I used to go out to a stately home in Plymouth as a consultant brought in by one of the enployees who a long time friend knows our love of koi and wanted me to maintain the health of the koi in their duck pond.
So having worked there forestry wise I thought hey why not I can go out and after checking the health of the koi take a look at all those trees we planted 15 years prior and see how they are maturing plus we got a free meal at the end of the day cooked by his long term Partner Lorriane, they with their family of three girls live in one of the trusts properties a double cottage situated by the banks of the river Plym
They koi in that pond where huge , it had ducks and ducklings on it too.
On the day in question I notice something "strange no small koi" , then all of a sudden amid loud cries from the ducks a tiny duckling just disapeared the rest hit the cobbled area where horses where once led to water.
Both Val and I where horrified until Brian my good friend pointed out anything under a certain size just didnt survive in the pond
Our curiosity peaked we asked why So without a word but in reply he stuck a large net in the water and pulled it out "yep you guessed it ", the pond was heaving with European eels all of good size OMG.
Brian pointed out that they make their way to the duck pond as elvers crawling over filds to get there then grow on up to adulthood before the all depart for the sargrasso sea by the same route.
Apparently they all head out there to mate then die leavng these tiny creatures to swim back to where their parents had come from i'e the Duck pond at Saltram House a National Trust Property ....
So my advice if you have smaller fish in your pond or ducklings on it and you value them don't try putting one of these eels into your pond
You never know that after the next migration if you'll find yourself with a pond full of eels
Dave
