Environmental Factors Influencing Spawning Escapement of Dungeness River Pink Salmon (Oncorhynchus gorbuscha) 1959-1993

摘要

The return to escapement of Dungeness River summer-run and fall-run pink salmon was examined in relation to annual measures of nine environmental factors for the period 1959-1993 using multiple regression analysis. return to escapement, as indicated by the ratio of spawning escapements in the adult return year to spawning escapement in the corresponding brood year was regressed against (1) brood year low flow, (2) mean streambed width in the floodplain, (3) level of annual high flow event, (4) mean air temperatures surrounding the year's coldest day, (5) an index of predation by hatchery coho smolts, (6) marine upwelling, (7) marine salinity, (8) sea surface temperature, and (9) low instream flow during adult return. Each independent variable was transformed where necessary to approximate normality and achieve a linear relation to the dependent variable. Relative importance of each independent variable was indicated by the product of its x-coefficient and its standardized mean. Sea surface temperature had the greatest influence on return to escapement for the summer run population. Peak instream flows and low winter aire temperatures were equally important as secondary influences. low flow between adult return to the river and spawning was third in importance. Low winter air temperature had the greatest influence on return to escapement for the fall run population; sea surface temperature was next in importance, followed by marine upwelling.