Southern Steelhead Trout Migration Improved by Weirs and Pools
Fish Passage Projects Are to Fish As Carpool Lanes Are to Motorists
[Click on photos to read captions.]
Imagine driving on a freeway and you come to a complete stop at a construction zone. There are no planned detours and no alternate routes. Others add to the congestion – you’re all blocked.
Now, imagine the same scenario, but you’re a fish trying to get upstream to spawn and preserve the species. Being blocked, you are now on a short road to the endangered species list.
This is what’s happening to the southern steelhead trout. This native fish has been listed as endangered in Southern California since 1997 and is a threatened species in the state’s central and northern coastline.
District 7 is planning a fish passage project at the mouth of Solstice Canyon Creek, which crosses State Route 1 (Pacific Coast Highway) at the Dan Blocker State Beach in Malibu (named after the actor who played “Hoss” in the 1960’s TV series ‘Bonanza’).
The multi-agency Southern Steelhead Restoration Project is a collective effort to increase this trout species. The joint partnership includes the National Park Service (NPS), the National Oceanic and Atmospheric Administration (NOAA), the National Marine Fisheries Service, the Department of Fish and Game, the Army Corps of Engineers, and the California Coastal Commission.
Solstice Creek is known to have historically supported southern steelhead trout. Documents show that southern steelhead were present in the creek until 1947 when Pacific Coast Highway was widened and residential and commercial development increased --- all of which contributed to blocking the trout’s habitat and migration pattern.
Planning to restore Solstice Creek and re-establish steelhead runs began in 1999 with a habitat assessment from the NOAA fisheries unit, a division of the Department of Commerce. Caltrans was contacted by the National Park Service to coordinate with other federal, state and local agencies to bring together fisheries experts and engineers to plan, design, and implement a restoration of the creek.
“Before the Endangered Species Act of 1973 and other environmental laws were enacted, people were not very focused on the importance of environmental protection,” said Ron Kosinski, Caltrans Deputy District Director, Environmental Planning. “The department is now mandated by law to restore the passage and migration of this species. We are confident that this project will work and we intend to bring the fish back to a vital habitat.”
“The design is a rock weir step pool system that will address the barriers to fish passage and lessen the impact on breeding and life cycles of the fish,” said Mansoor Khan, design manager, Caltrans Office of Design B.
For purposes of this specific project, a weir is a flow control made from natural rocks that is used to create appropriate conditions for fish migration.
“The project will remove the existing concrete lining on the stream bed and beach, in addition to removing the culvert bottom,” said Bruce Swanger, Caltrans senior hydraulics engineer from the Office of Highway Drainage Design in Sacramento. “In place of the concrete lining, a low-flow channel having step-pools and rock weirs will be built that will allow fish to rest and gather energy as they move upstream.”
The step pools and roughened channel will be backfilled with native sediment from the watershed to further mimic natural stream conditions.
“Our goal is to permanently return the species to Solstice Creek,” said Kosinski. “Modifications to this stream system will provide steelhead trout access to 1.8 miles of spawning habitat.”
Though project plans have met some obstacles, Caltrans is scheduled to move forward pending obtaining all necessary permits for the three month construction schedule.
Unlike motorists who often make several road trips daily, most species of anadromous fish (going from salt water to fresh water or up rivers to spawn) make only two significant journeys in their lives. The first is a year or two after birth, when they migrate away from their fresh water spawning grounds to the ocean where they will live for two to four years, and the second occurs when the fish return from the ocean to their spawning areas to breed or die. Steelhead trout can live up to 11 years and will migrate to and from the ocean multiple times over their lifetime and can spawn up to eight times throughout their lives.
Dan Blocker once said that he portrayed the kind, gentle-giant “Hoss” character with a Stephen Grellet excerpt in mind. Grellet, an 18th century French missionary said: "We shall pass this way on Earth but once. If there is any kindness we can show, or good act we can do, let us do it now, for we will never pass this way again."
Perhaps if Blocker were alive today to enjoy the Malibu beach that shares his name, he would hope that the trout could “pass this way again” into Solstice Creek.