Facts on Alaskan Orcas
Last night Dr. Naomi Rose shocked with these words, “I know for a fact, parks are looking at Alaska to catch killer whales”. For everyone interested, some basic information on the Alaskan orca communities.
In Alaska there live both resident and transient orcas. Offshores are encountered only rarely. The Alaska residents occur from southeastern Alaska to the Aleutian Islands and the Bering sea. In Southeast Alaska there are around 117 killer whales, in Prince William Sound an estimate of 500 and in Western Alaska another 500 (2004).
Shocking is the potential biological removal (PBR) level for Alaska residents: Under the Marine Mammal Protection Act (MMPA), a total of 11 orcas could be taken from these populations without harming them.
The Alaskan resident orca pods don’t seem to differ much from their cousins in the south: they feed on large, fatty salmon species like the chinook and coho, they aggregate in superpods during the summer months and enjoy to have a good rub on the rubbing beaches like the northern residents. Southern Alaskan resident are divided into two distinct clans: AB-clan and AD-clan. The pods are matrilineal and gather around a mature female. Her offspring of either sex are her constant companions. The social bonds are considered the strongest of any mammalian species.
Transient orcas are known to live in more fluid systems and the offspring may break from their mother to join another pod. In the Alaskan waters there lives a separate, genetically unique transient community: the AT1s or the Prince William Sound transients. They are found year-round in the area, share a distinct dialect and don’t mix with the Gulf of Alaska (GOA) transients. Their preferred prey are harbor seals and Dall’s porpoises. These two Alaskan transient population were never observed to mix with the B.C. transients.
Although the Alaskan orca population is regarded as stable, negative longline fishery interactions in parts of Alaska were observed. In Prince William Sound, the AB pod took almost 25% of caught fish from the longlines in April 1985. Fishermen shot the whales to protect their catch until it was forbidden by law.
Environmental toxins like DDT and PCB are known to negativly impact killer whales. Especially the transient orca population is heavily contaminated.
In 1989 the infamous Exxon Valdez oil spill impacted the untouched nature of Prince William Sound. Studies followed to monitor the resident and transient orcas of the region. The population number of the resident AB pod and the transient AT1 pod suffered extreme losses (up to 41%). Only the AB pod has recently started to recover their numbers, while the unique AT1 pod has lost most of their members and saw no birth after the oil spill. Their numbers have dropped from 22 animals to only 7 in 2005.
Angliss R. P. and R. B. Outlaw (2006): Killer Whale (Orcinus Orca): Eastern North Pacific Alaska Resident Stock, Alaska Marine Mammal Stock Assessments, NOAA
Matkin C. et al. (2003): Exxon Valdez Oil Spill Restoration Project - Photographic and Acoustic Monitoring of Killer Whales in Prince William Sound and Kenai Fjords. North Gulf Oceanic Society, Homer, Alaska.
Matkin C. and E. Saulitis (1997): Restoration Notebook – Exxon Valdez Oil Spill Trustee Council. North Gulf Oceanic Society, Homer, Alaska.
ID catalogue and list of the Southern Alaskan Clans