EXPOSURE OF FISH TO BIOLOGICALLY TREATED BLEACHED-KRAFT EFFLUENT. 1. BIOCHEMICAL, PHYSIOLOGICAL AND PATHOLOGICAL ASSESSMENT OF ROCKY MOUNTAIN WHITEFISH (PROSOPIUM WILLIAMSONI) AND LONGNOSE SUCKER (CATOSTOMUS CATOSTOMUS)

Abstract

A suite of biochemical, physiological, and pathological measures was used to assess possible effects of exposure to bleached-kraft mill effluent (BKME) on wild longnose sucker (Catostomus catostomus) and mountain whitefish (Prosopium williamsoni) in the Wapiti/Smoky river system, as compared to similar populations in a reference river system without BKME inputs. Individual fish body burden data (i.e., metals, polychlorinated dioxins and furans, fatty and resin acids, chlorophenolics) were examined for correlations between chemical exposure and biological response. General incidence of gross pathology and histopathology showed no relationship with exposure to BKME, and no neoplastic or preneoplastic lesions were observed in either exposed or reference fish. The few significant differences observed in longnose sucker blood parameters were not correlated with exposure to BKME and appeared to reflect, at least in part, habitat gradients. Liver somatic indexes were higher for female BKME-exposed longnose sucker, but were not significantly different in male sucker nor in mountain whitefish. Some differences in circulating sex steroid levels were observed in longnose sucker exposed to BKME (but not in mountain whitefish, the species with higher contaminant body burdens). Steroid profile differences may have been related to natural differences in duration of spawning periods in the two fish populations. Other measures of reproductive capacity (relative gonad size, fecundity, young-of-the-year) showed no reductions in exposed fish. The detoxification enzyme cytochrome P4501A was induced in both species, with greater induction in whitefish than in longnose sucker. Whitefish P4501A induction correlated well with some BKME exposure measures, but not with liver or gonad weights, pathology, reproductive capacity, or population-level parameters. Increased liver size and apparent differences in sex steroid profiles in longnose sucker did not translate to other health effects or population-level effects. Thus, exposure to this biologically treated BKME produced one consistent biochemical marker of exposure (P4501A) in the two fish species that was not associated with any discernible adverse effects on individual fish health.