27 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
established in 1881 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Using logbook data to determine the immediate 
mortality of bine sharks IPrionace glauca) and 
tiger sharks iGaleocerdo cuwier) caught in the 
commercial U.S« pelagic longline fishery 
Email address for contact author: derek.r.dapp@gmail.com 
’ School of Biological Sciences 
Monash University 
Wellington Road 
Clayton, Victoria 3800, Australia 
Present address for contact author; Washington Department of Fish and Wildlife 
600 Capitol Way North 
Olympia, Washington 98501-1091 
2 School of Biological Sciences 
Flinders University 
G.P.O. Box 2100 
Adelaide, South Australia 5001, Australia 
3 Anderson Cabot Center for Ocean Life 
New England Aquarium 
Central Wharf 
Boston, Massachusetts 02110-3399 
^ Department of Marine and Environmental Sciences 
Halmos College of Natural Sciences and Oceanography 
Nova Southeastern University 
8000 North Ocean Drive 
Dania Beach, Florida 33004 
Abstract-Commercial fisheries are 
recognized as one of the greatest 
threats to shark populations world- 
wide, but factors affecting the likeli- 
hood of shark mortality during fish- 
ery capture are poorly understood. 
We used the U.S. pelagic fishery log- 
book data from 1992 through 2008 to 
quantify the effects of several vari- 
ables (fisheries regulatory periods, 
geographic zone, target catch, and 
sea surface temperature) on mortal- 
ity of blue sharks (Prionace glauca) 
and tiger sharks (Galeocerdo cu- 
vier). Mortality rates and trends in 
both species closely matched those 
recorded from other sources, and 
therefore indicated that the data on 
sharks discarded dead and discarded 
alive in the U.S. pelagic fishery log- 
book are accurate. The introduction 
of fisheries management regulations 
(fin weight to carcass weight ratios 
in 1993 [to prevent finning] and the 
prohibition of J-hooks in 2004) pre- 
sumably decreased the immediate 
mortality rate of captured blue and 
tiger sharks (by 8.0% in blue sharks 
after 2004 and 4.4% in tiger sharks 
after 1993). Other factors that we 
examined had a statistically signifi- 
cant effect on mortality, but addi- 
tional variables should be recorded 
or made available in logbook data 
to enable the determination of other 
causes of mortality. Our results show 
that the U.S. pelagic fishery logbook 
data can be used as a powerful tool 
in future studies of the immediate 
mortality of iongline-caught animals. 
Manuscript submitted 18 March 2016. 
Manuscript accepted 17 October 2016. 
Fish. Bull. 115:27-41 (2017). 
Online publication date: 16 November 2016. 
doi: 10.7755/FB.115.1.3 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Derek R. Dapp fcontaet author)’ 
Charlie Huveneers^ 
Terence I. Walker’ 
John Mandelman^ 
David W. Kerstetter^ 
Richard D. Relna’ 
An estimated one-quarter of all 
chondrichthyan (sharks, rays, and 
chimaeras) species are classed as 
threatened according to the Inter- 
national Union for Conservation of 
Nature (lUCN) Red List Categories 
and Criteria, a system for the clas- 
sification of species by extinction 
risk, with fishing pressure being the 
primary threatening process (Dulvy 
et al., 2014). Targeted shark species 
often possess protracted life history 
strategies that make them inherent- 
ly vulnerable to overfishing (Hoenig 
and Gruber, 1990; Smith et al., 1998). 
These shark species are considered 
a lucrative target for commercial 
fisheries and are fished primarily 
for their flesh and fins (Dent and 
Clarke, 2015). However, some spe- 
cies are captured incidentally, con- 
sidered by catch, and discarded either 
because of low commercial value or 
in response to fisheries management 
requirements (also called regulatory 
discards) (Bonfil, 1994). Sharks can 
experience mortality before process- 
ing, retention, or release by fisher- 
men; we refer to such mortality as 
immediate mortality in this study 
