Low-level copper exposures increase visibility and vulnerability of juvenile coho salmon to cutthroat trout predators.
Copper contamination in surface waters is common in watersheds with mining activities or agricultural, industrial, commercial, and residential human land uses. This widespread pollutant is neurotoxic to the chemosensory systems of fish and other aquatic species. Among Pacific salmonids (Oncorhynchus spp.), copper-induced olfactory impairment has previously been shown to disrupt behaviors reliant on a functioning sense of smell. For juvenile coho salmon (O. kisutch), this includes predator avoidance behaviors triggered by a chemical alarm cue (conspecific skin extract). However, the survival consequences of this sublethal neurobehavioral toxicity have not been explored. In the present study juvenile coho were exposed to low levels of dissolved copper (5-20 microg/L for 3 h) and then presented with cues signaling the proximity of a predator. Unexposed coho showed a sharp reduction in swimming activity in response to both conspecific skin extract and the upstream presence of a cutthroat trout predator (O. clarki clarki) previously fed juvenile coho. This alarm response was absent in prey fish that were exposed to copper. Moreover, cutthroat trout were more effective predators on copper-exposed coho during predation trials, as measured by attack latency, survival time, and capture success rate. The shift in predator-prey dynamics was similar when predators and prey were co-exposed to copper. Overall, we show that copper-exposed coho are unresponsive to their chemosensory environment, unprepared to evade nearby predators, and significantly less likely to survive an attack sequence. Our findings contribute to a growing understanding of how common environmental contaminants alter the chemical ecology of aquatic communities.
School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Seattle, Washington 98105, USA. jen.mcintyre@wsu.edu
Jenifer K
JK
McIntyre
David H
DH
Baldwin
David A
DA
Beauchamp
Nathaniel L
NL
Scholz
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003300:Copper / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*; D017684:Oncorhynchus kisutch / Q000502:physiology*; D012903:Smell / Q000187:drug effects*; D014337:Trout / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*
D014874:Water Pollutants, Chemical; D003300:Copper