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Fishery Bulletin 112(2-3) 
The inclusion of the Survey Type variable in most 
models reflects some of those differences in survey ef- 
fort. The CalCOFI cruises in 1987-2004 consistently 
ranked lowest in sighting numbers for all species al- 
though those surveys had the most effort. This rank- 
ing was likely due to a single observer who covered 
both birds and mammals with a smaller effective strip 
width rather than to the multiple observers dedicated 
to monitoring marine mammals for the other 2 types 
of surveys. 
The SWFSC cruises had the highest number of ob- 
servations for 6 of the 7 models in which they were in- 
cluded, although those cruises had less effort than the 
CalCOFI cruises. The high number of observations may 
have been due to optimal sighting conditions during 
the SWFSC cruises, which were largely conducted in 
summer and fall. In addition, big eye binoculars were 
used on SWFSC cruises but were not used regularly 
on CalCOFI cruises. In another difference in Survey 
Type, CalCOFI surveys always were conducted in pass- 
ing mode in which the survey vessel does not leave the 
transect line when animals are sighted, but SWFSC 
ships operated in closing mode and could deviate from 
the transect line to confirm species. 
Finally, we used the number of groups sighted rath- 
er than the number of individuals observed as our met- 
ric for encounter rate. The correlation analysis did not 
indicate a strong relationship between the number of 
groups encountered and the size of the group for any 
of the modeled species. Therefore, our models may have 
misidentified trends if a change in group size as a re- 
sponse to any of these variables had better explanatory 
power than the overall encounter rates. 
Conclusions 
The models presented in this study indicated that fluc- 
tuations in SST regimes influenced the distribution of 
small cetaceans. However, the relationships were not 
as straightforward as predicted. The observed com- 
plexities likely are related to effects of SSTs on prey 
and subsequent responses by cetaceans. Dolphins have 
been shown previously to be sensitive to changes in 
SST and to shift their distributions in response to re- 
gime oscillations like ENSO. However, this study is the 
first one to model responses to multiple temperature 
shifts over a long time period for a variety of cetacean 
species in this region of the California Current system. 
The resulting models were unique to each of the 8 
species studies. This finding indicates that each spe- 
cies is characterized by a distinct pattern in habitat 
occurrence related to SST dynamics in this study area, 
despite the overlap in the overall distributions of the 
examined species in the Southern California study 
area. Results herein can be used to begin to predict the 
future distribution of these small cetaceans through- 
out the waters off Southern California. Results also 
provide a tool to understand, as global climate change 
intensifies, potential responses of these species to ris- 
ing ocean temperatures and the ecological mechanisms 
responsible for those responses. 
Acknowledgments 
We are grateful to SWFSC and CalCOFI for the use of 
their data sets, without which this analysis could not 
have been conducted, and to all of the visual observers 
over the years who gathered that data. We thank N. 
Mantua and S. Hare for permission to use their PDO 
index and NOAA scientists for permission to use their 
ENSO index. We also thank M. Ferguson, E. Archer, J. 
Moore, and E. Becker for assistance with the modeling 
and M. Kahru for help with the satellite data of sea- 
surface temperatures and WimSoft software. 
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