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Demographic data are sparse for Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri; YCT). Data for YCT in the spawning run (spring; 29 years) of a Yellowstone Lake tributary or caught in gill nets set (fall; 30 years) at established lake locations between 1977 and 2007 were examined. Female proportion in runs averaged 0.61 but was 0.48 among gillnetted “prespawner” YCT (i.e., mature fish whose excised gonads indicated the fish would have spawned the next year). Maturity proportion-total length (TL) relationships for gillnetted female and male YCT were logistic-shaped and similar in their inflection points; maturity onset occurred at 200–250 mm TL; ∼95% of YCT ≥ 400 mm TL were mature and ∼70% were prespawners. Fecundity was positively associated with YCT TL. Accuracy of scale-based YCT ages was affected by a frequently overlooked scale annulus and an inability to unequivocally identify fish of a single cohort on the basis of scale characteristics using associated, recognized ageing criteria for this population. Temporal differences in fits of a modified von Bertalanffy growth model to YCT TL at capture and scale-based age probably resulted from ageing errors evident among successive, annual scale analysts rather than differences in YCT growth. Nevertheless, when the age estimates of one, long-term analyst were used in analyses, the estimated growth parameters L∞ and ω; were concordant with empirical observations of the maximum TL of YCT and TL of age-1 YCT in Yellowstone Lake, respectively. The demographic relationships and linking, parameterized growth model provide a useful foundation for age-structured population modeling.
Mountain whitefish (Prosopium williamsoni) are among the most abundant native fishes in western North America, yet their role in ecosystems is largely unknown. We investigated their ecology in Big Creek, a 7th-order wilderness watershed in central Idaho. Based on underwater visual counts and hook and line surveys conducted during summer months, as well as tissue analysis, we estimated mountain whitefish distribution and abundance, total biomass, production, and energy and nutrient contributions along a 60 km segment of Big Creek. We observed that abundance decreased with distance upstream, and 93% of mountain whitefish surveyed in Big Creek were greater than 200 mm (≥ 3 years); few juveniles were observed, suggesting that rearing occurs in habitats downstream. Mountain whitefish were the dominant fish in Big Creek, in terms of both abundance (33% of fish observed) and biomass (57% of salmonid biomass). We estimated their production averaged across the study segment as 0.51 g m-2 yr-1, though it ranged up to 6.8 g m-2 yr-1 in downstream reaches. Mountain whitefish tissue energy content was 5.3 Kcal g-1 and its composition was 10.5% N, 3.0% Ca, 2.3% P, 1.2% K, 0.7% S, 0.3% Na, and 0.1% Mg. The ratio of N:P(4.5:1) was slightly lower than those observed in other salmonids and considerably higher than more bony taxa. Our results suggest mountain whitefish constitute an important pool of energy and nutrients in the Big Creek ecosystem, and seem likely to play important roles that have not yet been investigated in this and other rivers throughout their range.
Knowledge of female behavior while rearing young can have important implications for species conservation. We located dens and analyzed activity (defined as movement between consecutive GPS locations) for nine female lynx with kittens in the north-central Rocky Mountains in 2005 and 2007. We used GPS tracking collars to quantify the percentage of time a female spent active and her daily distance traveled for each of three reproductive stages, classified as predenning, denning, and postdenning. We also described the use and placement of maternal dens for these females. Female lynx in our study used one to six dens per breeding season, and increased both frequency of den relocation and distance between dens as kittens matured. Females typically left the den twice a day, and were gone for an average of five hours at a time. Females were active for 56% of a given 24 hour period during predenning, 48% during denning, and 61% during postdenning. Females traveled greater distances in 24 hours during predenning than denning. We conclude that reproductive female lynx alter the amount of time they spend active and daily distance traveled based on reproductive status.
In the Elwha River, two hydroelectric dams constructed nearly a century ago fragment previously continuous habitat and isolate migratory bull trout. Removal of the dams is scheduled to begin in 2011, and represents an opportunity to help recover this threatened species. Large-scale disturbance is expected when accumulated sediments behind the dams are released downstream, which may initially negatively affect bull trout. To inform restoration planning, we investigated levels of genetic variation within and among bull trout populations from six Olympic Peninsula watersheds with an emphasis on the Elwha River. We determined genetic relationships among Elwha bull trout from four distinct river sections and performed population assignments for fish collected from the lower Elwha and Dungeness rivers. There were greater levels of variation and gene flow in coastal watersheds (Hoh, South Fork Hoh, Kalaloch) compared to populations isolated by dams (Elwha, North Fork Skokomish). Elwha bull trout represented an independent spawning population and were highly differentiated from other populations. Bull trout from the Elwha (n = 21) and Dungeness (n = 18) estuaries all assigned to the river they there were collected from. Despite long-term fragmentation, there was no significant genetic variation among Elwha bull trout separated by the dams, although fish from the Elwha headwaters were genetically distinct. Results suggest that bull trout still migrate downstream through both Elwha River dams and that anadromous bull trout will likely help to recolonize the Elwha River following dam removal. Baseline data from this study will be useful for monitoring bull trout recovery following dam removal.
Ocean-type juvenile Chinook salmon (Oncorhynchus tshawytscha) can be present in the nearshore areas of Lake Washington and Lake Sammamish, WA for 4–5 months (January–June) and may encounter nonnatal tributaries. The use of these tributaries is not well known. We determined the presence of juvenile Chinook salmon in 12 tributaries through nighttime snorkel surveys from March to June. At one heavily-used tributary, we determined their temporal and spatial distribution by conducting surveys every two to three weeks from February to June. Additionally, we determined whether delta areas of tributaries are used by juvenile Chinook salmon by comparing their density and diet to other lakeshore sites. Of 12 streams surveyed, juvenile Chinook salmon were observed in eight. The abundance of Chinook salmon appeared to be related to a variety of factors including proximity to the natal stream, stream gradient, and stream size. In an intensively-monitored stream, juvenile Chinook salmon were found primarily in shallow areas in February and March and then shifted to deeper pools as juveniles increased in size. Within the lake nearshore area, juvenile Chinook salmon commonly used delta areas of nonnatal tributaries and their abundance was frequently greater than other nearby shoreline sites. Diet analysis indicated nonnatal streams are also a source of prey for lake-dwelling juvenile Chinook salmon, especially during rain events. Nonnatal tributaries in lake systems appeared to be valuable habitat features for juvenile Chinook salmon and can function in a variety of ways, including providing both stream and delta habitat.
A shed moose (Alces alces) antler eaten by a grizzly bear (Ursus arctos), which recently emerged from its winter den in western Alaska, contained 40.2% crude protein, 18.5% calcium and 8.5% phosphorous by dry weight. Bears emerging from dens could be experiencing skewed Ca:P ratios resulting in an appetite for bone phosphorus. Protein availability at this time of year in the Andreafsky Mountains may also be limiting. Antlers as part of bear diets may be seasonal, but can be a valuable source of minerals, especially Ca, P, and protein early after den emergence or other critical periods. Grizzly bears can obtain a valuable amount of nutrients by consuming the distal palm ends of shed moose antlers. Distal ends of antlers have thinner cortex where bone material is easier to break than at the antler base. In addition, the greater proportion of spongy bone in antler palms should be easier to digest by bears. The significance of shed antlers to bears as a mineral and protein source is still unclear, but antlers could be an important nutrient reserve across the landscape.
The desert nightsnake (Hypsiglena chlorophaea) is a small (< 60 cm snout-vent length), cryptic species of snake often associated with desert habitats of the intermountain western United States. This species is both an active and ambush foraging that feeds largely upon small snakes and lizards. For some nocturnal species, such as H. chlorophaea lower activity levels in response to a full moon may affect foraging time, as well as reduce the risk of predation. I collected snakes from May to August 2009 in central Washington State, and maintained in captivity using standard husbandry practices. Using moonlight levels gathered at the collection site, I compared the mean numbers of snake movements of 20 adult H. chlorophaea during three moonlight trials: new moon (0.05 lux), half moon (0.32 lux), and full moon (2.10 lux). For the 23 hr trial period, simulated moon-up during the half moon and full trials was from 2300 to 0300 hr. Based upon current field data on this species, I predicted that snakes would reduce activity in response to a full moon. During moon-up, there was no difference in the mean number of movements of snakes between the new or half moon trials. However, all snakes made fewer movements during the full moon trial.