New Subspecies of Twaite Shad Alosa fallax balticus (Clupeidae)

Abstract

We have carried out a comparative analysis of the morphological features of Twaite shad Alosa fallax based on our own data (Curonian Lagoon, Baltic Sea (2008 and 2009)) and comparative materials (collections of Russian and foreign natural history museums, including published data). The results of this study allow us to assign the Baltic Sea population of Twaite shad to the taxonomic status of subspecies Alosa fallax balticus subsp. nov. The Baltic Sea subspecies differs from other subspecies of Atlantic Twaite shad A. fallax by a lower number of gill rakers (mean 36.7) and vertebrae (53.6) and larger pre dorsal distance (46.2% SL or 41.6–42.7% TL). A. fallax balticus is one of the subspecies that have the lowest number of gill rakers on the first gill arch among subspecies of the species Alosa fallax in the northeastern Atlantic and seas of its basins.