Balonov balavac (Gymnocephalus baloni)
Ova vrsta je na popisu divljih vrsta od interesa za EU (Natura 2000). Živi u rijeci Dravi i pojavljuje se sporadično. Naraste do 12 cm, dakle upola manje od običnog balavca i manje gotovo upola od endemskog prugastog balavca. Tijelo mu je zbijeno. Od običnog balavca se razlikuje po četiri do šest tamnijih ponekad prekinutih poprečnih pruga koje se spuštaju od leđa prema trbuhu. Na škržnim poklopcima su po dvije duže bodlje. Hrani se sitnim rakovima, ličinkama kukaca i maločetinšima. Živi u srednjem i donjem toku većih rijeka i blizu ušća. Poznato je stanište na Dunavu kod Iloka.
Uzrok ugroženosti su regulacije vodotoka, izgradnja akumulacija i usporavanje brzine rijeka, te naravno onečišćenja voda.
Balon’s ruffe (Gymnocephalus baloni)
This species is on the list of wild species of interest to the EU (Natura 2000). It lives in the Drava River and appears sporadically. It grows up to 12 cm, so half the Balon’s ruffe’s size and less than almost half the size of the endemic striped ruffe. Its body is compact. It is dark brown and olive green on the back, with slightly lighter sides and a yellowish white belly. It differs from the ordinary ruffe by four to six darker, sometimes dashed, vertical stripes that descend from the back to the belly. There are two longer spines on the gill covers. It feeds on small crustaceans, insect larvae and oligochaetes. It lives in the middle and lower reaches of larger rivers and near the river mouths. The habitat in the Danube near Ilok is well known.
The cause of endangerment is the regulation of watercourses, the construction of reservoirs, rivers slowing down, and, of course, water pollution.