[MARMAM] New publications on North Atlantic whale abundance
Daniel Pike
kinguq at gmail.com
Sun Nov 29 13:10:50 PST 2009
Hello
I would like to announce the recent publication of the following 2 papers in
*NAMMCO Scientific Publications* Volume 7, North Atlantic Sightings Surveys:
Counting whales in the North Atlantic, 1987-2001. The volume is available at
www.nammco.no, and pdf reprints are available from me at kinguq at gmail.com.
Regards,
Daniel Pike.
Gunnlaugsson, Th., Víkingsson, G.A. and Pike, D.G. 2009. Combined
line-transect and cue-count estimate of sperm whale abundance in the North
Atlantic, from Icelandic NASS-2001 shipboard survey. NAMMCO Sci. Publ.
7:73-80.
Sperm whales (Physeter macrocephalus) pose a particular problem to shipboard
surveys as they dive for extended periods and are therefore likely to be
missed (not available) even if they are right under the track line. To
address these problems the NAMMCO planning committee for the NASS 2001
survey drew up guidelines to be followed when sperm whales were sighted.
This required every deep dive to be recorded and considered to be a cue,
from which a cue-count estimate is calculated if the cue rate is known. For
those whales that did not dive before coming abeam, a conventional
line-transect estimate is calculated, which gives an instantaneous surface
estimate from which a total estimate can be obtained if the proportion of
the time spent at the surface is known. These estimates are compared and
combined. Precise dive cycle information is missing for the mostly single
all male sperm whales in this area but a preliminary estimate of 11,185 (cv
0.34) is obtained for the surveyed area with an assumed surface time of 20%
and two deep dives per hour.
Borchers, D.L., Pike, D.G., Gunnlaugsson, Th. and Víkingsson, G.A. 2009.
Minke whale abundance estimation from the NASS 1987 and 2001 aerial
cue–counting surveys taking appropriate account of distance estimation
errors. NAMMCO Sci. Publ. 7:95-110.
We estimate the abundance of minke whales (Balaenoptera acutorostrata) from
the Icelandic coastal shelf aerial surveys carried out as part of the 1987
and 2001 North Atlantic Sightings Surveys (NASS). In the case of the 1987
survey, the probability of detecting animals at distance zero (g(0)) is very
close to 1 but there is substantial random measurement error in estimating
distances. To estimate abundance from these data, we use methods which
assume g(0)=1 but which include a distance measurement error model. In the
case of the 2001 survey, measurement errors were sufficiently small to be
negligible, and we use double platform methods which estimate g(0) and
assume no measurement error to estimate abundance. From the 1987 survey, we
estimate abundance to be 24,532 animals, with 95% CI (13,399; 44,916). From
the 2001 NASS survey
data, minke whale abundance is estimated to be 43,633 animals, with 95% CI
(30,148; 63,149).
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