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

items (Courtemanch and Gibbs 1980; Haines 1981; Hatakeyama, Shiraishi et al. 1990; Davies
and Cook 1993; Schulz 2004). Some invertebrates may drift actively to avoid pesticides and
settle further downstream, which can provide temporary spikes in available food items for
feeding salmonids. Catastrophic drift can also deplete benthic populations resulting in long-term
prey reduction that may affect salmonid growth at critical time periods. We located no studies
that address this line of reasoning directly with Pacific salmonids. Davies and Cook (1993) did
show aquatic invertebrate community changes, mortality of invertebrates, drift of dying and dead
invertebrates, and affected trout following spraying of a pyrethroid pesticide, cypermethrin, an
invertebrate and fish neurotoxicant (Davies and Cook 1993). Effect concentrations were
estimated at 0.1-0.5 μg/L cypermethrin. It is difficult to compare these effect concentrations to
carbamate insecticides. However, it is illustrative of how insecticides can damage multiple
endpoints of an aquatic community including reducing abundance of prey (Davies and Cook
1993).
Several scientific peer-reviewed publications and EPA documents have reviewed aspects of the
available information on multi-organism microcosm, mesocosm, and field test results for the
AChE insecticides (Leeuwangh 1994; Barron and Woodburn 1995; Schulz 2004; Van
Wijngaarden, Brock et al. 2005). Van Wijngaarden et al. (2005) conducted a literature review
that listed ecological threshold values (e.g., NOECeco and LOECeco) for carbaryl, carbofuran, and
bendiocarb (another N-methyl carbamate) from model ecosystems or “adequate” field studies. A
NOECeco represented “the highest tested concentration at which no, or hardly any, effects on the
structure and functioning of the studied model ecosystem were observed. The LOECeco is the
lowest tested concentration at which significant treatment-related effects occurred” (Van
Wijngaarden, Brock et al. 2005). Below we discuss some of this information in relation to
effects on salmonid prey. The majority of studies were conducted in littoral systems, i.e., ponds,
and other static systems, but one study with carbaryl was conducted in a running water (lotic)
system (Courtemanch and Gibbs 1980). Population densities of salmonid prey items (i.e.,
Ephemeroptera, Diptera, Amphipoda, Cladocera, Copepoda, Isopoda, Ostracada, Trichoptera)
decline following exposures to AChE-inhibiting insecticide concentrations, including carbaryl
and carbofuran (Van Wijngaarden, Brock et al. 2005). Adverse effects to these groups occurred
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