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potential expense of not following a rigorous survey route or sampling design), and 

 an effort to cover the whole area in a short period of time with repeatable survey 

 routes. The first component allows the development of the photo-ID catalog so that 

 sufficient numbers of marked dolphins are identified to estimate abundance 

 precisely, while the second component would provide a standardized effort each 

 year so that annual comparisons can be made. 



Method 3 (mark-resight method) would provide satisfactory estimates from 

 the second component of such a survey because the statistical properties of the 

 more-traditional mark-recapture methods are well-known and the sampling units 

 provided adequate sample sizes of marked animals. In Charlotte Harbor, as in 

 Tampa Bay, however, it proved difficult to conduct "complete surveys" within the 

 available survey window. Instead, we could only survey regions repeatedly while 

 conditions were favorable when other regions were unworkable, and then shift our 

 efforts opportunistically. If "complete surveys" can not be conducted, then Method 

 2 (mark-proportion) provides an acceptable alternative as long as the numbers of 

 sightings and proportion of marked dolphins are high, and the effort among 

 different regions is not greatly biased. This method is particularly useful because it 

 can be more-readily calculated from the first component of the survey design during 

 which the largest numbers of groups would be sighted. Methods 1 (catalog-size 

 method) and 4 (resighting-rate method) may provide double-checks on the trends 

 and estimates of the other two methods. 



Recommendations 



Monitoring should be continued at least annually to track and evaluate the 

 apparent trend. The more frequent the surveys, the better the chance of detecting 

 a trend towards a catastrophic decline. More-intensive surveys would permit 

 more-refined determinations of natality, immigration, emigration, transience, 

 and mortality. Although two or three annual surveys can detect large trends in 

 abundance, this study illustrates the difficulty of interpreting the causes for the 

 abundance changes without more detailed or longer-term information. 

 Photo-ID work should be expanded to other seasons to examine previous reports 

 of seasonal fluctuations in abundance. 



Empirical studies designed to identify the appropriate level of effort for mark- 

 recapture surveys should be conducted. 



Photo-ID efforts should be expanded to greater distances offshore and along the 

 coast to examine immigration, emigration, and transience in greater detail. 

 Patterns of habitat use in Charlotte Harbor should be examined through 

 integration of GIS habitat data with our sighting data. Efforts should be made to 

 integrate ecological studies of the dolphins of Charlotte Harbor with other 

 research efforts under the National Estuarv Program. 



Community structure needs to be examined in more detail to define biologically 

 meaningful management units. Existing information on residency, ranging and 

 social patterns, and genetics should be integrated to arrive at population 



