12-05-2010, 06:31 AM
They pass the dams the same way the juveniles do. As I understand it there are 4 ways to get past a typical Snake/Columbia river dam. They can go through the lock if it opens (but I've heard it's pretty rare for them to go that way), they can go through the turbines, over the spillway which is probably the best way, or through the juvenile fish bypass. I think you're describing the juvenile fish bypass. We sampled the majority of our fish this spring at the Lower Granite juvenile fish bypass, so I'm very familiar with that one, but I haven't seen the ones at other dams, though I assume they're similar.
Here's how the one at Granite works: There is a screen covering at least part of the opening that leads to the turbine. This screen stops the fish from going down that way and instead directs them up inside the dam where there is an opening to a pipe. (I believe there are lights on the opening to attract the fish but don't quote me on that one). The pipe leads the fish down to the juvenile fish facility, which is probably a quarter of a mile or so downstream from the dam. they have PIT-tag readers in several different locations throughout this facility to detect passing fish. When the fish first come down from the dam, they are passed over a grate that lets the juveniles pass through, but bigger things like sticks, or kelts, or the occasional pre-spawn fish that got
and went the wrong way, can't pass through and can be returned to the river (by another pipe) or diverted for research etc. the juveniles go to raceways where they're held until they're barged or trucked or whatever. they don't barge kelts, although we did barge and truck some this year, but that's not normal.
Check out this website, they explain it much better than I can:
http://www.ptagis.org/ptagis/Interpretiv...etive.html
The whole thing is interesting, but the juvenile fish bypass is explained with pictures if you click on the little circle at the bottom labeled "juvenile fish passage"
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Here's how the one at Granite works: There is a screen covering at least part of the opening that leads to the turbine. This screen stops the fish from going down that way and instead directs them up inside the dam where there is an opening to a pipe. (I believe there are lights on the opening to attract the fish but don't quote me on that one). The pipe leads the fish down to the juvenile fish facility, which is probably a quarter of a mile or so downstream from the dam. they have PIT-tag readers in several different locations throughout this facility to detect passing fish. When the fish first come down from the dam, they are passed over a grate that lets the juveniles pass through, but bigger things like sticks, or kelts, or the occasional pre-spawn fish that got
and went the wrong way, can't pass through and can be returned to the river (by another pipe) or diverted for research etc. the juveniles go to raceways where they're held until they're barged or trucked or whatever. they don't barge kelts, although we did barge and truck some this year, but that's not normal. Check out this website, they explain it much better than I can:
http://www.ptagis.org/ptagis/Interpretiv...etive.html
The whole thing is interesting, but the juvenile fish bypass is explained with pictures if you click on the little circle at the bottom labeled "juvenile fish passage"
[signature]