Fish Behaviour

quickcedo · Feb 3, 2010

Hi everyone, as some of you will be aware by now I live on a boat so every night i let my old dog out for a pee (not on the towpath!!) I take a torch and of course shine it on the water. On most nights I see small fish on or near the surface, some nights this can be a few and some many hundreds. The question is why? It doesn't make any sence to me as they must be perfectly silhouetted against the night sky, and indeed I quite often see Perch hitting them from below. This happens in all temperatures summer and winter. Whilst I appreciate any answer can only be speculative but the answer could have implications on how I night fish.

Rickrod · Feb 3, 2010

Years ago i use to work on a nightshift right next to a canal and you would see the same thing small fish just laying there just under the surface...no idea why but it would be nice to know

jcp01 · Feb 3, 2010

Is this happening right now Mark? At night in winter?

I have witnessed this behaviour only during the daylight hours of summer, many hundreds of small fish gathering in the top six inches, but the fish seem to disappear come the first sign of cooler weather.

Rodney Wrestt · Feb 3, 2010

Is it only small fish? I was thinking along the lines of the moons cycle?

Mark Wintle · Feb 3, 2010

The plankton come up to the surface at night and the small fish follow them to feed on the plankton.

quickcedo · Feb 3, 2010

This happens throughout the year and the fish don't appear to be feeding although I could be wrong. Some appear to be asleep as they startle quite badly with the torchlight whereas others appear indifferent to it. The behavior defies logic as they are so vunerable. I hear fish most nights and not taken much notice, however it appears the fish I hear are these small fish being predated on. The small fish are a mixture of Roach, Dace and Bleak as far as I can tell.

robhale · Feb 10, 2010

Interesting - they may be hunting for nymphs rising to the surface to hatch as do the plankton and other invertebrates.

Remember also that although you may think they would be perfectly silhouetted - by contrast - they will be much less visible than during the day.

If in the warmer months, they may move to the surface to take advantage of higher dissolved oxygen (DO) levels, weed and other plant life will compete for oxygen at night.

Lastly, it could be connected with the lunar cycles if this occurs at particular times in the cycle.

Hope this helps

Rob

Fish Behaviour

quickcedo

Well-known member

Rickrod

Well-known member

jcp01

Well-known member

Rodney Wrestt

Well-known member

Mark Wintle

Well-known member

quickcedo

Well-known member

robhale

Well-known member