goldfish moving upstream?

[keyworth63]

Twice this year I have found small goldfish in the upper tier of our pond, and cannot figure out how they got there, and am looking for some suggestions. Here are the details. The pump delivers water from the lower level of the pond into our filters at the top of our second tier, so it overflows down onto the second tier and then down a 9 inch waterfall into the lower level. The lower level is covered by a net. So 1) did the 2 inch fish manage to scale the waterfall, or 2) did it go through the skimmer and get pumped up to the higher level and somehow bypass the 3 layers of filter media, or 3) was an egg was inadvertently deposited in the upper layer by a bird who had previously picked up an egg on its body, or 4) did an egg find its way through the pump and filter media into the upper layer.
Thanks for any answers or other ideas?

 

[Lisak1]

My answer is yes. All of the above. Ha! They are wiley little devils.

 

[Dave 54]

My answer is yes. All of the above. Ha! They are wiley little devils.

I concur with Lisa on this and I've accyually whitnessed a goldfish swopping ponds in one of our former koi club members ponds whilst helping him out with a sick koi .
"They" he said where doing it all the time swimming backwards and forwards between the two

Dave .

 

[sissy]

Have had that happen every year .It still amazes me