[MARMAM] New publication on trends in cetacean density off southern California

Gregory Campbell tursiops44 at tamu.edu
Thu Nov 20 10:01:14 PST 2014

Dear Colleagues,

On behalf of my co-authors, I am pleased to announce the following

Campbell, G.S., Thomas, L., Whitacker, K., Douglas, A.B., Calambokidis, J.
and J.A. Hildebrand. 2014. Inter-annual and seasonal trends in cetacean
distribution, density and abundance off southern California. Deep Sea
Research II: Topical Studies in Oceanography.


Trends in cetacean density and distribution off southern California were
assessed through visual line-transect surveys during thirty-seven
California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises
from July 2004-November 2013. From sightings of the six most commonly
encountered cetacean species, seasonal, annual and overall density
estimates were calculated. Blue whales (*Balaenoptera musculus*), fin
whales (*Balaenoptera physalus*) and humpback whales (*Megaptera
novaeangliae*) were the most frequently sighted baleen whales with overall
densities of 0.91/1000 km2 (CV=0.27), 2.73/1000 km2 (CV=0.19), and
1.17/1000 km2 (CV=0.21) respectively. Species specific density estimates,
stratified by cruise, were analyzed using a Generalized Additive Model to
estimate long-term trends and correct for seasonal imbalances.  Variances
were estimated using a non-parametric bootstrap with one day of effort as
the sampling unit. Blue whales were primarily observed during summer and
fall while fin and humpback whales were observed year-round with peaks in
density during summer and spring respectively. Short-beaked common dolphins
(*Delphinus delphis*), Pacific white-sided dolphins (*Lagenorhynchus
obliquidens*) and Dall’s porpoise (*Phocoenoides dalli*) were the most
frequently encountered small cetaceans with overall densities of
705.83/1000 km2 (CV=0.22), 51.98/1000 km2 (CV=0.27), and 21.37/1000 km2
(CV=0.19) respectively. Seasonally, short-beaked common dolphins were most
abundant in winter whereas Pacific white-sided dolphins and Dall’s porpoise
were most abundant during spring. There were no significant long-term
changes in blue whale, fin whale, humpback whale, short-beaked common
dolphin or Dall’s porpoise densities while Pacific white-sided dolphins
exhibited a significant decrease in density across the ten-year study. The
results from this study were fundamentally consistent with earlier studies,
but provide greater temporal and seasonal resolution.

The full-text open access .pdf of the paper can be downloaded at
http://www.sciencedirect.com/science/article/pii/S0967064514002690 or
contact me via email at tursiops44 at tamu.edu for a copy.


Greg Campbell

Greg Campbell
Marine Mammal Behavioral Ecology Group
Department of Marine Biology
Texas A&M University Galveston
tursiops44 at tamu.edu
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