Saving salmonids: some technical fixes
March 19, 2009 § 1 Comment
Continuing on my earlier post from the Salmonid Restoration Federation‘s annual conference, I wanted to share progress and research on preserving and restoring steelhead and salmon runs along the California coast. Not surprisingly, most of the people & projects are from the Central Coast up to the North Coast, with scarce representation from Southern California. After all, we’ve pretty much extirpated (pushed out) most of our steelhead populations in the South Coast, and restoration is often a more difficult and less frequent undertaking.
One thing that is true in both So. Cal. and on up the coast, is that dams are a significant factor in the onset of the collapse of salmon and steelhead fisheries. (The list of issues for So Cal steelhead is a bit longer)
So while some folks work on dam removal (a largely political activity that gets us into water policy), others focus on technical fixes to get fish around the big barriers in the meantime. If you are an avid fisherperson or environmentalist, none of this is news to you. But for the rest of us, here’s a little info on these fixes. Some of these projects have also been done in the Santa Monica Mountains (topic for future posts, methinks).
Fish ladders. Under natural conditions, fish swim upstream by jumping from pool to pool. Adult and juvenile fish have different abilities to breach certain heights, and they also need eddies and places to rest, hang out, and even hide from predators. Dams – even small check dams – are often too high for fish to breach, so fish ladders are structures built to help fish gradually surmount them. The effectiveness of fish ladders vary, and there were a few skeptical eye-squinches by some of the participants as we toured some. I was mostly fascinated by how industrial they looked.
Dam notching. Small dams may be passable for salmon if a low-flow notch is carved out of the top. We were treated to a visit to one by fisheries biologist Matt Stoecker. The dam in question was for mostly recreational use, and the solution enabled the recreational activity to remain.
Culvert barrier removals and in-channel fish passage. If only we thought like fish. Humans don’t often notice that culverts at road crossings carve out deep pools below them, get choked with debris, and often have no internal stream channel – things that make it hard for fish to move on upstream. This is a particular problem in dry Southern California where the lower reaches of a stream may dry up – trapped endangered fish die every year because of this. Mauricio Gomez of South Coast Habitat Restoration showed us great examples of barrier removals, installing bridges where Arizona Crossings used to block fish on Carpinteria Creek (a SoCal project!). Outside of Santa Cruz, we also saw projects that created step-pools leading up to and through culverts so that the fish could continue up to safe waters upstream.
Off channel fish passage. As an alternative to fish ladders, fish-folk are experimenting with creating artificial side-streams that send low flows around the dam. These mimic more natural stream channel forms, making the journey upstream more desirable for the fish.
These fixes are helping localized steelhead and salmon populations to survive and rebound, but more is needed to ensure longevity of these species. With all the roads and dams crossing our coastal streams, these kinds of projects could easily consume a fair chunk of stimulus funding alone, yet these endangered fish deserve a concerted effort of that scale.
Coming soon: an attempt to make sense of a painful water policy discussion. (really a merging of several painful water policy discussions)