engleski

Insight in garfish Belone belone (L., 1761) diet in the Adriatic Sea

The main aim of this study was to describe and give an insight in garfish feeding habits by describing its prey and possible size-related changes in diet. Garfish, Belone belone (Linnaeus, 1761), is a pelagic, oceanodromous fish species largely spread in brackish and marine waters of the north-eastern Atlantic, Mediterranean and the Black Sea. Similar to other pelagic fish species garfish has migratory pattern ; generally it is found in offshore areas, except during the spawning period (January – May) when its specimens migrates into coastal regions. Biological knowledge of garfish population, that inhabiting Adriatic Sea, is partial and refers only to its reproduction traits, while there are no data concerning its diet. Garfish specimens (N=211, 23.1 cm<TL<72.0 cm) were collected during the night by seine net with stretched mesh size of 10 mm (the main net) to 34 mm (the net cod end) in the eastern part of the middle Adriatic Sea from February 2008 to February 2009. Immediately after landing on board garfish specimens were preserved in 10% buffered-formalin and analysed later on in the laboratory. Length and weights (total body weight, weight of full and empty gut) of all specimens were measured to the nearest 1 mm and 0.01 g, respectively. Prey items were identified under a binocular microscope (magnification from 1.6 X) to the lowest possible taxonomic level. In order to describe a diet composition the following indexes were calculated: frequency of occurrence (%F), abundance (%N), fullness index (%Jr) and vacuity index (%V). Analysis of gut content indicated that garfish preferred feeding on animal food (94%), while plant component found inside of garfish guts refereed to pieces of brown algae (Phaeophyta) and wads of Posidonia oceanica. A total of 24, 992 animal preys belonging to ten taxonomic groups were identified. According to presented data, copepods (56.9 %) and decapods (44.4 %) were the most frequent, while the most abundant prey items were euphausiids (59.9 %) and copepods (20.7 %). Diet composition of garfish specimens was not size related (TL-%N: 0.007<r2<0.417 ; P<0.05) as all examined garfish preyed mainly upon euphausiids, decapods and copepods. Fullness index decreased with garfish size (% Jr= 4.022 – 0.032TL) but not statistically significant (r=0, 382, p=0, 075). Conversely to a low value of fullness index (meanSD: 2.70±1.84 %) quite high vacuity index was obtained (% V=31.88 %). Analysis of gut content confirmed garfish as omnivore fish species but with a pronounce preference for animal food. Obtained knowledge of this fish trophic ecology should provide better comprehension of its functioning in an ecosystem.

Feeding; Belone belone; Adriatic Sea

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