monitoring of freeze-branded dolphins is presented for the periods of May 

 1992 through June 1993. 



METHODS 



Matagorda Bay, on the central Texas coast (28°30'N, 97°20'W), is 

 characterized by wide seasonal swings in temperature and salinity. Over the 

 bay as a whole, mean salinity ranges from 12.7 in spring to 16.5 in 

 summer/winter (Orlando et al 1993). In the study area, salinities ranged from 

 X = 17.3 ppt (SD = 11.12, n =119) in spring/early summer to 27.0 ppt in late 

 summer (SD = 6.40, n = 97) (Wiirsig, unpublished data). Temperature was 

 sampled less frequently but was 12-15 °C (« = 3) in winter and x = 31.3 °C in 

 late summer (SD = 1.31, n = 6) (Wiirsig, unpublished data). 



For radio-telemetric and photographic data analyses, statistical tests were 

 run with StatView 4.0fpu (Brainpower 1986) and Excel 4.0 (Microsoft 1992) for 

 Apple Macintosh microcomputers.' Two age classes were defined for 

 anadytical purposes: "immature" was comprised of females < 8 yr old, 

 males < 10; and "mature" as females ^ 8 yr old, males > 10. The boundary ages 

 were based on youngest pregnant female captured and age-at-maturity results 

 from Fernandez (1992). 



RADIO-TRACKING 



Radio Package Specifications 



The radio transmitters (Fig. 2), built by Telonics, Inc., Mesa, Arizona, 

 consisted of aluminum tubes 8.0 cm long and 1.6 cm in diameter, with a 

 0.1-cm thick and 39.0-cm long staiitless-steel antenna, topped by a 0.3-cm ball 

 to prevent injury by the tip of the antenna (configuration MOD-050 

 transmitter package with TAGL antenna). Transmitters broadcast in the 

 frequency range of 148-150 MHz, at a pulse rate of 90/min, pulse duration of 

 400 msec, bandwidth of 16.2 Hz, and pwwer output of approximately 

 10-20 milliwatts. Power was provided by sealed lithium batteries designed to 

 last approximately 6 weeks. 



The transmitters were attached to a rectangular 12.5-cm long, 4.0-cm high, 

 and 0.12-cm thick aluminum plate rounded at the four comers and backed by 

 0.4-cm thick open-cell "wetsuit" neoprene. Trai\smitters were attached to both 

 the aluminum /neoprene plate and the dolphin dorsal fm by two 0.64-cm 

 diameter bolts fabricated from Teflon rods supplied by Cadillac Plastic and 

 Chemictd Co., Houston, Texas. On the radio side, the Teflon bolts were 



' Use of trade-names does not imply endorsement by the National Marine Fisheries Service. 



