Douglas et al. Seasonal distribution and abundance of cetaceans off Southern California 
217 
3) that showed an even tapering of sightings with dis- 
tance from vessel. 
Our results on seasonal occurrence of the 6 fre- 
quently occurring delphinid species and the Dali’s 
porpoise are consistent with prior findings. The bottle- 
nose dolphin, long-beaked common dolphin, and short- 
beaked common dolphin generally favor warm-water 
(summer-fall) periods along the California coast (Dohl 
et al., 1986; Barlow, 1995; Forney et al., 1995). Dali’s 
porpoise, the Pacific white-sided dolphin, the northern 
right whale dolphin, and Risso’s dolphin commonly are 
found during the cold-water (winter— spring) periods off 
Southern California, and these species tend to migrate 
north into central California or Oregon and Washing- 
ton during the warm-water periods (Forney, 1994; For- 
ney and Barlow, 1998). These species have exhibited 
abundance shifts associated with oceanographic vari- 
ability on both seasonal and interannual time scales 
(Perrin et al., 1985; Heyning and Perrin, 1994; Forney, 
1997; Forney and Barlow, 1998; Becker, 2007). 
There were only 6 sightings of beaked whales, but 
all 3 genera ( Ziphius , Berardius, and Mesoplodon) 
known to be present off Southern California were de- 
tected. The single sighting of a Mesoplodon could not be 
confirmed to species. A single encounter with a group 
of Baird’s beaked whales ( Berardius bairdii) near the 
shelf break during a survey in the summer is consis- 
tent with other sightings of this species in continental 
slope waters from late spring to early fall (Balcomb, 
1989; Carretta et al., 2011b). 
Of the 11 dolphin species encountered, 5 species were 
represented by only 1-3 sightings per species: killer 
whale, false killer whale, short-finned pilot whale ( Glo - 
bicephala macrorhynchus), rough-toothed dolphin, and 
striped dolphin. Of these 5 species, only the killer whale 
is commonly found year-round off Southern California, 
with 2 U.S. stocks (Eastern North Pacific Transient and 
Eastern North Pacific Offshore [Carretta et al., 2011b]) 
that use the area. We were unable to confirm which 
stocks were represented in the 2 sightings of this spe- 
cies. The rough-toothed dolphin and false killer whale 
are considered rare off California, with no known current 
or historical populations along the West Coast of the 
United States; therefore, our sightings likely represent 
extralimital movements from populations farther south. 
There were too few encounters with striped dolphins 
in the study area to look at seasonal shifts in habi- 
tat; however, it is worth noting that the 3 sightings of 
this species occurred in surveys conducted in the sum- 
mer-fall period, in the deepest mean water depth, and 
at the greatest mean distance to land of any species 
observed in the study area (Table 6). Season, distance 
to shore, and depth of striped dolphin encounters cor- 
respond with those of previous surveys conducted in 
summer and fall and with habitat models that revealed 
the presence of striped dolphins in tropical to warm- 
temperate pelagic waters, with a continuous distri- 
bution outside upwelling coastal waters of California 
(Perrin et al., 1985; Jefferson et al., 1993; Mangels and 
Gerrodette, 1994; Archer and Perrin, 1999; Becker et 
al., 2012; Forney et al., 2012). 
Short-finned pilot whales were encountered com- 
monly off Southern California before the El Nino event 
in 1982-83 (Dohl et al. 1 ); on the basis of numerous sur- 
veys, including this one, it is apparent that this spe- 
cies now uses these waters only infrequently (Carretta 
and Forney, 1993; Shane, 1994; Barlow 3 ; Forney, 2007). 
The single encounter of false killer whales in the study 
area occurred during the 2008 winter cruise at a depth 
of 300 m and within 5 km of Santa Rosa Island. False 
killer whales are normally found in tropical to warm- 
temperate oceans; however, sightings have been made 
occasionally in cold-temperate areas as well (Stacey 
and Baird, 1991; Baird, 2008). 
Conclusions 
We collected sighting data from seasons and years that 
have not been reported previously, generated density 
and abundance estimates for 11 species of cetaceans off 
Southern California, and documented shifts in seasonal 
distribution for fin whales and Pacific white-sided dol- 
phins. In recent years, interest has increased in the 
development of predictive models to forecast near real- 
time marine mammal distribution as a way to inform, 
mitigate, and decrease the effect of potentially harmful 
human activities in the marine environment (Becker 
et al., 2012; Forney et al., 2012; Thompson et al., 2012; 
Henderson et al., 2014). Although our data set spans 
a 5-year period that ends in 2008, visual and acoustic 
data on detections of marine mammals continue to be 
collected with corresponding oceanographic data, both 
physical and biological, during CalCOFI cruises. As the 
CalCOFI data set grows, it potentially could become 
one of the most valuable collections of data both for 
monitoring and creating year-round habitat models of 
cetacean species and their environment off Southern 
California. 
Acknowledgments 
F. Stone, E. Young, and L. Petitpas and the Office of 
Naval Research provided funding and project manage- 
ment. We appreciate the efforts of all who were in- 
volved in the CalCOFI surveys in 2004-08: the cap- 
tains and crews of the New Horizon, David Starr Jor- 
dan, and Roger Revelle and the scientists, especially 
D. Wolgast, J. Wilkinson, A. Hays, R. Baird, S. Yin, 
M. Smith, A. Miller, L. Morse, V. Iriarte, E. Vazquez, 
N. Rubio, K. Merkens, J. Burtenshaw, E. Oleson, and 
E. Henderson. We also thank K. Forney and R. Baird 
for manuscript review. Finally, the authors would like 
to honor S. Claussen, whose presence and laughter is 
greatly missed. 
