SEA 



SCIENCE 



Be 



Jotdenose dolphins have been included 

 in seafarer legends for centuries, but today's 

 fishing captains are worried more about the 

 charismatic creatures getting caught up in nets 

 than folklore. 



Entanglement is a major issue for the 

 mid-Atlantic coastal gill net fishery, which is 

 comprised of several smaller, seasonal fisheries. 

 The fishery ranks among the highest in the 

 Western North Atlantic for entanglement-related 

 dolphin deaths. From New Jersey to North Caro- 

 lina, an estimated 210 bottlenose dolphins were 

 killed between 1992 and 2001, according to the 

 National Oceanic and Atmospheric Administra- 

 tion's (NOAA) most recent stock assessment. 



Dolphins may get tangled while eating fish 

 from nets, a behavior known as depredation. But 

 it is also possible they run into nets accidentally, 

 says Andrew Read, a Duke University marine 

 scientist who studies bottlenose dolphin behavior. 



Either way, it's a lose-lose situation — and 

 not just for dolphins. 



"Fishermen don't want to experience 

 depredation because it costs money," says Read. 

 "And, fishermen don't want to catch dolphins. 

 It's a big regulatory headache for them." 



Last summer, Read and Hatteras fisherman 

 Dave Swanner received a grant from the N.C. 

 Fishery Resource Grant (FRG) program to 



study whether acoustic deterrent devices 

 called "Save Waves" effectively keep 

 dolphins away from gill nets. The FRG 

 program is funded by the North Carolina 

 General Assembly and administered by 

 North Carolina Sea Grant. 



Used widely in Mediterranean fisheries, 

 Save Waves produce random pulses of sound 

 at the same level of intensity a dolphin uses 

 to echolocate, a physiological process that 

 involves emitting sound waves to locate distant 

 objects, such as prey. 



Save Waves are anecdotal successes in 

 Europe, but there has been very little scientific 

 study to assess their effectiveness, says Read. 

 If such devices can deter hungry or wayward 

 dolphins, depredation and entanglements could 

 be reduced, he adds. 



Read decided to study the Spanish 

 mackerel fishery in North Carolina because 

 it experiences both dolphin depredation and 

 entanglement. Bottlenose dolphins are capable 

 of reducing Spanish mackeral catches by nearly 

 40 percent, according to one of his reports. And 

 about one or two dolphins become entangled in 

 the fishery's nets each year. 



These bycatch numbers may seem low, 

 but the Spanish mackerel fishery is part of the 

 larger mid-Adantic coastal gill net fishery, and 



TOP: A bottlenose 

 dolphin surfaces near 

 the Endurance. 

 MIDDLE: Dave 

 Swanner hauls in his 

 nets as Erin Burke 

 documents his catch. 

 BOTTOM: Swanner 

 holds a basket of 

 Spanish mackerel 

 from his first set. 



the numbers must be factored into the collective 

 fishing effort among all the mid-Atlantic's 

 individual gill net fisheries, explains Read. The 

 resulting totals for dolphin bycatch often exceed 

 thresholds set by the National Marine Fisheries 

 Service (NOAA Fisheries) for ensuring that 

 botdenose dolphin populations remain stable. 



24 SPRING 2005 



