1999 

 OUR LIVING OCEANS 



Blue whale. 



Indian manatees. 



Recent assessments indicate that there is an 

 increasing trend in the tour seal stocks; the coastal 

 bottlenose dolphin stock is believed to be stable; 

 West Indian manatees are believed to be declin- 

 ing; and the trends for the remaining 84 stocks 

 are unknown. 



BOTTLENOSE DOLPHIN: 



GULF BAY, SOUND, AND 



ESTUARINE STOCKS 



Stock Definition and 

 Geographic Range 



There are now 33 recognized provisional stocks 

 that occupy the bays, soimds, and estuaries along 

 the U.S. Cult ot Mexico. Seaward of these are rec- 

 ognized an additional three coastal-to-shelt edge 

 and three offshore provisional stocks. Studies re- 

 lying on identification of individual dolphins sug- 

 gest that bottlenose dolphins inhabiting many of 

 the bays, sounds, and other estuaries form discrete 

 communities. Ahhough breeding mav occur be- 

 tween adjacent communities, the geographic na- 

 ture of these areas suggests that each community 



exists as a functioning unit of its ecosystem and, 

 under the MMPA, must be maintained as such. 

 Therefore, each of the areas forming a contiguous 

 enclosed or semi-enclosed body of water is provi- 

 sionally considered to contain a distinct bottle- 

 nose dolphin stock or management unit, but the 

 number of these will likely change as new infor- 

 mation on the biological uniqueness and degree 

 of mixing among these communities is obtained. 

 Although this is believed to be a risk averse ap- 

 proach to management, the small size of many of 

 these populations often results in estimates of sus- 

 tainable removal levels (i.e. potential biological 

 removal (PBR)) of less than one individual, and 

 this becomes problematic, io this end, a major 

 research objective is to develop biologically based 

 criteria to better define and manage this species in 

 the tlulf of Mexico. 



The continuous distribution ofbottleno.se dol- 

 phins around the Gulf coast theoretically allows 

 genetic exchange between adjacent communities. 

 However, long-term mark-recapture studies using 

 photo-identification of individual dolphins in the 

 vicinity of Sarasota and Tampa Bavs in Florida 

 demonstrate that individual dolphins remain in a 

 given area year-round. Three distinct dolphin com- 

 munities have been described in and around 

 Sarasota Bay. One community was formed by dol- 

 phins residing in the Clulf of Mexico coastal wa- 

 ters, another consisted of the dolphins in the deep- 

 water areas of Passage Key Inlet and Tampa Bay 

 (adjacent to Sarasota Bay), and a third commu- 

 nity resided in the shallow waters of Sarasota Bay. 



Females of the highly structured Sarasota dol- 

 phin communit)' form a stable, discrete, long-term 

 breeding unit with strong geographical fidelity 

 Electrophorctic isozyme analysis showed signifi- 

 cant differences between dolphins of the shallow- 

 water Sarasota communit\' and the iampa Bay 

 communitv, and from dolphins tiom Charlotte 

 Harbor, to the south; however, there was a high 

 degree of genetic heterozvgositv indicating that the 

 Sarasota comniuiiin, \\ hile socialK' and geographi- 

 cally distinct, is not genetically isolated. It has been 

 suggested that the Sarasota community is likely 

 one of a number of communities which comprise 

 an extended popul.ition, the limits of which are 

 unknown. 



I'hoto-identification and radio-tracking stud- 



250 



