COBIA (Rachycentron canadum)

enefit the rural poor, whereas offshore mariculture is currently restricted to corporateinitiatives which have the capacity for large capital investment, import of technology andassumption of significant risks. Individual offshore farmer ownership and operation in the tropicsis therefore still a substantial socioeconomic challenge due to the large initial investment required.While the warm climate regime between the tropics of Cancer and Capricorn offers numerousadvantages and potential for the cultivation of various marketable species, these are different to thespecies reared in temperate offshore farms. Whereas this may appear to be a trivial point, it isessential to note that the high cost and capital investment involved in offshore mariculture dictatesthe production of high-value species intended for export to the rich developed world. Mostoffshore projects have thus, focused on high-value predator species such as cobia, snapper,amberjack, seabream, red drum, pacific threadfin, seabass and tuna.125. Beltrán-Rodríguez, D.M. (2008). Spatio-temporal variation in organic nitrogen and carbon insediments associated with tropical submerged cage aquaculture. University of Puerto Rico,Mayaguez Campus. (M.Sc. dissertation). 94pp.The diminution of marine fish populations due to over-fishing has stimulated the increase ofmariculture activities, including in cages located near the coast. However, these activities may bedetrimental influence to marine sediments near the culture sites in coastal sites. The first openoceanmariculture operation began during 2002 south of Culebra Island, Puerto Rico to culture thefish Rachycentron canadum and Lutjanus analis. The purpose of this study was to evaluate theconcentrations of total organic nitrogen (TON), total carbon (TC), and organic matter (OM) inmarine sediments near the mariculture site to determine the spatial and temporal dynamics of thesenutrients during the first culture period. Results indicate significant differences in the concentrationof TON between the cage and control sites. The L. analis cage had a higher mean concentration ofTON (0.442 mg N/g) than the R. canadum cage (0.380 mg N/g) and control site (0.300 mg N/g). TCand OM mean concentrations were not significantly different; however, mean TC concentrationshad fluctuations similar to those of the mean TON concentrations. TON and TC meanconcentrations were significantly different over time, with an increase in the mean TON (0.66 mgN/g) and TC (199 mg C/g) concentrations from April 2003 to August 2003, with a peak in June2003, which agreed with the increase in the mean monthly feed input at the culture site (12,947 kg)and the increase of wastes because the fish had reached a commercial weight (4.5 kg). Harvestingbegan in June 2003, so numbers of fish decreased during subsequent months. Organic matterdecreased during June, but peaked during October 2003. Although the increase of the nutrientconcentration is relatively low compared with other studies, data represent only the first year ofmariculture activity. As the company increases the number of cages, this site should be monitoredto determine possible increases in nutrient concentrations in the sediments.126. Benetti, D.D., O'Hanlon, B., Ayvazian, J., Orhun, M.R., Rivera, J.A., Rice, P.H. & Doulliet, P.(2003). Advances in hatchery and growout technology of cobia (Rachycentron canadum) and othercandidate species for offshore aquaculture. International Sustainable Marine Fish CultureConference, Fort Pierce, FL (USA), 9-10 Oct. 2003, 13.Hatchery and growout technology for the reliable production of cobia (Rachycentron canadum) andother candidate species for offshore aquaculture are discussed in this paper. Most recently, we havebeen working towards the development of sustainable microbial management in live feeds andlarval rearing tanks, including disinfection methods and the use of probiotic bacteria. The strategy isto out-compete contaminant, pathogenic microbes by "competitive exclusion", increasingdigestibility and boosting the immune system of the larvae, thus avoiding the need for antibiotictreatments to prevent and control disease outbreaks. Strains have been selected based on researchconducted with red drum (Sciaenops ocellatus) larvae and tilapia (Oreochromis sp.) juveniles, aswell as with cultures of rotifers (Brachionus sp.) and Artemia nauplii. The selection had been basedon antagonistic properties towards bacteria pathogenic to fish such as Vibrio sp., enhancement ofdigestion and food conversion efficiency, and enhancement of overall growth and survival. Bothcobia and mutton snapper exhibit very good potential for commercial aquaculture development innet cages in the SE U.S. and the Caribbean. Cobia exhibits extraordinary rates of development andgrowth. During Snapperfarm's demonstration project off Culebra Is., Puerto Rico, cobia grew to anaverage of 6.03 kg (SD=2.4; CV=39%) or 13.3 lb in one year, ranging in size from 1.7-9.1 kg (4-20lb). Estimated survival rate is > 95%, and feed conversion rates (FCR) is 1:1. However, accuratefinal values will only be known once all fish are harvested. Snapperfarm has been harvesting 500-1000 kg of cobia per week (1,000-2,000 lb/week). Fish are being shipped to the continental U.S.,where they are being sold fresh for US$ 8/kg to the high-end market. Thus far, no noticeable37