February 15-18, 2009 Washington State Convention Center Seattle ...

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ASSESSMENT OF GROWTH AND SURVIVAL ON LARVAL COMMON SNOOK, Centropomus
undecimalis, FED ROTIFERS ENRICHED WITH ARACHIDONIC ACID
Matthew J Resley*, Nicole Rhody and Kevan Main
Mote Marine Laboratory
Center for Aquaculture Research and Development
Sarasota, Florida 34236 USA
resleymj@mote.org
Efforts to develop the culture technology for common snook (Centropomus undecimalis) have been ongoing for more than 20
years. Populations of this popular sportfish have been declining due to human influences. Because of their decreasing population
size research is underway to evaluate the potential to increase their populations using stock enhancement. Though there
have been some successes in producing this species for stock enhancement, rearing technology for common snook is still in its
infancy. Currently at Mote Marine Laboratory we are trying to increase culture efficiency and technology with work on captive
broodstock, and larval and juvenile rearing practices. Preliminary data from other studies at our facility revealed a possible
deficiency in arachidonic acid (ARA) in the captive broodstock and subsequently their eggs. This essential fatty acid plays an
important role in development and could be important through the larval phase. This project was set up to assess whether ARA
enrichment of rotifers can increase growth and survival of snook larvae.
The control treatment was our standard protocol for rotifer enrichment. The control enrichment used was Algamac 3050 tm and
protocols were obtained from the manufacturer (0.2 g/L of enrichment for 12 hr). The two experimental enrichments utilized
Algamac-ARA tm . The two treatments were a 10 and 20% replacement of the Algamac 3050. The 10% replacement was the
manufacturers suggested replacement, and the 20% replacement was used to evaluate higher levels of ARA in the larval feed.
Rotifers were harvested from the continuous culture system on site one day before feeding. They were held in 18 L PVC buckets,
where they were enriched. Three samples of enriched rotifers were also obtained from each treatment for lipid analysis.
Rotifers were maintained at 5/ml throughout the study. The study was initiated when larvae were 3 days post-hatch (day 1 of
the study).
Larvae for this experiment were obtained from captively held broodstock at Mote Aquaculture Park in Sarasota, Florida. Larvae,
1 DPH, were stocked into 12 100-L black conical experimental tanks at a density of 100 larvae per liter. To assess larval
survival from the tank stocking, six 1 L beakers were stocked with 20 larvae each, and survival was recorded the day following
the move. The remaining larvae were left in hatchers to be sampled two days later for initial larval measurements; standard
length, mean dry weight, and fatty acid profiles. There were 20 larvae removed for standard length, 50 for dry weight measurements,
and 3 x 200 for lipid analysis. Dry weights were obtained by rinsing the larvae with DI, and placed in a drying oven
at 60°C for 24hr. The larvae sampled for the lipid analysis were rinsed as described above for weighing, and placed in glass
vials and stored in a -80°C freezer. This procedure was repeated at day 7 (midpoint) and day 15 (end of study), with fish being
removed from each tank. Remaining fish at the end of the study were sieved and counted to assess tank survival.