Hi, the fact that P. glenii eats both newts and frogs (mostly as larvae) was reported by Reshetnikov and cited in our paper. In our studies we found remnants of tadpoles in the fish stomachs. Given the most abundant anurans in the area are common toads and common frogs, the tadpoles should belong to these species.

Best greetings,

Michal

Reshetnikov (2008, J. Ichthyol.) lists tadpoles and larvae (but not the eggs) of Rana temporaria, R. arvalis, R. lessonae, Triturus cristatus, and T. vulgaris as prey.

Michal Grabowski: "Hi, the fact that P. glenii eats both newts and frogs (mostly as larvae) was reported by Reshetnikov and cited in our paper. In our studies we found remnants of tadpoles in the fish stomachs."

I was thinking about the diet of Perccottus glenii, because with the occasion of the monitoring of amphibians, carried out in the lower Danube valley, in a small pond (it had at about 30 square meters) I found a lot of adult Smooth Newts and many fish (various species) - among them being two specimens of P. glenii. Up to that occasion I never saw this exotic fish, but later we found the species in some lakes of the Danube Delta. Anyway, in the aquarium from the office the Newts were not consumed by P. glenii... but this was may be due to the fact that there were also many dozens of guppies (Lebistes reticulatus), much smaller in size (in comparison with the Newts...). So after the "disappearance" of all guppies I took out the two P. glenii from that aquarium, because I had the feeling that the next victims of these fish will be the Newts...

I think that the adult newt is too big for Perccottus. Surely it may it larvae and newlt transformed individuals.

Jon Moore: "Reshetnikov (2008, J. Ichthyol.) lists tadpoles and larvae (but not the eggs) of Rana temporaria, R. arvalis, R. lessonae, Triturus cristatus, and T. vulgaris as prey."

Well, Rana lessonae and Triturus vulgaris are present here, and instead of T. cristatus we have (a little bit bigger) T. dobrogicus, but probably larvae are the most exposed for predation.

Thank you for mentioning Reshetnikov's work! I will try to contact the author for a copy of that work.

Michal Grabowski: "I think that the adult newt is too big for Perccottus."

Well, Triturus dobrogicus can reach (even if very rarely) 17 cm length, so probably it is a little bit big for the mouth of P. glenii.

But T. vulgaris is much smaller. (I do not measured the specimens caught with various occasions, but my impression is that the Smooth Newts from the Danube delta were smaller than the ones from the other regions of the country).

I assume that those populations that are breeding in ponds (even temporary ones) which are not connected to the river or to the lakes, will not really be affected by P. glenii. Excepting the cases if someone deliberately introduce that fish into the respective ponds.

Anyway, most of the newts use as breeding sites the lakes (those from the delta are quite shallow ones) and channels. Consequently, their larvae are certainly available for P. glenii.

Well, may be it will be worthwhile to perform a comparative study (taking into account pond with and pond without connection to the other aquatic bodies) in order to assess the impact of this fish which quite recently arrived into the delta. If I am not mistaking, somewhere in 2007 (or so) was captured here the first specimen...

Jelka Crnobrnja Isailovic: "As I remember from conversation with Andrey Reshetnikov, but the best is to read his papers, only Bufo bufo tadpoles are not tasteful for rotan. He considers rotan as a serious menace ..."

Thank you!

In the meantime I downloaded some of his work related to this issue.

p.s. Well, in the Danube Delta the Common Toad is actually very rare, so the rotan has to eat something else.

Hi Zsolt, write to my e-mail [email protected] and I will send you additional articles on rotan-amphibian interactions. The best!