This definitely happens. I have lost 4 koi and several large orfe to this phenomenon this Spring. They clamp the gills shut so suffocate the fish or just exhaust the fish by the additional weight the fish have to carry around or damage their eyes from they clamp on there. They only seem to clamp onto large fish from what I have seen. I remove them where I can but often this happens overnight and death has occurred by the time I check the pond in the morning.
I used to love frogs and toads but I have definitely gone off them now..........
On Sunday, July 5, 2020 at 12:45:05 AM UTC+1, wrote:
Myself and at least 3 others witnessed frogs clamping round the gills of koi carp in a pond in Bournemouth. We watched for a good half hour trying to work out what was actually happening. I genuinely believe they were trying to smother the fish. Definitely happened though no matter what the reason