COBIA (Rachycentron canadum)

This study reports the effect of different rearing densities on the growth and survival of cobiaRachycentron canadum larvae in a closed recirculating aquaculture system.198. Holt, G.J., Faulk, C.K. & Schwarz, M.H. (2007). A review of the larviculture of cobiaRachycentron canadum, a warm water marine fish. Aquaculture, 268(1-4), 181-187.Cobia Rachycentron canadum is a marine finfish species with emerging global potential formariculture. Positive culture attributes include capacity for natural and induced tank spawning,growth rates in excess of 6 kg/year, high disease resistance, high survival rates (post-larviculturestage) in tanks and net pens, adaptability to commercially available extruded diets, and high-qualityfillets suitable for the sashimi as well as white tablecloth restaurant markets. Nonetheless, cobiaproduction faces several bottlenecks limiting industrial expansion including limitations in fingerlingproduction per unit volume. This paper will provide an overview of production limitations, andfocus on recent spawning and larviculture research results and ongoing research initiatives.199. Liao, I.C., Su, H.M. & Chang, E.Y. (2001). Techniques in finfish larviculture in Taiwan.Aquaculture, 200(1-2), 1-31.Taiwan now has over 90 finfish species in which larviculture is possible. Billions of finfish fry canbe produced annually. The use of modern and advanced techniques in larviculture has won Taiwana leading position in the world. This achievement can be attributed to: (1) successful broodstockmanagement, including broodstock collection and cultivation, maturation and spawning, and eggcollection and incubation, (2) complete larval rearing using outdoor and indoor systems, and (3)establishment of techniques of live food preparation for larval feeding. Cannibalism, difficulties inwater quality control, and disease outbreak often cause mass mortality in the rearing larvae.However, the obstacles that hinder the development of larvae at their later stages are beingovercome. Through a systematic understanding of the complex behavioral patterns of finfish larvae,cannibalism can somewhat be controlled under larviculture conditions. Control strategies ofteninvolve physical manipulations such as grading and feeding adjustments. For water quality anddisease control, an indoor larval rearing system has recently been established. It adopts ozone orchlorine to disinfect fertilized eggs, the rearing water, and facilities. Additionally, utilization of thegreen water technique in rearing larvae and of ozone-disinfected recirculating water in weaninglarvae has improved the hygiene of the systems. For instance, the average survival rate in the fry ofgrouper used to be less than 0.1% until they attained a size of about 2 cm. With the improvedsystem, grouper fry grow from 3 to 10 cm with almost no mortality or viral infection, with a feedconversion rate of 0.7–0.9 and a daily weight increase rate of 4–27%. Application of live foodenrichment techniques with selected nutrients for short and long terms has proven beneficial tolarval growth. Studies determining the optimal environmental requirements of larvae have beenessential towards successful larviculture. This paper mainly discusses developments and advancedtechniques of finfish larviculture in Taiwan.200. Monroig, O., Webb, K., Ibarra-Castro, L., Holt, G.J. & Tocher, D.R. (2011). Biosynthesis oflong-chain polyunsaturated fatty acids in marine fish: Characterization of an Elovl4-like elongasefrom cobia Rachycentron canadum and activation of the pathway during early life stages.Aquaculture, 312(1-4), 145-153.Marine fish, unlike freshwater species, have been generally considered to have a limited ability tobiosynthesize long-chain polyunsaturated fatty acids (LC-PUFA) from C18 precursors due toapparent limited enzymatic activities involved in the pathway. Although LC-PUFA play importantphysiological roles throughout the entire life cycle, requirements for early life stages are especiallyhigh and provision of preformed LC-PUFA in egg lipids appears critical to support the formation ofdeveloping tissues where these compounds accumulate. No studies, however, have been conductedto explore the capability of marine fish embryos (here referring to life stages from zygote to theoesophagus opening) for de novo synthesis of the LC-PUFA required for normal growth anddevelopment. The present study aimed to investigate the activation of the LC-PUFA biosyntheticpathway during embryogenesis of the marine teleost cobia (Rachycentron canadum). First, a fattyacyl elongase with sequence similarity to mammalian elongase of very long-chain fatty acids 4(Elovl4) was isolated, and its biochemical function characterized showing that it catalyzed theproduction of very long-chain fatty acids (VLC-FA) including both saturated and polyunsaturatedfatty acids with chain lenghts ≥24 carbons. Notably, cobia Elovl4 was able to elongate 22:5n-3 to24:5n-3 and thus could play a key role in the biosynthesis of docosahexaenoic acid (22:6n-3), acritical fatty acid in neural tissues. Subsequently, the fatty acid dynamics of embryos at differentdevelopmental stages and the temporal expression patterns of target genes including elovl4, and the60