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Ecological risk assessment of pelagic sharks caught in Atlantic pelagic longline fisheries

Published online by Cambridge University Press:  07 October 2009

Enric Cortés ,
Freddy Arocha ,
Lawrence Beerkircher ,
Felipe Carvalho ,
Andrés Domingo ,
Michelle Heupel ,
Hannes Holtzhausen ,
Miguel N. Santos ,
Marta Ribera  and
Colin Simpfendorfer
Enric Cortés
Affiliation:
National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, 3500 Delwood Beach Road, Panama City, Florida 32408, USA
Freddy Arocha
Affiliation:
Instituto Oceanográfico de Venezuela, Universidad de Oriente, Cumaná 6101, Venezuela
Lawrence Beerkircher
Affiliation:
National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida 33149, USA
Felipe Carvalho
Affiliation:
University of Florida, Department of Fisheries and Aquatic Sciences, Florida Program for Shark Research, Gainesville, Florida 32653, USA
Andrés Domingo
Affiliation:
DINARA, Area de Recursos Pelágicos, CP 11200 Montevideo, Uruguay
Michelle Heupel
Affiliation:
School of Earth and Environmental Sciences, James Cook University, Queensland 4811, Australia
Hannes Holtzhausen
Affiliation:
Ministry of Fisheries and Marine Resources, Namibia
Miguel N. Santos
Affiliation:
INRB I.P./IPIMAR, 8700-305 Olhão, Portugal
Marta Ribera
Affiliation:
National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, Panama City Laboratory, 3500 Delwood Beach Road, Panama City, Florida 32408, USA
Colin Simpfendorfer
Affiliation:
Fishing and Fisheries Research Centre, School of Earth and Environmental Sciences, James Cook University, Queensland 4811, Australia
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Abstract

An ecological risk assessment (ERA; also known as productivity and susceptibility analysis, PSA) was conducted on eleven species of pelagic elasmobranchs (10 sharks and 1 ray) to assess their vulnerability to pelagic longline fisheries in the Atlantic Ocean. This was a level-3 quantitative assessment consisting of a risk analysis to evaluate the biological productivity of these species and a susceptibility analysis to assess their propensity to capture and mortality in pelagic longline fisheries. The risk analysis estimated productivity (intrinsic rate of increase, r) using a stochastic Leslie matrix approach that incorporated uncertainty in age at maturity, lifespan, age-specific natural mortality and fecundity. Susceptibility to the fishery was calculated as the product of four components, which were also calculated quantitatively: availability of the species to the fleet, encounterability of the gear given the species vertical distribution, gear selectivity and post-capture mortality. Information from observer programs by several ICCAT nations was used to derive fleet-specific susceptibility values. Results indicated that most species of pelagic sharks have low productivities and varying levels of susceptibility to pelagic longline gear. A number of species were grouped near the high-risk area of the productivity-susceptibility plot, particularly the silky (Carcharhinus falciformis), shortfin mako (Isurus oxyrinchus), and bigeye thresher (Alopias superciliosus) sharks. Other species, such as the oceanic whitetip (Carcharhinus longimanus) and longfin mako (Isurus paucus) sharks, are also highly vulnerable. The blue shark (Prionace glauca) has intermediate vulnerability, whereas the smooth hammerhead (Sphyrna zygaena), scalloped hammerhead (Sphyrna lewini), and porbeagle (Lamna nasus) sharks are less vulnerable, and the pelagic stingray (Pteroplatytrygon violacea) and common thresher (Alopias vulpinus) sharks have the lowest vulnerabilities. As a group, pelagic sharks are particularly vulnerable to pelagic longline fisheries mostly as a result of their limited productivity.


Keywords

Ecological risk assessmentLeslie matrixShark life historyVulnerabilityPelagic fisheries
Type
Research Article
Information
Aquatic Living Resources , Volume 23 , Issue 1 , January 2010 , pp. 25 - 34
Copyright
© EDP Sciences, IFREMER, IRD, 2009

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