Nir Stern

Although the eastern Mediterranean is recognized as the most heavily invaded marine region worldwide, such incursions have been documented almost exclusively in coastal and upper‐shelf habitats. Here, we present the first record of a fish invasion into the Mediterranean's aphotic zone, reporting nine specimens of the arrow bulleye Priacanthus sagittarius captured at a depth of 420 m on the sandy continental slope off the Israeli coast. DNA‐based analysis of stomach contents identified deep‐sea prey taxa, providing robust evidence that this non‐indigenous species is actively feeding within the deep benthic environments of the Mediterranean Sea. In addition, analyses of genetic population structure indicate a downward expansion of local continental populations and reveal cryptic diversity between native populations along the Indian and West Pacific Ocean and the Red Sea and invasive Mediterranean populations. The potential ecological consequences of colonizing and exploiting new deep‐sea habitats are also explored.

Although the eastern Mediterranean is considered as the most invaded marine region in the world, this remarkable phenomenon almost exclusively being reviewed and monitored along the coastal and upper shelf regions. In this study, we provide the first documentation of fish invasion to the aphotic layer of the Mediterranean by reporting a catch of nine specimens of the arrow bulleye Priacanthus sagittarius from 420 m along the sandy continental slope of the Israeli coast. Stomach content analysis using DNA-based approach revealed deep-sea prey taxon, providing solid evidence for feeding activities of a non-indigenous fish in these deep bottoms of the Mediterranean Sea.

Monitoring biodiversity constitutes a fundamental element in assessing the ecological status of sensitive and vulnerable habitats such as inland freshwater bodies. Although conventional capture-based methodologies in fish monitoring are still widely used, the development of alternative strategies is being vigorously pursued. The use of environmental DNA (eDNA) to detect species’ presence is now a standard practice in aquatic ecology and is generating considerable attention within the scientific community. Here, we present the first eDNA metabarcoding study of the Israeli freshwater ecosystems, aiming to detect and compare fish assemblages of previously surveyed sites. Four riverine systems with different characteristics and known fish fauna were sampled, in parallel to the preparation of a complete 12S rRNA barcode reference library for the Israeli freshwater ichthyofauna. In total, 25 fish species belonging to 15 families were detected from 63 water samples using 12S eDNA metabarcoding. Comparisons with previous capture-based data have shown that eDNA surveys provided better species coverage, including the first documentation of two non-indigenous species and regardless of water characteristics or volume of filtered water. Lastly, we explain and discuss discrepancies in false-negative and false-positive results between the two methods.

Ornamental aquaculture and fishkeeping are very popular with millions of enthusiasts worldwide. The number of newly imported fish species for ornamental purposes grew slowly from World War I until the 1980s. It then exponentially increased until now with more than 7900 species and a large number of scientifically undescribed morphotypes. Here we present the first comprehensive review of freshwater and brackish fish importations during the boom of ornamental fish keeping at the turn of the Millennium and discuss this with a cultural and socio‐economic lens in the European context. The increase in imports accelerated following the availability of air transport and the end of the Cold War. From the list of traded species, the largest number of species imported for ornamental purposes was found in the following groups: armored loricariid catfish (family Loricariidae), cory catfish (family Callichthyidae, subfamily Callichthyinae), cichlids of African Great Lakes (order Cichliformes), killifish (egg‐laying species of the order Cyprinodontiformes), and characids (order Characiformes). These taxa represent ca. 74% of all fresh and brackish water ornamental fish species. The species of fish with the ability to absorb atmospheric oxygen (e.g., Belontidae, including gouramis and bettas) have dominated the market, but their ratio to the other species has declined during the modern era of ornamental aquaculture (after the end of WWI). By identifying the most popular aquarium species traded through the history of the aquarium trade, our findings aim to guide present‐day management of ornamental aquaculture and better inform invasion risk assessments.

In this study, we document the first record of the glassfish Ambassis dussumieri in the Mediterranean Sea. Confirmation for taxonomic identity has been conducted using morphological and molecular approaches and was based on a sub-sample of six individuals that were collected from a large school that resides within an artificial protected bay of a local power plant in Tel Aviv, Israel. This unique occurrence of an undisturbed school of invasive species is hereby discussed.