Application of photoperiod manipulation and new extruded diets in seaurchin aquaculture

摘要

For the past two decades, sea urchin fisheries have become important commercial resources with US exports to Japan exceeding $150 million in 1995. However, sea urchin populations along the coasts of the US have been overexploited. In the largest US urchin fishery (State of Maine), landings and numbers of licensed urchin fishermen have declined between 1993 and 2001. To develop new aquaculture techniques and more effective diets we have used information on cellular changes occurring during game-togenesis. Individuals were exposed to ambient and July photoperiod, fed an extruded diet (Wenger) and were evaluated for gonad index, stereology of different gonadal cells, nutritive phagocyte and oocyte sizes and taste. Gonad indices (%) increased significantly in both treatments over five months. Amounts of nutritive phagocytes (%) increased significantly only under invariant pho-toperiod while sizes ( mu m) of nutritive phagocytes increased in both photoperiod treatments but were significantly greater at invariant photoperiod. Amounts of gonial cells (%) increased significantly under ambient photoperiod, Oocyte feret diameters ( mu m) increased in both treatments but were largest at ambient photoperiod. Gonad (roe) taste was not appealing to taste testers. Therefore, seven diets of varying protein concentrations and the Wenger diet were fed to individuals maintained at invariant photoperiod for five months. This resulted in increased gonad indices in all diet treatments, but enhanced marketability of individuals for only three diets all of low/medium protein and high carbohydrate composition. Our results indicate that photoperiod manipulation and new diets can yield marketable sea urchin roe.