Harbor. We followed the analytical procedures of Wells et al. (1995) as applied to 

 bortlenose dolphins in Tampa Bay during a similar study. 



Method 1 (catalog-size method) simply involves tallying the number of 

 positively identified ("marked") individuals (M) sighted within the study area 

 during the survey period. We derived our overall catalog of marked animals for 

 each survey year by considering all sightings during the survey period regardless of 

 the photo grade. The inclusion of a fin in the catalog was dependent on the 

 recogruzability of a dolphin, not the overall quality of coverage of a sighting. The 

 catalog-size method does not account for dolphins that are not distinctively marked. 

 The size of the annual Charlotte Harbor catalog (M) is an integral part of each of the 

 following three abundance estimation procedures. 



Assuming comparable levels of sighting effort from year to year, the catalog- 

 size approach may provide a reasonable index for detection of trends of abundance. 

 To conduct a power analysis, however, a coefficient of variation (CV = var 1/2 / N) 

 could only be calculated by considering each year (1990-1994) as a replicate sample. A 

 regression analysis of the five annual estimates was conducted to remove the effects 

 of a potential trend; a CV was then calculated from the residuals. 



Method 2 (mark-proportion method) calculated the proportion of positively 

 identified dolphins (m) relative to the total group size (n) in each sighting of 

 "Grade-1" quality. The accuracy of the population-size estimates depends on the 

 confidence in identifications. Therefore, only Grade-1 sightings were used to derive 

 the proportion of marked animals. There was no relationship between group size 

 and the proportion of dolphins identified (r 2 = 0.002). 



The proportions of marked dolphins to group size (m/n) for each sighting 

 were averaged for each year. The total number of marked dolphins in the catalog 

 for a given year (M) was divided by the average proportion of marked dolphins to 

 yield an annual population estimate (N). A similar method was used by Shane 

 (1987) to estimate abundance in Pine Island Sound. A 2000-replicate non-parametric 

 bootstrap resampled the m/n proportions from observed groups to produce 

 variance estimates and percentile confidence limits. 



Method 3 (mark-resight method) uses the Bailey modification of the Petersen 

 method to estimate abundance (Bailey 1951; Seber 1982; Hammond 1986). The 

 Bailey modification incorporates resampling with replacement in the model. 

 Because both marked and unmarked dolphins may be resighted multiple times, this 

 modification was deemed appropriate. The equation used was: 



N = M(n2 + l) / (m2 + 1) 

 with a binomial variance of 



