Scientia Marina (E-Journal)
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Nephrops norvegicus (L.): Biología comparada y pesca en el Mar Mediterráneo. Introducción, conclusiones y recomendaciones
Full text linkThe project, financed by the Directorate General XIV of the EC, has undertaken a comparative study on the biology and fisheries techniques of the Norway lobster in Mediterranean member states and adjoining Atlantic areas. The ultimate goal of the project has been to assess the conditions for a global regulation in the area and determine possible differences among exploited stocks. The areas selected are characterised by their importance in Norway lobster catch. The overall duration of the project has been three years. Sampling was concentrated in the first two years. Data analysis was conducted during the second and third years (1993-1995). The countries (areas) involved in the study, together with their target areas, were: Portugal (south coast of Algarve), Spain (Alboran and Catalan Seas), Italy (Ligurian, Tyrrhenian and Adriatic Seas) and Greece (Gulf of Euboikos). In order to make results perfectly comparable, each scientific subject has been developed by a specialised team using a unified and standardised methodology. From the biological standpoint, Norway lobster growth, reproduction, moult and feeding have been compared. Special studies on distribution and genetics have been also conducted. In the fisheries context, a comparison of fishing techniques has been undertaken. The fisheries studies have been complemented with reconstruction of virgin populations, comparison of yield per recruit, sensitivity analysis and transition analysis. Selectivity issues have been object of specific analyses. As a result of these studies, it is evident that Norway lobster populations in the Mediterranean follow a common life-cycle model. The differences among areas reported in this project respond to environmental variation and differential fishing pressure in each area. All populations are exploited near its carrying limit, although overexploitation is unlikely at this stage. However we identified varying levels of exploitation according to study areas: The Catalan, Tyrrhenian and Adriatic Seas populations are exploited at a high level; the Ligurian Sea and Euboikos Gulf populations at an intermediate level; and the Alboran Sea and Algarve populations are at a low level of exploitation. The regulation concepts could be applied globally to the Mediterranean, allowing for the differences observed. It is highly recommended that effort is not increased. It should rather be decreased as new technologies being implemented continuously are by themselves an effort increase. A effort reduction of 20% is desirable to ensure that stocks are maintained at their current levels. This measure should be foremost applied to those areas being subjected to the highest exploitation levels.El proyecto desarrolla un estudio comparativo de la biología y la pesca de la cigala en el Mediterráneo en los países miembros de la UE y en un área adjunta del Atlántico. Los países y áreas involucrados en el estudio fueron: Portugal (costa sur de Algarve), España (mar de Alborán y mar Catalán), Italia (mares Ligur, Tirreno y Adriático), y Grecia (Golfo de Euboikos). Ante las posibles diferencias que puedan existir entre poblaciones, el objetivo del proyecto es asesorar sobre las condiciones necesarias a tener en cuenta para llevar a cabo una regulación de la pesquería de esta especie en el Mediterráneo. La duración total del proyecto fue de tres años (1993-1995) concentrando los muestreos durante los dos primeros. El análisis de los resultados se realizó durante el segundo y tercer año. Los resultados procedentes de los distintos temas de estudio fueron tratados por un mismo científico especializado en el tema con el fin de que fueran completamente comparables. Se compararon aspectos de distribución, crecimiento, muda, reproducción, genética y alimentación respecto a la biología de la especie. En el contexto pesquero se compararon las técnicas de captura en cada zona y se hizo un estudio comparado de la dinámica poblacional. Estos estudios se complementaron con análisis de población virtual y comparaciones de producción por recluta. La selectividad de la especie fue también objeto de un estudio concreto. Como resultado principal se constata que la cigala presenta un modelo de ciclo vital común para todo el Mediterráneo y Atlántico adyacente. Las diferencias encontradas entre algunas poblaciones se atribuyen a las particulares condiciones ambientales de las áreas correspondientes. Todas las poblaciones parecen explotadas en intensidades próximas a su límite o punto óptimo, a pesar de que existen distintos grados. En orden de más a menos explotadas podemos presentar las distintas áreas estudiadas: Las poblaciones del Mar Catalán, Tirreno y Adriático son las más explotadas y soportan una fuerte intensidad de captura. Las del Mar Ligur y el Golfo de Euboikos, son poblaciones medianamente explotadas y las de Alborán y la costa sur del Algarve, son las poblaciones menos explotadas. Así, los conceptos de regulación pueden ser aplicados globalmente a todo el Mediterráneo respecto a las características biológicas de la especie. Recomendamos fuertemente que no se aumente más el esfuerzo al mismo tiempo que se inicie una disminución del mismo, ya que las nuevas tecnologías implican un aumento sostenido de la capturabilidad de la especie. Se recomienda una reducción aproximada en un 20 % del esfuerzo si se quiere mantener las poblaciones en un estado de producción similar al actual. Esta medida debería ser aplicada rápidamente en las áreas de mayor explotación. También se hacen consideraciones sobre medidas cualitativas de regulación en base al ciclo vital y comportamiento de la cigala
Approaches to otolith age determination: image signal treatment and age attribution
Full text linkPopulation studies of fish depend upon correct age estimates. However ageing from otoliths is often a subjective activity, based on experience. To produce more objective and reproducible results, image analysis systems for semi-automatic otolith reading are being developed. We propose determinig the daily growth and annual structures in each otolith by means of Fourier analysis of the luminous signal, after filtering the high frequencies by means of a moving threshold. A new approach using spatio-frequential wavelet analysis is discussed for otolith age determination. The different readings of each otolith are standardised and weighted to obtain a combined age determination and vector of increment widths.No disponibl
Primera cita de estadios larvarios de Coryphaena hippurus (Pisces: Coryphaenidae) en el Mar Mediterráneo
Full text linkThe occurrence of early larval stages of Coryphaena hippurus is reported for the first time in Mediterranean waters. Four larvae between 3.25 and 4.80 mm standard length were found in ichthyoplanktonic collections taken off the Balearic Islands between 1985 and 1995. Their capture is discussed in relation to the life cycle proposed for this species in the area.Se cita la primera captura de estadíos larvarios de Coryphaena hippurus en el Mediterráneo. Se han encontrado cuatro larvas de longitud estándar comprendida entre 3.25 y 4.80 mm, en muestras de ictioplancton recolectadas entre 1985 y 1995 en las Islas Baleares. Se discute su distribución espacio-temporal en relación con el ciclo vital propuesto para la especie en el áre
Down-regulation of Glial Fibrillary Acidic Protein (GFAP) during the development of a marine fish (Dentex dentex L.)
Full text linkA band of approximately 52-53 kDa, corresponding to glial fibrillary acidic protein (GFAP) was detected by immunoblot techniques in brain tissue of a marine fish (Dentex dentex L). The aim of this study was to quantify the density of GFAP during the life cycle of a marine fish in the wild. The levels of GFAP immunoreactivity were determined at two different stages of development: juvenile (body weight range: 180-360 g) and sexually developing-mature specimens (body weight range: 2329-5550 g) from a natural population in the Western Mediterranean Sea. Our results indicated a negative correlation between the immunoreactivity of GFAP and weight in the sexually developing-mature group of fishes (r=-0.785, pNo disponibl
Comparative technical aspects of the Nephrops norvegicus (L.) fishery in the northern Mediterranean Sea
Full text linkA comparative study of the technical characteristics of the Norway lobster fishery in the Mediterranean Sea is presented. The different trawl vessels, trawl gears, trawling manoeuvres, and status of the statistics compiled by the administrations are described. The main conclusions are that catchability has increased with technological advances, official landings statistics are flawed in most of the Mediterranean, and fishing methods differed from country to country.En este trabajo se presenta un estudio comparado de las características técnicas de la pesquería de cigala en el Mediterráneo. Se describen los tipos de embarcaciones, artes, maniobras y estado de las estadísticas procedentes de la administración. Las principales conclusiones destacan un aumento de la capturabilidad en relación al avance tecnológico, unas estadísticas oficiales deficientes en la mayor parte del Mediterráneo, y unas técnicas pesqueras bien diferenciadas entre paises
A new species of Bathymedon Sars, 1892 (Amphipoda: Oedicerotidae) from the western Mediterranean bathyal floor
Full text linkBathymedon longirostris sp. nov. (Amphipoda: Oedicerotidae) from the western Mediterranean bathyal suprabenthos is described. It is characterised by the well-developed rostrum; the discrete lateral lobe of head; the elongation of the peduncle segment 3 of the first antenna; the very slender propodus of the second gnathopod, which attains maximum width not at the palm angle, but at about midway along the palm margin; and by the relative length of the carpus of the foregoing limb, sub-equal to propodus. The discovery of a tiny remnant of the 2nd peduncle segment of the first antenna in the new species is commented with regard to the homologation of the peduncle segments in other members of the Family. The new taxon was captured below 593 m over muddy bottoms with pteropod shells and remains of planktonic foraminiferans. It was one of the most common amphipods in the lower slope (below ~ 1000 m), whereas in the depth range comprised between 1250 and 1859 m it was the second dominant species, representing 11.4 % of the total gammarideans captured. The area studied harbours three additional congeneric species, although their populations are mainly concentrated in the upper and middle slope. Over the bottom, adult males of the new species apparently tend to occupy higher levels beyond the water-sediment interface than the rest of demographic categories. The gut content of three individuals revealed a bulk of calcified foraminiferans, a diet in consonance with their massive mandibles. Juvenile individuals were more abundant in winter, whereas adult individuals were clearly dominant in summer, thus suggesting the biological cycle of the species follows some type of periodicity.No disponibl