Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice. However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available. We summarized available data on abundance and trend for each AMM species and recognized subpopulation. We also examined species diversity, the extent of human use, and temporal trends in sea ice habitat for 12 regions of the Arctic by calculating the dates of spring sea ice retreat and fall sea ice advance from satellite data (1979-2013). Estimates of AMM abundance varied greatly in quality, and few studies were long enough for trend analysis. Of the AMM subpopulations, 78% (61 of 78) are legally harvested for subsistence purposes. Changes in sea ice phenology have been profound. In all regions except the Bering Sea, the duration of the summer (i.e., reduced ice) period increased by 5-10 weeks and by >20 weeks in the Barents Sea between 1979 and 2013. In light of generally poor data, the importance of human use, and forecasted environmental changes in the 21st century, we recommend the following for effective AMM conservation: maintain and improve comanagement by local, federal, and international partners; recognize spatial and temporal variability in AMM subpopulation response to climate change; implement monitoring programs with clear goals; mitigate cumulative impacts of increased human activity; and recognize the limits of current protected species legislation.

Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change.

We review seven Arctic and four subarctic marine mammal species, their habitat requirements, and evidence for biological and demographic responses to climate change. We then describe a pan-Arctic quantitative index of species sensitivity to climate change based on population size, geographic range, habitat specificity, diet diversity, migration, site fidelity, sensitivity to changes in sea ice, sensitivity to changes in the trophic web, and maximum population growth potential (R(max)). The index suggests three types of sensitivity based on: (1) narrowness of distribution and specialization in feeding, (2) seasonal dependence on ice, and (3) reliance on sea ice as a structure for access to prey and predator avoidance. Based on the index, the hooded seal, the polar bear, and the narwhal appear to be the three most sensitive Arctic marine mammal species, primarily due to reliance on sea ice and specialized feeding. The least sensitive species were the ringed seal and bearded seal, primarily due to large circumpolar distributions, large population sizes, and flexible habitat requirements. The index provides an objective framework for ranking species and focusing future research on the effects of climate change on Arctic marine mammals. Finally, we distinguish between highly sensitive species and good indicator species and discuss regional variation and species-specific ecology that confounds Arctic-wide generalization regarding the effects of climate change.

Ocular lesions associated with attachment of the copepod Ommatokoita elongata (Lernaeopodidae: Siphonostomatoida) to corneas of Pacific sleeper sharks Somniosus pacificus captured off Alaska in Prince William Sound.

Twenty eyes from 10 Pacific sleeper sharks Somniosus pacificus, infected with the copepod Ommatokoita elongata, were collected in Prince William Sound, Alaska, and the eyes of an additional 18 S. pacificus captured in the same area were inspected for copepods. Prevalence of infection by adult female O. elongata was 97% (n = 28); mean intensity of infection was 1.89 (+/-1SD = 0.32) adult female copepods per infected shark and 1.0 (+/- 1SD = 0.0) adult female copepods per infected eye. Five of the 20 collected eyes were infected by O. elongata chalimi, and 9 of 20 eyes had 1 to several remnants of bullae embedded in the cornea. Bullae were each associated with a corneal opacity, and anchoring plugs of chalimi were associated with pinpoint lesions in the cornea or conjunctiva. All eyes exhibited marked edema and erosion of the bulbar conjunctiva, and this torus-shaped lesion corresponded to each O. elongata adult female's presumed feeding and abrasion radius. Histological examinations revealed lesions in the anterior segment of eyes to be generally similar, but graded, in severity, and in all eyes they involved the conjunctiva, cornea, filtration angle, and iris. Epithelial lesions were characterized by corneal ulceration, dysplasia, hyperplasia, and heterophilic keratitis, and by ulcerative conjunctivitis accompanied by epithelial hyperplasia with rete peg formation. Disorganization of fibers, necrosis, mineralization, minimal heterophilic influx, and perilimbic neovascularization were associated with bullae in the corneal stroma. Within the limbus there was diffuse histiocytic and lymphocytic inflammation and marked lymphofollicular hyperplasia. Heterophilic and mononuclear anterior uveitis affecting the filtration angle and anterior surface of the iris was also observed in most eyes. One eye had a partial transcorneal prolapse of a ruptured lens, with degenerative changes in the ruptured lens and severe keratitis associated with the anchoring devices of an adult copepod and several chalimi. Fourteen eyes exhibited 1 to several, randomly distributed, small, round to irregular, corneal opacities or pits that were not associated with copepods, and it is likely that these opacities represented lesions associated with adult female or larval anchoring devices from past infections. The avascular cornea represents a niche that is somewhat shielded from host immune reactions, and this, and the fact that the general body surface of sleeper sharks is covered by tall and sharp placoid scales, may partially explain the corneal attachment of O. elongata adult females. It was concluded that O. elongata infections can lead to severe vision impairment in Pacific sleeper sharks but that these infections do not significantly debilitate hosts because they probably do not need to rely on acute vision for their survival.