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PM05 Aquatic Vertebrate/Invertebrate Toxicology
(PM092) Sublethal Effects of the Carbamate Insecticide, Carbaryl, on Coastal Cutthroat Trout.
Davis, J.1, Labenia, J.2, Baldwin, D.2, French, B.2, Scholz, N.2, 1 U.S. Fish & Wildlife Service - Western Washington Fish & Wildlife Office, Lacey, WA, USA2 NOAA Fisheries - Northwest Fisheries Science Center, Seattle, WA, USA
ABSTRACT- Willapa Bay is a coastal estuary in Washington State that provides habitat for cutthroat trout (Onchorhynchus clarki clarki) as well as other salmonids. Cutthroat trout forage throughout the estuary in the summer months when carbaryl, a carbamate insecticide, is applied to oyster beds at low tide to control burrowing shrimp populations. On the day of spray, carbaryl has been measured in the estuarine water column at concentrations >1,000 ppb. Carbaryl is a neurotoxicant that inhibits acetylcholinesterase, an enzyme that hydrolyzes the transmitter acetylcholine at neuronal and neuromuscular synapses. The goals of this study were to determine: 1) if trout can detect carbaryl, as determined by in vivo recordings (electro-olfactograms) from the olfactory epithelium, 2) if trout will avoid dissolved carbaryl in a two-choice behavioral chamber, and 3) the effects of a short-term, environmentally-realistic carbaryl exposure on acetylcholinesterase activity in brain and muscle. We find that carbaryl does not evoke a measurable response from the cutthroat olfactory epithelium, and that animals do not avoid carbaryl-contaminated seawater. A short-term (6 hour) carbaryl exposure was sufficient to depress acetylcholinesterase activity for approximately two days. The onset of acetylcholinesterase inhibition in carbaryl-exposed animals was rapid (< 2 hrs) and enzyme activity was significantly reduced in a dose-dependent manner in brain and muscle (BMC20s of 32 ppb and 23 ppb, respectively). Consequently, cutthroat trout are unlikely to avoid carbaryl that is transported away from oyster beds in Willapa Bay. Moreover, a short-term exposure to carbaryl (i.e., within a single tidal cycle) can be expected to inhibit brain and muscle acetylcholinesterase, and thus may interfere with swimming performance and other behaviors that are critical for predator avoidance and survival.
Key words: cutthroat trout, carbaryl, carbamate pesticide, acetylcholinesterase inhibition
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