensive shrimp culture (from 10 shrimps m-2 at the beginning to 3.4 shrimps m-2 at harvesting), naturally occurring prey were the largest food source throughout the study, despite a daily supply of pellet food. Shrimps appeared to be opportunistic carnivores since they fed on all the salt marsh fauna, with a preference for halophilic insects, especially chironomids. However, a selection of prey, related to their size, was observed over the rearing period. The choice of prey shifted in the following order: zooplankton and harpacticoids (Day0-Day7) - harpacticoids (D7-D27) - chironomids (D27-D62) - macrobenthos and chironomids (D62-D86). Feeding rhythms and food preferences are discussed in relation to data obtained in similar studies. © 1990.