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Fishery Bulletin 112(2-3) 
Table 7 
Summary of results from Kruskal-Wallis and Mann-Whitney tests of seasonality for depth, dis- 
tance from vessel to land, and distance from vessel to shelf break for cetaceans encountered on 
the transect lines of the California Cooperative Oceanic Fisheries Investigation (CalCOFI) surveys 
conducted from 2004 to 2008 across all 4 seasons. Probability values that indicate significant results 
are shown in bold type. Asterisks indicate species for which tests were run with a limited number 
of sightings for one or more seasons; see Table 4 for number of sightings. 
Species 
Depth 
(P-value) 
Distance to 
land (P-value) 
Distance to 
shelf break (P-value) 
Humpback whale 
0.007 
0.149 
0.191 
Blue whale 
0.799 
0.611 
0.484 
Fin whale* 
0.003 
<0.000 
0.001 
Minke whale 
0.079 
0.040 
0.143 
Sperm whale* 
0.783 
0.729 
0.732 
Short-beaked common dolphin* 
0.122 
0.005 
0.008 
Long-beaked common dolphin 
0.247 
0.037 
0.015 
Common dolphin (unknown short- 
or long-beaked) 
0.773 
0.422 
0.587 
Pacific white-sided dolphin 
0.014 
0.005 
0.008 
Risso’s dolphin* 
0.581 
0.136 
0.087 
Bottlenose dolphin* 
0.256 
0.223 
0.252 
Northern right whale dolphin* 
0.518 
0.518 
0.518 
Dali’s porpoise* 
0.889 
0.941 
0.929 
photoidentification studies. The large whales repre- 
sented here are highly visible from a distance and of- 
ten occur in small groups; therefore, confidence levels 
on group-size estimates are higher and abundance es- 
timates likely are more accurate for them than for the 
smaller cetaceans that occur in large and more variable 
size groups. Group sizes for fin, humpback, and blue 
whales (Table 5) were similar to group sizes reported 
by Barlow (2010) and Barlow and Forney (2007). The 
number of unidentified large cetacean encounters (123) 
is to be expected from a survey conducted in passing 
mode. Although we did not apportion encounters of un- 
identified species in our analyses, on the basis of the 
proportion of large whale species positively identified, 
it is likely that fin, humpback, and blue whales made 
up the majority of these sightings. 
Fin whales were the most commonly encountered 
and most abundant large whale in the study area. As 
has been documented by Forney and Barlow (1998), 
fin whales were encountered during all seasons, but 
the encounter rate for this species increased during 
the summer and fall seasons. Our abundance of 679 
individuals (CV=0.25) in the study area during the 
summer-fall seasonal period is similar to Barlow’s 
(2010) estimate of 499 individuals (CV=0.27) from a 
2008 survey for Southern California and higher than 
the abundance estimate of 359 individuals (CV=0.40) 
from surveys conducted in 1991-2005 (Barlow and For- 
ney, 2007). Given the differences in survey design, we 
would have expected our abundance estimate to have 
been lower than the values presented in Barlow (2010); 
however, annual variability, which we do not address in 
this study of multiyear CalCOFI surveys, may account 
for the difference in abundance estimates. Broadly, 
these patterns of increasing abundance are consistent 
with the recently documented trend of an increasing 
population for fin whales (Moore and Barlow, 2011). 
Although there were few encounters during winter, fin 
whales used nearshore waters in the winter and spring 
and shifted into offshore waters in the summer and fall 
(Tables 6 and 7; Figs. 5 and 6); this movement seems 
to coincide with the observed coldest temperatures in 
nearshore waters recorded in winter and spring and 
with a slight increase of zooplankton biomass that oc- 
curs in the spring (Munger et ah, 2009). 
Although humpback whales were the second-most 
frequently encountered large cetacean, none were 
sighted during the winter. Our abundance estimate of 
309 individuals (CV=0.32) for the summer-fall period 
is almost 6 times larger than the estimates of 49 indi- 
viduals (CV=0.43) from the 2008 survey (Barlow, 2010) 
and of 36 whales (CV=0.51) from pooled 1991-2005 
surveys (Barlow and Forney, 2007); however, just over 
half of our on-effort humpback sightings came from 
the 2007 summer cruise near Point Conception, where 
and when zooplankton abundance was notably high 
(Munger et ah, 2009), indicating that an unusually 
large proportion of the population shifted into this area 
to take advantage of available prey. Because Southern 
California represents the southern end of the hump- 
back whale’s feeding range, such annual variation in 
available prey could strongly affect the abundance of 
