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Homer, AK, United States

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.

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.

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).

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 | Miller W.A.,University of California at Davis | And 7 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.

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.

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