Virginia Institute of Marine Science
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 oxyrinchus]; silky shark [Carcharhinus falciformis]; oceanic whitetip shark [C. longimanus]; and bigeye thresher [Alopias superciliosus]) in the central Pacific Ocean to determine speciesspecific movement patterns and survival rates after release from longline fishing gear. Only a single postrelease mortality could be unequivocally documented: 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% CI, 8.5-25.1%) and suggested that catch-and-release in longline fisheries can be a viable management tool to protect parental biomass in shark populations. Pelagic sharks displayed species-specific 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 Oscillation). Pelagic species can be separated into three broad groups based on daytime temperature preferences by using the unweighted pair-group method with arithmetic averaging clustering on a Kolmogorov-Smirnov Dmax distance matrix: 1) epipelagic species (silky and oceanic whitetip sharks), which spent >95% of their time at temperatures within 2 degrees C of sea surface temperature; 2) mesopelagic-I species (blue sharks and shortfin makos, which spent 95% of their time at temperatures from 9.7 degrees to 26.9 degrees C and from 9.4 degrees to 25.0 degrees C, respectively; and 3) mesopelagic-II species (bigeye threshers), which spent 95% of their time at temperatures from 6.7 degrees to 21.2 degrees C. Distinct thermal niche partitioning based on body size and latitude was also evident within epipelagic species.
Gulf-Of-Mexico; Southern California Bight; Western North-Atlantic; Shortfin Mako Shark; Prionace-Glauca; Blue Sharks; Alopias-Superciliosus; Isurus-Oxyrinchus; Longline Fishery; White Marlin
Musyl, Michael K.; Brill, Richard; Curran, Daniel S.; Fragoso, Nuno M.; McNaughton, Lianne; Nielsen, Anders; Kikkawa, Bert S.; and Moyes, Christopher D., Postrelease Survival, Vertical And Horizontal Movements, And Thermal Habitats Of Five Species Of Pelagic Sharks In The Central Pacific Ocean (2011). Fishery Bulletin, 109(4), 341-368.