Behavioral impairment and increased predation mortality in cutthroat trout exposed to carbaryl
Jay Davis Jana S. Labenia David H. Baldwin Nathaniel L. Scholz
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Willapa Bay is a coastal estuary in Washington
State that provides seasonal rearing habitat
for anadromous cutthroat trout Oncorhynchus clarki
clarki. Cutthroat trout forage throughout the estuary in
the summer months when carbaryl, a carbamate insecticide,
is applied to oyster beds via aerial spraying and
other application methods to control burrowing shrimp
populations. The insecticide interferes with normal
nervous system function in trout via the inhibition of
acetylcholinesterase, an enzyme that regulates neurotransmitter-
mediated signaling at synapses. In the present
study, we show that the olfactory system of trout
is unresponsive to carbaryl, and that trout do not avoid
seawater containing the pesticide at environmentally
representative concentrations. Short-term (6 h) carbaryl
exposures significantly reduced acetylcholinesterase
activity in both brain and muscle in a dose-dependent
manner. Enzyme activity gradually recovered over
42 h following carbaryl exposure (6 h at 500 -g l–1).
In tests of swimming performance, trout were unable
to orient to directional flow and swim effectively at
exposure concentrations -750 -g l–1. Finally, we determined
rates of predation by lingcod Ophiodon elongatus
on carbaryl-exposed and unexposed trout.
Exposed animals were consumed by predators at significantly
higher rates at concentrations -500 -g l–1.
We conclude that cutthroat trout are unlikely to avoid
carbaryl-contaminated seawater, and that estuarine
applications are likely to cause neurobehavioral impairments
in trout that may increase individual
mortality due to predation.
Marine Ecolology Progress Series
Inter-Research Science Center
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