78 
Fishery Bulletin 106(1) 
(Fig. 5). For example, the predicted bycatch for two HI- 
FI strandings per season was 14 animals, but may have 
equaled between -23 to 51 animals (68% Cl) or -65 to 
93 animals (95% Cl). The lower Cl bounds are nega- 
tive statistically; however, in reality they cannot be less 
than the number of HI-FI strandings recovered. 
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Figure 4 
Number of bottlenose dolphin (Tursiops truncatus) strandings classified as HI-FI 
(i.e., having evidence of fishery interaction) per month and the stranding threshold 
(mean + 2 standard deviations; horizontal dashed lines) by seasonal management 
unit (MU) in North Carolina (NC). During winter (November-April), the thresh- 
old was exceeded seven out of 18 months during time period (TP) 1 and only three 
out of 30 months during TP2. During summer (May-October), the threshold was 
exceeded once during TP1 and twice during TP2 for the northern NC MU, and once 
during TP1 for the southern NC MU. The vertical dashed lines indicate separation 
between TP1 and TP2. 
Discussion 
This study provides a unique 
situation in which three con- 
current data sets can be used 
to test the model of using 
strandings as an indicator of 
fishery bycatch. It was dem- 
onstrated that fisheries reg- 
ulations can affect the level 
of dolphin bycatch mortality 
and that increases in bycatch 
mortality can be detected in 
near real-time by monitoring 
changes in stranding rates. 
There was a significant posi- 
tive correlation between sea- 
sonal HI-FI strandings and 
bycatch estimates of bottle- 
nose dolphins in gill nets. 
That correlation was mir- 
rored by a marked decrease 
in winter stranding rates 
of bottlenose dolphins with 
entanglement lesions coinci- 
dent with a marked decrease 
in the fishing effort for spiny 
dogfish off NC. 
Many factors can influence 
the rate of deposition of dead 
dolphins on beaches. For ex- 
ample, the overall increases 
in the number of strandings 
during winter compared to 
summer are likely due, in 
part, to an increase in local 
bottlenose dolphin abundance 
when three MUs overlap off 
the NC coast (Waring et ah, 
2006). Within winter, strand- 
ing rates of HI-FI strandings 
were further influenced by 
changes in fishing effort for 
spiny dogfish between TP1 
and TP2 (Table 2) rather 
than to changes in environ- 
mental factors such as wind 
direction and currents. This 
finding was consistent with 
the reduction in bycatch esti- 
mates (Rossman and Palka 1 ) 
and the nonsignificant dif- 
ference for Hl-no strandings 
between the two time peri- 
ods. There were reductions, 
