California Sea Grant College Program

With the decline in wild fish stock due to over fishing, habitat loss and the increased demand for fish as a food source, the aquaculture industry has become an important component in the global economy not only in a consumable goods sense but also as a means of stock replenishment through release programs. Capture fisheries reached their maximum sustainable yield of 100 million metric tons (MMT) more than ten years ago, and the demand for seafood has shown no signs of abating (FAO 2004). The Food and Agriculture Organization (FAO) of the United Nations’ annual report states that in 2002, aquaculture supplied 29.9% of the global supply (FAO 2004). In aquaculture, fish are commonly reared in net cages, ponds, tanks, and raceways. Aquaculture systems are typically designed to optimize water quality, which results in flow parameters that may not be optimal for growth. Fish with increased growth rates reach marketable size faster and with a higher proportion of muscle mass. A faster growth rate also allows individuals to more rapidly achieve a size suitable for over-wintering in tanks, possibly decreasing the high mortality seen in fingerlings in aquaculture. This would lead to decreasing the release time, enhancing the stock replenishment, and decreasing the holding costs to the hatchery. The early rearing conditions have a substantial influence on muscle growth and proliferation of muscle fibers (Johnston 2001a) making exploration of growth conditions for early juveniles an attractive area of focus for aquaculture.