Differential loggerhead by-catch and direct mortality due to surface longlines according to boat strata and gear type

Authors

  • Juan A. Camiñas Instituto Español de Oceanografía, Centro Oceanográfico de Málaga
  • José C. Báez Instituto Español de Oceanografía, Centro Oceanográfico de Málaga
  • Xulio Valeiras Instituto Español de Oceanografía, Centro Oceanográfico de Santander, Santander
  • Raimundo Real Departamento de Biología Animal (Zoología), Facultad de Ciencias, Universidad de Málaga, Málaga

DOI:

https://doi.org/10.3989/scimar.2006.70n4661

Keywords:

Caretta caretta, drifting longline, fisheries, incidental capture, pre-release mortality, sea turtle

Abstract


Surface longline gears are used to fish different species, mainly albacore Thunnus alalunga (Bonnaterre, 1788), bluefin tuna Thunnus thynnus (Linnaeus, 1758), and swordfish Xiphias gladius Linnaeus, 1758, and are considered highly dangerous for threatened marine turtles. Loggerheads Caretta caretta (Linnaeus, 1758) can be incidentally captured by surface longlines. A number of captured individuals die during the fishing operation, which we consider direct mortality due to fishing. We analysed the relative loggerhead by-catch and direct mortality associated with each type of boat and gear from April to December during the period 1999-2004 in the Spanish surface longline fleet that fishes in the western Mediterranean Sea, an important fishing area for this fleet. We used different indices to compute the catch per unit effort (CPUE) according to the number of hooks and to the number of fishing operations for each type of boat and gear. Both by-catch and direct mortality differed significantly according to the type of boat and gear. With respect to the number of hooks, boats longer than 12 m not using a roller and targeting bluefin tuna captured the highest number of loggerheads, whereas boats longer than 12 m with a roller that targeted swordfish caused the highest direct mortality. With respect to the number of fishing operations, boats longer than 12 m without a roller that targeted albacore captured the highest number of loggerheads; the highest direct mortality was caused by this type of boat and by boats longer than 12 m using a roller and targeting swordfish.

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Author Biography

José C. Báez, Instituto Español de Oceanografía, Centro Oceanográfico de Málaga

Departamento de Biología Animal (Zoología), Facultad de Ciencias, Universidad de Málaga, Málaga

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Published

2006-12-30

How to Cite

1.
Camiñas JA, Báez JC, Valeiras X, Real R. Differential loggerhead by-catch and direct mortality due to surface longlines according to boat strata and gear type. Sci. mar. [Internet]. 2006Dec.30 [cited 2024Mar.28];70(4):661-5. Available from: https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/71

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