Biology of the Ringed Seal (Phoca hispida) in Alaska 1960-2010 (2011)

In Alaska, the ringed seal is one of four species of seals that are associated with sea ice during some portion of the year. (The other ice-associated species are the bearded seal, the spotted seal, and the ribbon seal.) Ringed seals have the widest distribution, which includes the Bering, Chukchi, and Beaufort seas near Alaska. They are also found throughout the Arctic, including Canada, Greenland, Svalbard, and Russia, and in freshwater lakes in Europe. Ringed seals feed on a variety of fish and invertebrates in the water column. They are the most ice adapted of the arctic phocids. They maintain breathing holes and subnivean lairs in shorefast ice where the adults breed and pups are born in March and April.

These research data span five decades and include time periods well before changes in sea ice or other factors attributed to global climate change were present. Our analyses show that ringed seals have been positively and negatively affected by past and current conditions. Currently, however, ringed seals are growing faster, have average blubber thickness, are maturing at the youngest age to date, and have the second highest pregnancy rate to date. Current environmental conditions have not had a negative effect on any of these factors. In addition, there are more pups in the harvest now. Because age ratios are proportional, a higher proportion of pups in the sample may indicate that adult survival is decreasing or that reproduction is increasing. Based upon other information, however, it is most likely that reproduction has increased. Sex ratios are currently male biased; however, this is probably not a concern as it corresponds to a period with high pregnancy rates and increasing numbers of pups. Levels of contaminants in ringed seals harvested in Alaska are lower than levels reported in Canada, Europe, and Russia, and the prevalence of diseases has remained stable.