72 
Abstract — Fisheries management 
actions taken to protect one species 
can have unintended, and sometimes 
positive, consequences on other spe- 
cies. For example, regulatory mea- 
sures to reduce fishing effort in the 
winter gillnet fishery for spiny dog- 
fish ( Squalus acanthias) off North 
Carolina (NC) also led to decreases 
in the number of bycaught bottlenose 
dolphins (Tursiops truncatus). This 
study found that a marked decrease 
in fishing effort for spiny dogfish in 
NC also corresponded with a marked 
decrease in winter stranding rates of 
bottlenose dolphins with entanglement 
lesions (P=0.002). Furthermore, from 
1997 through 2002, there was a sig- 
nificant positive correlation (r 2 = 0.79; 
P=0.0003) between seasonal bycatch 
estimates of bottlenose dolphins in 
gill nets and rates of stranded dol- 
phins with entanglement lesions. With 
this information, stranding thresholds 
were developed that would enable the 
detection of those increases in bycatch 
in near real-time. This approach is 
valuable because updated bycatch 
estimates from observer data usu- 
ally have a time-lag of two or more 
years. Threshold values could be used 
to detect increases in stranding rates, 
triggering managers immediately 
to direct observer effort to areas of 
potentially high bycatch or to institute 
mitigation measures. Thus, observer 
coverage and stranding investigations 
can be used in concert for more effec- 
tive fishery management. 
Manuscript submitted 20 April 2007. 
Manuscript accepted 30 October 2007. 
Fish. Bull. 106:72-81 (2008). 
The views and opinions expressed or 
implied in this article are those of the 
author and do not necessarily reflect 
the position of the National Marine 
Fisheries Service, NOAA. 
Effects of commercial fishing regulations 
on stranding rates of bottlenose dolphin 
(Tursiops truncatus ) 
Barbie L. Byrd (contact author) 
Aleta A. Hohn 
Email address for B. L. Byrd: Barbie.Byrd@noaa.gov 
National Marine Fisheries Service 
Southeast Fisheries Science Center 
National Oceanic and Atmospheric Administration, Beaufort Laboratory 
101 Pivers Island Road 
Beaufort, North Carolina 28516 
Fentress H. Munden 
North Carolina Division of Marine Fisheries 
3441 Arendell Street 
Morehead City, North Carolina 28557 
Gretchen N. Lovewell 
Rachel E. Lo Piccolo 
National Marine Fisheries Service 
Southeast Fisheries Science Center 
National Oceanic and Atmospheric Administration, Beaufort Laboratory 
101 Pivers Island Road 
Beaufort, North Carolina 28516 
The occurrence of beach-cast or 
stranded marine animals has been 
used to indicate fishery-induced (i.e., 
bycatch) mortality of marine birds 
(Salzman, 1989), turtles (Caillouet 
et ah, 1991; Epperly et ah, 1996), and 
mammals (Forney et al., 2001; Fried- 
laender et al., 2001). Direct documen- 
tation of bycatch mortality is obtained 
by placing trained observers on com- 
mercial fishing vessels (Edwards and 
Perrin, 1993; Epperly et al., 1995), but 
limited resources allow for observa- 
tion of only a small proportion of fish- 
ing trips and a few types of fisheries. 
Additionally, updated bycatch esti- 
mates can take years to become avail- 
able, preventing real-time responses to 
significant changes in bycatch rates. 
Strandings of marine animals, there- 
fore, can serve as the primary, and 
sometimes the only, evidence of cur- 
rent bycatch mortality. Gear is rarely 
present on stranded animals; however, 
entanglement lesions on the epidermis 
of cetaceans can help identify animals 
that have been captured incidentally 
by fishing gear (Kuiken et ah, 1994; 
Read and Murray, 2000). 
Early indications of bottlenose dol- 
phin ( Tursiops truncatus) bycatch 
mortality off North Carolina (NC) 
came from stranding data. From 
1993 through 1996, 29% of the 230 
stranded bottlenose dolphins recov- 
ered in NC exhibited signs of en- 
tanglement in fishing gear (War- 
ing et ah, 1997). Early observer 
data (1993-96) were inconsistent 
with stranding data because only 
one entanglement was documented 
in the observer program (Waring et 
ah, 1997). As a result, observer cov- 
erage was expanded in 1997 to in- 
clude more of the various ocean-side 
gillnet fisheries (Waring et ah, 1999). 
The annual estimated bycatch 
mortality in ocean gill nets from No- 
vember 1995 through October 2000 
confirmed high levels of mortality of 
bottlenose dolphins off NC. All but 
one observed entanglement was that 
of the coastal morphotype, which is 
morphologically and genetically dis- 
