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The diet of swordfish (Xiphias gladius) in Azorean waters

A dieta do espadarte (Xiphias gladius) em águas Açorianas
Authors: Clarke, M. R.; Clarke, D. C; Martins, Helen R.; Silva, Hélder M.;

The diet of swordfish (Xiphias gladius) in Azorean waters

Abstract

Foram recolhidos um total de 132 estômagos de espadarte durante os anos de 1992/93 em indivíduos capturados em palangre derivante perto do arquipélago dos Açores. Os conteúdos foram completamente separados em componentes que incluíam: todos os estados de digestão de peixes e cefalópodes, desde peixes completos até fragmentos de músculo, ossos e otólitos e bicos de cefalópodes. Os peixes e os ossos maiores, que podem ser identificados, pertenciam todos a Capros aper, Lepidopus caudatus, Pagellus bogaraveo, mictofideos e, o peixe que servia de isco, Trachurus picturatus. Músculo das lulas Todarodes sagittatus, Pholidoteuthis boschmai e a lula que servia de isco Illex sp. também foi encontrada. 1249 otólitos e 120 bicos (inferiores) de cefalópodes foram identificados até ao género ou espécie. Encontrou-se uma média de 3.1 espécies e 18 animais representados em cada estômago. 98.4% dos estômagos apresentavam restos de peixes que contribuíam com 93.4% dos animais na dieta. Encontraram-se cefalópodes em 37.4% dos estômagos que contribuíram com 5.8% dos animais. Estimou-se que os pesos dos cefalópodes e peixes contribuíam respectivamente com 50.5% e 49.5% dos conteúdos estomacais. Os constituintes mais importantes da dieta, determinados por depleção de % peso estimado são Ommastrephes bartrami (24.4%), Lepidopus caudatus (17.4%), Pholi-doteuthis boschmai (15.9%), Capros aper (14.9%), Beryx spp. (5.4%), Micromesistius poutassou Onychoteuthis sp. (3.9%), Moroteuthis sp. (2.7%) e Pagellus bogoraveo (2.2%). Ao todo, há mais do que 18 espécies de peixe e 22 de cefalópodes na dieta. Apresentam-se as distribuições por tamanho de otólitos e bicos. Há espécies bentónicas e mesopelágicas de águas oceânicas, costeiras e profundas. Aparecem, na dieta, algumas espécies raras e não registadas para os Açores. As dietas não variam de acordo com a dimensão do espadarte amostrado ou entre sexos. Cálculos preliminares sobre a biomassa mínima consumida pelo espadarte dos Açores apontam para um número entre 7280 a 8680 t por ano, sendo aproximadamente metade peixe e metade cefalópodes.

ABSTRACT: A total of 132 stomachs were collected in 1992-93 from swordfish caught on drifting longlines near the Azores. Contents were sorted completely into components which comprised all stages of digested fish and cephalopods from complete fish to fragments of muscle, bones, otoliths and beaks of cephalopods. Fish and larger bones which could be identified all belonged to Capros aper. Lepidopus caudatus, Pagellus bogaraveo, myctophids, and the fish used as bait, Trachurus picturatus. Flesh of the squids Todarodes sagittatus, Pholidoteuthis boschmai and the squid used as bait Illex sp. was also present. 1249 otoliths and 120 cephalopod lower beaks were identified to genus or species. There was a mean of 3.1 species and 18 animals represented in each stomach. Fish remains occurred in 98.4% of the stomachs and contributed 93.4% of animals in the diet. Cephalopod remains occurred in 37.4% and contributed 5.8% of animals. Estimates of the weights of fish and cephalopods show that cephalopods provide 50.5% and fish species 49.5% of the stomach contents. The most important constituents of the diet by decreasing % estimated weight are Ommastrephes bartrami (24.4%), Lepidopus caudatus (17.4%), Pholidoteuthis boschmai (15.9%), Capros aper (14.9%), Beryx spp. (5.4%), Micromesistius poutassou (4.3%), Onychoteuthis sp. (3.9%), Moroteuthis sp. (2.7%) and Pagellus bogaraveo (2.2%). In all, there are more than 18 species of fish and 22 species of cephalopod in the diet. Size distributions of otoliths and beaks are presented. The species include bottom and midwater forms from both oceanic and near island water and depths. A number of rare species of cephalopods and species not recorded for the Azores are in the diet. Diet does not differ according to the size of swordfish sampled or between female and male swordfish. Preliminary calculations were made on the minimum biomass eaten by the swordfish off the Azores as 7280 - 8680 t per year, approximately half fish and half cephalopods.

Country
Portugal
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Keywords

Swordfish, Xiphias gladius, Espadarte, Açores, Azores

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This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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