Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

Introduction
To assess the potential for adverse impacts of the anticholinesterase insecticides on Pacific
salmon populations, a model was developed that explicitly links impairments in the
biochemistry, behavior, prey availability and somatic growth of individual salmon to the
productivity of salmon populations. More specifically, the model connects known effects of the
pesticides on salmon physiology and behavior with community-level effects on salmon prey to
estimate population-level effects on salmon. The model used here is an extension of one
developed for investigating the direct effects of pesticides on the biochemistry, behavior, and
growth of ocean-type Chinook salmon (Baldwin et al., in press).
In the freshwater portion of their life, Pacific salmon may be exposed to insecticides that act by
inhibiting acetylcholinesterase (AChE). AChEe is a crucial enzyme in the proper functioning of
cholinergic synapses in the central and peripheral nervous systems of vertebrates and
invertebrates. Of consequence to salmon, anticholinesterase insecticides have been shown to
interfere with salmon swimming behavior (Beauvais et al. 2000, Brewer et al. 2001, Sandahl et
al. 2005), feeding behavior (Sandahl et al. 2005), foraging behavior (Morgan and Kiceniuk
1990), homing behavior (Scholz et al. 2000), anti-predator behaviors (Scholz et al. 2000), and
reproductive physiology (Moore and Waring 1996, Waring and Moore 1997, Scholz et al. 2000).
Anticholinesterase insecticides have also been found to reduce benthic densities of aquatic
invertebrates and alter the composition of aquatic communities (Liess and Schulz 1999, Schulz
and Liess 1999, Schulz et al. 2002, Fleeger et al. 2003, Schulz 2004, Chang et al. 2005, Relyea
2005). Spray drift and runoff from agricultural and urban areas can expose aquatic invertebrates
to relatively low concentrations of insecticides for as little as minutes or hours, but populations
of many taxa can take months or even years to recover to pre-exposure or reference densities
(Wallace et al. 1991, Liess and Schulz 1999, Anderson et al. 2003, Stark et al. 2004). For
example, when an aquatic macroinvertebrate community in a German stream was exposed to
runoff containing parathion (an AChE inhibitor) and fenvalerate (another commonly used
insecticide), eight of eleven abundant species disappeared and the remaining three were reduced
in abundance (Liess and Schulz 1999). Long-term changes in invertebrate densities and
community composition likely result in reductions in salmon prey availability. Therefore, in
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