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<br />species sampled in the Dolores River were as follows: 32.6 of aluminum, 2,100 of cadmium, 534 of
<br />copper, 613 of iron, 2.9 of lead, 2.4 of silver, and 177 of zinc (Table 45). All maximum values were
<br />from the same fish, a roundtail chub, which was captured at RM 109.6. ChemTech Laboratories were
<br />called to verify the high levels of metals observed in the one round tail chub. Although the results
<br />were verified by ChemTech, it is suspected that the high values are an error and may be an order of
<br />magnitude high. Cadmium levels of 2,100 mg/kg in liver and kidney tissues would certainly be fatal
<br />for an individual fish (Pers. comm. L Crist, BOR, from L Crist pers. comm. S. Hamilton USFWS,
<br />April, 1992). The fish in question appeared robust and healthy.
<br />
<br />The availability of a metal to a fish depends on such physio-chemical factors as the chemical
<br />species involved, the chemistry of the water itself, and the structure and chemistry of the sediment.
<br />Biological factors such as organism feeding behavior, feeding preference, and the physiology of the
<br />organism also regulate metal accumulation (Dallinger et a1. 1987). Metals may enter the body of a
<br />fish in three ways: through their skin, gills, or more commonly, through their alimentary tract (i.e.,
<br />from feeding on contaminated material) (Dallinger et a1. 1987). Bioaccumulation occurs when metals
<br />gradually buildup in target organs of final deposition. Sub-lethal metal contamination has been
<br />correlated with reduced spawning success, reduced larval and egg survival, smaller egg size, reduced
<br />longevity, and inferior mechanical properties of bones in white suckers (McFarlane and Fraozin 1978,
<br />Hamilton and Haines 1989).
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<br />Metal accumulation and concentration can increase along a given food chain (biomagnification).
<br />In the Dolores River, channel catfish were probably the primary top-level carnivore, feeding mainly
<br />on fish and large invertebrates (Coon 1965, Minckley 1973). Roundtail chubs are somewhat
<br />piscivorous, but rely on insects and flannelmouth suckers feed mainly on benthic insects and detritus
<br />(Minckley 1973). Based on the principle of biomagnification, channel catfish should accumulate the
<br />most metals, followed by roundtail chubs, and finally, flaooelmouth suckers. However, roundtail
<br />chubs had the highest average concentrations for every metal except iron (Table 46), although the
<br />sample size was only two fish, and average metal levels in flannelmouth suckers were higher than
<br />channel catfish for all metals. Dallinger et a1. (1987) reported that fish do not necessarily adhere to
<br />the principle of biomagnification for three reasons: 1) heavy metals are more available to organisms
<br />of lower trophic levels than to those of higher trophic levels, 2) fIsh seem to be able to reject large
<br />amounts of heavy metals ingested, and 3) comparison of concentration factors along a food chain may
<br />give an inaccurate description of the actual metal transfer, since fish concentrate heavy metals in
<br />certain organs which make a small contribution to total body weight.
<br />
<br />No historical data for fish tissue analysis could be found for the Dolores River, however Kunkle
<br />et ale (1983) performed bioassays on four species collected from the Gunnison River in October,
<br />1981. Average metal content in kidneys and livers of two roundtail chubs collected in the Dolores
<br />River in 1991 were substantially higher (up to 1,106 times higher in the case of cadmium) than
<br />equivalent metal concentrations in the same organs of rainbow trout and white suckers collected in
<br />the Gunnison River (Table 47). Flannelmouth suckers captured in the Dolores River had
<br />substantially higher concentrations of four of five metals compared to white suckers from the
<br />Gunnison River. Kunkle et a1. (1983) concluded that metal concentrations in fish from the Gunnison
<br />River were probably not high enough to cause concern about human health, but they failed to
<br />address concerns about the health of fish. Hamilton and Haines (1989) reported whole-fish
<br />concentrations of cadmium and lead in white suckers ranging from 0.7 - 1.2 mg/kg and 15.5 - 23.2
<br />mg/kg, respectively, and postulated that accumulation of these metals may have contributed to altered
<br />bone development observed in the fish.
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