Mendocino Coho Salmon Conservation RearingEffort
Background General Info: Central California Coast cohosalmon are both a federally and state-protected species. They were listed as threatenedunder the federal Endangered Species Act in 1996, and subsequently reclassified as anendangered species in 2005. The California Fish and Game Commission designated coho salmonfrom San Francisco to Monterey as endangered under the California Endangered Species Act in1995, and subsequently in 2002 designated coho salmon from Punta Gorda to San Francisco asendangered. A State coho salmon Recovery Strategy was adopted by the California Fish andGame Commission in 2004. The Federal Recovery Plan was released in 2012, and in 2015 NOAAFisheries included coho salmon in their
__________________________
Federal and stateagencies, along with landowners and non-governmental organizations, are taking extraordinarymeasures on the south coast of Mendocino County to save a critically endangered species.Members from the U.S. Army Corps of Engineers (USACE), the National Oceanic and AtmosphericAdministration (NOAA) Fisheries, California Department of Fish and Wildlife (CDFW), NorthCoast Regional Water Quality Control Board, The Nature Conservancy, The Conservation Fund,and Mendocino Redwood Company are banding together to conduct conservation rearing effortsfor endangered Central California Coast coho salmon.
This winter,adult coho salmon were returned to the streams where The Conservation Fund, The NatureConservancy, Mendocino Redwood Company, and agency partners have made big investments insalmon habitat restoration in the last decade. Fish were released in small groups withgenetically suitable partners―in time for them to do what they would naturally do at thistime of year―swim upriver and mate. Since the release, scientists have been thrilled toobserve the released coho salmon mating with each other and with returning salmon from theocean.
“The numbers of Garcia and Navarro River adult coho salmon returningto spawn in four of the last ten years have been below the threshold of fish necessary tomaintain a viable population,” said CDFW’s Allan Renger, “and this conservation rearingpilot project relies on fish population monitoring to make informed decisions on when, how,and where to act.”
To keep these salmon populations from becoming locally extinct,actions were taken to capture a small number of juvenile coho salmon from the Garcia andNavarro Rivers. Starting annually in 2018, approximately 200 juvenile coho salmon wereremoved from the two rivers and carried out of the woods in backpacks full of cold water.They were then transported three hours away to Warm Springs Hatchery in Geyserville, SonomaCounty.
“The diversity ofpartners involved in this effort―state and federal agencies, environmental non-profits, andtimberland owners―reflects the seriousness of the situation,” said Jonathan Warmerdam, withthe North Coast Regional Water Quality Control Board. “We simply can’t allow these salmon todisappear as they did in the Gualala in 2004. This is really an ‘all-hands-on-deck’ effortto maintain and then recover these salmon.” Salmon are a keystone species and represent thehealth of an ecosystem.
Researchers believe one of the reasons salmon populations are notresponding to habitat improvements and availability is due to the ecological and geneticeffects caused by severely depressed population numbers over the last decade.
Thesituation for these fish was exacerbated during California’s severe drought in 2014 and2015. During these years the river flows in Southern Mendocino County and elsewhere were solow that access for coho salmon to migrate upstream to spawn was extremely limited. Thisdrove their already historically low numbers to even more dangerous levels, hinderingsuccessful spawning.
Coho salmon in streams and rivers along California’s central coasthave been falling below critical threshold biologists call “population depensation.” Thisresults when there are so few salmon returning to a stream that they are unable to find amate, causing their numbers to decline until extinction. And if a male and female do crosspaths to spawn, they may be closely related, causing inbreeding. Such pairing can result infewer offspring and genetic defects which can weaken the overall population.
“We know what theapproximate depensation number for each watershed is based on its potential habitat size,”said Bob Coey, North Coast Branch Chief with NOAA Fisheries West Coast Region in Santa Rosa.“For example, the threshold in the Garcia River is about 75 returning adults and about 200in the Navarro. Unfortunately, numbers of returning adult coho salmon have fallen below thisthreshold in several of the last eight years, perpetuating and accelerating the downwardspiraling abundance towards local extinction. It became clear that 2018 was the right timeto act.”
This approach will supplement coho salmon populations in the Garciaand Navarro Rivers, minimizing further erosion of genetic variability for the species, andhopefully boost population numbers.
“Hopefully this will be the final step in a years-long process toimprove habitat through sediment reduction projects in the Garcia River watershed,” saidScott Kelly, North Coast Timberland Manager with The Conservation Fund. “This years-longeffort has improved the roads and forest infrastructure of our Garcia River Forest, directlyenhancing instream habitat by adding large wood for cover and to sort and restore spawninggravels in our streams.”
This conservation rearing effort closely mirrors the actions taken in2001 to help revive coho salmon in the Russian River watershed, in Sonoma County, when theirnumbers had declined to less than a dozen returning adults. A conservation rearing programthere used a similar breeding matrix to ensure the greatest genetic variability for theiroffspring. As a result of this conservation-based breeding program at Warm Springs Hatchery,and continuing efforts to improve fish habitat, during the winter of 2017-2018 the programhad its best year of returns to date and upwards of 700 adults returned tospawn.
