264 



Fishery Bulletin 100(2) 



al., 1996). As a result, the South CaroUna shad fishery re- 

 tained its original classification as a category-Ill fishery 

 (i.e. unlikely to take marine mammals in the course of op- 

 eration) as described in the MMPA amendments of 1988. 



Bottlenose dolphin mortality due to human interactions 

 is variable along the eastern United States and Gulf of 

 Mexico (Wang et al., 1994). Incidents of human interaction 

 in South Carolina were also variable over our five-year 

 study period. We believe that the number of bottlenose dol- 

 phins in our study showing positive human interaction is 

 a minimum because determination of human interaction 

 cases is difficult to assess owing to a lack of trained per- 

 sonnel, the decomposition of some carcasses, and the pre- 

 sumption that some interactions do not leave any physical 

 evidence. It was a rare occurrence to have gear attached 

 to the carcass; therefore, determination of human interac- 

 tion was usually made by obsei-ving external marks such 

 as cross-hatched lines or lines imprinted by the fishing 

 gear. Human interaction as a cause or contributing factor 

 in a dolphin's death can include fishery interactions (crab 

 pots, trawls, etc. ), boat collisions, gun shot wounds, environ- 

 mental contaminants (agricultural run-off, pesticide use, oil 

 spills ). These interactions can result in acute ( drowning in a 

 net) or chronic (environmental contaminants) death, show 

 physical evidence (net marks) on the body or none at all. 



The percentage of human interaction cases observed in 

 South Carolina was low compared with those in North Car- 

 olina strandings (>35'7( in some years; Wang et al., 1994; 

 FR, 1997). Resident bottlenose dolphins in South Carolina 

 appear to be exposed to different fishing operations than do 

 bottlenose dolphins that migi-ate through or inhabit North 

 Carolina waters. Net marks were the most common obser- 

 vation (10.5 animals per year) of human interaction cases 

 in North Carolina (FR, 1997), whereas in South Carolina 

 only one presumed net-caught animal was obsei-ved over a 

 five-year period. In South Carolina incidents of entangle- 

 ments as evidenced by rope or line marks are puzzling. At 

 this time, it is highly speculative as to which fishery in 

 South Carolina may be responsible for the incidence of en- 

 tanglements associated with rope or line marks. 



There is evidence to suggest that relationships exist be- 

 tween gender and lengths of various species of cetaceans 

 involved with human interaction (Perrin et al., 1994; Cox 

 et al., 1998). In our study small male bottlenose dolphins 

 and female bottlenose dolphins >220 cm showed evidence 

 that they were subject to human interaction. One study 

 found that females with calves spent more time feeding 

 at shrimp boats than did lone animals (Fertl, 1994). Food 

 intake for lactating females can increase dramatically 

 (Cockroft and Ross, 1990). Although heavy-feeding behav- 

 ior may be energetically beneficial, it may also be costly to 

 both the calf and mother by exposing them to fishing gear 

 and predation. 



In summary, the stranding data collected for bottlenose 

 dolphins in South Carolina from 1992 to 1996 provides 

 baseline information for the demographics, life history 

 studies, and management concerns for comparing future 

 stranding rates of bottlenose dolphins in South Carolina. 

 Although it cannot be definitively stated that stranding 

 rates coincide with a portion of a migratory stock, strand- 



ings in the northern portion (zone 1) do increase during a 

 period of greater dolphin abundance. More years of data 

 will further elucidate the seasonal reproduction distribu- 

 tion for bottlenose dolphin. Finally, the detection of human 

 interaction as a cause or contributing factor in the deaths 

 of some bottlenose dolphins in South Carolina has demon- 

 strated the need to continue the effort to report these inci- 

 dents for management purposes. 



Acknowledgments 



The authors would like to acknowledge the numerous 

 South Carolina marine mammal stranding volunteers, past 

 and present, who have contributed their time in the noti- 

 fication, recovery, transportation, and sample collection of 

 stranded marine mammals. Without their dedication, our 

 knowledge of marine mammals would be greatly reduced. 



We would also like to thank Sylvia Galloway, Pat Fair, 

 Larry Hansen, David Whitaker, and the reviewers and 

 the anonymous referees of the Fishery Bulletin; Keith 

 Bangerter, Lori Schwacke, and Laura Kracker for help 

 with statistical and spatial analyses; the Armed Forces 

 Institute of Pathology, Washington, D.C.; and finally coun- 

 ty, state, law enforcement, town administration person- 

 nel, and the numerous concerned citizens who helped in 

 many ways in the success of the South Carolina stranding 

 network. 



This work was made possible through NOAA's responsi- 

 bility under the Marine Mammal Health and Stranding 

 Response Act (1993), and under a Letter of Authorization 

 issued by the National Marine Fisheries Service to the 

 South Carolina Department of Natural Resources. Fund- 

 ing to support the South Carolina marine mammal strand- 

 ing network comes from the South Carolina Endangered 

 Wildlife Fund. 



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