Feeding Habits of European Hake, <I>Merluccius Merluccius</I> (Actinopterygii: Gadiformes: Merlucciidae), from the Northeastern Mediterranean Sea

Abstract

Background. European hake, Merluccius merluccius, is a major predator in demersal ecosystem, and of great importance for the fishery. Knowledge of the feeding ecology of fish species is essential for implementing a multispecies approach to fishery management. Therefore this work was intended to analyse stomach contents and dietary changes according to fish size, season, sex, and depth to better understanding the ecological role of this species in Adriatic demersal marine communities. Materials and methods.A total of 1646 specimens of hake were collected in the Adriatic Sea by oceanographic bottom trawl surveys carried out from 2005 to 2006 during summer-and winter seasons. Principal feeding indices, species diversity Bray-Curtis similarity index, feeding strategy plot, barplot on numeric, and weight abundance data were obtained in order to increase knowledge on the diet of hake.Results. The hake diet mainly consisted of crustaceans (particularly Decapoda) and teleosts (particularly European anchovy, Engraulis encrasicolus, and red bandfish, Cepola macrophthalma). Cluster analysis of %N (numeric prey abundance percent) showed different feeding habits of three mainly groups: small hakes (<150 mm), medium sized hakes (from 150 to 300 mm) and large hake (> 300 mm) from crustaceans (small specimens) to teleost fishes (medium and large specimens). Conclusion.Feeding habits were size-dependant with fish diet being higher in stomachs of larger specimens. Feeding activity seemed to increase during growth, being smaller in immature individuals compared to adults, while no differences were found between females and males diet. Seasonal variation in diet showed an increase of teleost fishes in winter and crustaceans in summer. Keywords:Merluccius merluccius, feeding habits, diet; northeastern Mediterranean Sea biology and current exploitation status are scarcely known (Arneri and Morales-Nin 2000) and no data as to its feeding habits in the Adriatic have been analyzed over the last thirty years (Stergiou and Karpouzi 2002). The purpose of this study was to determine the feeding habits and the trophic ecology of hake in the Adriatic Sea, northeastern Mediterranean. Our specific objectives were to examine the dietary changes according to fish size, sex, season, and depth to better understanding the ecological role of this species in Adriatic demersal marine communities. MATERIALS AND METHODSSampling. European hake, Merluccius merluccius, were collected between 15 to 350 m depth along the coast of the Adriatic Sea (northeast Mediterranean) from the Gulf of Trieste to the Tremiti Islands (Fig. 1) Catches were frozen to prevent digestion of their stomach contents (Carpentieri et al. 2005) and finally taken to the laboratory. A total of 1646 specimens was collected. Hake were measured (total length, TL, in mm) and weighed to the nearest 0.1 g. Sex was determined macroscopically and specimens were classified as females (F), males (M), undetermined (U, macroscopically unidentifiable sex) and not determinable (ND, individual not e...

Histology of the digestive system of the garfishBelone belone(Teleostei: Belonidae)

“…When analysing guts content of B. belone, Zorica and Čikeš Keč (2012) found that 94% of prey items were animals, mostly euphasiids and copepods. The kind and size of the prey are usually related to the morphology and the size of the fish (Ross 1978;Stagioni et al 2011). Generally, the jaw size, gut length, reproduction and spreading are related to trophic changes and to intraspecific resource distribution (Ross 1978).…”

A metabarcoding approach for the feeding habits of European hake in the Adriatic Sea

“…Nineteen individuals each of the 5 size class for a total of 95 individuals were selected for the metabarcoding and morphological analyses. The five size classes (size class 1 = TL 120–149 mm, size class 2 = TL 150–199 mm, size class 3 = TL 200–249 mm, size class 4 = TL 250–299 mm, size class 5 = TL ≥300 mm) were defined on the basis of previous results, keeping in mind size distribution by bathymetric and geographical strata, abundance and feeding habits (Stagioni et al., ). The stomachs were dissected and preserved in 95% ethanol at −20°C.…”

“…Although the feeding habits of European hake have been described widely in the Mediterranean (Bozzano, Sardà, & Ríos, 2005;Carpentieri, Colloca, & Ardizzone, 2008;Carpentieri et al, 2005;Cartes, Rey, Lloris, & De Sola, 2004;Froglia, 1973;Papaconstantinou & Caragitsou, 1987;Sartor, Carlini, & De Ranieri, 2003;Stagioni, Montanini, & Vallisneri, 2011;Ungaro, Mannini, & Vrgoč, 2003), they show important differences justified by the opportunistic behavior of this predator. According to these works based on the morphological identification of prey remains in stomachs, adult hakes feed mainly on fish (anchovies, pilchard and gadoid species) and squids whereas the juveniles (<160 mm) feed mainly on crustaceans (preferentially euphausiids and amphipods) in the Mediterranean.…”

“…Moreover, using a mock positive control, we evaluated metabarcoding efficiency in species identification and the possible range of OTUs (Operational Taxonomic Units) number for each individual sample. were defined on the basis of previous results, keeping in mind size distribution by bathymetric and geographical strata, abundance and feeding habits (Stagioni et al, 2011). The stomachs were dissected and preserved in 95% ethanol at −20°C.…”

Histological features of the digestive tract of the adult European hakeMerluccius merluccius(Pisces: Merlucciidae)

“…Hake diet shifts from euphauiids (Euphausia couchii, Euphausia krohnii) and decapods (Processa sp., Philoderas sp., Solenocea membranacea), consumed by the smaller hakes, to teleost fish (Engraulis encrasicolus, Cepola macrophthalma, Gaidropsarus biscayensis) consumed by larger hakes (Ungaro et al 1993;Carpentieri et al 2005;Stagioni et al 2011). Usually, prey kind and size are related to the morphology and the size of the fish (Ross 1978;Stagioni et al 2011).…”