Understanding the factors limiting copepod productivity in dense cultures is a prerequisite for the partial or entire replacement of Artemia and rotifers as live feed for finfish larvae. In dense cultures, high encounter rates between individuals may increase stress, cannibalism incidents and potentially trigger resting egg production.We conducted an experiment to evaluate the potential egg production and egg quality of Acartia tonsa stocked at densities ranging from 10 to >5000 ind. L À1 . Egg Production (EP), Delayed Hatching Eggs production (DHE), hatching success (HS), egg mortality and water quality were used as end points. In the present system, A. tonsa was raised at >5000 ind. L À1 without affecting the mortality, confirming that attaining this high density in culture is possible. However, egg harvest reached an optimum of 12 000 egg L À1 day À1 at~2500 ind. L À1 indicating that increasing stocking density above this level is not of practical interest. Calculations showed that the loss in egg harvest at stocking densities <2500 ind. L À1 is of 1.3% for every additional 100 adult copepods L À1 . The increasing adult density did not affected the proportion of DHE produced (~10% of harvest) but decreased significantly the HS, though not to a point that would be problematic in a commercial production.Understanding the biology of copepods when stocked at high density is important to improve copepod culture systems and increase egg harvest yields. Technical solutions such as the continuous separation of eggs from adults in the water column, recirculation and the continuous provision of food are seen as potential solutions.

Studies on the behavior of copepods require both an appropriate experimental design and the means to perform objectively verifiable numerical analysis. Despite the growing number of publications on copepod behavior, it has been difficult to compare these studies. In this study, we studied two species of copepods, Eurytemora affinis and Pseudodiaptomus annandalei, and employed recently developed scaling and non-scaling methodology to investigate the effects of density and volume on the swimming behavior of individual organisms in still water. We also compared the results of two-and three-dimensional projections of the swimming tracks. A combination of scale-dependent and scale-independent analysis was found to characterize a number of behavioral observations very effectively. We discovered that (i) density has no effect except to increase the time spent in the swimming state of ''breaking'', (ii) smaller volumes resulted in more complex trajectories, and larger volumes, like density, increased the time spent in the swimming state ''breaking'', and (iii) three-dimensional projections gave a more accurate estimation of speed and the time spent cruising. When only a vertical 2D projection was used, ''cruising'' could be confused with ''sinking''. These results indicate that both experimental conditions and the selection of 2D or 3D projection have important implications regarding the study of copepod behavior. The development of standardized procedures with which to compare the observations made in different studies is an issue of particular urgency.