The effects of lowering prey
density on the growth, survival and foraging behaviour of larval fat snook (Centropomus
parallelus poey 1860)
S. Temple, V.R. Cerqueira, J.A. Brown-2004
Aquaculture, 233(1-4): 205-217
Abstract:
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/ml. 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.
(Department of Biology, University of Victoria,
Victoria, British Columbia, Canada, e-mail of J.A. Brown: jabrown@mun.ca)