45 killer whales were captured and removed from the Southern Resident killer whale community until 1973, when the marine park industry was forced to put an end to the captures.
Growth rate defined by Duffield and Miller (1988) was used to estimate the age from the length at time of capture.
From the 45 killer whales a total of 19 females, 21 males and 2 whales of unknown gender were caught and measured. In addition to that, 1 adult female and 2 whales of unknown gender and age, died during capture activities without any measurement taken place.
35 whales were removed to human facilities, 10 whales died during the capture activities.
Of the removed animals only the female killer whale Lolita, captured in August 1970 at Penn Cove, is alive at the time of this study.
During scientific research of the Southern Resident killer whale community, a total of 5 females and 6 males were encountered which were estimated to be born between the years 1959 and 1966.
Not a single animal was encountered that was estimated to be born between the years 1967 and 1970.
Especially when killer whales were no longer captured by chance but through the professional marine park industry captures between 1967 and 1973, the number of killer whales born into the population (top) was considerably lower than the number of animals lost (bottom).
The number of reproductive females
within the population from 1973 up to 2004 averaged 13,48.
Without the captures this would have been an average of 19,28, more than 43% higher.
Not included are the possible number of females being born to those removed females, who may have added to the total after reaching reproductive age.
Resident killer whale females are considered reproductive between the ages 14 and 39. The gap between calves averages 4 years, or 2 years after the last calf died early. During this gap the female is not considered reproductive. The mortality of reproductive females is estimated to be about 3%.
The lower level of reproductive females led to a lower level of births in the population, bringing the average from a possible 4,84 down to an actual 3,39 births per year. Because of the captures an estimated total of 45 animals were not born to the community. Per year about 25% of the reproductive females have a calf.
Added to the 45 captured killer whales, this brings the total loss to the community to about 90 animals. This is more than the Southern Resident killer whale community numbers as of today.
Considering that the Southern Resident killer whale community is already under high pressure through declining food resources, increasing toxic contamination and increasing acoustic disturbance like military sonar experiments or boat traffic, the impact of the captures and strandings was very significant and could have been lethal to the whole population. Action is needed to protect those icons of the Pacific Northwest (more about the efforts to save the orcas at Orca Network).
Asper, Edward D. and Cornell, Lanny H. 1977. Live capture statistics for the killer whale (Orcinus orca) 1961-1976 in California, Washington and British Columbia. Aquatic Mammals Vol. 5: 21-26.
Balcomb, Kenneth C. 1999-2004. Personal communications.
Bigg, Michael A. and Wolman, Allen A. 1975. Live-capture killer whale (Orcinus orca) Fishery, British Columbia and Washington, 1962-1973. Journal of the Fisheries Research Board of Canada Vol. 32: 1213-1221.
Duffield, Deborah A. and Miller, Karen W. 1988. Demographic features of killer whales in oceanaria in the United States and Canada, 1965-1987. Rit Fiskideildar, Journal of the Marine Research Institute Reykjavik Vol. XI: 297-306.
Ford, John K.B., Ellis, Graeme M., Balcomb, Kenneth C. 2000.Killer Whales. UBC Press, 104 pp.
van Ginneken, Astrid and Ellifrit, David K. 2003. Official Orca Survey Field Guide, Center for Whale Research, Friday Harbor, 12 pp.
Hoyt, Erich 1984. Orca - The Whale Called Killer. E.P. Dutton, New York, 226 pp.
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