by Erin Tracy
This post is the tenth in a year-long series celebrating the 40th anniversary of the Endangered Species Act. Read the previous post here.
Coho salmon spawning season is almost upon us again, so if you want to see one of California’s most spectacular endangered fish in action, late November and December are the times to do it.
Starting in the late fall, coho begin their long journey from their two-year homes in the ocean back to the river of their birth. This is an incredibly strenuous and at times dangerous journey that every coho embarks on with the hopes of successfully reproducing, even though they meet an untimely end within a few weeks of spawning. Sense of smell is the key factor in the salmons’ travels from their distant ocean homes to their natal river. Salmon have a keener sense of smell than dogs, and in combination with ocean currents and the gravitational pull of the moon, they are able to make their way back to the river of their origin to start the whole process over again.
Spawning season is brought on by heavy rains that open up the waterways by breaching sand bars and providing the right amount of water depth and flow for the salmon to swim upstream. Once female salmon have made it upstream, they begin to build nests (called redds) near the heads of riffles where the water just begins to flow rapidly. This water flow allows for plenty of dissolved oxygen to reach the eggs and aids in growth.
To create these impressive nests the female fish must flip her body up and down to dig out a gravel pit and lay her eggs inside. Female coho can lay up to 2,600 eggs and, depending on the size of the fish, these pits can stretch the width of the stream. Once the eggs are deposited into the redd, one or two males will fertilize them, and then the female will immediately cover the eggs with gravel. She will protect this redd for as long as she can until she dies.
Although Lagunitas Creek supports one of the largest and most stable coho populations south of Mendocino County’s Noyo River, coho are found in fewer than half of the streams they once inhabited. Since coho numbers are still low enough to land them on the endangered species list, it is vital that we do everything we can during spawning season to ensure the health of the species. Here are a few simple things you can do during spawning season to help:
- Don’t go fishing! Fishing is prohibited in Lagunitas Creek. (You can, however, fish in MMWD’s reservoirs. Call 415-945-1194 for current information.)
- Cross streams only at established crossings.
- Keep pets out of the creek.
- Don’t remove woody materials from stream channels.
- When observing salmon, minimize noise and avoid sudden movements so that the fish may spawn undisturbed.
If you want to see these fish in action, go two to three days after a heavy rainstorm to MMWD’s Leo T. Cronin Fish Viewing Area in West Marin (find directions on our website).