The population of killer whales, known as the Southern Residents, that spends several months of the summer and fall each year in Washington State's Puget Sound, today achieved the highest level of species protection under US law. NOAA had announced its decision to list the Southern Resident killer whales as endangered under the ESA on 15th November 2005. The population is composed of three family groups, identified as J, K and L pods.
Individual animals are identified by a number based on pod membership and birth order. All three Southern Resident pods were reduced during 1965-75 because of captures for marine parks.
The Southern Resident population has fluctuated considerably over the 30 years that it's been studied. In 1974 it comprised 71 whales, peaked at 97 animals in 1996, and then declined to 79 in 2001. The population numbers some 89 animals.
NOAA Fisheries Service received a petition in 2001 to list these whales under the Endangered Species Act. That petition initiated the protection process and has aided the recovery these orcas.
There is a limited number of reproductive-age Southern Resident males, and several females of reproductive age are not having calves. The factors causing the decline of Southern Residents are not well known, and are likely to continue until NOAA Fisheries learns more about what needs to be done to reverse the trend.
Possible causes of decline, identified in other cetacean populations, are thought to be reduced quantity and quality of prey; persistent pollutants that could cause immune or reproductive system dysfunction; oil spills; and noise and disturbance from vessels.