@article{e765f44bba714524946b3b55f79db479,
title = "Predators, Disease, and Environmental Change in the Nearshore Ecosystem: Mortality in Southern Sea Otters (Enhydra lutris nereis) From 1998–2012",
abstract = "We compiled findings from 15 years (1998–2012) of southern sea otter (Enhydra lutris nereis) necropsies, incorporating data from 560 animals. Sensitive diagnostic tests were used to detect biotoxins, bacteria, parasites and fungi. Methods to classify primary and contributing causes of death (COD) and sequelae utilized an updated understanding of health risks affecting this population. Several interesting patterns emerged, including identification of coastal regions of high mortality risk for sea otter mortality due to shark bite, cardiomyopathy, toxoplasmosis, sarcocystosis, acanthocephalan peritonitis and coccidioidomycosis. We identified demographic attributes that enhanced the risk of disease in relation to age, sex, and reproductive stage. Death due to white shark (Carcharodon carcharias) bite increased dramatically during the study period and was the most common primary COD. However, when primary and contributing COD were combined, the most prevalent COD was infectious disease (affecting 63% of otters), especially fatal infections by acanthocephalans (Profilicollis spp.) and protozoa (e.g., Sarcocystis neurona and Toxoplasma gondii). Fatal bacterial infections were also extremely common as a primary process or a sequela, affecting 68% of examined otters. Substantial advances were made in identifying sea otters that died following exposure to the pervasive marine neurotoxin domoic acid (DA), and DA intoxication was conservatively estimated as a primary or contributing COD for 20% of otters. Cardiomyopathy was also highly prevalent as a primary or contributing COD (41%) and exhibited significant associations with DA intoxication and protozoal infection. For adult and aged adult females in late pup care through post-weaning at the time of death, 83% had end lactation syndrome (ELS) as a primary or contributing COD. This comprehensive longitudinal dataset is unique in its depth and scope. The large sample size and extensive time period provided an opportunity to investigate mortality patterns in a changing environment and identify spatial and temporal disease “hot spots” and emerging threats. Our findings will help improve estimates of population-level impacts of specific threats and optimize conservation and environmental mitigation efforts for this threatened species.",
keywords = "cardiomyopathy, domoic acid, infectious disease, mortality, pathology, risk factors, southern sea otter, white shark bite",
author = "Miller, {Melissa A.} and Moriarty, {Megan E.} and Laird Henkel and Tinker, {Martin Tim} and Burgess, {Tristan L.} and Batac, {Francesca I.} and Erin Dodd and Colleen Young and Harris, {Michael D.} and Jessup, {David A.} and Jack Ames and Conrad, {Patricia A.} and Packham, {Andrea E.} and Johnson, {Christine K.}",
note = "Funding Information: MAM directed, administered, and funded the project, conducted the histological analyses, completed all necropsy case reviews, and wrote the manuscript. MEM served as technical staff lead for the project, completed some epidemiological analyses, and helped substantially with manuscript completion. LH helped substantially with updating coding techniques, COD and sequelae, and led on non-epidemiological data compilation and analysis. MT had a substantial role in complex model development and drafting explanatory text and figures, especially for ELS and shark bite. TB led completion of spatial/temporal cluster analysis and aided development of the DA regression model and some of the core figures. FB assisted substantially with sea otter necropsy, data entry, data crosschecking, case coding, diagnostic testing, developing case definitions for key COD and sequelae, manuscript preparation and submission. ED assisted substantially with necropsy, data entry, data crosschecking, case coding, diagnostic testing, developing case definitions, and manuscript preparation. CY assisted substantially with necropsy, data crosschecking, developing case definitions, developing figures related to annual mortality proportions, and manuscript preparation. MH assisted substantially with necropsy, data crosschecking, developing case definitions, helped develop figures related to annual mortality proportions, and manuscript preparation. DJ provided core physical and financial support for development and funding of the CDFW sea otter pathology program and assisted with necropsies, sampling, testing, carcass recovery, and manuscript preparation. JA substantially assisted with sea otter capture, carcass recovery and necropsies, helped develop the spatial mapping system that was central to epidemiological analyses, and assisted with developing case definitions and manuscript preparation. PC and AP provided intellectual input on testing and sampling for serum collection, storage, evaluation, and interpretation, and organized and tested all serum samples. CJ served in a lead role for project design, method development, and completion of epidemiological analyses, and served as the core mentor and provided funding support for the collaborating graduate students (MEM and TB). She also had a lead role in optimizing sections of the manuscript pertinent to statistical analyses, modeling and sea otter disease. All the authors reviewed, edited, and approved the manuscript. Funding Information: We thank the citizens of California for making this work possible through contributions to the California Sea Otter Fund (Sea Otter Tax Checkoff). Tax checkoff funding to support this work was made available through the California State Coastal Conservancy, and the California Department of Fish and Wildlife – Office of Spill Prevention and Response. Megan Moriarty was supported by the Morris Animal Foundation Fellowship Training Grant (D17ZO-413) during this study.",
year = "2020",
month = nov,
day = "19",
doi = "10.3389/fmars.2020.00582",
language = "English (US)",
volume = "7",
journal = "Frontiers in Marine Science",
issn = "2296-7745",
publisher = "Frontiers Media S. A.",
}