[MARMAM] New paper on killer whales and whaling

Sally Mizroch Sally.Mizroch at noaa.gov
Fri May 12 11:25:05 PDT 2006

Hello all, 

This paper recently came out in the journal Marine Ecology Progress Series:

Mizroch, S. A., and Rice, D. W.  2006.  Have North Pacific killer whales
switched prey species in response to depletion of the great whale
populations?  Marine Ecology Progress Series 310:235-246.  

Springer et al. (2003) hypothesized that populations of seals, sea lions and
sea otters in the northern North Pacific Ocean and Bering Sea declined
because of increased predation by killer whales, in what they termed a
‘sequential megafaunal collapse’. They hypothesized that the killer whales
had been dependent on large whales for food, and that their increased
predation on the smaller marine mammals was directly due to the depletion of
great whale populations as a result of post-World War II industrial whaling.
The maps presented by Springer et al. (2003) masked the development and
precipitous decline of post-World War II industrial whaling. Our analysis
shows that north of 50°N, whaling developed slowly from 1948 to 1951,
expanded steadily from 1952 to 1962, and increased very sharply from 1963 to
1967. By 1968, there was near total drop-off in catches north of 50°N as the
whaling fleets moved south. Because of the extraordinary whale biomass
removals in the mid-1960s, any whaling-related prey shifting should have
started by 1968, not the mid-1970s as they suggested. 

We also present data that refute their assumption that North Pacific killer
whales depended on large whales as prey either prior to or concurrent with
the whaling era. During the years of the development and pulse of whaling
(i.e. prior to 1968), less than 3% of the mammal-eating killer whales were
observed to have large whale remains in their stomachs. Killer whales attack
healthy, adult large whales only rarely, and such attacks are usually
unsuccessful. Neither minke nor gray whales were depleted by post-World War
II industrial whaling, and they have always been available as prey for North
Pacific killer whales. 

A PDF can be downloaded from the Marine Ecology Progress Series website
<http://www.int-res.com/journals/meps/> or requested via email to
<Sally.Mizroch at noaa.gov>

Best regards,
Sally A. Mizroch
Alaska Fisheries Science Center
National Marine Mammal Laboratory
7600 Sand Point Way NE, Bldg 4
Seattle, WA  98115  USA
voice: (206) 526-4030
fax: (206) 526-6615
E-mail:  Sally.Mizroch at noaa.gov

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