AERIAL SURVEY OF THE BOTTLENOSED DOLPHIN, TVRSIOPS 



TRUNCATUS, AND THE WEST INDIAN MANATEE, TRICHECHUS 



MANATVS, IN THE INDIAN AND BANANA RIVERS, FLORIDA 



Stephkx Lkathkrwood' 



ABSTRACT 



Aerial surveys were conducted of the Indian and Banana Rivers, eastern Florida, to estimate numbers 

 of bottlenosed dolphins and West Indian manatees. Thirty-nine east- west transects, 4.63 km (2.5 n. mi.) 

 apart, were flown on six successive days in August. Observers at inlets from the ocean inventoried 

 dolphins and manatees entering or leaving the river during the hours of the surveys. There were 64 

 sightings of dolphins from aircraft, totaling 507 animals. Fifteen dolphins were seen entering or 

 leaving the river. Direction of movement within the inlets appeared unrelated to tidal flow. The 

 population of dolphins in the rivers during the week of the survey 1 10- 15 August 1 977 1 was estimated at 

 438 ±127. Calves composed 8.1 to 10. Kf of all animals seen. Feeding was observed at widely scattered 

 times and locations. There were 60 sightings of manatees totaling 151 animals. No attempt is made to 

 estimate the size of the manatee population. Calves made up 9.9 to 13.2^f of ail manatees seen. 



The portion of the intracoastal waterway of east- 

 ern Florida between about lat, 28'47'N and 

 27 lO'N consists of the connected waters of the 

 Indian and Banana Rivers (Figures 1, 2, 3). To- 

 gether they form a complex waterway just over 

 185.0 km (100 n. mi.) long and from <0.93 km (0.5 

 n.mi.) to 9.3 km (5.0 n.mi) wide. Below thejunc- 

 tion of the two rivers at the southern tipof Merritt 

 Island (approximately lat. 28'09'30"N), the Indian 

 River is connected to the adjacent Atlantic Ocean 

 by boating channels at Sebastian and Fort Pierce 

 Inlets. 



Like many other portions of the intracoastal 

 waterway, the Indian-Banana River complex is 

 home to Atlantic bottlenosed dolphin, Tursiops 

 tnnicatus. Although the numbers of dolphms in- 

 habiting the rivers is unknown, they have been 

 rumored to contain as many as 5,000 individuals 

 (Orr-I. Whatever its actual size, however, this 

 population is at the center of a grow;ing con- 

 troversy. Commercial fishermen in the river and 

 the adjacent ocean report that the dolphins are a 

 nuisance and menace, annually causing an esti- 

 mated $441,000 worth of damage to longlines and 

 trammel nets used in the Spanish and king mack- 



'Biomedical Group, Naval Ocean Systems Center, San Diego, 

 Calif, present address; Hubbs/Sea World Research Institute, 

 1700 South Shores Road, San Diego, CA 92109. 



-Orr. J M 1977 A survey of Tursiops populations in the 

 coastal United States, Hawaii and Territorial Waters. Contract 

 Report No PL92-522, to the U.S. Marine Mammal Commission. 

 Wash., DC, 18 p. 



erel fisheries and not infrequent injury to fisher- 

 men (Cato and Prochaska 1976), The fishermen 

 have reportedly requested assistance from the 

 Federal government in controlling the dolphin 

 populations. (White-M. Recent attempts to use 

 sounds projected underwater to deter the dolphins 

 from approaching fishing nets and boats have had 

 little effect (Caldwell and CaldwelH). Because of 

 restrictions imposed on the "taking" of marine 

 mammals by the Marine Mammal Protection Act 

 of 1972, and concerns about the dolphins' roles in 

 the ecosystem, any attempts to reduce the alleged 

 interference of dolphins with the fishing activity 

 must fall under close scrutiny. 



The river complex is also home, at least season- 

 ally, to some endangered West Indian manatees, 

 Trichechus manatus. The status of these and other 

 manatees of the mainland United States has been 

 most recently reviewed by Hartman'"' and Irvine 

 and Campbell (1978). 



During August 1977, 1 conducted an aerial sur- 

 vey of Indian and Banana Rivers to estimate the 

 size and productivity (number of calves) of the 

 bottlenosed dolphin population. In addition, I took 



Manu.^cnpl accfpU'd Aufjust I 97H 



FISHKRY mUJ.ETI.N VOL 77. NO 1.1979. 



^J. R White, Doctor of Veterinary Medicine, 16501 S.W. 184th 

 St., Miami, Fla.. pers. common Julv 1977. 



^Caldwell, D. K., and M. C. Caldwell. 1975. Dolphins and 

 fisheries. In A report on the Sea Grant program, p. 28-29. State 

 University System of Florida 



'•Hartman. D. S. 1974. Distribution, status and conserva- 

 tion of the manatee in the United States. Unpubl. rep in tiles of 

 U.S. Dep. Inter., Natl Fish Wildl. Lah . Wa.sh . DC , 126 p. 



47 



