A PERSPECTIVE ON THE ADAPTIVE IMPORTANCE OF GENETIC INFRASTRUCTURE INSALMON POPULATIONS TO OCEAN RANCHING IN ALASKA

Salmon hatcheries, like other resource management practices and tools, potentially have genetic effects on wild-spawning populations of salm on. These effects, which theory predicts will erode vital genetic dive rsity, would be expected to operate through straying and gene introgre ssion, and through other processes. Genetic diversity among population s is well known from analysis of neutral biochemical traits and is les s well known from observation of polygenic, ecologically adaptive, phe notype differences. We note increasing evidence of adaptively importan t polygenic genetic diversity within populations and evidence that thi s variability is partitioned temporally or spatially among distinct se gments of salmon populations, a partitioning we call infrastructure. F or,example, in one well-studied small population, Auke Creek pink salm on, there is evidence of genetically based variability of timing of an adromous migration and simultaneous evidence of the importance to surv ival of that timing. We believe that the adaptedness and productivity of salmon stocks are dependent on genetic infrastructure; fisheries ma nagement practices, including enhancement of harvests by hatcheries an d ocean ranching, potentially reduce genetic infrastructure as they ma y reduce other levels of genetic diversity. Rational resource manageme nt should seek to conserve genetic diversity at all levels. Treatment of salmon stocks as homogeneous units, neglecting within-stock diversi ty or infrastructure, will not be adequate to conserve fitness and pro ductivity of these commercially valuable resources.