Douglas E. Facey

Estimating Physiological Thresholds with Continuous Two-Phase Regression

Abrupt changes in the relationship between physiological responses and environmental parameters yield data that frequently cannot be described with a single regression equation. Many approaches used to deal with this problem result in incomplete description of the data and imprecise approximations of the physiological threshold(s) at which the relationship changes. We describe a technique for determining the best continuous two-phase, straight-line regression model and for statistically estimating the point at which the relationship between the independent and dependent variables changes (i.e., threshold point).

The metabolic cost of maintaining position for four North American stream fishes : effects of season and velocity

We used a swimming respirometer to measure oxygen consumption (i. e., metabolic cost) of four species of stream fishes while they held position at diferent velocities. We tested naturally acclimatized individuals during spring, summer, fall, and winter at seasonal temperatures and photoperiods. Rosyside dace (Clinostomus funduloides), longnose dace (Rhinichthys cataractae), mottled sculpin (Cottus bairdi), and juvenile rainbow trout (Oncorhynchus mykiss) all showed seasonal changes in oxygen consumption. Seasonal changes in standard metabolic rates seemed to be influenced by changes in reproductive condition as well as ambient temperature. The metabolic cost of maintaining position for rainbow trout and rosyside dace generally increased with velocity. At velocities below eight body lengths per second, longnose dace did not exhibit a significant change in oxygen consumption, because they held position without swimming. At higher velocities, however, long-nose dace swam to maintain their position and oxygen consumption increased rapidly. Mottled sculpin held position without swimming and therefore showed little or no change in energy use with changing current velocity.

The relationship between water velocity, energetic costs, and microhabitat use in four North American stream fishes

We employed field and laboratory data to test the hypothesis that microhabitat use by rainbow trout (Oncorhynchus mykiss), rosyside dace (Clinostomus funduloides), longnose dace (Rhinichthys cataractae) and mottled sculpin (Cottus bairdi) was affected by energetic constraints.Both rainbow trout and rosyside dace occupied water-column microhabitats in Coweeta Creek, North Carolina, U.S.A. These species were over-represented at velocities requiring lower rates of oxygen consumption, as predicted by an energetic cost hypothesis. Morphological and behavioral adaptations of the two benthic species (mottled sculpin and longnose dace) enabled them to hold position over a wide range of velocities without significant changes in oxygen consumption. Focal point velocities of longnose dace were not significantly different from those available, suggesting a lack of velocity preference. Mottled sculpin, however, consistently were over-represented at low velocities, even though oxygen consumption data showed that energetic costs were not decreased by occupying these microhabitats. Our results indicate that microhabitat use by rainbow trout and rosyside dace is consistent with predictions of an energetic cost hypothesis, whereas the morphological adaptations of longnose dace and mottled sculpin minimize the constraints of energetic costs in microhabitat selection.

Habitat use by migrant sandhill cranes in Nebraska

The principal spring staging areas of the midcontinent population of sandhill cranes (Grus can- adensis) are along the Platte and North Platte rivers in south-central Nebraska. Most of these lands are privately owned and managed for corn and cattle production. Diurnal habitat use by radio-tagged cranes was primarily in cropland (55%), native grassland (28%), and tame hayland (15%). Ninety-nine percent of the cropland use was in cornfields; 55% as grazed stubble, 36% as disced, cultivated, and plowed stubble, 7% as ungrazed stubble, and 1% unclassified. Grazed pastures accounted for 93% of the grassland locations and mowed alfalfa fields 77% of the tame hayland locations. Other habitats were seldom used. Time budget analyses indicated that cranes, while in croplands, grasslands, and haylands, spent 35, 36, and 50% of the time foraging, respectively Cranes roosted in the shallows and on nearby sandbars of about 111 km of river channel. Cranes usuallv roosted where the channel was at least 150 m wide and avoided stretches narrower than 50 m. Height of woody vegetation along shorelines and on islands influenced where cranes roosted when unobstructed channel width was less than 150 m; bridges or roads adjacent to the channel also reduced use by about half. Management recommendations are made for maintaining suitable habitat for sandhill cranes on their staging areas in Nebraska. J. WILDL. MANAGE. 48(2):407-4 17 Approximately one-half million sand- hill cranes (four-fifths of the continental population) gather annually along the Platte and North Platte rivers in Nebraska during March and early April while en route to their breeding grounds in central and arctic Canada, Alaska, and Siberia (US. Fish and Wildl. Serv., unpubl. data). Water developments in the upper Platte River Basin during this century have dras- tically reduced flows, causing major changes in channel width in the Big Bend reach (Williams 1978) where most of the cranes gather. Extensive encroachment by woody vegetation has accompanied chan- nel shrinkage (Currier 1982), and pro- posed developments would cause addi- tional habitat degradation and loss (Krapu et al. 1982), raising concern for the well-

Local Movements and Inshore Population Sizes of American Eels in Lake Champlain, Vermont

Abstract Local movements of 16 radio-tagged American eels Anguilla rostrata were monitored in Lake Champlain, Vermont. Within water depths to 10 m, total displacement distances (sum of straight-line distance between successive position fixes) ranged from 0.6 to 4.9 km per fish; these distances were not well correlated with tracking times (4 to 67 days). Displacement polygons defined by individual tracks had areas of 2.4 to 65.4 hectares. Some American eels showed substantial movement in the first few days after release, whereas others did not; most remained in shallow water, but some moved into deeper water. Fish were displaced up to 0.9 km between capture and release; only two returned to within 500 m from their capture site, indicating that little precise homing occurred. Inshore population-size estimates from multiple mark-and-recapture methods varied from 232 to 636 fish/hectare (161–421 kg/hectare). Seven tagged individuals have been recaptured outside the study area: five at St. Jean, Quebec, one in...

Using Fish Biomarkers to Monitor Improvements in Environmental Quality

Abstract The percentage of splenic tissue occupied by macrophage aggregates and hepatosomatic index (HSI) were evaluated in rock bass Ambloplites rupestris from Burlington Harbor, Vermont. In 1992, fish collected from the inner Burlington Harbor area had a significantly greater percentage of splenic tissue occupied by macrophage aggregates and greater HSI than did fish from reference sites. These biomarkers often are correlated with exposure to various contaminants (e.g., polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and some heavy metals, which were found in Burlington Harbor sediments during surveys in 1990 and 1991). Contaminants are believed to have entered Burlington Harbor through the citys main sewage treatment plant, which discharged effluent into the harbor for many years. In 1994, the city completed a significant upgrade of this treatment plant, which included an extension of the effluent pipe beyond the inner harbor area. In 1999, rock bass were again collected from Burlington H...

Biology of American Eels in Lake Champlain, Vermont

Abstract The lengths of 426 American eels Anguilla rostrata sampled in Lake Champlain were 43–90 cm with a mean of 67 cm. Mean age of 416 eels was 15.9 years with a range of from 8 to 23 years. The weight of 427 eels was between 120 and 1,665 g with a mean of 638 g. Insects appeared in 43% of the 279 stomachs that contained food, but accounted for only 10% of the total volume. Fishes and crayfish each were present in 26% of the stomachs and accounted for 38% and 30% of the total volume, respectively. All of 356 eels examined were females.

Responses of Atlantic Salmon Parr to Output of Pulsed Ultrasonic Transmitters

Abstract The output from some pulsed ultrasonic transmitters commonly used in fish movement studies is faintly audible to humans. This study was undertaken to determine if the output from these and some other transmitters is detectable by Atlantic salmon (Salmo salar) parr. Classical conditioning of cardiac deceleration was attempted using the transmitters output as the conditioned stimulus. The results from 29 experimental and 14 control fish suggest that the parr were unable to detect the output from these transmitters.