John Dory Zeus faber (Linnaeus, 1758) feeding off Galicia and in the Cantabrian Sea: Dietary shifts with size

Between 1990 and 1997, stomach contents of 647 Atlantic John Dory Zeus faber (Linnaeus, 1758) measuring from 5-58 cm, were analysed volumetrically. The species was found to be almost entirely icthyophagous: fishes constituted more than 99 % of its diet by volume, or 75 % in terms of number. Among these, there are some commercially and ecologically important gadoids and clupeoids. Using clustering and multi-dimensional scaling methods, four length ranges with a different diet composition were found: smaller fishes, measuring 5-9 cm, fed mainly on invertebrates (mysids and Allotheutis spp.) and small benthic fishes (e.g., gobiids and Callionymus maculatus Rafinesque-Schmaltz, 1810). In the transitional length range, 9-12 cm, Gadiculus argenteus Guichenot, 1850 replaced the invertebrates. From 12-30 cm, Z. faber's diet basically comprised gadoids, such as Micromesistius poutassou (Risso, 1826), G. argenteus and Merluccius merluccius (Linnaeus, 1758), whereas specimens longer than 30 cm fed on larger fishes, including M. poutassou, clupeoids (mainly Sardina pilchardus Walbaum, 1792), and Cepola rubescens Linnaeus, 1766. Feeding was more intense in the smallest length range, and within each length range, a different diet composition by depth strata was also observed.Entre 1990 Y 1997 se analizaron, con un método volumétrico, los contenidos estomacales de 647 ejemplares de pez de San Pedro Zeus faber (Linnaeus, 1758), abarcando un rango de tallas entre 5 y 58 cm. Se trata de una especie muy icliófaga: su dieta está compuesta por peces en más del 99 % en volumen y del 75 % en número. Dentro de ella destacan gadiformes y clupeiformes de importancia, tanto ecológica como comercial. Utilizando análisis de clúster y MDS se identifican cuatro rangos de talla con composiciones de la dieta diferentes: los individuos menores, entre 5 y 9 cm, se alimentan principalmente de invertebrados (misidáceos y Allotheutis spp) junto a pequeños peces bentónicos (Gobiidae y Callionymus maculatus Rafinesque-Schmaltz, 1810); a continuación, hay un rango de transición, de 9 a 12 cm, en el que el Gadiculus argenteus Guichenot, 1850 reemplaza a los invertebrados; entre 12 y 29 cm la dieta se compone fundamentalmente de gadiformes como Micromesistius poutassou (Risso, 1826), G. argenteus y Merluccius merluccius (Linnaeus, 1758); mientras, la alimentación entre los individuos mayores de 30 cm se basa en peces de mayor tamaño, entre los que destacan M. poutassou, clupeiformes (fundamentalmente Sardina pilchardus Walbaum, 1792) y Cepola rubescens Linnaeus, 1766, entre otros. También se observa mayor intensidad de alimentación en los peces del rango menor de tallas y diferentes composiciones de la dieta por estratos de profundidad dentro de cada rango de tallas.Instituto Español de Oceanografí

Feeding of Most Abundant Fish Species in Flemish Cap in Summer 1993

The stomach contents of 4320 fishes comprising 14 species were collected from Flemish Cap Bank (NW Newfoundland) at depths ranging from 130 to 730 m, during summer 1993. The general feeding intensity was high in all species. Three main feeding patterns were evident: the genus Sebastes consume primarily pelagic species, although they also feed on preys which migrate vertically such as shrimps, Euphausids and mysids. The benthic group is made up of American plaice (Hippoglossoides platessoides), witch flounder (Glyptocephalus cygnoglossus), arctic eelpout (Lycodes reticulatus), wolffishes (Anarhichas lupus and Anarhichas minor) and thorny skate (Raja radiata). Lastly, the group of benthopelagic fish remains, longf in hake (Urophycis chesteri), cod (Gadus morhua), grenadiers (Nezumia bairdi and Macrourus berglax) and Greenland halibut (Reinhardtius hippoglossoides). Pelagic and benthopelagic preys are an important food resource for all fish considered, the abundance of Hyperids, P. borealis and Sebastes sp. in summer makes them an important food resource in the diet of fish in Flemish Cap

Importance of Blue Whiting (Micromesistius poutassou) discarded in the diet of Lesser-Spotted Dogfish (Scyliorhinus canicula) in the Cantabrian sea

Blue whiting is the most important demersal species caught, in landed biomass as well as in discarded biomass, by the trawl fleet in the South part of the Gulf of Biscay. Dogfish' is not commercial by-catch and it is discarded inmediately after sorting. During 1994 were accomplished analysis of 1094 stomach contents of dogfish caught in commercial ships working in a discard sampling program and a cruise research. The results reveal that from 17 cm, this especie depredates on blue whiting along all the year. The length ranges found in the stornach contents (6-31 cm) is similar to the length ranges discarded in the fishery (7-39 cm). The average quantity of blue whiting in stomachs of dogfish between 40 and 60 cm constitutes the 25% of the stomachs volume. The state of digestion in which is found the blue whiting prey, and the comparative analysis of the size distributions of blue whiting of the stomachs and the one of the fishery, presuppose that the blue whiting consumed is dead material originated from discard. Finally it is discussed the importance that this supplementary material can have in dogfish abundance

Biometric relationships to estimate length and weight of Leucoraja naevus, Raja montagui and R. clavata, from wing landings in Cantabrian Sea.

Conference posterThe scarce elasmobranch information existing nowadays has received rapidly growing worlwide attention in targeted fisheries, and also as a by-catch in other fisheries. The landings of rays are significant as by-catch in the North of Spain fisheries, and not always individuals are landed whole. The ray wings are cut on board of commercial vessels, and this landing is recorded by fish-markets. One of the objectives of DELASS project (Development of Elasmobranch Assessments) is to obtain reliable data into a particular area. In this poster the degree of existent correlation between the round fresh weight and landing lenght distribution concerning these species is presented

Descartes de la flota española en el área del ICES

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Crónicas desde la Antártida.

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Fishes of the Bellingshausen Sea and Peter I Island

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Ictiofauna

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Relaciones tróficas de los peces demersales de las Islas Orcadas del sur

En enero-febrero de 1991 se ha realizado una campaña de biología pesquera demersal en la plataforma de las islas Orcadas del Sur. Para ir conociendo la estructura trófica del sistema demersal se analizaron los contenidos estomacales de 24 especies de peces. El flujo energético está marcado por pocas especies, entre las que seleccionamos las 10 más representativas en número y biomasa (Champsocephalus gunnari, Chaenocephalus aceratus, Notothenia gibberifrons, Chionodraco rostrospinosus, Pseudochaenichthys georgionus, Notothenia kempi, Notothenia neglecta, Nototheniops larseni, Gymnoscopelus nicholsi y Notothenia rossii). Estas especies corresponden a las familias Channicthyidae, Nototheniidae y Myctophidae. En la primera de ellas se encuentran clásicos depredadores de peces, con tamaños de boca grandes, pero tanto C. gunnari como C.rostrospinosus son comedores de krill, mientras que P.georgianus y sobre todo C. aceratus son ictiófagos. En la segunda familia los hábitos alimenticios de sus especies son variados, encontrando especies bentófagas, entre las que destacan N. gibberifrons como consumidor de poliquetos, equinodermo, y N. kempi gran consumidor de tunicados, más especializado en presas del epibentos. Excepto especies de esta familia que alcanzan gran tamaño y tienen un fuerte componente ictiófago en su comida, como Notothenia neglecta y Notothenia rossii, son predadores oportunistas de la fauna bentónica y del krill. La comparación de las dietas alimenticias de estas diez especies más características en la cadena alimenticia permite observar los diferentes grupos de alimentación existentes, mediante análisis multivariantes jerarquizados de agregación. Hay un fuerte solapamiento de dieta entre las especies comedoras de krill (C. gunnari, C. rastrospinosus, G. nicholsi, N. larseni). El resto de las especies forman un grupo no definido, apareciendo mayor afinidad entre las bentófagas N. gibberiffons y N. kempi. Las especies más especializadas son las consumidoras de crustáceos planctónicos que no varían su dieta con el crecimiento; en cambio las especies más generalistas varían de nicho trófico con el aumento de talla, sobre todo N. gibberifrons y C. aceratus, por lo que se realizaron nuevos análisis de clasificación jerárquica con los datos de las dietas de 24 grupos de talla de las 10 especies. Encontramos un gran grupo de comedores especialistas de eufausiáceos y misadáceos que tienen un gran solapamiento de dieta (C. gunnari, C. rastrospinosus, G.nicholsi, N. larseni, P. georgionus, C. aceratus menores de 30 cm, y N. neglecta mayores de 50 cm), mientras que N. kempi menores de 3O cm, N.neglecta menores de 50 cm y N.gibberifrons mayores de 50 cm, también pertenecen a este grupo aunque con un solapamiento menor. El resto de las dietas corresponden a: 1) presas del bentos (poliquetos, isópodos, anfípodos, tunicados, equinodermos, etc. como ocurre con N. gibberifrons menores de 30 cm, N. kempi mayores de 30 cm y N. rossii menores de 50 cm), 2) peces presa nototénidos (C. aceratus entre 30-40 cm y N. rossii mayores de 50 cm). 3) peces presa chaníctidos, destacando como predadores C. aceratus mayores de 40 cm; su presa fundamental es C. gunnari, llegando a ser el 50% de su alimento.In January-February 1991 a survey of demersal fishing biology was carried out the continental shelf of the southern Orkney Islands. To further the knowledge of the trophic structure of the demersal system, the stomach content of 24 species of fish were analysed. The energetic flux is determined by few species, from which the ten most representative in terms of number and biomass have been selected (Champsocephalus gunnori, Chaenocephalus aceratus, Notothenia gibberifons, Chianodroco rastrospinosus, Pseudo-chaenichthys georgianus, Notothenia kempi, Notothenia neglecta, Nototheniops larseni, Gymnoscopelus nicholsi and Notothenia rossii). These species correspond to the Channicthydae, Nototheniidae and Myctophidae families. In the former classic predators of fish are found, with large mouth sizes. but C. gunnari and C. rostrospinosus feed on krill, while P. georgianus and, above all C. aceratus are ichthyophagous. In the species of the second family feeding habits are varied, including benthophagous fish with N. gibberifrons as a predator of polycheta, echinoderms, and N.kempi feeding mainly on tunicata, being more specialised in epibenthos prey. Apart from species which grow to a large size and have a strong ichthyophagous component in their food, Notothenia neglecta and Notothenia rossii, are opportunist species feeding on benthic fauna and krill. The comparison of the feeding diets of these ten most characteristic species in the food chain allows us to observe the different trophic overlaps which exist. through cluster analysis. A great overlap of diet is seen among species which feed on krill (C. gunnori, C. rastrospinosus, G.nicholsi, N. larseni). The others species form a very undefined group, the benthophagous species N. gibberifrons and N. kempi having a greater affinity. The most specialised species are predators of planctonic crustaceans whose diet does not vary with growth; in contrast the more general species vary their trophic niche as their size increases, above all N. gibberifrons and C. aceratus, and new cluster analyses were made with the data of the diets of the 24 size groups of the 10 species. A large group specialising in euphausiacii and mysidacii, and having a large overlap in diet was found (C. gunnari, C. rastrospinosus, G. nicholsi, N. larseni, P. georgionus, C. aceratus less than 30 cm, N. neglecta less than 5 cm and N. gibberifrons greater than 50 cm also belong to this group although with a smaller overlap. The rest of the diets correspond to: 1) the prey of benthos (polychaeta, isopoda, amphipoda, tunicata, echinodermata, etc. as accurs with N. gibberifrons less than 30 cm, N. kempi greater than 30 cm, N. rossii less than 50 cm), 2) Notothenidae fish prey (C. acerotus between 30-40 cm and N. rossii greater than 50 cm), and 3) Channiyctiidae fish prey. with C. aceratus greater than 40 cm standing out; its fundamental prey is C. gunnari, reaching 50% of its total diet

El mar antártico

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