WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 67 Food security has become one of the major concerns of governments around the world as the human population rapidly expands. Food security is getting higher priority in this era of revolutionary information technology. Near saturated agriculture and livestock production sectors are struggling to meet the requirements of a growing population, especially for higher quality and cheaper sources of protein. Aquaculture is considered to be a promising potential production sector for high-protein food. In effect, aquaculture must share social responsibilities with agriculture because it is a rising sector in global food production. Blooming global aquaculture can go hand in hand with agriculture to aid in the mission of attaining food security. Aquaculture can be a food production sector for the poor because fish protein can be less expensive than other animal protein sources. However, the dependency of fed aquaculture on costly ingredients reduces its economic viability and limits demand from poorer members of society (Allison 2011). Also, the rise in the proportion of the population that consumes fish demands more from aquaculture than near-stagnant capture fisheries. Feed is the greatest fraction of operating cost of fed aquaculture systems and the cost and availability of ingredients limit the growth of fed aquaculture. Thus, fish nutrition is important to the progress of global aquaculture production. However, there are a multitude of challenges associated with the growth of the aquafeed industry and nutrition research. Systematic and technological interventions are essential for making aquaculture operations economical. At present, the aquafeed industry is struggling to include cheaper plant ingredients to replace costly animal protein sources to manufacture cost-effective aquafeeds. Challenges Scarcity of feed ingredients. The aquafeed industry relies heavily on fishmeal for meeting the protein requirements of farmed species. About 20.2 percent of the total global fish catch is currently used for the production of fishmeal and fish oil and around 60.8 percent of total fishmeal production is consumed by the aquafeed industry (FAO 2012). Fishmeal and fish oil production from marine capture fisheries decreased at annual average rates of 1.7 percent and 2.6 percent, respectively (FAO 2012). The future growth of aquaculture may be constrained by the availability of fishmeal, which is affected by environmental phenomena such as El- Nino. The search for alternative protein sources has become a necessity for sustainable aquaculture production. Although this has been a focus area by researchers, plant protein sources have limitations for inclusion in aquafeeds because of the presence of anti-nutritional factors and high carbohydrate content. Low carbohydrate utilization in fish. Plant ingredients, intended to replace high-value protein sources, contain large quantities of carbohydrates. The ability of fish to use dietary carbohydrates Aquaculture Nutrition: Turning Challenges into Opportunities V. Tincy, P. Mishal, M. S. Akhtar and A. K. Pal as energy sources to spare protein for growth is less than that of terrestrial vertebrates. Also, the physiological efficiency for utilizing carbohydrates as an energy source varies among and within species. Herbivorous and omnivorous fish have a greater ability to use carbohydrates for energy than carnivorous fish. Coldwater fish have less capability for carbohydrate utilization than warmwater fish. Thus, the considerable use of cheaper plant ingredients in the diets of coldwater and/or carnivorous fishes will be impractical, resulting in a higher production costs for those species. Anti-nutritional factors in plant-based ingredients. A major difficulty associated with inclusion of plant-based protein sources in feed is the presence of anti-nutritional factors. Anti-nutritional factors are components of feed ingredients that have adverse effects on digestive and metabolic function. Trypsin inhibitors, glucosinolates and phytic acid are the anti-nutritional factors of major concern. Legume seeds, such as peas, lupins and soybeans and lowglucosinolate rapeseeds, have been used as partial substitutes for fishmeal. Although continuous efforts have been made to reduce antinutritional factors, no major outcome has reached farmers. Climate change and environment stressors. Models have predicted a 1.7 oC rise in mean atmospheric temperature, which may change weather patterns, rainfall patterns, wind and storm directions. The threats arising from climate change are 1) stress from increased temperature, oxygen demand and reduced pH, 2) uncertainty in the supply of water in the future, 3) risk of disease and, 4) sea-level rise and the consequent changing oceanic boundaries. Impacts on aquaculture could be positive or negative, arising from direct and indirect impacts on natural resources, including water, land, seeds, feed and energy. Climatic changes cause increased physiological stress on cultured stock and long-term effects resulting from global warming are altered reproductive cycles, invasion of species, vulnerability to diseases and, in turn, higher risks and reduced returns to farmers (WFC 2009). Increased stocking density in present-day culture systems causes detrimental effects such as poor growth and increased incidence of diseases in fish from crowding. Inasmuch as fish is an ectothermic animal, any alterations in the water temperature is can be a pervasive factor that affects structures and functions at all levels of biological organization, causing metabolic stress. Exposure to increasing temperatures as a result of global warming and climate changes may cause respiratory stress, breakdown of compensatory general adaptive syndrome, reduction in growth and reproductive failure. Antibiotics and chemical use in feed. Although the use of certain antibiotics in aquaculture was banned in 2006, there are still many chemicals and several types of antibiotics that exist in practical aquaculture. This can causes side effects such as bioaccumulation in fish flesh and the generation of resistant strains of pathogens. During processing of pelleted feed, the leftover medicated pellets can (CONTINUED ON PAGE 68)
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