Prey preferences and ontogenetic diet shift of European hake Merluccius merluccius (Linnaeus, 1758) in the central Mediterranean Sea

This study focuses on the ontogenetic diet change of European hake (Merluccius merluccius) in the north sector of the Strait of Sicily (SoS), central Mediterranean Sea. The species is one of the most important fish predators within the Mediterranean marine ecosystem and one of the main target species for local fisheries. A total of 2669 hake specimens between 7.5 and 67 cm of total length (TL) were collected in 2014-2015. The sample was divided into nine size classes and quantitative feeding indices were calculated for each size-class in order to analyse ontogenetic changes in prey preferences. Hierarchical cluster analysis and non-metric multidimensional scaling (nMDS) showed the occurrence of three main hake feeding guilds separated at 50% similarity. Euphausiids and mysids dominated the diet of hake smaller than 14 cm TL and crustacean decapods and fish were the main prey of hake between 14.5 cm to 17.5 cm TL. A shift toward pelagic and necto-benthic fish occurred over 18 cm TL: hake between 18 and 32 cm TL prey mostly upon Atlantic horse mackerel (Trachurus trachurus) whilst the silver scabbardfish (Lepidopus caudatus) was an important prey for hake over 32 cm TL. The study highlighted the key role played by the Atlantic horse mackerel for hake diet in the SoS, which is different to what has been previously observed in other Mediterranean areas where piscivorous hake feed substantially on small pelagic fish, such as anchovy and sardine. Information on hake diet composition, as provided in this study, can be integrated with data on consumption rate and population size to develop multispecies models leading to a quantitative understanding of the role of hake in the ecosystem.