Northern fur seals (Callorhinus ursinus) migrate to the Bering Sea in summer, when the days are long, the temperatures mild, and the fish plentiful. On islands such as St Paul, they gather in their hundreds of thousands to breed. Males battle for territory and access to as many females as possible. Females give birth to a single pup which they suckle for 4 months. Only a week after giving birth, females mate and become fertilized for the next year. Once summer is over, mothers and pups separate and the seals disperse into southern waters where they remain continuously at sea until the next summer. Once numbering 2 million, the northern fur seal population has declined by about two-thirds in the last 50 years. Increasing temperatures have affected the sea ice and currents, causing a dramatic decline in the overall productivity of the Bering Sea. These images show the trials and tribulations of a summer breeding season at St Paul Island and were taken during research conducted under NMFS permit 14329.