Chapter 9: Use of Hatchery Fish for Conservation, Restoration, and Enhancement of Fisheries
Jesse Trushenski, Thomas Flagg, and Christopher Kohler
Aquaculture is the propagation of aquatic organisms under circumstances that facilitate greater productivity than would be observed in a natural setting. In terms of tangible resources and labor, culture methods and inputs vary from extensive (little effort or resources expended, minimal confinement of animals) to semi-intensive (pond production, limited input such as provision of supplemental feed or pond fertilization to enhance zooplankton productivity) to intensive (indoor production in tanks or raceways, provision of complete formulated feeds). Culture of finfishes, herein referred to as fish culture, is conducted for differing purposes, but most fish are raised for direct consumption as food fish or for stocking into natural habitats. Ornamental fishes are also cultured for the pet and aquarium trades. The approach taken by fish culturists differs among these scenarios with respect to production goals (rapid growth and food conversion efficiency versus genetic diversity and reproductive success in the wild) and specific culture methods (intensive production, high densities, and high performance feeds versus lower densities, reduced exposure to habituating elements, seminatural habitats, and predator avoidance and foraging training).
The approach undertaken to produce hatchery fish varies by management strategy. Stocking programs are implemented when increasing the number of fish in a population is desired, but the underlying reasons for increasing population size, and thus the preferred characteristics of the fish, will differ from one situation to the next. Selection of broodstock and day-to-day husbandry techniques can influence population genetics, individual behavior, and the ultimate success of propagated fishes in the wild. Misconceptions about the practice of fish culture and mismatch between the means (hatchery operation and culture techniques) and the ends (management objectives) of using propagated fishes in fisheries management has fostered some criticism of fish culture and hatchery fish. However, increased communications among culturists, geneticists, fisheries managers, and other stakeholders have supported development of best management practices for fish culture and an age of hatchery reform. In this chapter, a general description of fish culture practices is provided, how propagated fishes can be used to meet fisheries management objectives is described, and recommendations to improve the success of stocking programs under various management scenarios are given.