Now showing items 41-60 of 12112

    • Effects of placer gold mining on stream macroinvertebrates of interior Alaska

      Wagener, Stephen Mitchell (1984-12)
      Placer gold mining is an economically and politically important industry in Alaska which can have major impacts on the water quality of streams. To determine the effect of placer mining on benthic macroinvertebrates we determined water quality characteristics and sampled benthic invertebrates in nine hydrologicalIy similar and proximally located streams. Sampled streams ranged from unmined control streams to heavily mined streams. Placer mining caused increases in turbidity, settleable solids, percent substrate embeddedness, nonfilterable residue, and total recoverable arsenic, lead, zinc, and copper. Placer mining decreased invertebrate density and biomass. Substrate embeddedness and turbidity were the best predictive descriptors of reduced invertebrate density and biomass. Invertebrate communities in mined streams usually contained higher proportions of collector-gatherers, and lower proportions of crawlers, shredders, filter-feeders, predators, and oligochaetes compared to unmined streams.
    • Photosynthetic response of phytoplankton to changing light intensity in a southcentral Alaskan lake

      Vaught, Kyle Douglas (1989-12)
      Little fresh-water work has been done (compared with published ma­rine studies) using photosynthesis-irradiance (P-I) curves to determine photosynthetic response of natural assemblages of phytoplankton to light above and below thermal stratification structures. Limnological data including physical, chemical, and algal taxonomy and biomass were collected through the summers of 1985 and 1986 at Wasilla Lake, Alaska (approximately 61oN., 148oW.). Algal photosynthesis­irradiance relationships were also determined through the summer of 1986 by means of P-I curves. P-I curve light-limited initial slope (a) was ≈2.5 times higher in phytoplankton populations at 6 m than those in the wind-mixed zone when populations were separated by thermal stratification. Wasilla Lake’s trophic status was estimated to fall between mesotrophic and eutrophic classifications. Phytoplankton in Wasilla Lake were found to require approximately 4-5 days to best adapt to a changing light environment.
    • The morphology and chemistry of two willow species in relation to moose winter browsing

      Suter, Suzanne M. (1992-12)
      This study examines the interaction between moose (Alces alces gigas) and winter dormant willows (Salix alaxensis and Salix pulchra) in Alaska, emphasizing the impact of moose browsing on the forage produced by willow. In a two year field study, plant responses were examined with clipping treatments designed to simulate browsing by moose. The plant responses examined included biomass production, plant architecture, and concentration of plant tannins. Forage selection by moose in the study area is also addressed. Results suggest that a plant response of increased growth, decreased chemical defense, and redistribution of new biomass may explain the pattern of repeated browsing of plants by moose. The responses of clipped plants indicate that moose improve the quality of their willow hosts by browsing and repeated browsing negatively affects carbon reserves of willows. Among and within plant variation in tannin content was also examined among 5. alaxensis trees. Observations are related to within and among tree measurements of growth rate.
    • Marbled murrelet distribution and abundance in relation to the marine environment

      Speckman, Suzann G. (1996-08)
      I examined the effects of the physical variables season, time of day, tide stage, sea surface temperature, and weather and the biological variables phenology and productivity on Marbled Murrelet (Brachyramphus marmoratus) abundance and distribution in Auke Bay and Fritz Cove, Alaska. I surveyed murrelets daily from the shore and a small boat from May through August, 1992 and 1993, and evaluated the impacts of murrelet abundance patterns on a monitoring strategy. I also examined the breeding biology, behavior, and social structure of Marbled Murrelets in an effort to gauge the effects of declining populations on their daily activities, such as foraging and courtship behavior of adults, and foraging strategies of juveniles. I found significant effects of year, season, time of day, and tide stage on Marbled Murrelet numbers at sea that have important implications for designing monitoring surveys to assess changes in Marbled Murrelet populations in Alaska and elsewhere.
    • Distribution, abundance, and quality of forage within the summer range of the central Arctic caribou herd

      Smith, Michael D. (1996-12)
      Distribution, abundance, and quality of summer forage available to caribou (Rangifer tarandus granti) of the Central Arctic Herd were determined in July and August, 1989 -1990. Plant cover, an index of available biomass, was measured at three sites within 50 km of the arctic coast. In general, plant cover increased with distance from the coast. Cover of forbs and evergreen shrubs was higher at inland sites (P < 0.001), whereas cover of willows (Salix spp.) was highest at the coastal site (P < 0.001). Higher plant cover inland is largely attributable to a greater proportion of drier habitats. Differences in forage quality among sites, however, were small and inconsistent. I conclude that by feeding inland during insect-free periods, caribou realize a net energy benefit, because of higher plant biomass, higher proportion of drier habitat, and greater species diversity than coastal areas.
    • Evaluation of Arctic grayling enhancement: a cost per survivor analysis

      Skaugstad, Calvin Loren (1989-05)
      Age-O Arctic grayling Thymallus arcticus were stocked as sac fry and fingerlings in lakes in interior and south central Alaska to evaluate cost per survivor at age 1. When sac fry, 4-g, and 6-g fingerlings were stocked in the same lakes in 1986, estimates of the mean rate of survival at age 1 were 0.08, 0.63, and 0.75. The differences were significant. The mean costs per survivor at age 1 were $1.58, $0.24, and $0.21. The differences were significant between sac fry and both sizes of fingerlings. However, the difference was not significant between 4-g and 6-g fingerlings. When sac fry and 4-g fingerlings were stocked in different lakes in 1986 and again in 1987, estimates of the mean rate of survival to age 1 were 0.11 and 0.34. The difference was significant. The mean costs per survivor at age 1 were $0.82 and $0.70. The difference was not significant. I recommend stocking 4-g fingerlings because they require less rearing in a hatchery than 6-g fingerlings and the cost per survivor is usually less than that for sac fry.
    • Effects of placer mining sedimentation on Arctic graying of interior Alaska

      Simmons, Rodney C. (1984-05)
      During summer 1982 and 1983, I assessed the effects of placer mining sedimentation on Arctic grayling, Thymallus arcticus, in the headwaters of the Birch Creek and Chatanika River drainages, northeast of Fairbanks, Alaska. In each drainage I compared the differences between two streams near their confluence, one that was undisturbed and one with mining activity upstream. Although many age-0 and adult grayling used unmined streams for summer habitat, I found no grayling in the mined streams except during periods of migration. Apparently, grayling consistently chose clearwater streams for summer residence. Caged fish studies demonstrated that if grayling could not escape from streams carrying mining sediments, they would suffer direct, chronic effects, including gill damage, dietary deficiencies, and slowed maturation. The indirect effects of sedimentation on grayling populations, through loss of summer habitat for feeding and reproduction, are more severe than the direct ones.
    • Seasonal distribution and winter habitat use by Sitka black-tailed deer in the Prince William Sound region, Alaska

      Shishido, Neil (1986-05)
      Intensity of winter use of a variety of forest stands by deer (Odocoileus hemionus sitkensis) was measured. Information on vegetation, timber type, and topography was collected to find relationships between deer use and habitat variables. Seasonal use of forest stands by deer is best described in terms of: basal area of trees, amount of deer forage (Vaccinium spp. and Coptis aspleniifolia)r deviation in crown closure, and timber volume. Information from radio-collared deer indicated high use of forest habitat, particularly during winter. Alpine areas received more use than any other habitat during summer. South-facing slopes were used more often than other aspects across all seasons. Average winter home range size was 160 ha, significantly smaller than the spring average (282 ha). Most radio-collared deer made seasonal elevational movements within a single drainage. Retention of high timber volume, old growth forest is recommended to maintain preferred deer habitat in Prince William Sound.
    • Estimation of angler harvest, catch and effort in the Swanson River canoe trails system, Kenai National Wildlife Refuge, Alaska

      Shiffer, Mary P. (1989-08)
      Methods of estimating harvest, catch, angler effort and quality of catch were tested during the summer of 1988 on the Swanson River Canoe Trails System, Kenai National Wildlife Refuge, Alaska. Angler interviews at Trails System access points provided the best estimates of these sport fishing variables. Rainbow trout dominated the catch (95%); about three-fourths were less than 254 mm long and most were released. Total estimated catch of trout was 18,448 (10,221-26,675; ρ=0.95); estimated harvest was 25 percent of the catch: 4,651 (2,722-6,580; p=0.95). Aerial surveys (counts of cars and boats) and the trail head registers provided seasonal use trends for the Trails System, but there was no relationship between these indices and the variables of the fishery. Anglers must be personally interviewed in order to acquire data to evaluate the fishery.
    • Walrus feeding: a re-examination

      Sheffield, Gay Glover (1997-08)
      A new approach for analyzing walrus (Odobenus rosmarus) diet was examined. Controlled gastric digestion experiments determined the relative rates at which different kinds of food items became unidentifiable. The ability to identify prey items varied within and among prey types. The laboratory experiments provided a new basis for examining diet data by characterizing the condition of stomach samples based on the rates at which different prey types were digested. Stomach content data acquired during 1952-1991 from 798 Pacific walruses were compiled, and interpretations about feeding habits were re-examined. Walruses regularly consumed a wider assortment of benthic prey than was previously thought. The diet of the Pacific walrus varied seasonally and regionally. Males and females consumed essentially the same food items when in the same location.
    • Injury and survival of northern pike captured by electrofishing

      Roach, Stafford M. (1992-05)
      I exposed 240 northern pike Esox lucius to four levels of pulsed direct current (PDC). Incidence of spinal injury for 30 Hz was 5.0% at 100 V and 10.0% at 400 V; and for 60 Hz was 8.3% at 100 V and 11.7% at 400 V. Injury rates were not significantly different among treatments (P=0, 58) . I also electroshocked 140 fish with 120-Hz PDC at 300-600 V; spinal injury increased to 29% (P<0.01). These fish were held for 1 month in ponds to compare survival with 70 unshocked fish; survival was 91-92% for both groups (P=0.57). During field trials I captured about three northern pike with 60-Hz PDC for every one caught with DC and 30-Hz PDC (P=0.08). Conventional electrofishing (i.e., 60-Hz PDC at 100-400 V) did not cause significant injury in adult northern pike but did capture them efficiently. PDC at frequencies above 60 Hz should be avoided.
    • Seasonal allocation of energy in four tissues of northern pike from Minto Flats, Alaska

      Murphy, Robert Leo (1989-12)
      The seasonal changes in energy content of the gastrointestinal tract, gonad, liver, and muscle of 120 mature northern pike (Esox lucius Linnaeus) from Minto Flats, Alaska were estimated (bomb calorimetry) during winter, early spring (prespawning), late spring (postspawning), and fall 1988. Increases in the specific energy contnet of testes was completed by September, and did not change from September to March. Ovarian specific energy content remained unchanged between the postspawning (21.78 kJ/g) and fall (21.89 kJ/g) periods, then accumulated during the winter (24.80 kJ/g). Gastrointestinal tract specific energy content decreased in fish of both sexes during spawning, and increased during winter. Liver specific energy content occurred in females during summer, and in males during winter. Winter is a critical period for males and females; gonadal energy requirements in females must be met to assure reproductive success the following spring, and, important energy reserves necessary for survival are accumulated in males.
    • Effects of weather and parasitic insects on summer ecology of caribou of the Delta herd

      Mörschel, Frank Matthias (1996-08)
      The roles of weather and parasitic insects in caribou (Rangifer tarandus) ecology were investigated to determine their influence on population dynamics of the Delta Herd. Data on weather, insect abundance, and caribou behavior were collected during two summers. Mosquito season started 21 and 11 June and oestrid fly season 11 July and 21 June in 1994 and 1995, respectively. Mosquito activity was limited by windspeed at temperatures >7°C. Oestrid fly presence was influenced mainly by temperature. Presence of insects and temperature positively influenced, and windspeed negatively influenced rate of activity changes of caribou. Feeding decreased and standing increased with insect presence and temperature. Increasing temperature affected activity budgets even in the absence of insects by decreasing feeding activities. Weather, especially temperature, and parasitic insects, especially oestrid flies, affected caribou mainly by limiting forage intake and increasing energy expenditure. Estimated activity budgets in summers of 1976-1995 indicated possible limiting effects of temperature on population dynamics.
    • Stock assessment of arctic grayling at Ugashik Lakes, Alaska

      Meyer, Scott C. (1990-12)
      Arctic grayling (Thymallus arcticus) stocks were assessed at Ugashik Narrows and Outlet in Southwest Alaska during the open-water periods of 1987, 1988, and 1989. Abundance, size, and age data were collected, which were then compared with historical data for 1968-1984. The Narrows is the stream between Upper Ugashik Lake and Lower Ugashik Lake, and the Outlet is the source of the Ugashik River from Lower Ugashik Lake.
    • Habitat utilization by fishes in the Tanana River near Fairbanks, Alaska

      Mecum, Robert D. (1984-05)
      This study evaluated summer habitat utilization of fishes and the effects of floodplain developments on fish and aquatic habitat in the glacially-fed Tanana River near Fairbanks, Alaska. Aquatic habitats were quantitatively described on the basis of water velocity, depth, and clarity, and substrate, cover and vegetation. Lake chub and longnose sucker were abundant in all habitats. Whitefishes, juvenile salmon, and northern pike were captured most frequently in areas with high water clarity. Burbot preferred deeper, turbid waters. Young-of-the-year of lake chub and longnose sucker preferred shallow, silty backwaters; juvenile lake chub demonstrated no habitat preferences; and adult lake chub, juvenile longnose sucker, and juvenile/adult slimy sculpin preferred gravel riffles. Bank stabilization activities have significantly modified aquatic habitat and fish communities of Tanana River backwaters. In general, free-flowing sidechannels have become blocked-off sloughs resulting in reduced turbidities and lower flows.
    • Evaluation of some factors affecting food conversion by age-0 arctic grayling reared in floating net-pens

      McKinley, Timothy R. (1992-05)
      Two experiments were repeated three times to evaluate the effects of feeding frequency, loading density, and food particle size on food conversion of age-0 Arctic grayling Thymallus arcticus reared in floating net-pens. Growth in length or weight could not be evaluated because of the short (11 - 12 days) feeding trials. When fed to satiation, the optimal interval between feedings was 3 hours. The highest initial loading density used (5.6 kg/m3) consistently produced the best food conversions (1.10 - 1.51 g food/g weight gain). Food particles several sizes larger than those generally recommended were used with less waste and without adverse effects. Optimal food size for 60 - 73 mm Arctic grayling was 1.3 - 1.5 mm (2.1 - 2.5% fork length).
    • Crime in Alaska - 1999

      Alaska Department of Public Safety (1999)
    • Crime in Alaska - 1998

      Alaska Department of Public Safety (1998)
    • Crime in Alaska - 1997

      Alaska Department of Public Safety (1997)
    • Crime in Alaska - 1996

      Alaska Department of Public Safety (1996)