Many will remember the extra distance fish agencies went this past spring when they moved baby salmon in tanker trucks from upstream hatcheries down to the Delta and San Francisco Bay for release. This was done because drought conditions made Central Valley rivers deadly to migrating baby salmon.
It will be 2016 before we know whether it worked, but in the meantime, drought conditions persist, threatening adult salmon returning to spawn now through early fall. Salmon are encountering river temperatures in excess of 70 degrees, weakening them and the fertility of the eggs and milt they carry.
In salmon-dependent communities on the coast and along the Sacramento River and its tributaries, there’s deep concern for this parent generation of salmon. Salmon eggs incubating in river gravel die if river water temperatures exceed 56 degrees for more than three days. By October, when fall run salmon spawning usually peaks, most of the rivers and tributaries could be over 56 degrees. If we’re lucky, a small section of the far northern Sacramento River might be cool enough to support some spawning. But miles below it won’t be, meaning we could be facing the threat of no fish and no fishing in coming years.
This doesn’t have to be. There is something that can be done. The Golden Gate Salmon Association has proposed to capture adult fall run salmon, take their eggs and milt, and temporarily incubate the fertilized eggs at a hatchery. The fall run is the usually-numerous run that supports the commercial and recreational salmon fishery off California and most of Oregon. As fall turns to winter, and Central Valley rivers cool, the eggs could then be injected back into river gravel. They’d hatch out months later and live as wild salmon.
The Coleman National Fish Hatchery, located on a cold-water tributary of the Sacramento River called Battle Creek, might be a place where the work could be done prior to re-injection into the river. Coleman can reportedly handle 30 million juvenile salmon, but produces only about 12.5 million juveniles annually, which should leave room to temporarily harbor millions of drought-threatened eggs.
Egg injection back into the river could likely be done during November, when river temperatures have cooled to tolerable levels. This same action could be done on other Central Valley rivers with hatcheries, such as the Feather, American and Merced rivers.
Injection involves poking a hard plastic pipe into river gravel using water pressure from a portable pump, creating a cavity in the gravels, flushing out sediments, and then carefully pouring the fertilized eggs down the pipe into the riverbed where they’ll rest until they hatch.
Injecting fertilized salmon eggs into river gravel isn’t a new idea. It’s been done in Alaska, Oregon and elsewhere. This is probably the right year for California to join the list of states that have used this proven technology. The proposal doesn’t require more water, since there is none, but it would help save salmon jobs and keep coastal and inland river communities economically vital. That’s why GGSA is calling for this extraordinary measure to sustain salmon, which is needed in this extraordinarily dry year.
• • •