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- Effects (6)
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Articles 31 - 43 of 43
Full-Text Articles in Physical Sciences and Mathematics
Nutrient Limitation Of Oligotrophic Sockeye Salmon Lakes Of Idaho (Usa), Wayne A. Wurtsbaugh, H. P. Gross, Chris Luecke, Phaedra E. Budy
Nutrient Limitation Of Oligotrophic Sockeye Salmon Lakes Of Idaho (Usa), Wayne A. Wurtsbaugh, H. P. Gross, Chris Luecke, Phaedra E. Budy
Watershed Sciences Faculty Publications
"Phytoplankton production in lake ecosystems is frequently controlled by amounts of nitrogen and phosphorus (Smith 1982, Elser et al. 1990), as well as minor- and micro-nutrients (Wurtsbaugh & Horne 1983, Wurtsbaugh 1988, Lovstad & Bjorndalen 1990). Nutrient limitation is often studied to determine which nutrient(s) should be reduced to control lake eutrophication (Schindler 1974(. Conversely, nutrients have been used for decades to stimulate plankton and, subsequently, fish production in aquaculture (Bardach et al. 1972). More recently, lake fertilization has been used to augment salmon runs for commercial exploitation (Hyatt & Stockner 1985, lye et al. 1988), and it has been …
Effects Of Daphnia Availability On Growth And Food Consumption Of Rainbow Trout In Two Utah Reservoirs, R. Tabor, Chris Luecke, Wayne A. Wurtsbaugh
Effects Of Daphnia Availability On Growth And Food Consumption Of Rainbow Trout In Two Utah Reservoirs, R. Tabor, Chris Luecke, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
We monitored the diet and growth of stocked rainbow trout Oncorhynchus mykiss in two Utah reservoirs during 1986 and 1989–1990. For the first month after stocking, juvenile rainbow trout in both reservoirs fed extensively on large Daphnia spp. In East Canyon Reservoir where Daphnia were abundant, this pattern continued throughout the summer, fall, and winter. Growth of rainbow trout in East Canyon Reservoir was generally good throughout 1989–1990. In Causey Reservoir, where Daphnia were less abundant and smaller, rainbow trout fed progressively less on smaller Daphnia throughout the summer, fall, and winter, while other prey items (snails, aquatic insects, and …
Simulated Growth And Production Of Endangered Snake River Sockeye Salmon: Assessing Management Strategies For The Nursery Lakes, Chris Luecke, Wayne A. Wurtsbaugh, Phaedra E. Budy, H. P. Gross
Simulated Growth And Production Of Endangered Snake River Sockeye Salmon: Assessing Management Strategies For The Nursery Lakes, Chris Luecke, Wayne A. Wurtsbaugh, Phaedra E. Budy, H. P. Gross
Watershed Sciences Faculty Publications
We examined the potential of employing a series of lake management strategies to enhance production of endangered Snake River sockeye salmon (Oncorhynchus nerka) in its historical nursery lakes in central Idaho. We used a combination of limnological sampling, experimentation, and simulation modeling to assess effects of lake fertilization and kokanee reduction on growth and survival of juvenile sockeye salmon. Juvenile sockeye salmon from a broodstock of this endangered species are being introduced into the lakes from 1995 to 1998. Results of our analyses indicated that several lakes were suitable for receiving broodstock progeny. Field experimentation and simulation modeling indicated that …
Summer Habitat Use Of Littoral-Zone Fishes In Lake Tahoe And The Effects Of Shoreline Structures, D. Beauchamp, E. Byron, Wayne A. Wurtsbaugh
Summer Habitat Use Of Littoral-Zone Fishes In Lake Tahoe And The Effects Of Shoreline Structures, D. Beauchamp, E. Byron, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
We used scuba observations to determine summer habitat use and the effects of piers on the littoral-zone fish community in Lake Tahoe, California–Nevada. Habitat complexity declined with depth. Over 50% of the littoral zone less than 2 m deep was composed of complex boulder substrates, but this substrate represented less than 10% of the habitat between 10 and 18 m deep. A severe drought lowered the surface elevation of the lake 2 m and reduced the wetted complex rocky habitat by 20% between the 0- and l0-m isobaths (referenced to the mean lake level of 1,899 m above sea level). …
Effects Of Moonlight And Daylight On Hydroacoustic Estimates Of Pelagic Fish Abundance, Chris Luecke, Wayne A. Wurtsbaugh
Effects Of Moonlight And Daylight On Hydroacoustic Estimates Of Pelagic Fish Abundance, Chris Luecke, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
To determine how moonlight and daylight affect hydroacoustic estimates of fish abundance, we used a dual-beam transducer and echo integration to survey pelagic fish (primarily Bonneville ciscoes Prosopium gemmifer) in Bear Lake, Utah and Idaho. During the new moon, the fish were dispersed (not schooling) below the thermocline, chiefly at the depths of 10–20 m. At full moon, they were dispersed but much closer to the bottom, where they were difficult to detect. Acoustic estimates offish density and biomass during full moons were approximately 50% of values derived during new moons. A diel survey during a new moon indicated that …
An Empirical Model Of Gastric Evacuation Rates For Fish And An Analysis Of Digestion In Piscivorous Brown Trout, E. He, Wayne A. Wurtsbaugh
An Empirical Model Of Gastric Evacuation Rates For Fish And An Analysis Of Digestion In Piscivorous Brown Trout, E. He, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
The gastric evacuation rates of brown trout Salmo trutta (0.9–1.6 kg) feeding on fingerling rainbow trout Oncorhynchus mykiss (3.5–7.6 g) were measured in the laboratory at five temperatures (4.5, 9.0, 14.0, 19.0, and 22.5°C). Instantaneous gut evacuation rates (Re) increased exponentially with temperature (T): Re = 0.053se^0.073T, r^2 = 0.98; they varyied from 7%sh^–1 at 4.5°C to 29%sh^–1 at 22.5°C. Linear regressions described the relationship between time and qualitative measures of fish digestion, thus allowing investigators to determine how long an ingested fish would be identifiable at different temperatures. An analysis of published evacuation rates (N = 121) of 22 …
Visual Feeding By Juvenile Bear Lake Sculpin, D. Neverman, Wayne A. Wurtsbaugh
Visual Feeding By Juvenile Bear Lake Sculpin, D. Neverman, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
Young-of-the-year Bear Lake sculpin Cottus extensus feed throughout the day on benthic invertebrates and cease feeding at night when they migrate to the metalimnion. We investigated their reliance on vision by conducting feeding trials at different light levels in the laboratory. Feeding rate reached a maximum at intermediate light levels (near 10^16 photons sm^–2 ss^–1; approximately 1 lux) but decreased as light intensity increased beyond this range. At this maximum rate, the fish fed nine times faster than they were able to feed in the dark, showing that young Bear Lake sculpin rely heavily upon vision to feed. The light …
Lake Trout Spawning In Lake Tahoe: Egg Incubation In Deepwater Macrophyte Beds, D. A. Beauchamp, B. C. Allen, R. C. Richards, Wayne A. Wurtsbaugh, C. R. Goldman
Lake Trout Spawning In Lake Tahoe: Egg Incubation In Deepwater Macrophyte Beds, D. A. Beauchamp, B. C. Allen, R. C. Richards, Wayne A. Wurtsbaugh, C. R. Goldman
Watershed Sciences Faculty Publications
Although most populations of lake trout Salvelinus namaycush spawn over rocky shoals, use of these substrates by lake trout has not yet been found in Lake Tahoe. Large cobble substrate exists at depths less than 20 m, and steep, fractured, rocky substrate can be found in isolated areas from the surface down to at least 100 m, but no evidence of spawning activity in these areas has been found. Instead, at least a portion of the population spawns on deepwater mounds (40–60 m deep) over beds of the macrophyte Chara delicatula. This is the first known report of lake trout …
Predation Risk And The Importance Of Cover For Juvenile Rainbow Trout In Lentic Systems, R. A. Tabor, Wayne A. Wurtsbaugh
Predation Risk And The Importance Of Cover For Juvenile Rainbow Trout In Lentic Systems, R. A. Tabor, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
Juvenile rainbow trout Oncorhynchus mykiss stocked in midelevation reservoirs in Utah inhabit shallow nearshore areas and are vulnerable to predation from piscivorous fish and birds. We determined the use and importance of nearshore habitats by (1) measuring habitat selection by, prey availability to, and feeding of juvenile rainbow trout in two reservoirs with populations of predators, and (2) measuring survival and growth rates in the presence and absence of cover in a pond experiment where adult brown trout Salmo trutta were predators. In the reservoirs juvenile rainbow trout (60–120 mm standard length) were abundant in complex inshore habitats but avoided …
A Mass Mortality Of Fishes In Lake Titicaca (Peru-Bolivia) Associated With The Protozoan Parasite Ichthyophthirius Multifiliis, Wayne A. Wurtsbaugh, R. Alfaro
A Mass Mortality Of Fishes In Lake Titicaca (Peru-Bolivia) Associated With The Protozoan Parasite Ichthyophthirius Multifiliis, Wayne A. Wurtsbaugh, R. Alfaro
Watershed Sciences Faculty Publications
In December 1981 , an epizootic of the protozoan parasite Ichthyophthirius multifiliis killed an estimated 18 million killifish Orestias spp. in Lake Titicaca, a high-altitude tropical system. Of the dead fish collected, 93% were adult O. agassii, a commercially important species that is abundant in the littoral zone. Juvenile Orestias spp., pelagic species, and some other littoral zone fis hes were slightly affected. lchthyophthirius multifiliis was probably introduced with exotic fishes brought to Lake Titicaca in the 1940s and 1950s.
Growth And Activity Of Juvenile Mosquitofish: Temperature And Ration Effects, Wayne A. Wurtsbaugh, J. Cech
Growth And Activity Of Juvenile Mosquitofish: Temperature And Ration Effects, Wayne A. Wurtsbaugh, J. Cech
Watershed Sciences Faculty Publications
The effects of constant temperatures (10, 15, 20, 25, 30, and 35 C) and ration size on the growth rates and activity of juvenile mosquitofish Gambusia affinis (mean wet weight, about 20 mg) were measured in laboratory experiments. On ad libitum rations of Tubifex spp. worms, food-consumption rates of mosquitofish were very high, ranging from 7% dry body weight/day at 10 C to 83%/day at 35 C. Growth increased from 0% dry body weight/day at 10 C to 21%/day at 30 C and declined slightly at 35 C. Gross efficiencies (100 growth/food consumption) increased from 0 at 10 C to …
Laboratory Apparatus For Providing Diel Temperature Regimes For Aquatic Animals, Wayne A. Wurtsbaugh, G. Davis
Laboratory Apparatus For Providing Diel Temperature Regimes For Aquatic Animals, Wayne A. Wurtsbaugh, G. Davis
Watershed Sciences Faculty Publications
In studies of the effects of elevated temperature on aquatic organisms, little emphasis has been placed on modeling the fluctuating temperatures to which organisms are exposed in nature. To some extent this may be related to problems of design and maintenance of apparatus for fluctuating temperature control. The complexity of apparatus used to provide cycled temperatures has ranged from manually controlled valves for introducing water of different temperatures into aquariums (Kelso 1972), to a complex and expensive feedback system, regulated by rotating cams, that controls the temperature of influent water (Honeywell Cam Programmer Thermometers, Fort Washington, Pennsylvania). To facilitate studies …
Food And Distribution Of Underyearling Brook And Rainbow Trout In Castle Lake, California, Wayne A. Wurtsbaugh, R. Brocksen, C. Goldman
Food And Distribution Of Underyearling Brook And Rainbow Trout In Castle Lake, California, Wayne A. Wurtsbaugh, R. Brocksen, C. Goldman
Watershed Sciences Faculty Publications
A difference was found in the summer distribution of underyearling brook trout, Salvelinus fontinalis (Mitchill), and planted rainbow trout, Salmo gairdneri Richardson, in Castle Lake, California. Brook trout underyearlings oriented to the bottom and were found primarily in shallow water on the eastern shore of the lake near springs. The rainbow trout underyearlings were more pelagic and were found in the littoral areas along the entire shoreline. Gravimetrically, the food eaten during the summer by brook trout underyearlings was 13% terrestrial, 11% limnetic, and 76% benthic. Rainbow trout ate 15% terrestrial, 15% limnetic, and 70% benthic food. In summer, rainbow …