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<br />Ii C{ 0 <br /> <br />Waflt~, tf- vt/ <br /> <br />~ <br /> <br />qt:J /) <br /> <br />Genetic Approaches to the Management of <br />. Pacific Salmon! <br /> <br />I <br />Robin S. Waples, Gary A. Winans, Fred M. Utter, ~nd Conrad Mahnken <br /> <br />ABSTRACT <br /> <br />The complex problems involved in managing Pacific salmon (Ollcorhynchus spp.) are largely a consequence of the <br />unusual life history features of these species. The strong homing instinct leads tp the formation of discrete, locally- <br />adapted spawning populations, each of which has the potential to evolve as an ~ndependent evolutionary unit. It is <br />important, therefore, that the genetic consequences of different management pol ides be carefully evaluated. If current <br />management goals (e.g., doubling the abundance of anadromous salmonids in ithe Columbia River basin through <br />increased hatchery production and supplementation of natural populations) are tealized, genetic issues will assume <br />even greater importance in the future. To date, however, genetic concerns have mit been adequately incorporated into <br />the management process. We identify three genetic approaches, primarily based on!easily obtained electrophoretic data, <br />that can provide valuable information on which to base management decisions: (1) 4sing the Genetic Stock Identification <br />method for identifying stocks contributing to oceanic, mixed-stock fisheries. Genetic Stock Identification has several <br />advantages over traditional tagging methods, including cost-effectiveness and easy access to wild as well as hatchery <br />stocks. (2) Monitoring genetic changes in hatchery stocks. Analysis of the nature a~d magnitude of such changes is the <br />best means of identifying stocks in which potentially dangerous levels of inbreed'ng may be occurring. (3) Detecting <br />mixtures of gene pools. The ability to detect hybridization and introgression is nece~sary for an evaluation of the genetic <br />consequences of releasing artificially propagated fish into the wild. . <br /> <br />Introduction <br /> <br />Anadromous Pacific salmon (Oncorhynchus spp.) are <br />such an important resource in the Pacific Northwest <br />that efforts to control production began over a century ago <br />(Mahnken et a1. 1983). In spite of concerted management <br />efforts in recent decades, the abundance of most Pacific <br />salmon species in recent years has been substantially below <br />historical levels (Fredin 1980; Fraidenburg and Lincoln <br />1985), and a number of stocks have been identified that may <br />qualify for protection under the Endangered Species Act <br />(W. Nehlsen, AFS Endangered Species Committee, per- <br />sonal communication). As we near the last decade of the <br />20th century, major new enhancement programs are being <br />considered, with goals as ambitious as a doubling of the <br />run size of anadromous salmonids in the Columbia River <br />basin (NWPPC 1987). Achieving such goals will not be easy. <br />Pacific salmon have proved to be among the most chal- <br />lenging species to manage effectively, primarily as a con- <br />sequence of their unusual life history features. <br /> <br />Spawning in Discrete Freshwater Populations <br /> <br />Because of the strong tendency of Pacific salmon to return <br />to their natal stream to spawn, different populations may <br />follow essentially independent evolutionary pathways. To <br />the extent that directional forces (natural selection) and <br />random factors (founder effect and genetic drift) have <br />individually shaped the genetic makeup of these popula- <br /> <br />Robin S. Waples and Gary A. Winans are geneticists with <br />the Coastal Zone and Estuarine Studies (CZES) Division, North- <br />west Fisheries Center, National Marine Fisheries Service, 2725 <br />Montlake Boulevard East, Seattle, WA 98112. Fred M. Utter <br />recently retired as head of the genetics program for CZES. Conrad <br />Mahnken is head of the Fisheries Enhancement Task in CZES. <br /> <br />September - October 1990 <br /> <br />tions, each repre~ents a potentially separate stock (Ricker <br />1972). Given the ~xtensiv~ geographic range of some of the <br />species (e.g:, chiIitook salmon [0. tshawytsclza] spawn from <br />central Califbrnia!to the USSR, and as far inland as eastern <br />Idaho and the Caradian Yukon), the number of stocks that <br />might meriUndividual management consideration is daunt- <br />ing. <br /> <br />Oceanic Harvest <br /> <br />The above pict~re is enormously complicated by the fact <br />that almost all hilirvests of Pacific salmon occur away from <br />the spawning grqunds. Because the massive physiological <br />changes salmon tindergo in the spawning migration greatly <br />reduce market v41ue of the flesh, most fisheries occur at <br />sea or near the Imouth of major river systems. In such <br />fisheries, targeti'ig specific stocks is generally impossible; <br />some oceanic fis~eries, such as the troll fishery off the <br />Washington coasit, harvest fish spawned as far away as <br />California and AI~ska (Utter et a1. 1987). <br />The mixed-stoqk nature of most Pacific salmon fisheries <br />has two important consequences for management purposes. <br />First, effective regulation of individual stocks is difficult. <br />For example, it is loften not possible to restrict catches from <br />endangered or depleted stocks without limiting the entire <br />fishery. Second, because anadromous fish are considered <br />to be a resource ~f the state or country in whose waters <br />they were spa wIled, fishing rights cannot be determined <br />simply on the ba~is of geographical location of the fishery. <br />The questions, "~ho is catching whose fish?" and "What <br />compensation is d~e as a result?" are of considerable interest, <br />but answers satisf~ctory to all parties are difficult to achieve. <br /> <br />14rtificial Propagation <br /> <br />Increased fishirjg pressure, destruction of spawning hab- <br />itat, and blockage lof migratory routes by hydroelectric dams <br />have all contribqted to the reduction in abundance of <br /> <br />@ Copyright 1990 by the American Fisheries ?ociety. <br /> <br />19 <br />