Postrelease survival vertical and horizontal movements and thermal habitats of five species of pelagic sharks in the central pacific ocean. pp. 341-368 - Washington National Marine Fisheries Service 2001
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 15percent (95percent CI, 8.5-25.1percent) 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 gt;95percent of their time at temperatures within 2 degrees C of sea surface temperature; 2) mesopelagic-I species (blue sharks and shortfin makos, which spent 95percent 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 95percent 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.
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