Population Status
The Hawaiian monk seal was designated as depleted under the Marine Mammal Protection Act in 1976, following a 50% decline in beach counts from the late 1950s and mid 1970s. It was also listed as endangered under the Endangered Species Act in 1976.
In 1988, critical habitat was designated from beaches to a depth of 20 fathoms (37 m) around breeding islands and at Maro Reef. To further protect Hawaiian monk seal habitat, a Protected Species Zone was designated in 1991 that prohibited longline fishing within 50 nautical miles around the Northwestern Hawaiian Islands and corridors between the islands.
In December 2000, President Clinton created the Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve by Executive Order 13178.
Distribution and Movement Patterns
Hawaiian monk seals are distributed among discrete populations at eight locations from Nihoa Island to Kure Atoll in the Northwestern Hawaiian Islands, a distance of 2000 km. A small number of individuals are seen in the main Hawaiian Islands and, over the past decade, a few seals have been born on Niihau, Kauai, Oahu, Maui, and Molokai. The first confirmed births on Kaho'olawe and the Island of Hawaii occurred in 2001. A few monk seals have been sighted at Johnston Atoll and a birth was documented in 1969. Approximately 90% of Hawaiian monk seals remain at their natal island for life; the remaining 10% move between or among major population centers.
Birth and Beach Count Trends
Counts declined about 5% yr-1 from 1985 to 1993, remained relatively stable through 2000, and declined again in 2001 and 2002. The annual number of births has varied substantially over the past decade (Fig. 1, above), but is expected to decline in the near future due to poor reproductive recruitment of females at French Frigate Shoals. The total of mean beach counts at all main sites declined by 4% to 5% per year from 1985 to 1993 (Fig. 2, below). Further declines are likely due to high juvenile mortality. Total population size is about three times the beach count because all seals are not on the beach at any one time.
