Dapp et al.; Immediate mortality of Prionace glauca and Galeocerdo cuvier caught by pelagic longlines 
31 
Geographic zone Target catch 
Figure 2 
The effect of analyzed factors: (A) sea-surface temperature, (B) regulatory period, (C) geographic 
zone, and (D) target catch (swordfish or tunas), on the immediate mortality of discarded blue sharks 
(Prionace glauca) in the U.S. Atlantic pelagic longline fishery. Regulatory period refers to the period 
before the establishment of fin-to-carcass ratios (Januaryl992-February 1993), prior to the prohibi- 
tion of the use of J-hooks (March 1993— August 2004), and during which the use of circle hooks was 
mandatory (August 2004-December 2008), denoted as prefinning, precircle hook, and circle hooks only 
in the figure. Bars represent the mean immediate mortality, and error bars indicate 95% confidence 
intervals. The geographic zones are Caribbean (CAR), Florida east coast (FEC), Mid-Atlantic Bight 
(MAB), north central Atlantic (NCA), northeast coastal (NEC), northeast distant (NED), South Atlan- 
tic Bight (SAB), Sargasso Sea (SAR), and tuna north (TUN). 
analysis of tiger shark because its examination re- 
quired the use of a reduced data set. The model cre- 
ated by using the reduced data set that included the 
interaction explained less deviance (expressed as a per- 
centage) in the model than did a model that used the 
full data set (Suppl. Table 3). The final model used for 
tiger sharks was 
Immediate mortality = SST + ^2) 
Regulatory period + Geographic zone. 
Predictor variables were SST (measured in degrees 
Celcius), regulatory period (January 1992-February 
1993, March 1993-July 2004, August 2004-December 
2008), and geographic zone (CAR, GOM, FEC, MAB, 
NCA, NEC, NED, SAR, SAB, TUN, TUS). Wald tests 
were used to determine whether the overall effect of 
each predictor variable on immediate mortality was 
statistically significant (P<0.05). To portray biological- 
ly meaningful results, statistically significant predictor 
variables were examined in isolation in Figures 2, 3, 
and 4. 
The variable regulatory period was defined accord- 
ing to changes in the management of the fisheries. 
During the first period (January 1992-February 1993), 
shark finning was legal and few regulations existed 
to protect shark populations. The implementation of 
the first fishery management plan for sharks of the 
Atlantic marked the beginning of the second regula- 
tory period (March 1993— July 2004; NMFS^). This 
plan provided management for 39 species of sharks, 
establishing bag limits and a fin-to-carcass weight ra- 
tio of 5% or less and requiring the release of sharks 
not retained under commercial quotas or bag limits. 
J-hooks were the predominant hook type used during 
this regulatory period (Hoey and Moore^; Watson et 
ah, 2005). The final period examined (August 2004- 
