In July 2004 and 2006, tributaries of the River Neretva and surrounding karstic fields (polje) in Bosnia and Herzegovina were sampled, and new data on spined loaches (Cobitis) and accompanying freshwater fish fauna gathered. spined loaches were found in the River Bregava and Hutovo blato wetland, which are directly connected to the River Neretva, in the River Trebišnjica in Popovo polje, in Lake Krenica and the River Matica in Imotsko polje, and in the River Lištica drainage in Mostarsko blato. However, Cobitis were not found in karstic fields situated more westward (Livanjsko polje, Duvanjsko p., Kupreško p. and Glamočko p.), nor in karstic fields situated northward from the River Trebišnjica (Nevesinjsko polje, Fatničko p., Dabarsko p. and Gatačko p.). Neither were they found in the River Trebižat, which lies closer to the River Neretva than does Imotsko polje. Based on morphological and molecular characters, spined loaches inhabiting the rivers Trebišnjica and Bregava, and Hutovo blato were identified as Cobitis narentana Karaman, 1928, while specimens from Imotsko polje and Mostarsko blato were classified as Cobitis sp. Until now, a single species of spined loach, C. narentana, had been recorded from the lowermost part of the River Neretva basin. Our new findings suggest that the species diversity of the spined loaches in the Neretva basin in Bosnia and Herzegovina might be underestimated and that a detailed taxonomic study is required to determine the Cobitis diversity in this area.
The genetic differentiation of Oxynoemacheilus bureschi (Drensky, 1928) from all three drainages (Struma=Strymon, Mesta=Nestos, Vardar=Axios) where this species occurs, as well as its phylogenetic relationships with other European stone loaches, was assessed using the mitochondrial cytochrome b gene. The phylogenetic reconstruction revealed two distinct clades within the European stone loaches with high bootstrap values. Very low genetic variability with no internal haplotypic structure has been found between and within all examined O. bureschi populations, indicated by low polymorphism and similar haplotypes. According to the nesting design and demographic patterns, the range of O. bureschi was not constant, but underwent expansion in the recent past. Lack of variation, a rather unusual phenomenon for fishes from the southern Balkans, is ascribed to facilitation of dispersal due to seashore regression, confluence events and river capture during the Pleistocene.