L. Forró - É. Murai szerk.: Miscellanea Zoologica Hungarica 6. 1991 (Budapest, 1991)

Csányi, B.: Changes of the fish assemblages in the Kis-Balaton Reservoir between 1985 and 1989

year. In 1989, 3 additional taxa were captured (Table 1): they were found in the Kiskomáromi-channel upstream to the reservoir in the summer of 1989. They are obviously not the members of the fish stock living in the eutrophic water body. Their presence close to the reservoir - especially the river goby (Neogobius fluviatilis) - has a faunistical importance. The dominant species of the adult fish stock caught in 1985 were the crucian carp (Carassius auratus gibelio) and the carp (Cyprinus carpio) with 43.9 and 20.9 % relative frequencies, respectively. The amount of tench (Tinea tinea) was 8.6 %, the pike (Esax lucius) occurred in 4.5 %, and the other species were represented only occasionally. The specimens of the far-eastern Pseudorasbora parva were found already in the first year. The largest amount of juveniles came from the bleak population (Alburnus alburnus, 60 %), followed by the bream (Abramis brama) and the crucian carp (13.6 and 11.9 %, respectively). Table 1. Values of abundance classes based on yearly average relative frequency data of fish taxa caught in the Kis-Balaton Reservoir. (Legend: 0 = absence; * = presence; other numbers = values for abundancy classes based on yearly averages of relative frequencies (RF): 1 ifRF<4%;2ifRF <8%;3ifRF <16%;4ifRF <32%;5ifRF <64 % ). NOTE: all of the data collected by different fishing methods are included! SPECIES LIST 1985 1986 1989 Juv. Ad. Juv. Ad. Juv. Ad. Esox lucius 1 2 1 2 1 1 Cyprinus carpio 2 4 2 3 1 1 Abramis brama 3 1 2 1 * 1 Alburnus alburnus 5 1 4 3 1 0 Blicca bjoerkna 0 1 * 1 * 0 Aspius aspius 0 0 0 * 1 1 Carassius carassius 1 1 * 1 1 * Carassius auratus gibelio 3 5 3 4 4 5 Rhodeus sericeus amarus 0 0 1 2 3 3 Rutilus rutilus 1 1 2 3 2 1 Scardinius erythrophthalmus 1 1 2 2 1 1 Tinea tinea 1 3 2 3 2 2 Misgurnus fossilis 0 0 0 * 0 0 Lepomis gibbosus 0 0 2 2 4 3 Perca fluviatilis 0 0 * 1 1 1 Gymnocephalus cemuus 0 0 0 0 0 1 Pseudorasbora parva 1 1 1 1 4 3 Silurus gjtanis 0 * 0 * 0 * Anguilla anguilla 0 0 0 1 0 1 Hypophthalmichtys molitrix 0 1 0 0 * Leuciscus cephalus — * Cobitis taenia * Neogobius fluviatilis Total number of individuals 546 244 768 422 675 1243 Total number of taxa 13 19 19 The basic dominancy conditions have changed in the second year because other cyprinids became common. The relative frequency of the crucian carp decreased to 23.9 %, and the roach (Rutilus rutilus), the rudd (Scardinius erythroph-