10 



option was selected. Given these parameters, a maximum CV of 0.05 is required to 

 detect an increasing trend and a CV of 0.07 is required for a decreasing trend. 



Assuming that the calculated estimates and variances are the true population 

 parameters, then a less conservative z-distribution can be used and the maximum CVs 

 would be 0.16 (increasing trend) and 0.23 (decreasing trend). Conversely, if a more- 

 conservative 2-tailed test were used, the maximum CVs would be 0.02 (increasing 

 trend) and 0.03 (decreasing trend). We chose the 1-tailed t-distribution option 

 because it better fits the situation of considering a change in only one direction at a 

 time and because it could be argued that calculated variances may not truly represent 

 those of the population. 



Estimation procedures: Natality 



Natality was calculated as the proportion of dolphins in each sighting 

 considered to have been born within the year. Though the total number of calves 

 was recorded for each group sighted, only the subset of calves considered to be 

 young-of-the-year was considered to be relevant to the measurement of natality 

 (Wells and Scott 1990). The average proportion of young-of-the-year was calculated 

 for each year. 



Estimation procedures: Mortality 



We obtained stranding records from the Southeast U.S. Marine Mammal 

 Stranding Network (D. Odell, pers. comm.) for bottlenose dolphins recovered from 

 Manatee, Hillsborough and Pinellas counties from 1977 to 1993 to estimate a minimum 

 mortality rate for the Tampa Bay area. We examined photographs of dorsal fins of 

 carcasses provided by the Florida Marine Research Institute and Clearwater Marine 

 Science Center and compared them to our photo-ID catalog to identify known 

 mortalities (Urian and Wells 1993). We used photographs of animals that died during 

 the period 1988 through 1993 and were recovered within the counties encompassing 

 the Tampa Bay study area. Stranding records from outside our specified study area 

 may be included because the exact locations of strandings within the counties were 

 not available and Pinellas and Manatee county waters extend beyond our Tampa Bay 

 study area. Photographs of the stranded animals were examined to determine if the 

 markings occurred post-mortem or if decomposition obscured recognition. 



Estimation procedures: Immigration/Emigration/Transience 



To estimate rates of immigration and emigration, the Tampa Bay catalog of 

 marked animals from 1988-1993 was used to identify individuals that showed 

 "permanent" movement into or out of the study area during our entire survey period. 

 "Permanent" is defined as being present or absent for a period of at least two years 

 (Wells and Scott 1990). Marked dolphins were considered to be "residents" during the 

 survey season if they were identified in at least five of the six survey years. 



To derive an immigration rate, we identified individual dolphins not sighted in 

 the first two years of the surveys, 1988 and 1989, but were initially sighted in 1990 

 and subsequently in 1991, 1992, and 1993. We also identified animals that were not 

 sighted in 1988, 1989, and 1990 but were first sighted in 1991 and subsequently in 

 1992, and 1993. We searched for these animals in our photo-ID catalogs from other 

 regions (e.g., Sarasota Bay, Charlotte Harbor and the inshore waters of the Gulf of 

 Mexico) and searched for sighting records from times other than during our survey 

 period. An immigration rate was calculated based on the proportion of the number 



