Changes in the Proportion of Fish Species Caught by Artisanal Fishers in the Croatian Section of the Sava River

The number of artisanal fishers, and consequently their catch, in the Sava River has declined significantly over the past two decades. The average weight of some species has also changed significantly. Therefore, the aim of this paper is to investigate possible changes in the biomass proportion in the catch of the most important taxa during this period. Most of the investigated species showed considerable variation in catch from year to year, but without a clear trend (P > 0.05). The largest fluctuations, with a coefficient of variation (CV) over 90%, were found in Acipenser ruthenus, Cyprinus carpio, Leuciscus aspius and allochthonous species. Esox lucius, Leuciscus idus, Silurus glanis and Sander lucioperca had CVs between 41% and 73%. The smallest variations in the proportion of catch were recorded for Abramis brama and other autochthonous species (the most abundant being Rutilus virgo), with CVs of 37.77% and 33.43%, respectively. These two taxa also showed significant opposite trends (R² = 0.34; P < 0.01) and had a combined average biomass proportion of 67.03%.