Introduction 



The National Marine Fisheries Service (NMFS) is responsible for establishing 

 quotas for take of bottlenose dolphins {Tursiops truncatus) and for monitoring the 

 populations of dolphins in the southeastern United States waters. Quotas have 

 been based on a rule-of-thumb developed by the Marine Mammal Commission in 

 which the annual quota has been set at 2% of the estimated dolphin abundance for a 

 geographical location. Most of the live-capture fishery for bottlenose dolphins has 

 occurred in the coastal Gulf of Mexico and the Florida east-coast waters. In recent 

 years, large scale mortalities of bottlenose dolphins have occurred in several 

 locations in southeastern U.S. waters. The NMFS completed sampling surveys in 

 these areas for abundance estimation, and recognized a need for low-level 

 monitoring of bottlenose dolphin stocks in southeastern U.S. waters, designed to 

 detect catastrophic changes in the stocks. The main goals of the monitoring were 

 detection of large-scale changes in dolphin abundance and establishment of archival 

 databases for long-term trend detection. Low-level monitoring could provide a 

 short-term means of detecting large-scale changes in population abundance and give 

 decision makers the information necessary to determine if modification of 

 management plans is necessary. To these ends, in 1987 the NMFS began funding 

 several local research efforts in the southeastern U.S. with the following stated 

 objectives: 



1) Detection of large-scale (halving or doubling) interannual changes in relative 

 abundance and /or production of the bottlenose dolphin stocks in the southeast 

 U.S. The population rate parameters of relevance include: a reliable index or 

 estimate of local relative abundance, natality, mortality, emigration, and 

 immigration. 



2) Establishment of archival databases for long-term trend detection in localized 

 geographical regions around the southeast US. 



One of the regions selected by the NMFS for low-level monitoring was 

 Charlotte Harbor, along the southwestern coast of Florida. Charlotte Harbor was of 

 interest to management agencies at least in part because of the use of this region for 

 commercial dolphin collection. In addition to those removed by several active 

 collectors prior to regulation under the Marine Mammal Protection Act of 1972 (R. 

 Wells, pers. obs.), 43 dolphins were collected from these waters during 1973-1988 

 (Scott 1990). More recently, Charlotte Harbor has been designated as a National 

 Estuary under the Clean Water Act. 



Aerial surveys to estimate bottlenose dolphin abundance in Charlotte Harbor 

 have been conducted on four occasions since 1975: by Odell and Reynolds (1980) 

 during 1975-76, and by the National Marine Fisheries Service during 1980-81, 1983- 

 1986, and 1994 (Thompson 1981; Scott et al. 1989; Blaylock et al. 1995). The aerial 

 survey study area included Charlotte Harbor proper, as well as Pine Island Sound to 



