Commercial testing of a sorting grid to reduce catches of juvenile hake (Merluccius merluccius) in the western Mediterranean demersal trawl fishery

5 pages, 5 figuresMediterranean demersal fisheries have experienced an ongoing decline in catches over the past 20 years as a result of excessive increases in effort caused both by growth in trawler engine power and by rapid technological advances in fish finding and fishing technology. This has led to an overexploitation of these resources. An increasing share of the catches consists of immature individuals. This study was undertaken to test a sorting grid with a bar spacing of 20 mm as a means of excluding juveniles in the commercial hake (Merluccius merluccius) fishery in the Catalan Sea, western Mediterranean. The grid was placed in the extension section of the gear 5 m in front of a cod-end. Divided cod-end design was used to collect the escapees and target species. The mean selection length (L50) of the ten hauls was 14.2 ± 0.7 cmSE, with a selection range of 7.3 cm ± 0.4 SE. The biomass of hake under L50 that escaped through the grid represented 50.1% ± 6.7 SE of the total hake biomass. These results are promising and indicate that a sorting grid can be used in excluding young hake. This was a first step toward implementation of sorting grids in commercial trawl gears as means of avoiding unwanted catches of small individuals in the hake fisheries in the Mediterranean Sea. Further trials are required to improve the sorting efficiency of the gridThis experiment was conducted in the framework of the “Graella” project (PETRI, 1995-0497-OP), funded by Spanish Ministry of Science and Technology (Ministerio de Ciencia y Tecnología) and the Catalonian Bureau of Fisheries and Maritime Affairs (Generalitat de Catalunya’s Direcció General de Pesca i Afers Marítims, DGPAM)Peer reviewe

El uso de copo de malla cuadrada y rejillas separadas para reducir las capturas de peces juveniles y mejorar la sostenibilidad de una perquería multiespecífica de arrastre de fondo en el Mediterráneo

In order to improve the capacity of bottom trawl fishing gears to reduce catches of young fish and discards in a highly exploited demersal trawl fisheries in the Mediterranean, the size-selection performance of a 36-mm square-mesh codend and two sorting grids with 20 and 15 mm bar spacing was assessed. Alternate hauls were used to assess the selectivity of 36-mm square-mesh codend. Selectivity of sorting grids was assessed using a double codend in which fish that escaped through the grid were captured in the lower codend while other fish were guided into the upper codend. The mean selection length (L50) for European hake was 18.5 cm and that for the Atlantic horse mackerel was 14.0 cm with the 36-mm square-mesh codend . These values are close to their current minimum landing sizes (20 cm for hake and 12 cm for horse mackerel). The sorting grid with 20-mm bar spacing showed L50 value of 13.3 cm for hake, suggesting that a larger grid-spacing would be needed to obtain sufficient sorting performance. Similarly, for Atlantic mackerel the estimated L50 of 14.3 cm indicates that larger grid spacing is required to attain an L50 that would be close to the current MLS (18 cm). For Atlantic horse mackerel and red mullet, the L50 obtained with the sorting grid with 20-mm bar spacing was close to the MLS of these species (the MLS of red mullet is 11 cm). The selectivity of the sorting grid with 15-mm bar spacing was generally very poor. Size-selection performance of sorting grids was assessed for the first time in the local fisheries. In order to effectively improve size-selection, seasonal and depth-dependent differences between target and by-catch species must be taken into account, which is a good indicator of the difficulty of implementing a single mesh size or grid spacing in the Mediterranean demersal trawl fishery.Con el propósito de mejorar la capacidad de las redes de arrastre de fondo para reducir las capturas de peces juveniles y descartes en una pesquería multiespecífica altamente explotada en el Mar Mediterráneo, se evaluó la selectividad de las tallas de diversas especies demersales mediante el uso de una malla cuadrada de 36 mm y dos rejillas con separación entre barras de 20 y 15 mm. Se usó el método de lances alternativos para evaluar la selectividad del copo de malla cuadrada. La selectividad de las rejillas se evaluó mediante un doble copo. Los peces que escaparon de la rejilla se capturaron en el copo inferior y el resto del pescado se guió y capturó en el copo superior. Con el copo de malla cuadrada, la talla media de madurez (L50) de la merluza y el jurel fue respectivamente de 18,5 cm y 14,0 cm. Estos valores se aproximan a la talla mínima de selección (MLS para la merluza es de 20 cm y para la jurel es de 12 cm). Con la rejilla con separación entre barras de 20 mm, la L50 de la merluza fue de 13,3 cm, lo cual sugiere que sería conveniente aumentar la separación entre barras para obtener una L50 más próxima a la MLS. La caballa se seleccionó con una L50 de 14,3, por debajo de la MLS de 18 cm. El jurel y el salmonete mostraron L50 cercana la MLS (MLS del salmonete es 11 cm). La rejilla con espacios de 15 mm fue muy poco selectiva. Este es el primer trabajo que se realiza en el área en el que se compara el funcionamiento de la malla cuadrada y las rejillas separadoras. La tecnología de las rejillas separadoras se aplicó por primera vez con el objetivo de mejorar la explotación de las pesquerías locales. La mejora en la selección de tallas requiere tener en cuenta la variación estacional y en profundidad de las especies objetivo y especies acompañantes, lo que demuestra la dificultad de implementar una sola malla o rejilla en toda la pesquería demersal de arrastre del Mediterráneo.

The cephalopods of the Namibian coast ( SE Atlantic)

Suplemento de Investigación Pesquera.-- 20 pages, 19 figuresPeer Reviewe

An annotated list of cephalopod larvae collected off the Mediterranean coasts of Spain, 1976-1981

3 pages, 1 figure[EN] The identified cephalopod larvae come from biological samples collected during four surveys with a 40 cm diameter Bongo device fitted with 333 u.m and 505 um mesh size nets : Mediterraneo I (October 1976), Mediterraneo II (March 1977), Tanit (August 1979) and Maira I (December 1981). The area covered included the Mediterranean coast of Spain between Cabo Creus in the north and Cabo Palos in the south, and between Spain's mainland and the Balearic Islands. The following cephalopod taxa were identified : Rossia macrosoma, Abraliopsis morisii, Thelidioteuthis alessandrinii, Onychoteuthis banksi, Ancistroteuthis lichtensteini, Histioteuthis reversa, Ctenopteryx sicula, Illex coindetii, Rynchoteuthion larvae, Galiteuthis sp., Octopus vulgaris, Octopus sp., Eledone cirrhosa, Macrotritopus larvae, Argonauta argo, and some unidentified représentatives of the families Sepiolidae, Loliginidae, Cranchiidae and Octopodidae[FR] Les larves de Céphalopodes identifiées ont été récoltées pendant quatre campagnes à l'aide de filets Bongo (mailles de 333 à 505 u.m) : Mediterraneo I (Octobre, 1976), Mediterraneo II (Mars, 1977), Tanit (août, 1979) et Maira I (Décembre, 1981). L'aire d'étude est située entre le Cap Creus au nord et le Cap Palos au sud, et entre la côte espagnole et les îles Baléares. Les espèces suivantes ont été trouvées : Rossia macrosoma, Abraliopsis morisii, Thelidioteuthis alessandrinii, Onychoteuthis banksi, Ancistroteuthis lichtensteini, Histioteuthis reversa, Ctenopteryx sicula, Illex coindetii, Rynchoteuthion larvae, Galiteuthis sp., Octopus vulgaris, Octopus sp., Eledone cirrhosa, Macrotritopus larvae, Argonauta argo, et quelques représentants non identifiés des familles Sepiolidae, Loliginidae, Cranchiidae et OctopodidaePeer reviewe

Age and growth of the sparids Diplodus vulgaris, D. sargus and D. annularis in adult populations and the differences in their juvenile growth patterns in the north-western Mediterranean Sea

7 pages, 2 figures, 1 tableAge and growth patterns of adults of three common species of sparids, Diplodus vulgaris, D. sargus and D. annularis from the north-western Mediterranean Sea are analyzed. Length-at-age values are estimated from otoliths and growth patterns are well described by the von Bertalanffy growth equation. The sampled length interval ranged from 8–40, 28 and 20 cm for D. sargus, D. vulgaris and D. annularis, respectively. The estimates of t0 for D. vulgaris and D. sargus, −0.67 and −0.74 respectively, indicate that the growth of these species during the first months of life do not adhere to the von Bertalanffy model. In contrast, for D. annularis the estimation of the origin of the von Bertalanffy model is close to zero (t0 = −0.03), suggesting that this species is faithful to this growth model from the beginning of settlement. The variations from juveniles to adults in the growth pattern are explained by the permanence or the variations of the habitat of each of the species throughout their lifeThis research was funded by CICYT (MAR 95-1785)Peer Reviewe

Preservación de juveniles de merluza (Merluccius merluccius L.) en la pesquería demersal de arrastre del Mediterráneo occidental, mediante el uso de rejillas separadoras

The Mediterranean fishery has experienced a decline in catches over the past 20 years due to an excessive increase in effort caused by both increased trawler engine power and rapid technological advances in fishing technology and fish location. This has led to overexploitation, in which immature individuals support an increasing portion of the catches. The present study was undertaken to test a sorting grid and square-mesh-panel as juvenile exclusion systems. Our experience was a pilot study of such a system in the western Mediterranean. The purpose of these exclusion systems was to help juvenile hake escape from the net. The results demonstrate that the use of sorting grids for small fish in trawl gears in the Mediterranean is an efficient and practical means of avoiding the capture and discarding of unwanted individuals, with escape rates of over 50% (ranging between 50 and 90%). The grids were efficient and useful for excluding hake (Merluccius merluccius) on bottoms located at depths between 50 and 300 m, where hake are found all year round. A bar spacing of 20 mm yielded escape rates of L50 at 18.8 cm TL (L25 = 16.8 cm and L75 = 20.9 cm). Panels made of square meshes achieved poorer results than the grids. The grid system was effective for most of the species caught in the study area.Durante los últimos 20 años la pesca en el Mediterráneo ha experimentado un descenso de capturas al mismo tiempo que se detecta un excesivo incremento del esfuerzo, tanto en potencia de las embarcaciones como en avances tecnológicos y de detección de peces. Esto lleva a la sobreexplotación de crecimiento en la cual las capturas recaen principalmente sobre los individuos inmaduros. Este estudio pretende probar varias rejillas separadoras y paños de malla cuadrada como sistemas de exclusión de juveniles en artes de arrastre de fondo, lo cual constituye una primera experiencia piloto en el Mediterráneo. El objetivo del uso de las rejillas y mallas cuadradas es permitir el escape de juveniles de merluza en cantidad y en buenas condiciones. Los resultados demuestran que el uso de los sistemas selectivos rígidos constituye una buena solución, efectiva y práctica, para reducir drásticamente los descartes de especies no deseadas. Las tasas de escape calculadas superan el 50% de los ejemplares pequeños (entre el 50 y el 92%). Estos sistemas fueron muy eficientes para la merluza en fondos entre 50 y 300 m donde se distribuye durante la mayor parte del año. El espacio entre barras fue de 20 mm, el cual produjo tallas de L50 de escape de 18.8 cm (L25 = 16.8 cm y L75 = 20.9 cm). La malla cuadrada dió peores rendimientos de escape que las rejillas

Growth performance of four wrasse species on the north-western Mediterranean coast

8 pages, 3 figures, 3 tablesAge and growth patterns of four common species of wrasses, Labrus merula, Coris julis, Symphodus roissali and Symphodus tinca, from the north-western Mediterranean sea are analyzed. Length-at-age values are estimated from otoliths from which the first annual hyaline ring is determined by reading daily rings. The growth patterns are well described by the yon Bertalanffy growth equation with the exception of S. tinca which showed an extremely high dispersion in the length-at-age distribution. The daily rings show the second hyaline ring as the first annual hyaline ring, whereas the first hyaline ring was formed after 2 months of life coinciding with the settlement period of these species, which indicates that changes in otolith crystal growth during the first year of life could be driven by biological or physiological changes in the individualsThis research was funded by CICYT (MAR 95-1785)Peer Reviewe

Length-weight relationships of mesopelagic fishes in the North-Western Mediterranean

40th CIESM Congress: The largest Forum on Mediterranean and Black Sea Research, 28 October - 1 November 2013, Marseille, France.-- 1 page, 1 tableIn the present study we analysed the length-weight relationships of the most common and abundant mesopelagic fishes of the northwestern Mediterranean: 11 Myctophidae, 1 Gonostomatidae, 1 Phosichthyidae and 1 Sternoptichydae. Data of fish length and weight were fitted to a power function, and estimations of the fitted equation parameters were given as background information for subsequent studies on body condition. The slope estimation was taken as indicative of the relative increase in weight in relation to growth in length. The small fish Cyclothone braueri has a lower allometric coefficient with significant negative value, than that corresponding to larger species such as myctophids (some of them showing positive allometric growth)This research was funded by Spanish program CTM2008-04489-C03-01-02Peer Reviewe