|GARCIA-ORTEGA, ARMANDO - University Of Hawaii|
|STEELE, LAURA MARTINEZ - University Of Hawaii|
|GONSALVES, DENNIS - Retired ARS Employee|
|SARNOSKI, PAUL - University Of Florida|
Submitted to: Journal of Aquaculture Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2015
Publication Date: 5/18/2015
Citation: Garcia-Ortega, A., Steele, L., Gonsalves, D., Wall, M.M., Sarnoski, P.J. 2015. Use of biofuel by-product from the green algae Desmochloris sp. and diatom Nanofrustulum sp. meal in diets for nile tilapia Oreochromis niloticus. Journal of Aquaculture Engineering. 1(4):144-154.
Interpretive Summary: The aquaculture industry in Hawaii and the Pacific Basin is interested in using locally available sources for fish feeds manufacture. Fish meal is a widely used, but expensive, dietary protein source in most commercially farmed fish species. Therefore, algal by-products from the Hawaiian biofuels industry were evaluated as alternative protein ingredients in feeds for Nile tilapia. A positive effect in fish growth was observed when replacing of up to 75% of fishmeal and 100% of soybean meal by green algae by-product meal as the protein source in tilapia feeds. The nutritional composition of the harvested fish was similar for algae, fishmeal, and soybean based tilapia diets, indicating that microalgae feeds derived from local biofuel production are a potential protein source for aquaculture feeds.
Technical Abstract: Algal by-product meals from the Hawaiian biofuels industry were evaluated as protein ingredients in diets for juveniles of Nile tilapia (Oreochromis niloticus). Four experimental diets were formulated to contain 40% protein and were made with fish meal, soybean meal, whole diatom (Nanofrustulum sp.) meal, or defatted green algae (Desmochloris sp.) meal as the major protein source. A feeding experiment with juvenile tilapia of 2.6 ± < 0.0 g initial weight was done in a freshwater recirculation system with each diet treatment tested in triplicate tanks. Fish were fed the experimental diets to apparent satiation twice a day during 12 weeks and fish weight was measured every three weeks. Water temperature during the experiment was maintained at 22.7 ± 0.8 °C, salinity at 0.1 ± 0.0 ppt and dissolved oxygen at 5.6 ± 0.5 mg/L. At the end of the experiment a significant effect (P<0.05) of diet treatments was found in fish growth and feed utilization, with the best results specific to growth rate, food conversion ratio, and retained nitrogen efficiency obtained with the green-algae-based diet. The protein content in fish bodies showed no significant difference (P>0.05) among diets. Results indicate a positive effect in fish growth when replacing of up to 75% of fishmeal and 100% of soybean meal by green algae by-product meal as the protein source in Nile tilapia diets. Diatom meal also showed an interesting potential to be used as a protein source in tilapia diets.