Eric A. Laux wrote:
>
> I did my graduate work on fish and egg survival after passing through hydro
> power turbines.  We would collect eggs in the tailrace and try and incubate
> them in floating, flow thru chambers.  I noted that we had some egg survival
> in early parts of the year, prior to excessive periphyton growing on the
> chambers, but in the heat of the summer, when periphyton levels were high, we had no survival of eggs.  I had pondered the idea that periphyton may be the cause, but found nothing pertinent in the literature.

It may be worthy of note that a number of bottom egg laying fishes,
including cyprinids, scour the bottom or build fresh nests of pebbles,
before laying their eggs.  Perhaps this avoids problems with periphyton
- night-time oxygen consumption, dampening of water flow over the eggs
reducing oxygen supply, or even possible toxic effects from the algae.

don


--
Don E. McAllister             /& Canadian Centre for Biodiversity
Ocean Voice International          /Canadian Museum of Nature
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