Experts recognize two subspecies, I. geoffrensis geoffrensis in the Amazon and Orinoco basins of South America and I. geoffreniss boliviensis in the upper Maderia river system of Bolivia. 2. Reasons for endangerment. Scientists are concerned about the river dolphin because of ever-increasing environmental deterioration. Though some deliberate hunting of dolphins exists, the greatest direct threat to dolphins is accidental drowning in gill nets. Of equal importance are the indirect threats to their food supply, including overfishing, deforesting of the river-edge, agricultural polluting, paper milling and mining, and hydroelectric dam building.
Hydroelectric dams reduce the number of fish species and isolate populations of dolphins.
E. Hawaiian monk seal. The five major breeding sites are Kure Atoll, pearl and Hermes Reef, Lisianski Island, Laysan Island, and the French Frigate Shoals. They're also found on the Midway Islands, Maro Reef, Gardner Pinnacles, Necker Island, and Nihoa Island. Reasons for endangerment. NMFS estimates the monk seal populations to be slightly more than 1,000 individuals.