I have been doing a lot of work on the East Alcove since putting lots of woody debris into the Alcove in January.
After the Coho fry emerged from the gravel in March they were quickly swept downstream into the man made alcoves. This is by design, to give the fry refuge from the violent water flows to do the large storm drain catchment area.
I have spotted many fry in both alcoves, the West one is particularly dense. I would esitmate anywhere from 1,000 - 2,000 fry take refuge in this alcove.
The East, an area just as large, on the other hand has only 100 - 250 by my estimates - Here's why.
Unlike the largely fence protected West Alcove, the East Alcove has no fencing and so it is an all access dog swimming pool.
There are many issues heavy dog traffic contributes to:
During the spring months there was little evidence of the dog traffic being a major issue. Largely due to the fact that it was so cold that not many dogs took the opportunity to take a swim, and that rains filled & flushed the alcoves on a consistent basis.
However, as the weather became warmer the dog pressure became a significant issue as the stirred silt stays suspended for long periods of time - several hours on end.
Upon close viewing one can see the Coho fry going through a process in which they flare their gills in an attempt to clear them of the silt. A process called gill extrication, or when the fry are forced to clean their gills in an attempt to breathe. My fear is many fry are simply suffocating to death, and if holding on are under major stress likely causing stunted growth. As the water recedes further and the temperature rises it is likely more fish will succumb to stress & suffocation.
Here is a photo from mid Spring when the water was actually somewhat translucent. Was even able to get a half decent photo with a Coho fry at the top of the water.