Conservation Hatchery Protocols for Pacific Salmon
Thomas A. Flagg, Conrad V. W. Mahnken, and Robert N. Iwamoto
Abstract.—Artificial propagation is a potential mechanism to aid recovery of U.S. Endangered Species Act (ESA)-listed stocks of Pacific salmon on the West Coast of the United States. Theoretically, one of the fastest ways to amplify population numbers for depleted stocks of Pacific salmon is through culture and release of hatchery-propagated fish. However, past attempts to use supplementation (i.e., the use of artificial propagation in an attempt to maintain or increase natural production) to rebuild naturally spawning populations of Pacific salmon have often yielded poor results. One solution is to develop protocols that increase fitness of hatchery-reared salmonids, thereby improving survival. A framework of conservation hatchery strategies to reduce potential impacts of artificial propagation on the biology and behavior of fish is presented. Operational guidelines for conservation hatcheries to help mitigate the unnatural conditioning provided by hatchery rearing are discussed and contrasted to those for production hatchery operation. These include (1) mating and rearing designs that reduce risk of domestication selection and produce minimal genetic divergence of hatchery fish from their wild counterparts to maintain long-term adaptive traits; (2) simulation of natural rearing conditions through incubation and rearing techniques that approximate natural profiles and through increasing habitat complexity (e.g., cover, structure, and substrate in rearing vessels) to produce fish more wildlike in appearance and with natural behaviors and higher survival; (3) conditioning techniques such as antipredator conditioning to increase postrelease behavioral fitness; (4) programming aspects of release size, stage, and condition to match the wild population in order to reduce potential for negative ecological interactions and to promote homing; and (5) aggressive monitoring and evaluation to determine success of conservation hatchery approaches. High priority must be given to basic scientific research to meet three principal goals: (1) maintain genetic integrity of the population, (2) increase juvenile quality and behavioral fitness, and (3) increase adult quality.