Boulêtreau, S., Fauvel, T., Laventure, M., Delacour, R., Bouyssonnié, W., Azémar, F., & Santoul, F. (2020). “The giants’ feast”: predation of the large introduced European catfish on spawning migrating allis shads. Aquatic Ecology, 1-9.
is a large non-native opportunistic predator able to develop hunting strategy in response to newly available prey where it has been introduced. Migrating spawning anadromous prey such as allis shad Alosa alosa could represent this available and energy-rich food resource. Here, we report an impressive catfish hunting behavior on shad spawning act in one of the main spawning grounds in Europe (Garonne River, Southwest France). Shad spawning act consists of at least one male and one female swimming side by side, trashing the water surface with their tail which, therefore, produces a splashing noise audible from the river bank. The catfish hunting behavior on shad spawning act was studied, at night, during spring months, using both auditory and video survey. Simultaneously, catfish individuals were fishing to analyze their stomach content. Catfish disturbed 12% of the 1024 nocturnal spawning acts we heard, and this proportion increased to 37% among the 129 spawning acts when estimated with low-light camera recording. Stomach content analyses on 251 large catfish individuals (body length> 128 cm) caught in the same river stretch revealed shad represented 88.5% of identified prey items in catfish diet. This work demonstrates that European catfish predation must be considered as a significant factor of mortality of allis shad. In a context of the extension of the European catfish range area in western and southern European freshwaters, this new trophic impact, with other ones previously described for salmon or lamprey, has to be considered in European conservation plans of anadromous species.
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Fig. 2 Nocturnal scene of one allis shad spawning act (S), showing four European catfish individuals (#1–4) and one catfish (#1) coming close to the spawning act (panels a, b and c) to attack it (panel d).
What strikes me a bit is reading that Siluris glanis is not native, without stating where.
Further down it looks like the where is the Garonne River, Southwest France - but as far as I know, the catfish is native in whole Europe. Perhaps the British island excluded.
Pretty sure not native in Ireland, all of Scandanavia etc. too? Is it not Danube or Rhine basin it's origin range? Might not be mind you, it's maybe an introduction into Europe from further east, don't know. Pretty destructive alien I would have thought, I remember our local pond (Inverleith Pond, Edinburgh) being drained and a single monster being pulled from the mud.
In the text of the paper the native distribution of S. glanis is given as below (based on a referenced paper from 2009). It has, of course, been widely introduced elsewhere:
"The species is native from Eastern Europe. Its native distribution extends from Germany eastward through to Poland, up to Southern Sweden, and down to Southern Turkey and Northern Iran through the Baltic States to Russia and to the Aral Sea of Kazakhstan and Uzbekistan..."
As it is a native species in The Netherlands, and protected, I am not allowed to keep them. (not that I intended to do so). But the Netherlands is west of Germany, and thus not on this list.
Thanks for your inputs on the Netherlands population situation with S. glanis. The distribution patterns of catfishes, especially around the broader population edges (whether natural or human influenced), is an interesting topic. Various known, and theoretical concepts, with S. glanis populations in the Netherlands (I took a dive into a number of published works) have made for some interesting general reading. I don't "have a dog in that show", but do just enjoy reading various catfishes topics. Thanks for the stimulation... and oh yes, thanks to Eric also for initially posting reference to the paper.
