John D. Woodling

Some aspects of hepatic function in feral brown trout, Salmo trutta, living in metal contaminated water

Brown trout, Salmo trutta, exposed to heavy metals (mainly Cd and Zn) for at least 2 years in the Eagle River, Colorado, were examined for liver size and activity of the growth-promoting enzyme, ornithine decarboxylase (ODC) and compared to trout living in an uncontaminated site. Liver-somatic index (LSI) was greater for trout living in the uncontaminated site with the LSI of females being significantly greater than that of males. The LSI for females at the uncontaminated site was greater than that of females at the contaminated site, but males were not different statistically. ODC activity in the livers of both males and females was lower at the contaminated site. However, males and females did not differ with respect to ODC activity. These data suggest that chronic exposure to heavy metals may have important implications for growth and reproduction and possibly survival. The activity of ODC in liver might serve as a useful biomarker when assessing chronic toxicity of metals to naturally reproducing fish populations.

Chronic Toxicity of Ammonia to Early Life Stage Rainbow Trout

Abstract A 90-d ammonia toxicity test for early life stage rainbow trout Oncorhynchus mykiss was conducted using newly fertilized eggs from a wild strain of fish. The toxicity test was conducted at a pH of 7.75 and temperature of 11.4°C. Hatch success and survival of sac fry were not affected by ammonia exposure. Survival, growth, and biomass of swim-up fry were significantly reduced at an ammonia-nitrogen (NH3-N) concentration of 16.8 mg NH3-N/L of water but were unaffected by exposures to 7.44 mg NH3-N/L or lower concentrations. The chronic toxicity value was 11.2 mg NH3-N/L, and the EC20 (concentration estimated to cause a 20% reduction in organism performance compared with the control) based on biomass at test termination was 7.72 mg NH3-N/L. Development of sac fry to the swim-up stage was retarded by ammonia, but fry exposed to 7.44 mg NH3-N/L or lower concentrations appeared to recover by the end of the test. Histological analysis of the gills of exposed fry did not detect any gill pathology. U.S. E...

Zinc toxicity to the mottled sculpin (Cottus bairdi) in high-hardness water.

The median 96-h lethal zinc concentration (LC50) was 439 microg Zn/L (hardness of 154 mg/L as CaCO3) for feral mottled sculpin (Cottus bairdi), decreasing to a median incipient lethal level of 266 microg Zn/L after 13 d. The 30-d chronic value was 255 microg Zn/L. The acute toxicity-hardness (ln-ln) slope of 1.022 exceeded that of the current U.S. Environmental Protection Agency zinc criteria. The mottled sculpin is the second most sensitive fish species for which toxicity data are available.