The developers for the controversial Pebble Mine at the headwaters of Bristol Bay have now encountered another barrier to development of a copper and gold mine in that location.

This time the barrier comes in form of a sea mammal. The Center for Biological Diversity petitioned the federal government this week, asking them to protect one of five known populations of seals that live exclusively in fresh water in the northern hemisphere. Other populations are in Finland, Northern Quebec, and Russia.

The formal petition filed this week is to protect the Iliamna Lake seals that live in the eastern half of Alaska’s largest and deepest body of fresh water. The population at one time was considered to be only a visiting group of seal that traveled frequently up from the waters of Bristol Bay. But recent aerial footage surveys have shown that the population of harbor seals present in the lake winter there and even bear their young at the lake in the spring.

Locals at the lake say that this population of seals at the lake have darker and oilier pelts and are much fatter than their salt-water counterparts. It is said that the seals also have a unique pattern on their fur distinguishing them from other seal populations in Alaska. The locals at the Lake also have a small subsistence harvest of the seals.

Very little is known about this unique group of seals, they have not been studied extensively, but it is known that the population utilizes the abundant salmon that return every year to the lake as their main food source. They may also feed on freshwater fish that are in the lake.

The Center for Biological Diversity is conserned that the large open pit Pebble Mine planned for the area 17 miles upstream from the area will disturb the seal population and pollution from the mine will poison both the seal population and the salmon that they use for their food source.

Pebble officials say that they are aware of the freshwater seals through their environmental work, but that the debate continues whether the population differs any from the salt water seals in the region downstream. Pebble also said that there is no barrier preventing the seals access to the ocean.

The National Marine Fisheries Service says that it will review the petition and determine within 90 days if the petition is warranted.