European catfish (Silurus glanis) as a freshwater apex predator drives ecosystem via its diet adaptability

Lukáš Vejřík,Martin Čech,Mikko Kiljunen,Ivana Vejříková,Luboš Kočvara,Zuzana Sajdlová,Antti P Eloranta,Jiří Peterka,Son Hoang The Chung,Petr Blabolil,Marek Šmejkal

doi:10.1038/s41598-017-16169-9

Abstract

Apex predators play a key role in ecosystem stability across environments but their numbers in general are decreasing. By contrast, European catfish (Silurus glanis), the European freshwater apex predator, is on the increase. However, studies concerning apex predators in freshwaters are scarce in comparison to those in terrestrial and marine ecosystems. The present study combines stomach content and stable isotope analyses with diet preferences of catfish to reveal its impact on the ecosystem since stocking. Catfish niche width is extremely wide in comparison to the typical model predator, Northern pike (Esox lucius). Catfish and pike have different individual dietary specialization that results in different functional roles in coupling or compartmentalizing distinct food webs. The role of both species in the ecosystem is irreplaceable due to multiple predator effects. The impact of catfish is apparent across the entire aquatic ecosystem, but herbivores are the most affected ecological group. The key feature of catfish, and probably a common feature of apex predators in general, is utilization of several dietary strategies by individuals within a population: long-term generalism or specialization and also short-term specialization. Catfish, similar to other large-bodied apex predators, have two typical features: enormous generalism and adaptability to new prey sources.

Highlights

Large-bodied apex predators play a key role in community dynamics and ecosystem stability[1,2,3] due to their generalist foraging strategy on prey at different trophic levels and from different habitats[4,5,6,7]
We focused on the total niche width of European catfish and Northern pike, and on the food origin, whether they utilize food sources only from the aquatic food web[7,35,36]
The semiaquatic vertebrates were isotopically distinct from aquatic food sources due to lower δ15 N values (Fig. 1)

Summary

Introduction

Large-bodied apex predators play a key role in community dynamics and ecosystem stability[1,2,3] due to their generalist foraging strategy on prey at different trophic levels and from different habitats[4,5,6,7]. Contrary to general apex predator decline, European catfish (Silurus glanis) metapopulation size and distribution range has increased in recent decades[23]. It is the largest freshwater fish in Europe and the third largest in the world (it reaches 2.7 m and 130 kg)[22,23]. Pike is an ideal reference species because it is a high-level freshwater predator, the second biggest fish predator in Europe (it reaches 130 cm and over 25 kg), and it has the widest extent of distribution in freshwaters[33]

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Discussion

Conclusion