telemetered and visually sighted position for each animal and compared by a 

 variance ratio F-test (Zar 1984). 



Surfacing interval data consisted of dive duration, dive rate, and surface 

 duration. Dive duration was measured as the time interval between 

 surfacings. Dive rate was calculated by dividing the number of surfacings by 

 the duration of the sampling period (usually about 30-min). Time sf>ent at the 

 water surface between dives (surface duration) was indicated by the number 

 of pulses heard. Statistical tests were performed on these pulse counts and 

 subsequently transformed into the presented durations in seconds by 

 multiplying the pulse count by 1.5 pulses/sec, the transmitters' pulse rate. 

 The 30-min sampling periods were coded by time of day: "day" = 0700-19(X), 

 "night" = 2100-0500, and "crepuscular" = 0500-0700 and 1900-2100. 



The three surfacing-interval-data types were averaged for each dolphin 

 over the 30-min sampling f)eriods to minimize dependence within a 

 scimpling period. These means were compared statistically by time of day, and 

 among individual dolphins (Kruskal-Wallis, followed by Fisher's LSD); 

 pregnant vs. non-pregnant, with-calf vs. without-calf, and sex (Mann- 

 Whitney U); and age, and across each other {e.g., dive duration was regressed 

 on dive rate and surface duration, simple linear regression). 



PHOTOGRAPHIC TECHNIQUES 



Study Site 



The primary photographic survey area included most of the range of 

 radio-tracked individuals. Areas with particularly high-density coverage were 

 western Matagorda Bay, from Sand Point south to the Matagorda Ship 

 Channel Jetties; and west to eastern Espiritu Santo Bay, including Vanderveer 

 Island and the Ferry Channel. This area also includes the Intra-Coastal 

 Waterway (ICW) near Port O'Connor, and Pass Cavallo (Fig. 1). Survey effort 

 was not uniform (Fig. 4). 



Data Collection 



Photographic surveys required three people: boat-driver, note-taker, and 

 photographer. Unstructured, meandering censuses were conducted from 5.5- 

 and 7-m outboard vessels. Upon encountering a dolphin group, behavioral 

 and environmental data were collected on a data sheet and dorsal fin 

 photographs were attempted of all animals in the group (Wiirsig and Wiirsig 

 1977, Wiirsig and Jefferson 1990). Typically, dorsal fins were photographed 

 with a 35-mm camera from distances of 5-15 m with a 70-21 0-mm-zoom 

 lens, using 200-ISO slide film. An estimated 50-80% of Texas shore dolphins 



