The effects of lowering prey density on the growth, survival and foraging behaviour of larval fat snook (Centropomus parallelus poey 1860)

Fat snook (Centropomus parallelus) is a candidate species for aquaculture, but little work has been done towards commercialization of this species. A major constraint has been the inability to obtain consistent and predictable larval survival to metamorphosis, a consequence of high mortality during the first-feeding stage. Attempts have been made to increase survival by increasing prey density to levels (30-40 prey/ml) exceeding those used for rearing most marine species (5-20 prey/ml). Our objective was to investigate the effects of lowering prey densities during larval rearing on the foraging behaviour, growth and survival of fat snook. Larvae were raised from hatch to the commencement of metamorphosis (16 days) at four prey densities: 5, 10, 20 and 30 rotifers/ml. Survival was high in all treatments, but highest (38.8%) at 5 prey/mt. Fat snook larvae were found to be visually guided predators that forage with a saltatory search pattern. In the presence of prey, fat snook larvae spent the majority of their time in the pause or non-swimming state punctuated by occasional swimming bursts usually directed towards a prey item. The range of prey densities tested did not significantly affect growth rates or survival, and there were no differences in foraging behaviours between treatments. Therefore, we recommend production scale trials at these lower rotifer densities for larval fat snook as the results of this work imply that reducing prey densities to 5 rotifers/ml during the larval period would not affect juvenile production and would be more cost effective. (C) 2004 Elsevier B.V. All rights reserved.