Abstract
The European catfish Silurus glanis (Linnaeus, 1758) is an expanding apex piscivorous predator whose predation may drive fish harvest rates and fish populations. This study aimed to analyze the relationships between intensive catfish stocking/harvesting and harvest rates of putative catfish prey–three rheophilic fish species: vimba bream Vimba vimba, nase Chondrostoma nasus, and barbel Barbus barbus (Linnaeus, 1758). The GAM (generalized additive model) was used to analyze the relationships between the harvest rate and the stocking intensity rate of the catfish and the three rheophilic fish species. The harvest rates and stocking intensity rates were obtained from mandatory angling logbooks collected from 38,000 individual recreational anglers by the Czech Fishing Union on 176 fishing sites over the years 2005–2017 in central Bohemia and Prague (the Czech Republic). Our results show that a higher intensity of catfish stocking and harvesting resulted in a lower harvest rate of rheophilic fishes. Conversely, the stocking rates of rheophilic fishes were not significantly correlated to their harvest rates. In conclusion, a significant negative relationship was found between the harvest rate and the restocking rates of rheophilic fishes and their predator, suggesting that fisheries managers should not perform intensive stocking of both catfish and rheophilic fishes on the same rivers.
Highlights
The European catfish Silurus glanis (Linnaeus, 1758) is an apex predatory fish species in the freshwater ecosystems of central Europe
This study aimed to analyze the relationship between the harvest rate and the stocking intensity of the predator European catfish and the harvest rates of its prey, the rheophilic fish species (Barbus barbus, Chondrostoma nasus, and Vimba vimba-Linneaus, 1758) in lowland mesotrophic rivers in Prague and the Czech Republic in central Europe
It was found that the harvest and stocking rates of the catfish were strongly correlated with the harvest rates of barbel, nase, and vimba bream (Tables 1–3)
Summary
The European catfish Silurus glanis (Linnaeus, 1758) is an apex predatory fish species in the freshwater ecosystems of central Europe. Its populations are expanding due to climate change, river damming, and introductions [1,2,3]. Catfish predation may potentially drive freshwater ecosystems and wild fish populations. The predation pressure may be further increased by an intensive catfish stocking that causes unnaturally high predation pressure on local fishes. Anglers can significantly reduce the catfish populations through intensive angling [4,5]. The possible negative effect of catfish predation on local fish populations has been discussed [1,2,3,5]. While the catfish occupies various habitats, it mostly lives in larger rivers which are the natural habitat of the rheophilic fish species
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