Environmental, spatial, temporal and operational effects on swordfish (Xiphias gladius) catch rates of eastern Mediterranean Sea longline fisheries

Damalas, Dimitrios; Megalofonou, Persefoni; Apostolopoulou, M.

doi:10.1016/j.fishres.2006.11.001

Cited by 70 publications

(72 citation statements)

References 15 publications

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“…Attacks on surfers in Recife (Brazil), for example, are much more common during new and full moons than during first and last quarters (Hazin et al 2008). Moon phase also appears to have an important effect on shark catches in Atlantic waters (Hernandez-Milian et al 2008) in the Pacific (Pallares andGarcia-Mamolar 1985, Bigelow et al 1999) and the Mediterranean (Damalas et al 2007). While most of these studies analyse the effect of the different phases of the moon on individual species, our results show that the effect of the moon can (1) be even at a day scale, (2) affect groups of species from the same taxonomical group, and (3) be related to other factors such as the kind of habitat.…”

Section: Discussionmentioning

confidence: 99%

Factors affecting the fishing impact on cartilaginous fishes in southeastern Spain (western Mediterranean Sea)

Mendoza¹,

Garrido²

2014

Sci. Mar.

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Summary:We propose a global index of impact based on the relative vulnerability of the local population of every species and the further application of regression trees globally optimized with evolutionary algorithms to study the fishing impact on the cartilaginous fish in southeastern Spain. The fishing impact is much higher in areas of less than 40 m depth within 11 km of the Cape Palos marine reserve. The impact also depends on the state of the sea and the kind of habitat. Deep-sea habitats associated with hard substrata and sandy beds show the highest impact, and sublittoral muds and habitats associated with circalittoral rocks with moderate energy show the lowest impact. The fishing impact changes throughout the moon cycle, showing different day-scale patterns associated with different habitats and different species compositions. Finally, we show that the global optimization of the regression trees can be essential to find some important patterns and that these trees are a useful tool for determining which areas are considered to be more important in terms of protection, taking into account specifically the vulnerability of the local populations.Keywords: Cape of Palos MPA; conservation; cartilaginous fish; fishing impact; regression trees; evolutionary algorithms; vulnerable species. Factores que afectan el impacto pesquero sobre peces cartilaginosos en el sureste español (Mediterráneo Suroccidental)Resumen: Proponemos un índice global de impacto basado en la vulnerabilidad relativa de las poblaciones locales de cada una de las especies y la posterior aplicación de árboles de regresión globalmente optimizados con algoritmos evolutivos, para estudiar el impacto de la pesca en los peces cartilaginosos del sureste español. El impacto de la pesca es mucho mayor, dentro de los 11 km de la reserva marina de Cabo de Palos, en aquellas zonas de menos de 40 m de profundidad. El impacto también depende del estado de la mar y el tipo de hábitat. Los hábitats de aguas profundas asociados a sustrato duro y fondo arenoso muestran los máximos impactos, mientras que, tanto los fondos fangosos sublitorales como los hábitats rocosos circalitorales con moderada energía de las corrientes, muestran un menor impacto. Además, se dan cambios a lo largo del ciclo lunar en el impacto de la pesca, lo que significa que existen diferentes patrones diarios, asociados a distintos hábitats, con distinta composición específica. Finalmente, mostramos que la optimización global de los árboles de regresión es esencial para revelar patrones importantes y son una herramienta útil para determinar aquellas áreas mas importantes en términos de protección, teniendo en cuenta, concretamente, la vulnerabilidad de las poblaciones locales Palabras clave: Área Marina Protegida de Cabo de Palos; conservación; peces cartilaginosos; impacto pesquero; árboles de regresión; algoritmos evolutivos; especies vulnerables. Citation/Como citar este artículo: Mendoza M., Garrido D., Jose M.

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Section: Discussionmentioning

confidence: 99%

Factors affecting the fishing impact on cartilaginous fishes in southeastern Spain (western Mediterranean Sea)

Mendoza¹,

Garrido²

2014

Sci. Mar.

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“…As noted, swordfish longlines equipped with chemiluminescent attractors and fished at night entangle more leatherback turtles (Witzell 1999). Such light attractorequipped longlines also catch more swordfish (Hazin et al 2005, Damalas et al 2006, and so discontinuing their use would not be desired by fishers. However, reducing the attractiveness of such devices to leatherbacks, while maintaining their attractiveness to swordfish, could resolve some of the entanglement problems.…”

Section: Discussionmentioning

confidence: 99%

Leatherback sea turtle Dermochelys coriacea visual capacities and potential reduction of bycatch by pelagic longline fisheries

Crognale

Eckert²,

Levenson³

et al. 2008

Endang. Species Res.

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Leatherback and other marine turtles are classified as Critically Endangered or Endangered by the International Union for Conservation of Nature (IUCN), largely due to anthropogenic factors (e.g. poaching, habitat destruction and incidental mortality in fisheries). A need to understand the visual capacities of marine turtles has arisen from mortality caused by attraction of these turtles to chemiluminescent lights used by swordfish longline fisheries. Finding light sources that do not attract turtles, but enhance swordfish catch, could remove a major source of anthropogenic mortality to the Critically Endangered leatherback sea turtle. Using field-adapted non-invasive electrophysiology (corneal electroretinogram), we determined that leatherback spectral sensitivities differ significantly from those of green and loggerhead turtles with peak sensitivity in the shorter wavelengths. Leatherback temporal sensitivities also differ greatly from those of green turtles and peak at lower frequencies. Our results show that while leatherback and swordfish spectral sensitivities are similar, temporal response frequencies are very different. This difference provides a possible means to reduce the attraction of leatherbacks to swordfish longline gear by switching to electroluminescent attractants that use rapidly flickering light sources. Light sources flickered at >16 Hz should be difficult for leatherbacks to detect as flickering, while remaining readily seen as flickering by swordfish.

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“…De Metrio and Megalofonou (1988) calculated the CPUE between 41.1 kg and 98.3 kg/1000 hooks in the Gulf of Taranto from 1978 to 1986. Di Natale et al (1995) reported 101 kg/1000 hooks as average for Tyrrhenian Sea and Strait of Sicily in 1992; Damalas et al (2007) computed as 8.96 specimens/1000 hooks for eastern Mediterranean; Relini et al (2008) reported the CPUE of swordfish longline as 116.5 kg/1000 hooks for northwestern Mediterranean. Cambiè et al (2013) also reported it from the southern Italy for both 2007 and 2011 as 3.2 specimens/1000 hooks and 0.4 specimens/1000 hooks, respectively.…”

Section: Discussionmentioning

confidence: 99%

Untitled

Ceyhan¹,

Akyol²

2014

Turk. J. Fish. Aquat. Sci.

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This study presents the results based on catch per unit effort (CPUE) and incidental catch ratios of surveys on the Turkish swordfish longliners during the fishing seasons between 2008 and 2013. A total of 50 surveying operations were carried out, including 45 in Fethiye, 5 in Özdere in the southern Aegean coasts along the eastern Mediterranean Sea. A total of 217 (4061 kg) swordfish were obtained during 50 operations. The mean CPUEs for swordfish by number and weight were computed as 10.8±1.59 specimens and 179.6±21.48 kg per 1000 hooks, respectively. Although, there was no significant differences among means of CPUEs by number of swordfish (P>0.05), the CPUEs by weight of swordfish were significantly different among years (P<0.05). A total of 14 species, belonging to 12 families (276 specimens; 5535 kg) were caught. The target swordfish had the highest ratio both in number (78.6%) and in biomass (73.3%), followed by Mobula mobular, Alopias vulpinus, Prionace glauca, Isurus oxyrinchus, Ruvettus pretiosus, Coryphaena hippurus, Thunnus alalunga by weight, respectively. Biomass and number ratios of the non-target species to the target swordfish were 1:0.27 and 1:0.36, respectively. A total of two specimens of which P. glauca (10 kg) and M. mobular (300 kg) were released lively and the others were retained due to commercial value. A significant difference was not found between weight of by-catch species and weight of the swordfish according to years (P>0.05).Keywords: Swordfish, Xiphias gladius, surface longline, incidental catch, Aegean Sea, Eastern Mediterranean. Doğu Akdeniz'de Kılıç Balığı Hedefleyen Türk Yüzey Paraketa Balıkçılığı Üzerine ÖzetBu çalışma, 2008-2013 arasındaki balıkçılık sezonu boyunca Türk kılıç balığı paraketa tekneleri üzerine olan araştırmaların birim çaba başına düşen av (CPUE) verileri ve tesadüfü av oranları sonuçlarını vermektedir. Doğu Akdeniz boyunca Güney Ege'de 45'i Fethiye ve 5'i Özdere'de olmak üzere toplam 50 operasyon için gözlemler yapılmıştır. 50 operasyon boyunca toplam 217 (4061 kg) kılıç balığı elde edilmiştir. Kılıç balığının sayıca ve ağırlıkça ortalama CPUE değerleri sırasıyla 10,8±1,59 birey/1000 iğne ve 179,6±21,48 kg/1000 iğne olarak hesaplanmıştır. Kılıç balığının yıllar arasında sayıca CPUE ortalamaları arasında önemli bir fark bulunmamasına (P>0,05) rağmen, ağırlıkça CPUE'leri arasında önemli bir fark bulunmuştur (P<0,05). Toplam 12 familyaya ait 14 tür (276 birey, 5535 kg) yakalanmıştır. Hedef tür kılıç balığı hem sayıca (%78,6) hem de ağırlıkça (%73,3) en yüksek orandaydı; onu ağırlıkça Mobula mobular, Alopias vulpinus, Prionace glauca, Isurus oxyrinchus, Ruvettus pretiosus, Coryphaena hippurus, Thunnus alalunga izlemiştir. Kılıca karşın hedef dışı türlerin biyokütle ve sayıca oranları sırasıyla 1:0,27 ve 1:0,36'ydı. P. glauca (10 kg) ve M. mobular (300 kg) bireyleri denize canlı olarak geri bırakılmış ve diğerleri ticari amaçla alıkonulmuştur. Yıllara göre kılıç balığının ağırlığı ile hedef dışı türlerin ağırlığı arasında önemli bir fark bulunmamıştır (P>...

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Environmental, spatial, temporal and operational effects on swordfish (Xiphias gladius) catch rates of eastern Mediterranean Sea longline fisheries

Cited by 70 publications

References 15 publications

Factors affecting the fishing impact on cartilaginous fishes in southeastern Spain (western Mediterranean Sea)

Factors affecting the fishing impact on cartilaginous fishes in southeastern Spain (western Mediterranean Sea)

Leatherback sea turtle Dermochelys coriacea visual capacities and potential reduction of bycatch by pelagic longline fisheries

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