The following M.Sc. thesis was recently accepted by Hawai‘i Pacific University.
Aschettino, J.M. 2010. Population size and structure of melon-headed whales
(Peponocephala electra) around the Main Hawaiian Islands: evidence of multiple
populations based on photographic data. M.Sc. Thesis, Hawai‘i Pacific
University. 117 pp.
A pdf copy available at
http://www.cascadiaresearch.org/hawaii/melonheadedwhale.htm
ABSTRACT: Despite the presence of melon-headed whales in tropical and
sub-tropical waters world-wide, little is known about this species.
Melon-headed whales frequent offshore waters surrounding the Main Hawaiian
Islands where aerial surveys by Mobley and colleagues suggest a relatively
small population (154 individuals (CV=0.88)). A 2004 near mass-stranding in
Hanalei Bay, Kaua‘i occurred when an embayment of 150 – 200 animals coincided
with naval mid-frequency sonar use. To assess population size and movements in
Hawai‘i, more than 40,000 photos were collected from 47 encounters around the
Main Hawaiian Islands between 2002 and 2009, and additional photos were
obtained from collaborators from 1986 – 2001. Using only good quality
photographs, there were 1,433 unique individuals in the photo-identification
catalog, of which 1,046 were distinctive. Of these, 330 (31.5%) were seen on
more than one occasion. Re-sighting data combined
with social network analyses showed evidence of two distinct populations – a
smaller, resident population, seen exclusively off the northwest region of the
island of Hawai‘i, and a much larger Main Hawaiian Islands population, seen
throughout the entire range of the Main Hawaiian Islands. Depth of encounters
with the resident population were significantly shallower (median = 381 m) than
those with the Main Hawaiian Island population (median = 1,844 m).
Re-sightings of individuals have occurred up to 22 years apart for the Hawai‘i
resident population and up to 13 years apart for the Main Hawaiian Islands
population, suggesting long-term residency for both populations. Dorsal fin
disfigurements suggest that fisheries interactions occur with members of both
populations. Abundance estimated through mark-recapture analyses (corrected
for the non-distinctive individuals), was 447 (CV = 0.12) for the Hawai‘i
residents and 5,794 (CV = 0.20)
for the Main Hawaiian Islands population. These estimates provide more
accurate and precise population estimates of melon-headed whales in Hawai‘i.
Although the total population size of melon-headed whales in Hawai‘i is higher
than once believed, the restricted range of the small resident population may
pose additional management implications for these individuals.
_____________________
Jessica Aschettino, M.Sc.
[email protected]
Hawai‘i Pacific University
Kaneohe, HI 96744
and
Research Associate
Cascadia Research Collective
_______________________________________________
MARMAM mailing list
[email protected]
https://lists.uvic.ca/mailman/listinfo/marmam
