Biology of the Ribbon Seal in Alaska

INTRODUCTION Four species of seals live in association with sea ice in Alaska; these are the ringed seal (Phoca hispida), spotted seal (P. largha), bearded seal (Erignathus barbatus), and ribbon seal (Histriophoca fasciata or Phoca fasciata). Ribbon seals, the focus of this paper, range from the Sea of Japan and the Sea of Okhotsk eastward into the Bering Sea and northward into the Chukchi Sea. In the Bering Sea, ribbon seals concentrate along the front of the ice pack in late winter and spring (Burns 1981). They rely on sea ice to provide a platform for pupping, nursing, and molting. Pupping occurs between early April and mid-May; nursing lasts three to four weeks. Breeding and molting occur before the sea ice recedes (Burns 1981). The distribution of ribbon seals shifts northward as sea ice recedes in May and June. When sea ice melts, the majority of the population probably becomes pelagic in the central Bering Sea, although some seals follow receding ice into the Chukchi Sea (Burns 1981). The status of the ribbon seal is currently under scrutiny due to concerns regarding how changes in sea ice habitat may be affecting the species suggests changes in the ecosystem may be occurring as well. Of the ice seals, ribbon seals are the least common in Alaskan waters and because of this are the least understood. Population estimates for ice seals are not easily attainable due to their wide distribution and the problems related to marine mammal surveys in remote, ice-covered waters. However, there is some information regarding ribbon seal abundance. In 1961, the Russians began a commercial harvest of ribbon seals in the Bering Sea (Burns 1986). that the population had grown to approximately 140,000 and had completely recovered from commercial sealing. Currently, there are no estimates of abundance available for ribbon seals. The current harvest in Russia is also unknown. The Alaska Department of Fish and Game (ADF&G) has been collecting information from the Alaska Native subsistence harvest on ribbon seals for over 40 years. We rely on the cooperation of several coastal communities to provide information and 2 samples of seal tissues for information on the health and status of seal populations. With these samples, we monitor species distribution, harvest availability, contaminant levels, and indices of population status (e.g., pregnancy rates, age at first reproduction, growth rates, and body condition). Villages participating in the biomonitoring program span from Hooper …