EVALUATION OF GROWTH PERFORMANCE, CONDITION INDICES AND BODY COMPOSITION OF JUVENILE RED DRUM Sciaenops ocellatus FED FISHMEAL- AND FISH OIL-FREE DIETS

Global increases in aquaculture production has led to heightened demand and increasing costs of fishmeal and fish oil products for use in the diets of highly carnivorous fish species, such as the red drum. Therefore, viable alternative protein and lipid sources are needed to substantially replace fishmeal and fish oil in commercial diets. In the current study, a commercial reference diet containing 51% crude protein (CP) on a dry-matter basis and six isonitrogenous (50% CP) experimental diets that completely replaced menhaden fishmeal and/or menhaden fish oil were evaluated with juvenile red drum.  The experimental control diet (Diet 2) contained menhaden fishmeal  at 28.3%  of dry  weight  and 6.5 % menhaden fish oil. Diet 3 had all of the menhaden fishmeal replaced with a combination of peptide product MrFeed Pro50S, poultry by-product meal and soy protein concentrate but contained menhad en fish oil at 7.7% of dry weight .  All other  experimental diets were isolipidic (13% crude lipid) and contained no fishmeal or fish oil which was replaced by  various combinations of canola, flax, and algal oils.

In the comparative feeding trial, groups of 15 fish (~4.4 g/fish initial weight) were stocked in 28, 38-L aquaria fashioned as a recirculating aquaculture system with quadruplicate aquaria randomly assigned  to  each diet and  fed  for an 8-week duration. At the end of the trial, juvenile red drum fed the commercial reference diet exhibited significantly (P<0.05) reduced percentage weight gain, fillet yield, feed efficiency (FE), protein conversion efficiency (PCE), and survival compared to fish fed  all  experimental diets as analyzed by one-way ANOVA (Figure 1).  Red drum fed the six experimental diets did not show any significant differences in any growth parameters. Fish fed the commercial reference diet also showed significantly (P<0.05) higher viscerosomatic indices, including hepatosomatic index (HSI) and intraperitoneal fat (IPF) ratio than fish fed most experimental diets that replaced fishmeal and/or fish oil. Whole-body proximate analysis revealed no significant differences in crude protein content; however, red drum fed the  commercial diet had a significantly higher ash and lower whole-body  lipid composition than fish fed all other diets. The current study provides evidence that juvenile red drum can be successfully raised using practical diets devoid of fishmeal and fish oil.