New publication:
Reeves, R.R., S. Leatherwood, and
R.W. Baird. 2009. Evidence of a possible decline since 1989 in false killer
whales (Pseudorca crassidens) around the main Hawaiian Islands. Pacific Science
63:253-261.
From Randy Reeves:
Steve Leatherwood died 12 years ago,
at the age of 53, leaving behind not just an aggrieved family and a host of
cherished friends and colleagues, but also a great deal of “unfinished
business.” A small item in the last category was a set of observations made
during a one-off aerial survey project in Hawaii. Next to other, weightier
projects, the task of bringing this one to the publication stage kept getting
put off. In fact, both Steve and I had basically forgotten about it by the time
he died. When, about a year ago, Robin raised the idea of publishing our
findings, I was able to locate only the data sheets and a handwritten narrative
describing methods and results of the 1989 surveys. The photographs, which would
provide very useful confirmation of both the species and the numbers, are still
missing. Maybe some day they will surface. Meantime, we welcome this chance not
only to complete this little item of unfinished business, but also to remind
others in the field of marine mammal science and conservation of Steve’s many
contributions to it.
Abstract
Recent evidence indicates there is a
small, demographically isolated, island-associated population of false killer
whales (Pseudorca crassidens) around the main Hawaiian Islands. Although it is
known that false killer whales in Hawai‘i are sometimes killed or seriously
injured in the Hawai‘i-based long-line fishery, it is not known whether such
interactions have resulted in a reduction in population size, or whether other
factors have been negatively influencing population size. We report the results
of an aerial survey in June and July 1989, the purpose of which was to obtain a
minimum count of the number of false killer whales around the main Hawaiian
Islands. The false killer whale was the third most commonly seen species of
odontocete off the island of Hawai‘i during the survey, representing 17% of
sightings. Groups of more than 300 individuals were seen on three different
days, with minimum counts of 380, 460, and 470 individuals in these groups. The
encounter rate, relative species ranking, and average group size from the 1989
survey were all substantially greater than those from more recent aerial and
ship-based surveys. The largest group observed in 1989 (470) contained almost
four times as many whales as estimated for the entire main Hawaiian Islands from
recent aerial surveys (121 individuals, CV = 0.47) or mark-recapture analyses
(123 individuals, CV = 0.72). Therefore, the population of false killer whales
around the main Hawaiian Islands may have declined substantially since 1989. The
cause or causes of such a decline are uncertain.