L. Forró szerk.: Miscellanea Zoologica Hungarica 7. 1992 (Budapest, 1992)

Gulyás, P.; Forró, L.: Composition and abundance of microcrustacean fauna in the Upper Reservoir (Hídvégi-tó) of the Kis-Balaton

Table 1. List of Cladocera and Copepoda species found in funnel traps Cladocera Alona affinis Alona rectangula Alonella excisa Bosmina longirostris Ceriodaphnia quadrangula Chydorus sphaericus Daphnia longispina Diaphanosoma brachyurum Disparalona rostrata Dunhevedia crassa Graptoleberis testudinaria Iliocryptus sordidus Leydigia acanthocercoides Macrothrix hirsuticornis Moina micrura Pleuroxus aduncus Tretocephala ambigua Copepoda Acanthocyclops robustus f. limnetica Cyclops vicinus Eucyclops serrulatus Eudiaptomus gracilis Macrocyclops albidus Megacyclops viridis Mesocyclops leuckarti Thermocyclops crassus Thermocyclops dybowsskii Table 2 shows the quantitative results of collections made by means of funnel traps. The values are expressed in individual/m

2 unit. On each occasion number of individuals were most surprisingly the greatest at Station I. Another rather general feature was the fact that in each sample the density of Copepoda greatly exceeded that of Cladocera. At each station, density of crustaceans living on sediment surface diminished in late summer and during fall. Table 2. Abundance of epibenthic crustaceans in Hídvégi-tó (ind./m

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) (I, II and III refer to the collecting sites shown in Fig. 1.) 1987 1988 July October June July August Cladocera 1083 3057 3723 1486 147 I Copepoda 38517 29151 ' 8692 20243 4773 Total 40131 32380 22111 23286 5164 Cladocera 366 339 403 127 II Copepoda 26913 2888 1359 1062 Total 27895 3269 2378 1854 Cladocera 6808 1194 4151 393 III Copepoda 23611 4741 7655 2771 Total 37484 6030 11901 3450 The values obtained along the longitudinal axis of the lake were different between 1987 and 1988. In July and October 1987 the smallest number of individuals occurred at Station II in the central part of the lake, and numbers increased again at Station III. In 1988, the abundance was smaller than in the preceding year, and in general a decrease from north to south could be observed.