Experts for the taxonomy of marine fish have brought to an end the study of the Mediterranean Shags’ diet in the Slovenian sea. The study is based on analysis of 500 shags’ pellets, collected in summers 2012 and 2013 at communal roosting sites near Debeli rtič, Strunjan and Sečovlje.
The study deals with taxonomical prey composition, number of prey specimens, relative frequency and biomass of prey species in the pellets. The analysis has confirmed our presumption that the Mediterranean Shags in Slovenian sea prey mainly on economically unimportant fish species. More than 3/4 of prey specimens or 85% of total biomass of fish taken were species from the family of gobies (Gobiidae), mostly the black goby (Gobius niger). The second place was taken by the brown comber (Serranus hepatus) with 13% of prey specimens or 7% of total prey biomass. More than 1% of specimens taken were represented by the red bandfish (Cepola macropthalma) and the big-scale sand smelt (Atherina boyeri). Gobies, brown combers and red bandfish are all sea-bed dwelling fish, confirming that the shags mainly forage at the sea bottom.
The results of the study conducted in this project are very similar to the results of the study conduted by researchers from the University of Trieste in the Italian part of the Gulf of Trieste. These researchers have also compared the diet at the post-breeding sites with the diet at the Croatian breeding sites. They have found out that the diet of the Mediterranean Shags is much more diverse in the breeding area than in the post-breeding area. Moreover, the portion of gobies is substantially lower, while the portion of small pelagic fish, mainly sand smelts (Atherina sp.), is much bigger in the breeding area.
The entire report about the Mediterranean Shags’ diet in the Slovenian sea is available here*. You can read more about the diet in the Italian part of the Gulf of Trieste and at the Croatian breeding sites in the original scientific article of the italian colleagues.
*in Slovenian – English abstract available on request