Byrd et al.: Effects of commercial fishing regulations on stranding rates of bottlenose dolphin ( Tursiops truncatus) 
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Figure 1 
The coastal bottlenose dolphin ( Tursiops truncatus ) is divided into seasonal manage- 
ment units (MUs). During summer ( May-October), two of the management units (MUs) 
occur off North Carolina ( NC ; ) the northern NC MU and the southern NC MU. During 
winter (November-April), two summer MUs overlap with a third MU, the northern 
migratory MU, which occurs north of the Virginia-NC border during the summer. 
These three MUs are referred to collectively as the winter mixed MU (Waring et al., 
2006). Solid horizontal lines represent latitudinal boundaries of MUs and does not 
imply offshore (i.e., longitudinal) distribution. The dashed horizontal line represents 
the northern boundary of the NC portion of the winter mixed MU. 
tinct from the offshore morphotype (Mead and Pot- 
ter, 1995; Hoelzel et al., 1998; Waring et al., 2002). 
The bycatch estimates for the coastal morphotype were 
stratified according to current stock structure of coastal 
bottlenose dolphins, which consists of seven seasonal 
management units (MUs) (Waring et al., 2002). Three 
of the MUs are seasonal off NC: the summer (May-Oc- 
tober) northern NC MU, the summer southern NC MU, 
and the NC portion of the winter (November-April) 
mixed MU (see Fig. 1 for delineations of the units). 
Bycatch exceeded the potential biological removal (PBR) 
level (i.e., the sustainable anthropogenic mortality level) 
(MMPA 16 U.S.C. 1362 [20] ; Barlow et ah, 1995) for one 
of the two summer MUs and for the winter MU (Waring 
et al., 2002, 2006). During the summer, the annual esti- 
mated bycatch for the northern NC MU was 23 animals, 
exceeding the PBR level (20), and the annual estimated 
bycatch for the southern NC MU was zero, not exceed- 
ing the PBR level (10). For the winter mixed MU (NC 
and VA submanagement units), the annual estimated 
bycatch was 180 animals, more than twice the PBR lev- 
el (68). The majority of this bycatch (146 out of 180 ani- 
mals) was attributed to the NC submanagement units 
(Rossman and Palka 1 ). The spiny dogfish (FAO common 
name: picked dogfish) fishery was the primary contribu- 
tor to the bycatch mortality in the winter mixed MU. 
In 2005, new annual bycatch estimates, based on 
observer data from ocean gill nets from November 2000 
through October 2002, became available (Rossman and 
Palka 1 ; Waring et al., 2006). The new bycatch estimate 
for the summer northern NC MU decreased to eight 
animals per year and the new estimate for the NC win- 
1 Rossman, M. C., and D. L. Palka. 2005. A review of coastal 
bottlenose dolphin bycatch mortality estimates in relation to 
the potential effectiveness of the proposed BDTRP. Bottle- 
nose Dolphin Take Reduction Team Document No. 1-13-05F, 
9 p. National Marine Fisheries Service, Northeast Fisheries 
Science Center, 166 Water Street, Woods Hole, MA 02543. 
