The elusive Mediterranean gobies (Actinopteri: Gobiidae and Oxudercidae), their geographic pattern and the discussion on the rareness of Mediterranean fishes

Abstract

Among the 64 native Mediterranean gobies (Gobiidae and Oxudercidae), a rather high number of species was historically considered rare, and until today, some of these species have only a limited number of published records with a positive identification. Reviewing published data and applying quantitative thresholds shows that out of the 64 native species, 25 remain rarely recorded and can be considered elusive. Additional 13 species had been considered rare historically or just a decade ago. However, the increasingly high number of publications on gobies since the turn of the century revealed that the latter ones now have to be considered rather common. Almost all elusive gobies appear to be restricted to northern and eastern Mediterranean areas. The four areas with the highest elusive species richness showed no clear biogeographic pattern. Rather, an increased diversity counts of elusive gobies are likely sampling artifact of a high level of research activity in these areas. Almost all elusive Mediterranean gobies are very small littoral fish with no recognizable general preference for a specific bottom habitat or depth range. The best available published source was used to review and discuss the rarity of Mediterranean fishes in general. However, most of the elusive and potentially rare Mediterranean fish species lack a review of all their positive published records that would allow quantified discussion and conclusion on their elusiveness.