World Aquaculture December 2018

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2018 15 I n 2019, the Journal of the World Aquaculture Society (JWAS) will publish its 50th volume. For the past five decades, JWAS has represented the part of the World Aquaculture Society’s overall mission that is devoted to effective dissemination of research information directed towards contributing to the growth and development of sustainable aquaculture. The aquaculture scientific research reported in JWAS over the decades has contributed to the rapid expansion of culture methods for many new species, the development and adoption of new aquaculture technologies and to the phenomenal global growth of aquaculture industries. Through its reinvigoration efforts of the last several years, JWAS is looking to not just continue its contributions to growth and development of aquaculture worldwide but to accelerate the JWAS: 50 Years as the Journal of the World Aquaculture Society technological advancements and scientific breakthroughs that are necessary for future aquaculture growth and development. The Forward to the 1970 Proceedings of the World Mariculture Society (now the World Aquaculture Society) highlighted the purpose of the Society, to bring together professionals and fish farmers. The journal stays true to the original purpose of the Society through its focus on research that advances aquaculture production. JWAS seeks manuscripts related to all aspects of ecologically, socially and economically sustainable production of all aquatic species worldwide. Manuscripts to be considered should make substantive contributions to the aquaculture scientific literature with an emphasis on those that address critical bottlenecks, problems and issues faced by aquaculture producers. —Carole Engle, Executive Editor, JWAS T his issue’s selected article, in volume 49(5) of the Journal of the World Aquaculture Society, is titled “Nutritional contribution of biofloc to the diet of growout and broodstock of Litopenaeus vannamei determined by stable isotopes and fatty acids” by E. Magaña-Gallegos, R, González-Zúniga, G. Cuzon, M. Arevalo, E. Pacheco, M.A. J. Valenzuela, G. Gaxiola, E. Chan-Vivas, K. López-Aguiar and E. Norena-Barroso of the Universidad Nacional Autónoma de México. Under biofloc technology (BFT) conditions managed for the culture of juvenile growout and broodstock maturation of white shrimp in tanks, analysis of stable carbon and nitrogen isotopes (juveniles, broodstock and eggs) and fatty acids (broodstock and eggs) were used to provide “signatures”or “fingerprints” that identify the relative contribution of different sources of food to growth and reproductive performance. Stable isotope analysis has often been used to describe food preferences of the organisms that are components of food webs in ecological communities. Stable isotopes were calculated as the proportional deviation of the stable isotope ratios (13C/12C or 15N/14N) of samples of food sources and shrimp muscle from those of a standard. The objective was to provide information about those food resources that contribute to growth and reproduction. Additionally, a strong relationship between fatty acid composition of the food of many aquatic species and the proportional composition of fatty acids in their muscle tissue, particularly essential dietary fatty acids that cannot be metabolically synthesized, has been commonly observed. White shrimp postlarvae were grown for 12 months in outdoor 20-m 3 circular BFT tanks under constant aeration and an input C:N ratio of 20:1 that was maintained through addition of sugarcane molasses. An initial culture density of 100/m 3 was successively reduced at particular stages as the shrimp grew Recent Research Highlight from the Journal of the World Aquaculture Society larger. At the beginning of the seventh month, a daily feeding of a 35-percent crude protein formulated feed commenced and the total amount fed was equally divided into five independent feedings. Feeding rates were adjusted biweekly based on mean weight determination of samples. Biofloc samples were collected weekly and separated into different size classes for stable isotope analysis. At the end of the growth period, stable isotope analysis was also performed of samples of shrimp muscle tissue. Biofloc particles and formulated feed differed significantly in the values of carbon stable isotopes but not nitrogen stable isotopes. The stable isotope signatures of biofloc particles, formulated feed and muscle tissues of shrimp revealed that the principal nutritional sources were biofloc particles that were > 250 µm, followed by formulated feed, and then biofloc particles that ranged from >50 µm to <250 µm. Large bioflocs contained proportionately greater amounts of crude protein and lipid. The third maxillipeds of the shrimp are used to capture biofloc particles prior to ingestion. At the end of the 12-mo growout experiment, a group of shrimp was selected to serve as broodstock and stocked at 4/m 2 (1:1 male:female ratio) in a 20-m 3 outdoor tank. Adult Artemia, polychaetes, squid, mussels (20 percent of the total shrimp biomass, in equal proportion) and a semi-moist formulated feed (3 percent of the total shrimp biomass) were provided as sources of nutrition. When broodstock reached 35-40 g, they were transferred to another 20-m 3 tank in a maturation room and unilateral eyestalk ablation was effected on females. Samples of female tissue, freshly spawned eggs and different feeds were collected to determine stable isotope ratios and fatty acid composition. Principal components analysis (PCA) was used to determine the relative contribution of feeds and muscle of white ( C O N T I N U E D O N P A G E 7 2 )