EFFECTS OF GRADED LEVELS OF DIETARY SOYBEAN MEAL INCLUSION ON GROWTH OF COBIA Rachycentron canadum

The demand for quality seafood continues to increase while production from natural fisheries have stabilized over the last few decades requiring aquaculture to increase in production to meet this increased demand.  Aquaculture raised fish are typically fed diets high in fishmeal as its primary protein sources which are harvested from these wild fisheries.  Research utilizing alternative protein sources are being implemented for many aquaculture species both to ensure sustainability of these wild fisheries as well as to allow producers efficient and cost-effective choices for fish feeds.  Cobia is considered a great candidate for aquaculture by scientific and industry professionals due to its high growth rates and excellent flesh.  Cobia are an upper trophic level carnivore requiring moderate levels of crude protein typically obtained from fish meal.  This research uses graded levels of soybean meal (SBM) to determine inclusion levels which optimize growth and feed conversion in cobia. A natural diet was used as a positive control of optimum growth to compare to pelleted diets.  

A 12-week feeding study was conducted on juvenile (initial mean weight, 93.3 g) cobia utilizing four experimental pelleted diets: a 0% SBM control diet, a 10% SBM, a 20% SBM, a 40% SBM,.  Fish (n=20) were held in fifteen 1,500 L recirculating tanks, with three randomly assigned replicate tanks per diet, and fed twice daily to satiation.  Weight gain, feed conversion ratios (FCR), standard growth rate (SGR) and intestinal morphology were compared between treatments at the conclusion of the trial to determine effects from increased SBM.  Growth rates were not statistically different between treatments suggesting diets including up to 40% protein replaced by soybeans are viable options for cobia diets. Growth rates of cobia fed pelleted diets were comparable to natural diets.