How do fish do it?

[phong]

Following an interesting week in the aftermath of Irene, an old question of mine came back up..."How do fish manage to not get washed away when streams/brooks reach insane flow levels"? School me.

Here are some pictures and videos of a local brook AFTER the water had receded a bit...

Normal summer flows:


Crazy washout roads flood stage:


Video:
http://youtu.be/LJJ6r-B3meU
(can't get embedding to work)

Stream Resident:


In case there is any question in peoples minds, VT was absolutely devastated by this storm. I have never seen anything like this in my 36 years on this earth...

[Ernest]

I don't know the answer. In the Midwest we have flood events where the driftwood is sometimes and in some places 10 feet up in the trees. When the water recedes, the fish have swum against the tide and are further upstream than before.

[mems]

How do fish do it? From my understanding they spawn. How do the survive floods? They find a current break and hold on. Mems.

[Satoshi]

I don't have a conclusive answer, but when the riverbed is wide, it seems fish take refuge in calm waters close to the shore. I have once caught many fish in such a water where it is usually grass land, when water level was very high. If the stream geology does not allow the existence of such shelters, like when a stream runs through the bottom of a deep gorge surrounded by steep rocky walls, trout seem to be washed away. In such places, there are years when there is almost no fish, while you find a lot of fish in the other years. I heard this was actually the case in a famous trout river in “Japan Alps”.
I saw your video, but I think this is not a big problem for trout. Flood like this occurs more than once every year in our mountain streams.
Our region has just been hit by a strong typhoon. The mountain area, where my homewaters lie, received 1500mm (60 inches) of rain within 72 hours. In such rain, you would feel as if you were under a waterfall. I’m afraid not many trout are left this time for the fishing in the next spring.

Satoshi