Invasives in the dark: An established population of the arrow bulleye Priacanthus sagittarius on the aphotic continental slope of the eastern Mediterranean.

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.