Endemic taxa are distributed in a specific, often small area, and do not appear anywhere else. If that area is very small, then they are called stenoendemic. Of the about 140 fish species inhabiting Croatia’s rivers and lakes, there are some 50 endemic species. This wealth of biodiversity is the consequence of Croatia’s geographic position, which includes both the Danube Basin and the Adriatic Basin.
The Krbava minnow is endemic to the Danube Basin and is stenoendemic to the Krbava Polje field. In summer, when the rivers dry up, it retracts into underground waters, where it also spends the winter. Due to this, it can withstand long periods of not eating.
The Neretvan spined loach is endemic to the Adriatic Basin and stenoendemic to the Neretva River catchment. It grows up to 10 cm in length, feeding on tiny invertebrates, such as crustaceans and insect larvae. It feeds with its bottom lip using a filtration mechanisms in the pharynx that is covered in mucous, which food particles stick to as they pass over.
The Zrmanja dace is a stenoendemic species that inhabits the Zrmanja and Krka Rivers. It grows up to 30 centimetres in length, and feeds on algae, plankton, aquatic invertebrates and fish. The data on the lifecycle and spawning are very sparse, as this is a rare, endemic species that has not been well studied.