FISHERY BULLETIN VOL 77, NO 1 



( Leatherwood 1975), and dolphins sometimes be- 

 come entangled as a consequence (Mitchell 1975). 

 An entangled adult dolphin, struggling for escape, 

 is certainly capable of ripping a small-mesh net 

 apart. Further, bottlenosed dolphins have been 

 documented stealing fish from longlines (Iver- 

 son'''). Even so, dolphins may not actually be re- 

 sponsible for all or even the majority of the dam- 

 age in Indian River. Cato and Prochaska (1976) 

 refer to damage to nets by sharks and cite the need 

 for deterrents. D. K. Caldwell'^ reviewed the evi- 

 dence and concluded that the majority of damage 

 to nets in the Indian River was probably caused by 

 sharks and not by dolphins, citing as support 

 numerous reports by fishermen and others work- 

 ing the area of sharks around nets. He also con- 

 cluded, however, that dolphins were stealing fish 

 and damaging gear in the king mackerel fishery in 

 the nearby Atlantic Ocean. During the aerial sur- 

 veys, I observed huge concentrations of sharks on 

 the sand bars at the entrance of St. Lucie Channel. 

 Therefore, the question of what causes the damage 

 to nets is still open and regulation of the dolphin 

 population based on its supposed size and levels of 

 damage to the fisheries would be premature. 



Irvine et al. (see footnote 12) reported that in 

 spring calves composed as much as 147^ of the 

 bottlenosed dolphin population near Tampa Bay. 

 Shane (see footnote 13) reported that calves con- 

 stituted from 3.65% (February) to 12.92% (May) of 

 the dolphins in the Port Aransas area (x = 7.61); 

 Leatherwood et al. (1978) reported summer 

 figures from 7.7 to 7.9% calves for coastal Ala- 

 bama, Mississippi, and Louisiana. The 8.1-10.1% 

 calves observed during this survey therefore are 

 well within the reported ranges of percentages of 

 calves in local bottlenosed dolphin populations. 



It has been noted that in areas where tidal flow 

 is negligible, as is the case within these rivers, 

 dolphin movements appear to be related to some 

 factor other than tide (Shane and Schmidley see 

 footnote 10). Shane and Schmidley found that the 

 dolphins in areas of swiftest current moved 

 against tidal flow. The inability to ascertain a 

 relationship between swimming direction of 



'■•Iverson.R, T. B. 1975. Bottlenosed dolpliins stealing fish 

 from Hawaiian fishermen's lines. Unpubl- manuscr., 12 p. 

 Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service. NOAA, P O. Box .3830, Honolulu, HI 

 96812. 



"'D. K. Caldwell. University of Florida, Biocommunication 

 and Marine Mammal Research Facility. Rt. 1, Box 121, St. Au- 

 gustine, FL 32084, pers. commun. September 1977. 



groups and tidal flow in the river inlets in this 

 study is perhaps related to our small sample size. 



Manatees 



Hartman (see footnote 5) and Irvine and 

 Campbell (1978) reported that Florida manatees 

 concentrated near warmwater refugia during 

 winter months but dispersed during the remain- 

 der of the year. The 151 manatees (some no doubt 

 repeats on successive days) sighted during this 

 survey were distributed throughout the nearshore 

 waters of the Indian-Banana River complex, in- 

 cluding several less saline canals, and animals 

 were not concentrated near the St. Lucie power 

 station or other potential warmwater areas where 

 winter concentrations have been reported (Irvine 

 and Campbell 1978). No manatees were observed 

 in the deeper open water of the rivers. All were in 

 shallower coastal waters, marinas, creek mouths, 

 bayous, and canals. The number of calves ob- | 

 served, composing from 9.9 to 13.2% , depending on 

 the correct classification of the intermediate-sized 

 animals observed, falls within the ranges of 9.6% 

 calves (winter) and 13.4% calves (summer) re- 

 ported by Irvine and Campbell (1978). 



ACKNOWLEDGMENTS 



I thank the following for help with this project: 

 aircraft from Orlando Flying Service, Orlando, 

 Fla., were flown by Steve Negrich. Glen Young, 

 Sea World of Florida, flew as second observer. Both 

 men were very competent and patient with the 

 arduous flight schedule. Ed Asper,Sea World, Inc., 

 provided observers at the ocean inlets and offered 

 valuable advice on the animals of the river. Leola 

 Hietala and Louise Anello Irwin typed the manu- 

 script. D. K. Caldwell, A. B. Irvine, Mari Schaef- 

 fer, J. Powers, T. J. Quinn, S. Shane, and R. Wells 

 reviewed the manuscript and made useful sugges- 

 tions for its improvement. Fishery Bulletin re- 

 viewers L. L. Eberhardt and J. R. Gilbert were 

 especially thorough in their treatment. 



LITERATURE CITED 



Caldwell. D, K 



1955. Evidence of home range of an Atlantic bottlenose 

 dolphin J. Mammal. 36:304-305. 

 C.-^LDWELL. D. K., AND M. C. CALDWELL, 



1972. The world of the bottlenosed dolphin J B Lippin- 

 cott Co., Phila.. 157 p. 



58 



