Effects of stocking density on egg production, survival and growth of the planktonic copepod Acartia tonsa (Dana)
The use of copepods in the larviculture of fish and crustaceans has been suggested as an alternative solution to the use of Artemia, mainly due to its high nutritional value. However, the lack of cultivation methods that allow its large-scale production, still limits its application in aquaculture. In this study, the effects of stocking density on the production of nauplii, survival and growth of the planktonic copepod Acartia tonsa were evaluated with the aim of optimizing large-scale crops. For egg production, densities of 50, 100, 200, 400 and 800 L-1 copepods were evaluated. Copepods were grown in 250 mL flasks, with S = 33 ups, T = 25 ° C, fed with Thalassiosira fluviatillis and acclimated to a 12C: 12E photoperiod.To test the possible effects of storage on the survival and growth of nauplii and copepodids of A. tonsa, densities of 1,000, 2,500, 5,000, 10,000 and 20,000 L-1 copepods were used. During the experiment, copepods were kept in 2.5 L flasks, with S = 34 ups, T = 25 ° C, and fed in excess with the micro algae Isochrisis galbana and T. fluviatillis. Regarding the production of nauplii, it can be seen that the reproductive potential of A tonsa was affected in the density of 800 L-1 copepods, as there was a significant reduction in the production of female eggs-1 day -1. Survival between different treatments was not significantly affected by stocking density, however copepods grown at densities of 10,000 and 20,000 L-1 copepods, grew less,with a delay in the phase shift from nauplius to copepodite. The reduction in reproductive potential, growth and development of copepods grown at high densities may be related to factors dependent on stocking density, such as water quality, physical stress and available food. In intensive cultivation systems, the stocking density of 400 L-1 copepods would allow the production of relatively high amounts of A. tonsa, without affecting the copepods' reproductive potential. The use of a storage density of 5,000 copepods L-1, in the growth tanks of A. tonsa, would allow obtaining live food in high quantity and of adequate size for use in the larviculture of shrimp and marine fish.