Cod-end selectivities of a modified bottom trawl for three fish species in the Aegean Sea

Tokaç, Adnan; Lök, Altan; Tosunoğlu, Zafer; Metin, Cengiz; Ferro, Richard

doi:10.1016/s0165-7836(98)00172-6

Cited by 36 publications

(32 citation statements)

References 5 publications

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“…Differences in escape behaviour can also be responsible for part of the variability observed, with Figure 10 suggesting a more active escape behaviour for the axillary seabream. Although this hypothesis is subject to confirmation by direct observation of the catch process, it is in accordance with observations by Tokaç et al (1998), who report heavy meshing of axillary seabream in cod ends that is compatible with active escape behaviour.…”

Section: Discussionsupporting

confidence: 89%

“…However, Tokaç et al (1998), in selectivity trials in the Aegean Sea using diamond and square mesh cod ends, reported higher selectivity for this species in the diamond cod ends (SF between 2.95 and 3.22, corresponding to L 50 estimates of 10.61 to 14.16 cm), but at the same time found non-significant differences in selectivity between diamond and square mesh cod ends of the same mesh size. Once more, differences in selectivity between those data and data presented in this work could be related to differences in length composition and range of mesh sizes tested (smaller fish from 10 to 15 cm and cod end mesh sizes from 36 to 44 mm in their experiments), as well as differences between cod end material (polyamide versus polyethylene in the present work) and cod end geometry and mesh opening, particularly with respect to the diamond cod ends.…”

Section: Discussionmentioning

confidence: 85%

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Selectivity of diamond and square mesh cod ends for horse mackerel (Trachurus trachurus), European hake (Merluccius merluccius) and axillary seabream (Pagellus acarne) in the shallow groundfish assemblage off the south-west coast of Portugal

Campos¹,

Fonseca²

2003

Sci. Mar.

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2003Selectivity of diamond and square mesh cod ends for horse mackerel (Trachurus trachurus), European hake (Merluccius merluccius) and axillary seabream (Pagellus acarne) in the shallow groundfish assemblage off the south-west coast of Portugal* AIDA CAMPOS and PAULO FONSECA IPIMAR, Avenida de Brasília, 1449-006, Lisbon, Portugal. E-mail: acampos@ipimar.pt SUMMARY: The effects of an increase in cod end mesh size from 65 to 70 and 80 mm and a change of mesh configuration from 65 mm diamond to 65 mm square mesh on the size selectivity of horse mackerel (Trachurus trachurus), hake (Merluccius merluccius) and axillary seabream (Pagellus acarne) of the shallow groundfish assemblage off the Portuguese southwest coast were evaluated. The increase in mesh size had a small but significant effect on size selectivity for the three species, while the change in mesh configuration led to a much more pronounced increase in the selectivity parameters. For horse mackerel, the L 50 estimates ranged from 14.4 to 16.0 cm in the diamond mesh cod ends-values that are close to the minimum landing size of 15 cm. For hake, L 50 of 17.0 and 18.3 cm were estimated for the 70 and 80 mm diamond cod ends respectively, while for the axillary seabream the L 50 estimated was 13.9 cm for the 80 mm diamond mesh cod end. These values are well below the minimum landing sizes of 27 and 18 cm for these species. The corresponding estimates in the square mesh cod end were 21.9, 32.4 and 19.6 cm, with the loss of a high percentage (76%) of horse mackerel above the minimum landing size. For all the cod ends tested, the observed retention was presented as a function of maximum girth/mesh perimeter, which allowed a better understanding of the selection process for the species in study. Selectivity estimates for horse mackerel and hake were also compared to those obtained by Campos et al. (2003) for the same species in 1993 off the south coast, where they are captured as a by-catch in the crustacean fishery.Key words: cod end selectivity, mesh size, mesh configuration, length-girth relationships, by-catch, Trachurus trachurus, Merluccius merluccius, Pagellus acarne. RESUMEN: SELECTIVIDAD DE COPOS CON MALLA DE DIAMANTE Y CUADRADA PARA JUREL (TRACHURUS TRACHURUS), MERLUZA EUROPEA (MERLUCCIUS MERLUCCIUS) Y ALIGOTE (PAGELLUS ACARNE) EN LOS POBLAMIENTOS DE PECES DEMERSALES DE AGUAS SOMERAS FRENTE A LAS COSTAS DEL SUROESTE DEPORTUGAL. -Los efectos de un incremento en la dimensión de la malla del copo desde 65 a 70 y 80 mm, así como un cambio en su configuración entre malla de diamante de 65 mm y malla cuadrada de 65 mm han sido evaluados sobre la selectividad por talla del arte de arrastre para jurel (Trachurus trachurus), merluza europea (Merluccius merluccius) y aligote (Pagellus acarne) en los poblamientos de peces demersales de aguas someras frente a la costa del suroeste de Portugal. El incremento del tamaño de la malla ha tenido un efecto pequeño pero significativo sobre la selectividad por tamaños de las tres especies, mientras que el cambio de la configu...

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 85%

Selectivity of diamond and square mesh cod ends for horse mackerel (Trachurus trachurus), European hake (Merluccius merluccius) and axillary seabream (Pagellus acarne) in the shallow groundfish assemblage off the south-west coast of Portugal

Campos¹,

Fonseca²

2003

Sci. Mar.

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“…natural and fishing mortalities have been estimated in atlantic waters (Pajuelo and lorenzo, 2000). selectivity of the fishing gears has been studied for this species in Greek (Petrakis and stergiou, 1996;tokaç et al, 1998) and Portuguese waters (santos et al 1995;Campos and fonseca, 2003).…”

mentioning

confidence: 99%

Feeding habits of Pagellus acarne (Sparidae) in the Gulf of Tunis, central Mediterranean

Fehri-Bedoui¹,

Mokrani²,

Hassine³

2009

Sci. Mar.

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summaRY: the feeding habits of the axillary seabream, Pagellus acarne (Risso, 1810), from the Gulf of tunis were investigated in relation to season, sex and fish size (juveniles tl<14.5 cm and adults tl≥14.5 cm). a total of 536 specimens (males, females, unsexed and hermaphroditic), ranging between 11.0 and 25.2 cm tl, were collected with trammel nets from June 2005 to July 2006. their stomach contents were analysed. of the total number of examined stomachs, 279 stomachs were empty (Vacuity index, VI = 52%). the VI did not reveal significant seasonal differences when all of the specimens were analysed together; however, significant seasonal variations were observed for females. the diet of the axillary seabream was composed of 36 different prey species. the most important prey were arthropoda, mollusca and echinodermata. Both the dietary indices and the spearman's coefficient of correlation indicated seasonal variations in the diet. the diet was more diversified in adults than in juveniles. the axillary seabream fed on a wide range of prey items, endofauna and nekton, and can be considered a carnivorous and euryphagous predator.Keywords: Pagellus acarne, diet, dietary indices, Gulf of tunis, central mediterranean.Resumen: La dieta de Pagellus acarne (Sparidae) en el golfo de Túnez, Mediterráneo central. -se estudió la dieta del aligote, Pagellus acarne (Risso, 1810), del golfo de túnez en función de las estación del año, del sexo y de dos grupos de talla: juveniles (lt <14.5 cm) y adultos (lt ≥14.5 cm). entre junio 2005 y julio 2006 se recolectaron con trasmallos, un total de 536 ejemplares (machos, hembras, sexos no determinados) cuya longitud total oscilaba entre 11 y 25.5 cm. se analizó el contenido estomacal; 279 estaban vacíos (índice de vacuidad, Vi = 52.0%). este índice no reveló diferencias significativas en relación a la estación del año. sin embargo, se observaron importantes variaciones estacionales para las hembras. se identificaron un total de 36 especies de presas en la dieta. las más frecuentes eran artrópodos, moluscos y equinodermos. los índices de alimentación calculados, así como la aplicación del coeficiente de correlación de spearman, mostraron variaciones estacionales. el análisis específico de las presas evidenció que la dieta de los machos era diferente a la de las hembras y era más variada en los adultos que en los juveniles. P. acarne se alimenta de un amplio espectro de presas, endofauna y necton, y podría considerarse como depredador carnívoro y eurífago.Palabras clave: Pagellus acarne, dieta, índices de alimentación, golfo de túnez, mediterráneo central. ,[667][668][669][670][671][672][673][674][675][676][677][678] Barcelona (spain) issn: 0214-8358 Scientia Marina73(4) december 2009

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“…Recent studies have shown that selectivity of the trawl codends is rather poor for many commercially important species in Turkey (Tokaç et al, 1998(Tokaç et al, , 2004Tosunog %lu et al, 2007;Özbilgin et al, 2005), and other Mediterranean areas (e.g., Petrakis and stergiou, 1997;stergiou et al, 1997;bahamon et al, 2006). Therefore, many researchers have suggested increasing the mesh size and/or changing the mesh shape in the codend.…”

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confidence: 99%

Selectivity of commercial, larger mesh and square mesh trawl codends for deep water rose shrimp Parapenaeus longirostris (Lucas, 1846) in the Aegean Sea

2009

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sUMMaRy: We investigated the differences between size selectivity of a commercial codend (40 mm diamond mesh -40d), a larger mesh codend (48 mm diamond mesh -48d), and a square mesh codend (40 mm square mesh -40s) for Parapenaeus longirostris in international waters of the aegean sea. selectivity data were collected by using a covered codend method and analysed taking between-haul variation into account. The results indicate significant increases in l 50 values in relation to an increase in mesh size and when the square mesh is used in the commercial trawl codend. The results demonstrate that the commercially used codend (40d) is not selective enough for P. longirostris in terms of length at first maturity. Changing from a 40d to a 48d codend significantly improves selection, with an increase of about 15% in the l 50 values (carapace length 14.5 mm for 40d and 16.6 mm for 48d). similarly, 40 mm square mesh, which has recently been legislated for eU Mediterranean waters, showed a 12.4% higher mean l 50 value (16.3 mm) than 40 mm diamond mesh for this species. However, despite these improvements, the 48d and 40s codends still need further improvements to obtain higher selectivity closer to the length at first maturity (20 mm carapace length).Keywords: Parapenaeus longirostris, mesh size, mesh shape, diamond mesh, square mesh.ResUMen: Selectividad para malla más grande y malla cuadrada de los copos comerciales en la pesca de la gamba blanca ParaPenaeus longirostris (Lucas, 1846) en el mar Egeo. -se estudian las diferencias entre la selectividad de los copos comerciales (40 mm de malla de diamante -40d); copos de malla más grande (48 mm de malla de diamante -48d), y copos de malla cuadrada (40 mm -40s), en la pesquería de Parapenaeus longirostris en aguas internacionales del mar egeo. Para su estudio se utilizó el método del sobrecopo, y para su análisis, se tuvo en cuenta la variación intra-lances. los resultados indican un incremento de los valores de l 50 cuando se incrementa el tamaño de malla, y también con el uso de la malla cuadrada. los resultados demuestran que el copo comercial actual (40d), no es suficientemente selectivo para P. longirostris en relación a la talla de primera madurez. el cambio, la malla de 48d, produce una mejora significativa en la selectividad cercana al 15% de incremento en los valores de la l 50 (longitud del caparazón de 14.5 mm para 40d y 16.6 mm para 48d). igualmente, la malla 40s, la cual ha sido legislada recientemente por la Ue en aguas del Mediterráneo, muestra un incremento de la selectividad aproximadamente de un 12% en los valores de la l 50 (16.3 mm) respecto a la de 40d. no obstante, a pesar de estas mejoras, los copos de 48d y 40s, todavía deberían ser ampliados para obtener selectividades más elevadas y acercarse a la talla de primera madurez (20 mm de caparazón).Palabras clave: Parapenaeus longirostris, tamaño de malla, forma del malla, rombo, malla cuadrada. , 597-604, barcelona (spain) issn: 0214-8358 Scientia Marina73(3) september 2009

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Cod-end selectivities of a modified bottom trawl for three fish species in the Aegean Sea

Cited by 36 publications

References 5 publications

Selectivity of diamond and square mesh cod ends for horse mackerel (<i>Trachurus trachurus</i>), European hake (<i>Merluccius merluccius</i>) and axillary seabream (<i>Pagellus acarne</i>) in the shallow groundfish assemblage off the south-west coast of Portugal

Selectivity of diamond and square mesh cod ends for horse mackerel (<i>Trachurus trachurus</i>), European hake (<i>Merluccius merluccius</i>) and axillary seabream (<i>Pagellus acarne</i>) in the shallow groundfish assemblage off the south-west coast of Portugal

Feeding habits of <i>Pagellus acarne</i> (Sparidae) in the Gulf of Tunis, central Mediterranean

Selectivity of commercial, larger mesh and square mesh trawl codends for deep water rose shrimp <em>Parapenaeus longirostris</em> (Lucas, 1846) in the Aegean Sea

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