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Fishery Bulletin 108(1 ) 
foraging success and efficiency. Group sizes of pan- 
tropical spotted ( Stenella attenuata), spinner ( Stenella 
longirostris ), and short-beaked common dolphins in the 
eastern Pacific Ocean have been observed to mirror 
the diurnal group-size fluctuations of yellowfin tuna 
( Thunnus albacares), one of their common prey (Scott 
and Cattanach, 1998). Cockroft and Peddemors (1990) 
noted the synchrony of pilchard (Sardinops ocellatus) 
movements with the migration of common dolphins 
during winter months up the eastern coast of South 
Africa. Both Corkeron (1990) and Grigg and Markow- 
itz (1997) identified food patchiness and interspecific 
interactions as important influences on Tursiops spp. 
group size. 
Applications of a microhabitat approach 
The ability to describe cetacean habitat hinges on the 
capacity to measure the suite of important and appro- 
priate environmental variables at the correct scale for 
which they exert influence (Ingram and Rogan, 2002; 
Redfern et al., 2006). This task is not trivial and noted 
issues with describing and researching cetacean habi- 
tat include the following: it is often unknown which 
variables (and how many) are the most pertinent to 
study; it is difficult to obtain measurements for some 
variables (even when they might be considered impor- 
tant); the scale at which the variable may influence 
cetacean distribution may be masked or uncertain; and 
the relationship between cetacean distribution and the 
given environmental variable may be correlated with 
and confounded by additional variables or factors. Our 
investigations into dolphin foraging habitat addressed 
some of these difficulties. Specifically, foraging habitat 
was measured on the same scale and with variables 
similar to those that have been used for habitat char- 
acterization studies of potential prey items in the same 
study area (Baltz et al., 1993; Baltz et al., 1998). Such a 
basis created a strong premise for asserting that forag- 
ing habitat could be characterized in the same manner. 
In addition, the collection of a suite of variables was 
instructive for investigating variables that might be 
synergistic or correlated. 
A description of the characteristics of cetacean forag- 
ing habitat is also contingent on accurately assessing 
and identifying feeding behavior and possibly account- 
ing for variations in feeding strategies, both of which 
are particularly pertinent for bottlenose dolphins given 
that they are both flexible and opportunistic in their 
feeding activity (Shane et al., 1986). Observations of 
feeding in association with shrimp boats have been 
documented in Texas waters (Brager, 1993) and feeding 
on mudbanks by partial beaching has been observed 
in some salt-marsh areas (Hoese, 1971). In Shark Bay, 
Western Australia, a number of individuals have been 
observed carrying sponges on their rostra in what is 
hypothesized to be a foraging aid (Smolker et al., 1997). 
Furthermore, in different habitats bottlenose dolphins 
have been observed to forage on different prey items 
(Gannon and Waples, 2004), while individuals of some 
cetacean species have been documented using distinc- 
tive foraging patterns while in close proximity to one 
another (Hoelzel et al., 1989). These considerations 
emphasize the need to understand the complexity of 
foraging behavior for a given species and may also sup- 
port the need to analyze different foraging techniques 
separately. 
Our findings provide a useful approach to identifying 
variables that are important in describing bottlenose 
dolphin foraging habitat; however, other unquantified 
variables such as boat activity (Lusseau, 2005), presence 
of competitors and predators such as sharks (Heithaus 
and Dill, 2006), El Nino events (Bearzi, 2005), seabed 
gradients (Ingram and Rogan, 2002), and weather and 
climate front patterns (Mendes et al., 2002) may have 
confounded these observations. 
Conclusions 
Long-term site fidelity and residency of many bottlenose 
dolphin populations indicate that individual populations 
likely have unique relationships with the given bay, 
estuary, or coastline that they inhabit. Characterizing 
foraging habitat for the bottlenose dolphin population in 
Barataria Basin is therefore a useful exercise because 
this small population (Miller, 2003) is presently man- 
aged as a distinct estuarine stock within the northern 
Gulf of Mexico (Waring et al., 2007). 
Acknowledgments 
The authors would like to acknowledge the many volun- 
teers who participated in field and laboratory work for 
this project, particularly H. Holwager. In addition, the 
first author is grateful for financial assistance from the 
Louisiana Board of Regents Fellowship program and 
for support from the Department of Oceanography and 
Coastal Sciences at Louisiana State University during 
her dissertation research. This article was improved by 
comments from three anonymous reviewers. Research 
was undertaken through a NMFS permit granted to 
the authors. 
Literature cited 
Allen, M. C., and A. J. Read. 
2000. Habitat selection of foraging bottlenose dolphins 
in relation to boat density near Clearwater, Florida. Mar. 
Mamm. Sci. 16:815-824. 
Allen, M. C., A. J. Read, J. Gaudet, and L. S. Sayigh. 
2001. Fine-scale habitat selection of foraging bottle- 
nose dolphins Tursiops truncatus near Clearwater, 
Florida. Mar. Ecol. Progr. Ser. 222:253-264. 
Bailey, H., and P. Thompson. 
2006. Quantitative analysis of bottlenose dolphin move- 
ment patterns and their relationship with foraging. J. 
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