Ecological fish production in the inland delta of the Middle Danube, a floodplain river

Synopsis Ecological fish production in one parapotamal arm of the Middle Danube inland delta in Slovakia, based on 10 samplings during 5 consecutive years, ranged from 349 to 3272 (bar|x = 1066) kg ha^–1 in total production (P_T) and from 39 to 662 (bar|x = 204) kg ha^–1 in available production (P_A). Young-of-the-year fish made up an estimated 49–62% (bar|x = 54) of the P_T. According to the food production/food consumption budget calculated by three different methods, less than half of the P_T is of autochthonous origin, while most is from other sources. Floodplain fish production includes two components: fish originating within the floodplain and fish that are temporary immigrants. The latter component varies considerably in response to the hydrological regime. To assess the P_T in riverine ecosystems, different seasons and years are needed to give realistic values.This paper is dedicated to my friend and sometime co-worker, Eugene K. Balon, at the occasion of his 65th birthday and transition to University Professor Emeritus. He was one of the first ichthyologists to undertake quantitative studies in large rivers in the late 1950's, when most fish biologists thought that fishes inhabit only the sea, lakes, reservoirs and small streams.