341 
Abstract — From 2001 to 2006, 71 
pop-up satellite archival tags (PSATs) 
were deployed on five species of 
pelagic shark (blue shark [ Prionace 
glauca]; shortfin mako [Isurus oxy- 
rinchus]; silky shark [ Carcharhinus 
falciformis]; oceanic whitetip shark 
[C. longimanus]; and bigeye thresher 
[Alopias superciliosus ]) in the central 
Pacific Ocean to determine species- 
specific movement patterns and sur- 
vival rates after release from longline 
fishing gear. Only a single postrelease 
mortality could be unequivocally doc- 
umented: a male blue shark which 
succumbed seven days after release. 
Meta-analysis of published reports 
and the current study (n= 78 reporting 
PSATs) indicated that the summary 
effect of postrelease mortality for blue 
sharks was 15% (95% Cl, 8.5-25.1%) 
and suggested that catch-and-release 
in longline fisheries can be a viable 
management tool to protect paren- 
tal biomass in shark populations. 
Pelagic sharks displayed species-spe- 
cific depth and temperature ranges, 
although with significant individual 
temporal and spatial variability in 
vertical movement patterns, which 
were also punctuated by stochastic 
events (e.g., El Nino-Southern Oscil- 
lation). Pelagic species can be sepa- 
rated into three broad groups based 
on daytime temperature preferences 
by using the unweighted pair-group 
method with arithmetic averaging 
clustering on a Kolmogorov- Smirnov 
D max distance matrix: 1) epipelagic 
species (silky and oceanic whitetip 
sharks), which spent >95% of their 
time at temperatures within 2°C of 
sea surface temperature; 2) meso- 
pelagic-I species (blue sharks and 
shortfin makos, which spent 95% of 
their time at temperatures from 9.7° 
to 26.9°C and from 9.4° to 25. CPC, 
respectively; and 3) mesopelagic-II 
species (bigeye threshers), which 
spent 95% of their time at tempera- 
tures from 6.7° to 21.2°C. Distinct 
thermal niche partitioning based on 
body size and latitude was also evi- 
dent within epipelagic species. 
Manuscript submitted 11 January 2011. 
Manuscript accepted 16 May 2011. 
Fish. Bull. 109(41:341-368 (2011). 
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. 
Postrelease survival, vertical and horizontal 
movements, and thermal habitats of five species 
of pelagic sharks in the central Pacific Ocean 
Michael K. Musyl (contact author ) 1 
Richard W. Brill 2 
Daniel S. Curran 3 
Nuno M. Fragoso 
Lianne M. McNaughtom 1 
Anders Nielsen 5 
Bert S. Kikkawa 3 ' 
Christopher D. Mayes 6 
Email address for contact author: michael.musyl@noaa.gov 
Deceased 
1 University of Hawaii 
Joint Institute for Marine and Atmospheric 
Research (JIM AR) 
Kewalo Research Facility/NOAA 
1125B Ala Moana Boulevard 
Honolulu, Hawaii 96814 
2 Northeast Fisheries Science Center 
National Marine Fisheries Service 
Woods Hole, Massachusetts and 
Virginia Institute of Marine Science 
P.O. Box 1346 
Gloucester Point, Virginia 23062 
3 Pacific Islands Fisheries Science Center 
NOAA Fisheries 
2570 Dole Street 
Honolulu, Hawaii 96822 
4 Large Pelagics Research Center 
108 East Main Street 
Gloucester, Massachusetts 01930 
5 Technical University of Denmark 
National Institute of Aquatic Resources 
Jaegersborg Alle 1 
2920 Charlottenlund, Denmark 
6 Department of Biology 
Queen's University 
Kingston, ON, K7L 3N6, Canada 
Although there is considerable dis- 
agreement and uncertainty about the 
current state of pelagic fish popula- 
tions (Burgess et al., 2005; Hampton 
et al., 2005; Sibert et al., 2006), there 
is general agreement that large apex 
predators, particularly sharks, are 
at greatest risk of overfishing (Baum 
et al., 2003; Baum and Myers, 2004; 
Camhi, 2008). Possessing life-history 
characteristics (e.g., slow growth, long 
gestation, late maturity) that evolved 
in the absence of industrial fishing, 
pelagic shark species are susceptible 
to overfishing, and declining trends in 
some populations need to be reversed 
for parental biomass to rebuild stocks 
(Camhi, 2008; Chang and Liu, 2009; 
Dulvey et al., 2008). With food web 
models, Schindler et al. (2002) pre- 
dicted that continued mortality of blue 
shark (Prionace glauca) in longline 
fisheries in the central Pacific could 
adversely affect their populations 
and the role of this species as apex 
predators. Moreover, commercial and 
recreational fishing activities gener- 
ally remove the largest animals (i.e., 
parental biomass) and heavy selec- 
tion pressure over several decades can 
potentially cause evolutionary effects 
(e.g., heritable changes in life-history 
traits such as body size, growth, 
age-at-maturity, and fecundity; Law, 
2000; DiBattista et al., 2009; Genner 
et al., 2009). 
Large pelagic sharks, particularly 
blue sharks, which form a large part 
of the international shark fin trade 
(Clarke et al., 2006), are generally 
not targeted but are by far the ma- 
jority of the bycatch in pelagic gill 
nets and longline fisheries targeting 
swordfish (Xiphias gladius) (Camhi, 
2008; Mandelman et al., 2008; Na- 
kano and Stevens, 2008). Effective 
strategies to mitigate shark bycatch 
requires knowledge of species-specif- 
ic horizontal and, more importantly, 
vertical movement patterns (e.g., Wat- 
