[MARMAM] New tech memo: Results from the April 2009 Gulf of Alaska marine mammal survey

Brenda Rone Brenda.Rone at noaa.gov
Wed Jun 2 15:51:01 PDT 2010

The following NOAA Technical Memorandum was published:

Rone, B. K., A. B. Douglas, A. N. Zerbini, L. Morse, A. Martinez, P. J. 
Clapham, and J. Calambokidis. 2010. Results from the April 2009
Gulf of Alaska line transect survey (GOALS) in the Navy training 
exercise area. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-209, 39 p.

Little is known about the present-day occurrence of cetaceans found in 
offshore waters in the Gulf of Alaska; however, whaling records and a
few recent surveys have shown this area to be important habitat. The 
U.S. Navy maintains a maritime training area in the central Gulf of 
Alaska, east of Kodiak Island,
and has requested additional information on marine mammal presence and 
use of this area. To describe the occurrence and distribution of marine 
mammals in and around
the U.S. Navy training area, a line transect visual and acoustic survey 
was conducted 10-20 April 2009 from the NOAA ship /Oscar Dyson/. The 
primary survey area
encompassed nearshore and offshore pelagic waters of the central Gulf of 
Alaska. Survey lines were designed to provide equal coverage of the 
nearshore and offshore habitat.

During this project, the visual survey covered a total of 760 km (410 
nautical miles, nmi) on-effort (visible horizon, Beaufort sea state 5 or 
less, and survey speed of 10 knots
through the water) while transit (visible horizon, Beaufort sea state 5 
or less, and survey speed of 12 knots) and fog effort (no horizon, 
Beaufort sea state 5 or less) legs
accounted for 553 km (298 nmi). There were a total of 96 sightings (453 
individuals) of 11 confirmed marine mammal species; these included fin 
(/Balaenoptera physalus/),
humpback (/Megaptera novaeangliae/), gray (/Eschrichtius robustus/), 
minke (/B. acutorostrata/) whales, and killer whales (/Orcinus orca/), 
Dall’s (/Phocoenoides dalli/)
and harbor (/Phocoena phocoena/) porpoise, Pacific white-sided dolphins 
(/Lagenorhynchus obliquidens/), Steller sea lions (/Eumetopias 
jubatus/), harbor seals (/Phoca vitulina/),
and sea otters (/Enhydra lutris/). Additionally, there were 36 sightings 
(46 individuals) of unidentified large whales, dolphins, and pinnipeds. 
Passive acoustic operations were
conducted 24 hours/day surveying a total of 3,519 km (1,900 nmi) and 
recorded 49 acoustic detections of sperm whales and killer whales. 
Photographs of 19 individual
killer whales and 4 fin whales were obtained on this cruise and compared 
to existing photo-identification catalogs.

Density and abundance estimates were calculated for fin and humpback 
whales by stratum using line transect methods with and without 
covariates in detection probability
models. Additional sightings from a previous cruise on a comparable 
vessel were used for improving estimation of detection probability. All 
results were fairly similar given the
constraints of the sample sizes involved. Estimates of abundance in the 
inshore and offshore strata were 594 (CV = 0.29) and 889 (CV = 0.57) for 
fin whales, and
219 (CV = 0.57) and 56 (CV = 0.57) for humpback whales, respectively. A 
small proportion of large whales were not identified to species but were 
probable fin or humpback
whales based on observations, and estimates of these unidentified whales 
were assigned to these species based on the proportion of fin and 
humpback whales identified in each
stratum. This raised fin whale estimates of abundance to 666 (CV = 0.3) 
and 938 (CV = 0.57) and humpback whale estimates to 265 (CV = 0.48) and
63 (CV = 0.51, inshore and offshore strata, respectively).

Despite a number of logistical and time limitations, the survey provided 
new information on the occurrence and abundance of marine mammals in the 
region. Sighting sample
sizes were adequate to provide density and abundance estimates for fin 
and humpback whales. Identification photographs obtained on this cruise 
also verify the seasonal presence
of individual fin and killer whales in a study area that is rarely surveyed.

This document may be downloaded at: 

Kind Regards,
Brenda Rone

North Pacific Right Whale Project
U.S. National Marine Mammal Laboratory
Alaska Fisheries Science Center
7600 Sand Point Way NE
Seattle, WA 98115
brenda.rone at noaa.gov

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