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

up to 100 m off the carbaryl application area (Doty, Armstrong et al. 1990). Levels decrease to
below 1 mg/L when transported more than 200m or more. Washington DOE reports that
carbaryl concentrations in the “potential effects threshold range” of 0.1-0.7 μg/L have been
detected at locations several miles from oyster beds soon after large areas were treated (Johnson
2001).
Measured Concentrations in Invertebrates
Samples of crustaceans from carbaryl treated areas in 1984 showed high tissue levels (Table 68).
A single ghost shrimp and Dungeness crab were analyzed and contained concentrations of 24.9
and 41.9 mg/kg (ppm), respectively (Hurlburt 1986). Analysis of dead shrimp in 1985 following
treatment at 7.5 lbs carbaryl/acre revealed average concentrations of approximately 4.5 mg/kg.
When left on the treated oyster beds the concentrations declined to approximately 10% of the
initial concentration 24 h post-treatment, then remained relatively stable at the 48, 72, and 96 h
sampling events. Concentrations in shrimp and annelid worms were investigated following the
1985 applications and associated with different application rates (Tufts 1989). Average
concentrations in shrimp ranged from 5.3 to 13.8 mg/kg. The concentration in worms ranged
from 57-58.6 mg/kg. The 10 lb application rate is less relevant as the current label restricts
applications to 8 lbs a.i./acre. Concentrations in other, more relevant salmonid prey items were
apparently not assessed although we assume they may be comparable for other organisms that
occupy similar habitat.
Table 68. Carbaryl concentrations in aquatic organisms on treated sites (mg/kg).
Year Dungeness Crab Burrowing Shrimp Annelid Worms
1984 41.9 24.9 (rate not reported) -
1985 - 4.5 (7.5 lb a.i./acre) -
1986 -
Ecological Effects
377
13.8 (10 lb a.i./acre)
8.7 (7.5 lb a.i./acre)
5.3 (5 lb a.i./acre)
75.5 (5 lb a.i./acre)
57 (7.5 lb a.i./acre)
58.6 (5 lb a.i./acre)
There have been concerns that carbaryl applications in Willapa Bay and Grays Harbor may have
adverse effects to the commercial Dungeness crab fishery (Feldman, Armstrong et al. 2000).
Consequently, Washington Department of Fisheries conducted several surveys to estimate the
number of crabs killed (Hurlburt 1986; Creekman and Hurlburt 1987; Tufts 1989; Tufts 1990).