Portfolio II: Applications of Technology

Aquaculture: Linking Research to Restoration

After collapse of the American shad fishery in Maryland more than a quarter century ago, fish are beginning to rebound. Two significant factors in restoration have been the opening of fish passages, so that adult shad can now return to freshwater spawning grounds, and annual release of hatchery-reared larvae into river systems. Spawning of shad has been optimized by controlled-release gonadotropin-releasing hormone (GnRH) delivery technology that Yonathan Zohar (Univ. Maryland Center of Marine Biotechnology) developed for striped bass with support by Maryland Sea Grant. GnRH induces final oocyte maturation, ovulation and spawning. Once released into Bay tributaries, shad larvae are subject to high levels of predation &emdash; in 1998, an estimated 1.5 million of 30 million survived to become juveniles. Laboratory research by Edward Houde (University of Maryland Center for Environmental Science) indicates that larvae are also sensitive to environmental stresses that could potentially be avoided. If average daily mortalities could be decreased by only one percent, the number of larvae that progress to the juvenile stage could increase by almost 50 percent. To determine whether survival can be improved under optimum conditions, Maryland Sea Grant is currently supporting "Evaluating and Improving Larval Stocking as a Method to Restore American Shad in Chesapeake Bay" (R/F-90), a three-year project by Houde and Steven Minkkinen (Maryland Department of Natural Resources).

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