Homer, AK, United States
Homer, AK, United States

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Natanson L.J.,National Oceanic and Atmospheric Administration | Adams D.H.,Florida Fish And Wildlife Conservation Commission | Winton M.V.,Coonamessett Farm Foundation | Maurer J.R.,Kachemak Bay Research Reserve
Transactions of the American Fisheries Society | Year: 2014

Age and growth estimates for the Bull Shark Carcharhinus leucas were derived from 121 vertebral centra collected from Bull Sharks (59.1-223.5 cm FL) between 1966 and 2010 in the western North Atlantic Ocean. Size at birth was confirmed with an additional 20 embryos (44.2-54.4 cm FL). The maximum age based on vertebral band pair counts was 25 (184 cm FL) and 27 (196 cm FL) years for males and females, respectively. The logistic and Gompertz growth models fitted the size-at-age data best for males and females, respectively. Based on previously published estimates of length at maturity, males mature at 15-17 years (176-185 cm FL) and females at 15 years (189 cm FL). Bull Sharks in the western North Atlantic Ocean and the Gulf of Mexico have similar growth rates and reach similar sizes at age. © American Fisheries Society 2014.


Whigham D.F.,Smithsonian Environmental Research Center | Walker C.M.,Kachemak Bay Research Reserve | King R.S.,Baylor University | Baird S.J.,Kachemak Bay Research Reserve
Wetlands | Year: 2012

Vegetation of wetlands adjacent to headwater streams on the Kenai Lowlands was dominated by Calamagrostis canadensis, indicating that it is a keystone species that influences stream-wetland interactions across a wide range of geomorphic settings from which headwater streams have their origin. We sampled 30 sites as part of a project to determine the relationships between landscape features and the biological and chemical characteristics of headwater streams and their associated wetlands. In this paper we consider vegetation in wetlands adjacent to headwater streams. Calamagrostis canadensis was the only species that occurred at all sites and only a few species were widespread and abundant across the range of sites sampled. Nonmetric multidimensional scaling of species importance values indicated that the distribution of sites and species was primarily related to stream-reach scale environmental and biological factors. Sixteen stream-reach factors were significantly correlated with the distribution of sites and species on one axis of the ordination. Headwater streams that were located in relatively flat areas with extensive wetlands had species characteristic of nutrient poor wetlands and sites located in steep valleys with narrow wetlands had species characteristic of uplands and wetlands on mineral soils. The distribution of sites and species on the second ordination axis was interpreted to be a response to biological interactions; primarily the negative relationship between C. canadensis and the diversity of other species. We concluded that large-scale watershed features of the landscape are less important than local scale factors in determining the characteristics of vegetation in headwater stream-wetland complexes in the Kenai Lowlands. There was no evidence, however, that differences in the stream-reach scale conditions across the study sites resulted in distinct plant communities associated with the headwater wetlands even though the headwater streams had their origin in different landscape settings. © US Government 2012.


King R.S.,Baylor University | Walker C.M.,Kachemak Bay Research Reserve | Whigham D.F.,Smithsonian Environmental Research Center | Baird S.J.,Kachemak Bay Research Reserve | Back J.A.,Baylor University
Freshwater Science | Year: 2012

Conservation and management of headwater streams amid rapid global change require an understanding of the spatial and environmental factors that drive species distributions and associated ecosystem processes. We used a hierarchical analytical framework to model effects of catchment-scale topography and wetland geomorphic classes on stream physical habitat, chemistry, and macroinvertebrate and fish communities in 30 headwater streams across the Kenai Lowlands, southcentral Alaska, USA. We identified 135 macroinvertebrate taxa, 122 of which were aquatic insects, of which 79 were dipterans. We collected only 6 species of fish, but juvenile coho salmon and Dolly Varden were collected in 17 and 25 of the 30 streams and reached densities >500 and 1300/km, respectively. Flow-weighted slope, an indicator of water residence time and gradient, was the best catchment-scale correlate of macroinvertebrate and fish community structure, and its effect was mediated by wetland geomorphic classes and numerous water chemistry, substrate composition, and channel geomorphology variables measured at the reach scale. Many macroinvertebrate taxa showed high fidelity to different levels of the topographic gradient, resulting in high β diversity but relatively similar levels of α diversity across the gradient. Juvenile salmonids were segregated among streams by both species and age classes. Coho salmon fry and parr (<10 cm total length [TL]) had significant unimodal distributions that peaked in streams with intermediate slopes and gravel substrate, whereas presmolts (≥10 cm) were found only in lowest-sloping streams with mostly peat substrate and deep, slow channels. Large Dolly Varden (≥8 cm) were found across the entire gradient but were most abundant in high-sloping catchments, whereas small Dolly Varden (<8 cm) followed a similar distribution but were absent from the lowest-gradient sites with low flow velocity, dissolved O2, and gravel substrate. Predictive modeling indicated that all of the 547 km of headwater streams in the study area might serve as potential habitat for ≥1 species and age class of salmonids. Our study should assist in development of catchment management tools for identifying and prioritizing conservation efforts in the region and may serve as a framework for other studies concerning biodiversity and focal species conservation in headwater streams. © 2012 The Society for Freshwater Science.


Dekar M.P.,Baylor University | King R.S.,Baylor University | Back J.A.,Baylor University | Whigham D.F.,Smithsonian Environmental Research Center | Walker C.M.,Kachemak Bay Research Reserve
Freshwater Science | Year: 2012

We used dual-isotope mixing models (δ13C/δ 15N and δ2H/δ15N) in a Bayesian framework to partition allochthonous and autochthonous energy sources for salmonids in 2 headwater streams in the Kenai Lowlands, Alaska (USA). Our 1 st objective was to estimate the production base for juvenile coho salmon (Oncorhynchus kisutch) and Dolly Varden (Salvelinus malma). We hypothesized that consumers would be reliant on both autochthonous (filamentous algae and periphyton) and allochthonous sources, but that autochthonous sources would dominate because of the open canopy and lower-quality litter inputs provided by the riparian wetland vegetation, primarily bluejoint grass (Calamagrostis canadensis). Our 2nd objective was to evaluate the utility of stable H isotopes for tracing energy pathways in a northern-latitude ecosystem. We hypothesized that δ2H-based models would provide more precise estimates of source partitioning than δ13C-based models because of greater source separation. Allochthonous source contributions consistently exceeded autochthonous sources for all fish species and size classes at both study sites. However, diet shifted during ontogeny, and larger Dolly Varden relied more on autochthonous sources than did smaller individuals of both species. Last, we found good correspondence and similar levels of precision between the δ13C- and δ2H-based models despite greater source separation by δ2H. Our results highlight the importance of allochthonous sources in headwater streams, and we suggest that litter inputs from grasses may be an under-appreciated subsidy to salmon production. Stable H isotopes can be an effective foodweb tracer in northern-latitude streams, but source partitioning results were not sufficiently different from stable C isotope models for us to recommend unequivocally using them to replace or enhance δ13C in similar studies. © 2012 by The Society for Freshwater Science.


Hoem Neher T.D.,University of Alaska Fairbanks | Hoem Neher T.D.,National Oceanic and Atmospheric Administration | Rosenberger A.E.,University of Alaska Fairbanks | Rosenberger A.E.,U.S. Geological Survey | And 3 more authors.
Transactions of the American Fisheries Society | Year: 2013

For Pacific salmon, estuaries are typically considered transitional staging areas between freshwater and marine environments, but their potential as rearing habitat has only recently been recognized. The objectives of this study were two-fold: (1) to determine if Coho Salmon Oncorhynchus kisutch were rearing in estuarine habitats, and (2) to characterize and compare the body length, age, condition, and duration and timing of estuarine occupancy of juvenile Coho Salmon between the two contrasting estuaries. We examined use of estuary habitats with analysis of microchemistry and microstructure of sagittal otoliths in two watersheds of south-central Alaska. Juvenile Coho Salmon were classified as estuary residents or nonresidents (recent estuary immigrants) based on otolith Sr: Ca ratios and counts of daily growth increments on otoliths. The estuaries differed in water source (glacial versus snowmelt hydrographs) and in relative estuarine and watershed area. Juvenile Coho Salmon with evidence of estuary rearing were greater in body length and condition than individuals lacking evidence of estuarine rearing. Coho Salmon captured in the glacial estuary had greater variability in body length and condition, and younger age-classes predominated the catch compared with the nearby snowmelt-fed, smaller estuary. Estuary-rearing fish in the glacial estuary arrived later and remained longer (39 versus 24 d of summer growth) during the summer than did fish using the snowmelt estuary. Finally, we observed definitive patterns of overwintering in estuarine and near shore environments in both estuaries. Evidence of estuary rearing and overwintering with differences in fish traits among contrasting estuary types refute the notion that estuaries function as only staging or transitional habitats in the early life history of Coho Salmon. Received December 5, 2012; accepted June 10, 2013. © 2013 Copyright Taylor and Francis Group, LLC.


Counihan-Edgar K.L.,University of California at Davis | Gill V.A.,U.S. Fish and Wildlife Service | Doroff A.M.,Kachemak Bay Research Reserve | Burek K.A.,Alaska Veterinary Pathology Services | And 8 more authors.
Journal of Clinical Microbiology | Year: 2012

Pulsed-field gel electrophoresis (PFGE) was used to type 128 Streptococcus infantarius subsp. coli isolates from sea otters and mussels. Six SmaI PFGE groups were detected, with one predominant group representing 57% of the isolates collected over a wide geographic region. Several sea otter and mussel isolates were highly related, suggesting that an environmental infection source is possible. Copyright © 2012 American Society for Microbiology. All Rights Reserved.


Stewart N.,University of Alaska Fairbanks | Stewart N.,Boston University | Konar B.,University of Alaska Fairbanks | Doroff A.,Kachemak Bay Research Reserve
Bulletin of Marine Science | Year: 2014

Sea otters, Enhydra lutris (Linnaeus, 1758), forage in a mosaic of habitat types. The relative use of heterogeneous environments by sea otters is largely unknown. Here, we examined whether foraging sea otters selectively use habitats based on substratum grain size and/or prey availability. Use by foraging sea otters was determined by the occurrence of foraging activity documented by VHF radio-tagged otters and by field collected data on substratum types and prey. Selection for substratum type and prey was determined by comparing currently used vs available foraging locations. We found that foraging sea otters used rocky habitats to a greater extent than soft sediment habitats, but did not necessarily use areas with higher prey abundance, biomass, or potential energy density per unit area. © 2014 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.


Kelly B.P.,University of Alaska Southeast | Kelly B.P.,National Oceanic and Atmospheric Administration | Badajos O.H.,University of Alaska Southeast | Badajos O.H.,Kachemak Bay Research Reserve | And 7 more authors.
Polar Biology | Year: 2010

Population structure and patterns of habitat use among ringed seals (Phoca hispida) are poorly known, in part because seasonal movements have not been adequately documented. We monitored the movements of 98 ringed seals in the Beaufort and Chukchi seas between 1990 and 2006 using three forms of telemetry. In the winter-spring period (when the seals were occupying shorefast ice), we used radio and ultra-sonic tags to track movements above and below the ice, respectively. We used satellite-linked transmitters in summer and fall (when the seals ranged away from their winter sites) to track at-sea movements. In the shorefast ice habitat, the home ranges of 27 adult males ranged from <1 to 13.9 km2 (median = 0.628) while the home ranges of 28 adult females ranged from <1 to 27.9 km2 (median = 0.652). The 3-dimensional volumes used by 9 seals tracked acoustically under the ice averaged 0. 07 (SD = 0.04) km3 for subadults and adult males and 0.13 (SD = 0.04)km3 for adult females. Three of the radio-tracked seals and 9 tracked by satellite ranged up to 1,800 km from their winter/spring home ranges in summer but returned to the same small (1-2 km2) sites during the ice-bound months in the following year. The restricted movements of ringed seals during the ice-bound season-including the breeding season-limits their foraging activities for most of the year and may minimize gene flow within the species. © 2010 The Author(s).


Goldstein T.,Sea For Life | Goldstein T.,University of California at Davis | Gill V.A.,U.S. Fish and Wildlife Service | Tuomi P.,Sea For Life | And 11 more authors.
Journal of Wildlife Diseases | Year: 2011

Northern sea otter (Enhydra lutris kenyoni) abundance has decreased dramatically over portions of southwest Alaska, USA, since the mid-1980s, and this stock is currently listed as threatened under the Endangered Species Act. In contrast, adjacent populations in south central Alaska, USA, and Russia have been stable to increasing during the same period. Sea otters bordering the area classified in the recent decline were live-captured during 2004-2006 at Bering Island, Russia, and the Kodiak Archipelago, Alaska, USA, to evaluate differences in general health and current exposure status to marine and terrestrial pathogens. Although body condition was lower in animals captured at Bering Island, Russia, than it was at Kodiak, USA, clinical pathology values did not reveal differences in general health between the two regions. Low prevalences of antibodies (,5%) were found in Kodiak, USA, and on Bering Island, Russia, to Toxoplasmagondii, Sarcocystis neurona, and Leptospira interrogans. Exposure to phocine herpesvirus-1 was found in both Kodiak, USA (15.2%), and Bering Island, Russia (2.3%). Antibodies to Brucella spp. were found in 28% of the otters tested on Bering Island, Russia, compared with only 2.7% of the samples from Kodiak, USA. Prevalence of exposure to Phocine distemper virus (PDV) was 41% in Kodiak, USA, but 0% on Bering Island, Russia. Archived sera from southwest and south-central Alaska dating back to 1989 were negative for PDV, indicating exposure occurred in sea otters in Kodiak, USA, in recent years. Because PDV can be highly pathogenic in nai{dotless}̈ve and susceptible marine mammal populations, tissues should be examined to explore the contribution of this virusto otter deaths. Our results reveal an increase in exposure to pathogens in sea otters in Kodiak,Alaska, USA, since the 1990s. © Wildlife Disease Association 2011.


Carrasco S.E.,University of California at Davis | Chomel B.B.,University of California at Davis | Gill V.A.,U.S. Fish and Wildlife Service | Doroff A.M.,Kachemak Bay Research Reserve | And 7 more authors.
Vector-Borne and Zoonotic Diseases | Year: 2014

Since 2002, an increased number of northern sea otters (Enhydra lutris kenyoni) from southcentral Alaska have been reported to be dying due to endocarditis and/or septicemia with infection by Streptococcus infantarius subsp. coli. Bartonella spp. DNA was also detected in northern sea otters as part of mortality investigations during this unusual mortality event (UME) in Kachemak Bay, Alaska. To evaluate the extent of exposure to Bartonella spp. in sea otters, sera collected from necropsied and live-captured northern sea otters, as well as necropsied southern sea otters (Enhydra lutris nereis) unaffected by the UME, were analyzed using an immunofluorescent antibody assay. Antibodies against Bartonella spp. were detected in sera from 50% of necropsied and 34% of presumed healthy, live-captured northern sea otters and in 16% of necropsied southern sea otters. The majority of sea otters with reactive sera were seropositive for B. washoensis, with antibody titers ranging from 1:64 to 1:256. Bartonella spp. antibodies were especially common in adult northern sea otters, both free-living (49%) and necropsied (62%). Adult stranded northern sea otters that died from infectious causes, such as opportunistic bacterial infections, were 27 times more likely to be Bartonella seropositive than adult stranded northern sea otters that died from noninfectious causes (p<0.001; 95% confidence interval 2.62-269.4). Because Bartonella spp. antibodies were detected in necropsied northern sea otters from southcentral (44%) and southwestern (86%) stocks of Alaska, as well as in necropsied southern sea otters (16%) in southcentral California, we concluded that Bartonella spp. exposure is widely distributed among sea otter populations in the Eastern Pacific, providing context for investigating future disease outbreaks and monitoring of Bartonella infections for sea otter management and conservation. © Mary Ann Liebert, Inc. 2014.

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