Saturday, 24 August 2019

A new species of alien fish in the Gulf of Trieste

Lately we've been doing regular snorkeling sessions in the Gulf of Trieste and very few other field trips, so here's another, short post to notify a recent interesting find. At the very beginning of this week we observed and photographed a Sergeant Abudefduf sp. (above) in the sea near Tanki rtič/Punta Sottile, right on the border between Slovenia and Italy. This tropical fish, belonging to the family Pomacentridae (damselfish) is usually observed in shoals along coral reefs. In the Mediterranean sea it's an alien fish, already recorded in several places (Gulf of Naples, Gulf of Genoa, Malta, Israel, Lebanon). However our find is extremely interesting as it represents the first record for the Gulf of Trieste (and maybe for the entire Northern Adriatic?), The identification to species level isn't sure yet as two sister species have been reported in the Mediterranean: the Indo-Pacific Sergeant A. vaigiensis (native to the Pacific ocean, seas of Eastern Africa and the Red Sea) and the Sergeant-major A. saxatilis (native to the central Atlantic ocean). Both species are apparently very difficult to distinguish and DNA is usually needed for a final confirmation. Our record has already been submitted to local marine biologists both in Slovenia and Italy, who are officializing the record. What is sure is that no environment is free from alien and invasive species. The last photo above sums up quite well the current situation in the Gulf of Trieste, showing the newest recorded alien, the Abudefduf, together with a Sea Walnut Mnemiopsis leydi, a very abundant and invasive comb jelly in our sea in recent years.
For those of you who would like to read more about the occurrence of Abudefduf in the Mediterranean, see this article from Malta.