Tissue toxicants and prespawn mortality in Willamette River Chinook salmon

摘要

In some Pacific salmon Oncorhynchus spp. populations, many adults die after reaching freshwater spawning sites but prior to spawning, a phenomenon known as prespawn mortality (PSM). Causal factors for PSM are often uncertain, but pathogens, warm water temperature, and environmental toxicants have been implicated in several studies. In this two-year project, we examined the relationship between toxicants and PSM in a threatened population of spring-run Chinook salmon O. tshawytscha (Walbaum) in the Willamette River, Oregon. Muscle and skin samples from 63 female carcasses were screened for similar to 125 potential toxicants, including trace elements, pesticides, and organohalogens. Mean concentrations for five toxicants selected for their known adverse effects on salmonids were: 4.3 (SD = 2.0) ng/g cadmium, 72.9 (122.7) ng/g nickel, 10.0 (9.0) ng/g lead, 12.7 (8.6) ng/g polychlorinated biphenyls (PCBs), and 17.6 (10.3) ng/g DDT (an organochlorine pesticide). Using generalized linear models, we found no statistical differences in toxicants concentrations between successful (n = 37, 58.7%) and unsuccessful (n = 26, 41.3%) female spawners. We conclude that selected contaminants did not provoke acute toxicity in Willamette River Chinook salmon. It remains unknown whether sub-lethal or chronic toxicant effects on adult salmon physiology or behavior have affected the fitness of this threatened population.