Browsing UAF Graduate School by Subject "Health"
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Alaskan king crab: Bering Sea distributions and a parasitic castratorKing crab play an integral role in both marine ecosystems and fisheries; they influence benthic community structure through predation, help regulate trophic cascades, and are an important food source for large fishes, marine mammals, and humans. To sustainably manage king crab fisheries in a changing climate, it is essential to have a thorough understanding of king crab biology and behavior, as well as knowledge on how they utilize and interact with other components of the ecosystem. I investigated factors important to king crab sustainability and management, including distribution patterns and a parasitic castrator. Rhizocephalan barnacles in the genus Briarosaccus parasitize and castrate king crab hosts, thereby preventing host reproduction and potentially altering host abundance. In Alaska, prevalence is generally low (< 1% infection rate), yet higher prevalence has occurred in localized bays and fjords. I studied the larval biology of Briarosaccus regalis infecting Paralithodes camtschaticus (red king crab) to better understand how environmental factors in Alaska may influence prevalence. Maximum larval B. regalis survival occurred from 4 to 12°C and at salinities between 25 and 34. Given these parameters, current conditions in the Gulf of Alaska and Bering Sea appear favorable for high survival of B. regalis larvae. Rhizocephalans not only castrate their hosts, but they cause changes in host morphology, physiology, and behavior. I used an untargeted metabolomics (liquid chromatography mass spectrometry) approach to compare the metabolite profiles (e.g., signaling molecules, hormones) of P. camtschaticus and Lithodes aequispinus (golden king crab) with and without rhizocephalan infections. Hundreds of putative metabolites were identified, yet few differed with crab sex and no metabolites could differentiate infected from healthy crab (regardless of crab sex). There were large variations in the crab metabolome with collection year and location, perhaps associated with environmental variability, which likely masked differences between sex and infection status. Summer distributions of Bristol Bay red king crab are well documented from surveys, but their distribution patterns at other times of year are poorly understood. Daily fishing logs, kept by vessel skippers in the red king crab fleet since 2005, contain detailed information on the spatial distribution of fishery effort and catch of legal sized male crab during the autumn crab fishery. However, data contained in these hand-written logbooks have not been readily accessible. I digitized daily fishing logs from 2005 to 2016 and used spatial information to infer geographic distributions. These distributions were compared across temperature regimes. In warm years (2005, 2014 - 2016) crab aggregated in the center of Bristol Bay, while in cold years (2007 - 2013) they were closer to the Alaska Peninsula. There are regions in Bristol Bay that are closed to the bottom trawl fisheries to protect red king crab; these results have management implications because they show the extent to which crab use these closure areas in the autumn, shortly before the winter trawl fisheries begin. As temperatures continue to shift in the Bering Sea, it will be important to continue monitoring crab distributions outside the summer survey period. Overall, these studies should help guide the placement of trawl closure areas, predict crab movement with temperature changes, understand the larval biology of B. regalis and what that could mean with climate change, and lead to a better understanding of the physiology of Briarosaccus infection.
Steller sea lion (Eumetopias jubatus) strandings and the role of pathogens in reproductive failureSteller sea lions (SSL, Eumetopias jubatus) have faced severe population fluctuations over the last five decades with a myriad of possibilities affecting their SSL population including disease, malnutrition, predation, climate change, entanglement in marine debris, and other factors. This thesis examined the effects that anthropogenic factors and disease may play in SSL strandings and reproductive failure. The goal of this study was to characterize long-term seasonality and spatial trends in SSL strandings and to investigate the role Brucella spp., Coxiella burnetti. Chlamydophila spp. and morbilliviruses may play in reproductive failure including spontaneous abortion and premature parturition. In Chapter 1, we utilized stranding data (n=1507) collected in Alaska, Oregon, and Washington from 1990-2015. We assessed temporal trends by identifying seasonality patterns across all years, analyzing sex, age class, body length, and characterizing signs of human interaction including factors contributing to mortality. Clear seasonality trends were evident, with the greatest number of reported strandings occurring during the spring and summer. Gunshot wounds and fishery interactions accounted for a large proportion (46%) of human interaction cases in strandings. Adult males were the most frequently stranded sex and age class in the Alaska and West Coast Regions. This study attempted to quantify efforts to monitor strandings and determined that the apparent increase in strandings following 2000 was likely due to increased stranding response effort resulting from increased federal grant awards. We encourage conducting further spatial analyses of strandings in addition to continued stranding surveillance monitoring with attempts to improve stranding response time. In Chapter 2 of my thesis, we analyzed archived lung, skin lesion and placenta tissues for the pathogens of interest in SSL fetuses (n=18) and neonatal pups (n=2) collected from 1998 2015 in Alaska. Associated pathological findings and morphometric data were examined to identify signs of pathology or abnormalities in all cases. Marine mammal Brucella was detected in the lung tissue of three cases. This is the first documented detection of Brucella in SSL by PCR methods. Phocine distemper virus was also detected in the skin lesion of two cases and in the placenta of one case, in which the cases with skin lesions exhibited abnormal pathology that included vesiculoulcerative dermatitis. Currently, there is very little available information on the significance of Brucella spp. and morbilliviruses in marine mammal populations inhabiting Alaskan waters. Therefore, this study demonstrates the clear need to continue disease surveillance programs and further investigate the role disease may play in SSL reproductive health, and more generally on cohort population stability.