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By-catch frequency and size differentiation in loggerhead turtles as a function of surface longline gear type in the western Mediterranean Sea

Published online by Cambridge University Press:  12 February 2013

José Carlos Báez ,
David Macías ,
Juan Antonio Camiñas ,
José María Ortiz de Urbina ,
Salvador García-Barcelona ,
Juan Jesús Bellido  and
Raimundo Real
José Carlos Báez*
Affiliation:
Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto pesquero s/n Fuengirola, Málaga, Spain Biogeography, Diversity, and Conservation Research Team, Department of Animal Biology, University of Malaga, Spain
David Macías
Affiliation:
Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto pesquero s/n Fuengirola, Málaga, Spain
Juan Antonio Camiñas
Affiliation:
CopeMed II and ArtFiMed Project Coordinator, Fisheries and Aquaculture Resources Use and Conservation Division (FIR), Fisheries and Aquaculture Department, Food and Agriculture Organization of the United Nations (FAO). Office: Subdelegación del Gobierno, Paseo de Sancha 64, Despacho 306, Málaga, Spain
José María Ortiz de Urbina
Affiliation:
Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto pesquero s/n Fuengirola, Málaga, Spain
Salvador García-Barcelona
Affiliation:
Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto pesquero s/n Fuengirola, Málaga, Spain
Juan Jesús Bellido
Affiliation:
Biogeography, Diversity, and Conservation Research Team, Department of Animal Biology, University of Malaga, Spain
Raimundo Real
Affiliation:
Biogeography, Diversity, and Conservation Research Team, Department of Animal Biology, University of Malaga, Spain
*
Correspondence should be addressed to: J.C. Báez, Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto pesquero s/n Fuengirola, Málaga, Spain email: jcarlos.baez@ma.ieo.es
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Abstract

Fisheries by-catch is considered to be a major threat to loggerhead turtles in the Mediterranean Sea. Technical differences in both gear configurations (e.g. hook and bait type) and fisheries operations carried out by the Spanish Mediterranean surface longline fleet could have an effect on by-catch rates and size selectivity. The aim of the present study was to test the differences in by-catch per unit effort and body size of loggerhead sea turtles caught using different gear types in the Mediterranean surface longline fishery. Our results suggest that differences in the gear type used have an effect on catch rates and size selectivity. Thus, surface longliners targeting albacore (LLALB) using smaller hooks tend to capture smaller loggerheads but have the highest by-catch per unit of effort (BPUE), whereas other longlines, such as surface longliners targeting bluefin tuna (LLJAP) and traditional surface longliners targeting swordfish (LLHB), using larger hooks tend to select the larger animals; moreover, LLHB had the lowest BPUE. Disproportionate rates of fisheries-induced mortality on certain size/age-classes can differentially affect sea turtle populations, as each sea turtle age-class contributes differently to current and future reproduction. Thus, fisheries management should not only be focusing on preserving the large juvenile and mature turtles, but also on reducing the total by-catch. Thus, we recommend encouraging the use of LLHB versus other surface gears. We suggest that it is very important to take into account the gear type (and its particular catch rates) when making inferences about the impact of longline fisheries on sea turtle populations.

Keywords

by-catchconservation biologyfisherieslong-lived animals
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 93 , Issue 5 , August 2013 , pp. 1423 - 1427
Copyright
Copyright © Marine Biological Association of the United Kingdom 2013 

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