Page 811 - The Toxicology of Fishes

Mining Impacts on Fish in the Clark Fork River, Montana: A Field Ecotoxicology Case Study 791

2200
Cu (ppm) = 62,609.578–30.723 * Year; R * 2 = .226
1800
Copper (ppm) 1400

1000

600
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
2200
Downward Trend Upward Trend
1800
Copper (ppm) 1400

1000

600
Y1991 Y1992 Y1993 Y1994 Y1995 Y1996 Y1997 Y1998 Y1999 Y2000 Y2001 Y2002 Y2003

FIGURE 19.7 Fluctuation in and annual mean (with standard deviations and ranges) of copper concentrations at a location
near Deer Lodge on the Clark Fork River (Moore et al., unpublished data). Concentrations were at their minimum in 2000
but may have begun to increase after that.

body contaminated by particulate mine wastes (e.g., dissolved metal that passes across the gill and body
surface, ingested food and particles ingested with food). Contaminated organisms from lower trophic
levels (e.g., plants or detritus and their consumers) are eaten by upper-trophic-level animals (e.g., fish).
Determinations of bioaccumulated metal offer a method for directly evaluating the dose of metal that
different species are experiencing. The insect community is one of the most important faunal components
in cobble-bottom streams, an important source of food for fish, and an excellent choice as an indicator
of bioavailable metal contamination (Cain et al., 1995). Metal concentrations in these invertebrates,
therefore, can be used to complement water, sediment, and fish tissue analyses as exposure indicators
(Phillips and Rainbow, 1994). One indicator species used in studies of Clark Fork contamination was
the caddisfly (Hydropsyche sp.) (order Trichoptera) (Cain et al., 1992). These animals are relatively
sedentary, widespread in occurrence, and of sufficient mass for analysis. They live for a year or more
as aquatic larvae and inhabit riffle zones where they are an important food for local fish.
In general, copper concentrations in the Hydropsyche were about 10% of the concentrations in fine-
grained sediments in the Clark Fork. Bioavailable metal (both whole-body and cytosolic concentrations
in insects) followed the same general gradient as did sediment concentrations of copper and cadmium
through the mid-1990s (Figure 19.8). Spatial trends in bioaccumulation seen in the Hydropsyche were
generally seen in other species as well, although absolute concentrations of copper and cadmium differed
widely among species (Cain et al., 1992). All taxa were contaminated relative to reference sites (tribu-
taries). Strong correspondence to other indicators of contamination (e.g., sediments or water) were also
evident.
Cain et al. (1995) found that the presence of undigested gut content resulted in approximately 30%
higher whole-insect copper concentrations, compared to animals whose digestive tract were removed.
The presence of undigested gut content also slightly increased the variability in metal concentrations
among samples; nevertheless, undigested gut content did not affect comparisons of contamination among