Now showing items 21-40 of 3900

    • 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).
    • Habitat selection and reproductive ecology among Townsend's warblers (Dendroica townsendi) in southcentral Alaska

      Matsuoka, Steven Mark (1996-05)
      I investigated habitat selection and reproductive ecology among Townsend's Warblers (Dendroica townsendi) in mature mixed forests near Anchorage, Alaska. I examined selection of territories, nest sites, and foraging sites to identify habitat features associated with each resource. Male pairing and nest survival were monitored to identify factors influencing reproductive success. Females were highly selective for large white spruce (Picea glauca) as nest sites. Foraging behavior varied temporally and was specialized toward medium white spruce early in the breeding season but subsequently generalized across substrates. Territories were heterogeneous in habitat and were characterized by habitat features selected for nesting and foraging, suggesting specific demands for resources influenced choice of territories. Pairing success (98%) and nest success (51%) were generally higher than that of migratory songbirds breeding in forest fragments. Nest predation and blow fly (Protocalliphora) parasitism, factors constraining reproductive output, varied with microhabitat, suggesting that habitat selection may mitigate their effects.
    • Evaluation of sampling gears for fish population assessment in Alaskan streams and rivers

      Lorenz, William Reed (1984-12)
      During summers, 1982 and 1983, a variety of habitats were sampled on the Tanana and Kenai River drainages to evaluate sampling gears used for fish population assessment in Alaskan streams and rivers. Experiments were conducted to investigate sampling efficiency, length and species selectivity, and injuries to fish by three active (backpack electroshocker, electrofishing boat, seine), and two passive (minnow trap, fyke net) gear types. Gears were compared using a common set of attributes: accuracy, portability, scope or species detection, labor required, fishing power, fish savings (low mortality), and initial cost. Electrofishing systems were best for species detection and fishing power, while passive gears had higher catch per hour of labor. Large fyke nets and seines were effective under limited environmental conditions. A linear model was developed to assist in selecting an optimum fishing gear, or array of gears, for any level of fisheries population assessment, considering all applicable sampling constraints.
    • Climate and caribou: effects of summer weather on the Chisana caribou herd

      Lenart, Elizabeth A. (1997-08)
      In 1989, the Chisana caribou (Rangifer tarandus) herd in the northern Wrangell Mountains, Alaska declined substantially in population size and productivity. Summers were significantly warmer and slightly drier during years the herd was declining (1989-1995) compared with years when the herd was stable or increasing (1981-1988). We increased air temperature and decreased precipitation with a plastic tent, decreased light intensity with a shade cloth, and increased precipitation by adding water to determine climatic effects on nutrient content and biomass of caribou forage during summer in 1994 and 1995 in the subarctic tundra. We determined that short-term variations in climate affected nutrient quality, particularly nitrogen content, in above-ground biomass of caribou forage. The warmer, drier summers (1989-1995) may have affected the Chisana population adversely by increasing insect harassment and decreasing nitrogen content in their forage.
    • Resource partitioning and behavioral interactions among young-of-the-year salmonids, Chena River, Alaska

      Lee, Kristine M.; Reynolds, James B. (1985-09)
      The partitioning of habitat and food and the behavioral interactions of young-of-the-year Arctic grayling (Thymallus arcticus), Chinook salmon (Oncorhynchus tshawytscha), and round whitefish (Prosopium cylindraceum) were studied in the laboratory and in their natural habitat. Individuals of all three species defended territories. Arctic grayling were the most aggressive of the three and appear to displace round whitefish from their preferred habitat. In sympatry, there is a segregation of habitat use between Arctic grayling and chinook salmon. Stomach content analysis showed an overlap in diet among the three species. Larvae of the three species emerged at different times and sizes, resulting in a size divergence among coexisting species during their first summer. The three species were found to inhabit faster moving and deeper water as they grew, resulting in a spatial separation of the species and a reduced probability of interactions and competition among them.
    • Phylogeographic variation and the island syndrome in holarctic tundra voles (Microtus oeconomus)

      Lance, Ellen Weintraub; Cook, Joseph A.; Klein, David R. (1995-12)
      Phylogeographic patterns of genetic and morphologic variation were explored among six subspecies of the Holarctic tundra vole (Microtus oeconomus). but focused on those populations occurring in southcoastal Alaska. Allozyme electrophoresis and karyotyping revealed that, although levels of intraspecific variation were low compared to other species of Microtus. allozymic divergence was concordant with regional glacial history. Tundra voles from interior Alaska became established prior to the last glacial retreat. However, populations from southcoastal Alaska were founded more recently. Tundra voles from Montague Island, an endemic subspecies, exhibited features of the island syndrome (i. e., gigantism, older age structure). Factors potentially responsible for insular gigantism were assessed. The findings of this study fail to support the hypothesis that the island syndrome is a direct result of interspecific competition. Other density-dependent factors, such as predation, may be responsible for body size and demographic changes in these insular rodents.
    • Diet and nestling growth of red-legged and black-legged kittiwakes: an interspecies cross-fostering experiment

      Lance, Brian K. (1996-05)
      I conducted an interspecific cross-fostering experiment to investigate how diet composition and feeding rates affected nestling survival, growth, and gastrointestinal development of Red-legged and Black-legged kittiwakes on St. George Island, Alaska. Red-legged Kittiwakes (Rissa brevirostris) fed nestlings primarily lanternfish (Myctophidae), a high-lipid diet, whereas Black-legged Kittiwakes (R. tridactyla) fed nestlings mostly walleye pollock (Theragra chalcogramma), a low-lipid diet. Nestling meal size was similar for the two species, but Red-legged Kittiwakes fed nestlings at about half the rate of Black-legged Kittiwakes. Interspecific differences in nestling growth were explained by differences in adult body mass. Survival rates and lean body mass did not differ between fostered nestlings and conspecific controls. Nestlings raised by Red-legged Kittiwakes had 50% larger fat reserves than those raised by Black-legged Kittiwakes. Thus growth rates of lean tissue were genetically constrained, while rates of fat deposition were determined by diet Interspecific differences in gastrointestinal anatomy were partly genetic and partly dietary in origin.
    • Evaluation of models and assumptions for closed population abundance estimators from from cutthroat trout mark-recapture data

      Laker, Mark William; Reynolds, James B. (1994-09)
      The goal of this project was to improve cutthroat trout Oncorhynchus clarki mark-recapture experiments in southeast Alaska lakes. A mark-recapture experiment was conducted at Hasselborg Lake, Admiralty Island, southeast Alaska. The sampling design, nine abundance models and their assumptions were evaluated. Evaluation of model assumptions led to conclusions that the population was closed and no tag loss occurred. Probability of capture varied due to effects of time (sampling occasion) and heterogeneity (differences among individual fish) during 1992, and time and behavior (capture effects) during 1993. Chao M(h) was selected as the best abundance estimator for 1992, and Chao M(t) for 1993. Evaluation of sampling design led to several conclusions: angling was the most effective gear type; catch per unit effort decreased with depth; dispersal distance was not related to time; length distributions were depth specific; and gear selectivity took place.
    • Life-history consequences of maternal condition in Alaskan moose

      Keech, Mark A. (1999-05)
      We studied characteristics of life-history of Alaskan moose (Alces alces gigas) including the effects of maternal condition of adult females on survival and physical condition of young during their first year-of-life. We also examined the relation between maternal condition and reproductive parameters of individual adult moose. We found that females in better physical condition, as indexed by rump-fat thickness, had higher rates of pregnancy, gave birth to more twins, and produced young with higher birth masses than did females with less rump fat. Expected time-to-death for individual young increased as birth mass increased and decreased with increasing birth date and litter size. Our results indicated maternal condition influenced subsequent variables associated with birth, which ultimately influenced future survival of offspring. Timing of parturition also occurred earlier for individual females with greater rump-fat thickness. That outcome suggested that timing of parturition was the result of environmental factors acting on females prior to birth.
    • Aquatic ecology of two subarctic lakes: Big and Little Minto Lakes, Alaska

      Jacobs, Laura Lee (1992-05)
      During 1988, three sampling trips were made to Big and Little Minto Lakes to study their limnological features. Physical and chemical measurements were made of both lakes, while the invertebrate community and habitat characteristics were investigated along Big Minto Lake's shoreline (5-35cm water depth) . Both lakes are shallow and eutrophic, with high dissolved oxygen and pH, and moderate alkalinity. Invertebrate abundance averaged 7,352/m2 (±SE = 406, n = 60) , and was dominated by Diptera (38%) . Gastropoda comprised the largest portion (41%) of total biovolume (11.28 mL/m2, ±SE = 1.28, n = 60). Diptera and Coleoptera contained the majority of invertebrate families. Scrapers (41%) and collectors (23%) dominated the food web in biovolume. Overall, invertebrate abundance was significantly correlated with low detritus biomass; however, Trichoptera abundance was significantly correlated with low vegetation biomass, shallow water, and the August sample period; and both diversity indices, were significantly correlated with aquatic plant biomass (AFDW).
    • Life histories and community structure of the caddisflies (Trichoptera) of two Alaskan subarctic streams

      Irons, John G., III (1985-05)
      The ecology of Trichoptera was studied in two streams in interior Alaska. Monument Creek and West Fork are characterized by cold water temperatures, low allochthonous input and periphyton biomass, and lengthy ice cover. Nine species were found, Rhyacophila vofixa ? (Rhyacophilidae), Glossosoma verdona, G. alascense (Glossosomatidae), Brachycentrus americanus (Brachycentridae), Hydatophylax variabilis, Ecclisomyia conspersa, Onocosmoecus unicolor, Chyranda centralis and Apatania crymophila (Limnephilidae). There were four shredders, three scrapers, one omnivore, and one predator. Within shredders and scrapers, species had sequentially overlapping life histories, perhaps allowing functionally similar species to use the same food resources. Latitudinal gradients in the North American Trichoptera fauna were investigated using approximately 90 studies from the literature and unpublished Alaskan data. Taxonomic richness showed a weak negative correlation with latitude in light trap studies. Hydropsychoidea showed an inverse correlation, while Limnephiloidea and Limnephilidae showed positive correlations with latitude. Density and biomass were also negatively correlated to latitude.
    • Life histories and community structure of Ephemeroptera and Plecoptera in two Alaskan subarctic streams

      Howe, Allen L. (1981-05)
      Development of water quality and quantity standards required for improved management of stream fisheries depends on understanding life cycles of the major benthic components. Because temperature is a major factor influencing aquatic insect life histories, subarctic streams provide excellent opportunities to examine organisms existing under extreme environmental conditions. Life histories and community structure of Ephemeroptera and Plecoptera were examined in two Alaskan subarctic streams during 1979 and 1980. Biweekly benthos samples were collected during the ice-free period in a second and a fourth order stream. Seventeen stonefly species and at least seven mayfly species were collected as nymphs or adults. Nymphal abundance and biomass were greater for all taxa in erosional zones (P < 0.05). Coexistance of systematically-related species occurred because of seasonal separation of life histories, or differ­ences in food exploitation patterns.
    • Stock identification and homing of arctic grayling, Thymallus arcticus (Pallas), in interior Alaska

      Hop, Haakon; Reynolds, James B. (1985-12)
      The objectives were to determine techniques for identification of Arctic grayling Thymallus arcticus (Pallas) stocks in interior Alaska and evaluate homing. Starch gel electrophoresis was used to identify three stocks in the Tanana River and the upper Koyukuk River drainage. Photoidentification could not be used to separate these stocks based on the number of spots on their sides. The spot pattern seemed to have potential for identification of individual grayling. It was feasible to tag young-of-the-year grayling with coded micro-wire tags. The 30-day tag loss was high (27.8%) for the smallest, but significantly lower (7.7%) for the largest size group. Analysis of back-calculated fork lengths at first annulus indicated that Badger Slough and Chena River grayling represent separate stocks. Mature Badger Slough grayling had similar numbers of whole circuli to young-of-the-year grayling from Badger Slough, suggesting that they were homing to their natal stream.