Originally Posted By: Smalma
Bonaro-
As often is the case with fish issues the devil is in the details.

There is little disagreement in the literature regarding impacts from dredge type activities that eggs and the young fry before emerging from the gravel are at risk during dredging activities. While the mortality of the egg/fry will vary depending on the situation some (in some cases 100%) will die.

The rub is that here in the PNW and north Puget Sound especially with multiple species with diverse spawning times there can be eggs in the gravel for most of the year (and in some cases all year round).

Just one example would be in the Skagit basin where steelhead (and resident rainbows) spawn from early March into July. Spring Chinook begin spawning in August and September, the other races of Chinook and salmon species can be found spawning from September into March.
With the fry from the spawning steelhead still coming out of the gravel into September it should be clear that there is potential to kill fish or their eggs year-round.

The TU project you referenced in previous post was in Colorado which to my knowledge have not salmon (except kokanee in few isolated areas) so the time window for work would be much wider than some areas here in Washington. As I said the devil is in the details.

curt


Smalma, you are correct and I agree, dredging up eggs is bad for the eggs. Our Gold and Fish pamphlet is our rule book. It was crafted by WDFW with fish and habitat protection begin the main priority. We worked with then to help for common sense rules and it was a good collaboration. Our work windows are specifically designed to avoid the spawning times of fish and this is determined on a stream by stream basis. We typically are in the water after all eggs have hatched. There are many streams that have endangered bull trout or golden trout that are closed completely. Again, WDFW took the lead in determining what safe timing would be.

We are after gold and gold tends to collect in the deep rocky runs, boulder patches and low pressure areas downstream of obstructions like large boulders. The natural spanning areas tend to be the slower gravelly areas. Gold does not collect here and the gravel tends to run very deep...we don't even look here for gold.

Most mountain streams where gold is found do not support anadromous fish like salmon and steelhead.

Maybe you can explain something to me...
How can dredging be harmful to spawning fish or eggs during times when fish are not spawning and eggs are not laid....but ... during spring runoff when eggs are in the gravel, they seem to survive just fine?
The following pic shows typical spring runoff. Every particle of gravel smaller than a baseball is in motion in this river. How can eggs survive this but a dredge can kill thousands?
I truly would appreciate an explanation because I cant make sense of it.



Regarding the TU project in Colorado. Assuming there are no anadromous fish and we are only talking about trout. Does this mean running a loader up and down the river and digging in the water with an excavator have a lessor impact than a gold dredge?