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Recent trends of CPUE in the barbel zone of the Sava river in Croatia

The water quality of the Sava river in its barbel zone in Croatia (Fig. 1 and 2) improved since the beginning of 1990’s, as the result of Slovenia’ s abandonment of heavy industry and mining during the transition period (Table 1). Ichthyofaunal changes followed. The aim of this work was to investigate trends since 2001. The fish were caught 15 times by electric gear in spring, summer and fall from 2003 to 2006. Catch per unit effort (CPUE) was expressed by the mass of fish in grams caught along the 100 m of the river course. The overall CPUE continued to vary around 3 kg (2773.4 g average). Throughout the last three decades, Leuciscus cephalus has always remained an outstandingly dominant species. Its CPUE is responsible for about half of the overall CPUE, varying between 44.1 % over 1991-1994 period and 54.5 % in 2001 (Fig. 3). Other significant constantly present species in the same period have been Barbus barbus, Alburnus alburnus, Cobitis spp. and Silurus glanis (Fig. 4). Two other typical species, Alburnoides bipuncatatus and Barbus meridionalis, although not even present in catches before the water quality improvement, showed later sudden growth and today their populations are stable (Fig. 5). The share of all mentioned species together, after only 70 % in 1978, jumped on and kept up over 85 % since the beginning of 1990’ s (Fig. 3). The species non-typical for barbel zone either significantly dropped in quantities – Rutilus rutilus and Perca fluviatilis, or showed peaks only occasionally – Cyprinus carpio and Vimba vimba carinata (Fig. 6). The remaining species have been either caught by electric gear sporadically in small quantities or reported to exist, but were not registered in this investigation (Table 2). The presence of some typical species stabilized after significant changes caused by the water quality improvement at the beginning of 1990’s.

CPUE; Sava river; Croatia

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