WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2018 49 sustainability of snakehead culture in Vietnam and Cambodia. A major aspect of the project was the development of diets and feeding strategies that would obviate the need for small fish usage in snakehead culture. This occurred in a series of steps, as follows. Assessment of Species Composition and Nutritional Value of Small Fish Used in Snakehead Culture in Cambodia in Vietnam In Cambodia, three types of feed sources were traditionally supplied to snakehead fish farms. Homemade, freshwater trash fish feed was the most common feed, and marine trash fish, crabs and snails were also used (Hap et al. 2010). Around 200 species of trash fish were used for snakehead culture, including small life stages (larvae and fingerling) of economically important species that contribute about 10 percent of the total collection of trash fish. In Vietnam, sampling of small fish from fish distribution sites in the Mekong Delta indicated that freshwater small fish used in snakehead culture came from 33 species, of which 12 were actually the juvenile stages of commercially important species (Hien et al. 2015a). Because the freshwater small fish were obtained locally, they were reasonably fresh, but marine fish, collected from farther away (and not delineated by species), showed greater degrees of deterioration in nutritional quality. This step reinforced the idea that pelleted diets must be developed to eliminate the wild capture of small fish. Development of Weaning Strategies for Snakehead Based on anecdotal information that snakehead would not accept pelleted diets if they were introduced to them after a certain life stage, scientists at Can Tho University (CTU) developed weaning protocols for snakehead (Hien et al. 2017). The snakehead murrel Channa Prior to 2006, the predominant method for culturing snakehead in Vietnam and Cambodia was to collect wild juveniles from natural sources like the Mekong River and Tonle Sap. Particularly in Cambodia, aquaculture farmers, who were also fishermen, would collect their own fingerling snakehead. They would then also collect “small fish” (also known as low-value fish or trash fish) from natural sources, chop them up and feed them to the snakehead in culture. A conflict existed between users of these fish: the aquaculture/fishing people and the remainder of the Cambodian population who rely on small fish (Fig. 1) for a variety of products, including fish sauce and prahok, that provide protein to the Cambodian people throughout the year. As a result, and to protect the nutrition of the Cambodian people, aquaculture of snakehead was banned in the country in 2004. Snakehead culture continued in Vietnam. Wild fingerlings were collected from the Mekong River, but anecdotal reports indicated that wild fish could never be induced to eat pelleted feed. Farmers continued to rely on chopped-up small fish that were also collected from the wild. Beginning in the late 1990s, efforts were made to develop hatcheries to domesticate snakehead for a steady supply of fingerlings that did not rely on natural sources. Although common breeding techniques from around the world could be used to induce spawning, larval rearing practices relied on use of live feed (the cladoceran Moina spp.) followed by chopped small fish as a weaning diet. Grow-out production continued to rely on chopped small fish. Concerns mounted that harvesting small fish from the Mekong River for an expanding snakehead aquaculture industry would eventually lead to detrimental impacts on those populations of small fish. In 2007, the U.S. Agency for International Development-funded Aquafish Collaborative Research Support Program, later re-named the AquaFish Innovation Lab, funded a project to address the Alternative Feeding Strategies and Feed Ingredients for Snakehead Farming in Cambodia and Vietnam Tran Thi Thanh Hien, Pham Minh Duc, Nen Phanna, Hap Navy, Chheng Phen, So Nam, Robert Pomeroy and David A. Bengtson (CONTINUED ON PAGE 50) FIGURE 1. Cambodians sorting small fish to use in products for human nutrition. Snakehead farmers collect “small fish” from natural sources, chop them up and feed them to the snakehead. A conflict existed between users of these fish: the aquaculture/ fishing people and the remainder of the population who rely on small fish to provide protein to the Cambodian people throughout the year.
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