large enough to be seen consistently in typical good-quality field-photographs 

 were counted. 



RESULTS 



Thirty-six dolphins were captured in July 1992 (biological data from 

 Sweeney 1992). Animals ranged in age from 2-34 yr. Of non-calves captured, 

 females had an older mean age and more variability in age than males 

 (females: x = 19.7 ± 9.34 (SD) yr old, n = 11; males: x = 12.9 ± 4.89 (SD) yr old, 

 n = 15; f-test P = 0.02). Five mother-calf pairs were caught (three female calves, 

 two male). Four mothers were pregnant, as were two-three other females. All 

 pregnant females were in the first trimester. Five males and five females 

 were radio-tracked. Males ranged in age from 8-19 yr, while females were 

 from 8 to as old as 31 yr (from tooth aging data supplied by NMFS). One 

 8-yr-old female (FB505) was pregnant, one 31-yr-old (FB521) was mother to a 

 2-yr-old calf and pregnant, one 19-yr-old (FB511) was mother to a 1-yr-old calf 

 and pregnant, and one 12-yT-old (FB515) was mother to a 2-yr-old but 

 apparently not pregncmt. Appendix 1 summarizes the age and sex 

 information for all 36 dolphins captured. Appendix 2 provides a summary of 

 the capture information. 



Radio transmissions lasted from a minimum of 13 days (FB505) to a 

 maximum of 61 days (FB518). The mean was 30.7 days, (SD = 16.85, n = 10) 

 (Table 1). As is usually the case with radio telemetry, only rarely was the 

 status of a transmitter or dolphin known when transmissions first ceased. 

 Several transmitters apparently suffered broken antennas before the packages 

 fell off. Four dolphins were seen within 5 wk of transmission cessation still 

 wearing the radios. Radio-tags #4 (FB505) and #5 (FB511), which transmitted 

 for 13 and 21 days, respectively, were seen on 8 August and 5 August, 

 respectively, with broken antennas. Some tags which lasted about 3 wk 

 (FB504, FB522) probably released from the dolphins as planned (FB522 was 

 seen on 24 August without the radio package). The long-lasting 8-9 wk tags 

 quit due to either package release or end of battery life. We received a report 

 of FB501 seen on 23 October still carrying the radio package. FB501 probably 

 experienced much lower salinities than the others due to the amount of time 

 she sf>ent in the semi-enclosed San Antonio Bay. As a result, the release 

 mechanism took longer to corrode than had been calculated. FB518, however, 

 experienced salinities similar to the other dolphins. Behavioral differences 

 (e.g., evasiveness, described below) or chance mounting differences may also 

 account for failure of the packages to release earlier. 



When certain radio-tagged dolphins (e.g., FB501, FB505, FB511, FB518) 

 were approached by boat, they displayed pronounced evasive behaviors, 

 especially within 2 weeks of radio attachment. This behavior at times resulted 



10 



