No abstract

Estimates of numbers, biomass, and diversity of benthic macroinvertebrates were made quarterly over a two-year period to investigate microhabitat preferences. Although biomass of most taxa was significantly different among sampling times, physical factors also appeared to be important in determining abundance of many taxa. Optimum depth, velocity, substrate type, and turbulence were determined for major taxa. Optimum conditions for diversity appeared to be 34 cm depth, 60 cm s -1 velocity, and rubble and boulder substrate type. Habitat preference functions were derived for several taxa based on significant polynomial regressions of biomass on depth, velocity, substrate, and Froude number (turbulence). The relationship between abundance and physical habitat conditions was tested by using the product of the preference factors (range: 0 I) for depth, velocity and substrate type as a measure of habitat suitability (joint preference factor). There were significant correlations between biomass [transformed by loge (x + )] of 10 benthic species and the joint preference factor. The joint preference factors accounted for from 11 to 61% of the variation of biomass of the 10 benthic species. The intercepts of the relationships between biomass of individual species and the joint preference factor were not significantly different from zero for any species. Therefore, the joint preference factors appear to be valid indicators of biomass. The preference functions have utility in habitat assessment studies, specifically with regard to minimum instream flow determinations.

No abstract

Electroshocking elicited an immediate increase in plasma corticoid and lactate concentrations and thrombocyte:leucocyte ratio in rainbow trout (Salmo gairdneri). Plasma glucose concentrations increased significantly after 3 h. Plasma protein, calcium, magnesium, and androgen levels were not measurably affected. Plasma lactate returned to preshock levels within 3 h, but corticoid and glucose concentrations remained elevated for at least 6 h. The fish coughed violently or did not resume normal breathing rates for 60 s post shocking. Although breathing frequency did not increase, buccal pressure increased substantially and required at least 1 h to return to preshock levels. Cardiac activity was irregular immediately after shocking, but no predictable alterations in rate were evident thereafter. The height of the T wave in ECGs increased markedly 1–3 min after shocking. The electrophoretic patterns of 13 isoenzymes from liver, white muscle, and plasma did not differ between fish captured by dipnet and those captured by electrofishing.Responses exhibited by fish to shocking are most likely attributable to combined effects of trauma, factors associated with paying off of an oxygen debt, and attributes associated with the general adaptation syndrome of stress. A substantial period of time of more than 6 h is required for fish to return to "normal" preshock conditions.

Acute and chronic toxicity tests for malathion, diazinon, copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), nickel (Ni), and iron (Fe) were conducted. Mortalities of Barilius vagra and Cyprinus carpio (common carp) were variable but LC50-96 hr were similar for pesticides. Adult B. vagra seem to be more sensitive to malathion than juvenile carp. Both juvenile carp and adult B. vagra were extremely sensitive to diazinon. Long-term exposure to pesticides modified morphology and behavior. The LC50-96 values for Cu, Hg, and Pb were 0.3, 0.16, and 0.44, respectively, for smaller fish and 1.0, 0.77, and 1.33, respectively, for larger fish. Replicate LC50 values for Zn, Ni, and Fe were somewhat variable, and for these metals, the size of the fish seemed to affect response because LC50 values increased as fish size increased. Copper, Pb, Zn, and Fe residues following exposure to sublethal concentrations of these metals for 15 d were significantly greater in whole juvenile common carp than in controls.