Good story from Environmental Monitor.
Recent research led by California Sea Grant Extension Specialist Mariska Obedzinski reveals that even small amounts of running water in coastal California streams can mean survival instead of death for juvenile coho salmon. In fact, less than a gallon per second allows the young salmon to persevere through the heat and aridity of summer by keeping pools interconnected.
A gallon per second may sound like a lot of water, but in the context of a stream or river, it’s negligible: “It is approximately 2.5 average garden hoses (all the way on) running through the stream channel,” clarifies Dr. Obedzinski.
The peaks and valleys of saving Russian River coho salmon
Since 1996, when Russian River coho salmon were listed as threatened, various conservation plans for the species have been tried—mostly without much success. By the early 2000s the species was in more serious trouble, and by 2005, they were endangered. That year, scientists monitoring the population observed fewer than 10 of the fish returning to the annual spawning grounds in the Russian River.
To rescue the species from the brink of extinction, federal, state, and local agencies collaborated on a conservation hatchery program. The aim of the program was to breed healthy fish and release them to hospitable locations to maximize their chances of survival. California Sea Grant established a monitoring program as part of the hatchery plan to track fish released from the hatchery and study which factors were hampering the recovery of the coho. They focused on four coastal watersheds: Dutch Bill, Green Valley, Mill and Grape creeks.
“They were chosen by the Coho Water Resources Partnership, a collaborative group funded by National Fish and Wildlife Foundation to address the low-flow bottleneck for Russian River coho salmon, because they are critical for the recovery of coho salmon in the Russian River, yet are flow-impaired,” details Dr. Obedzinski.
“The environmental data we collected included continuous streamflow and temperature, wetted volume, days of pool disconnection, and dissolved oxygen,” states Dr. Obedzinski. “For streamflow, we collected stage data using a pressure transducer and periodic discharge measurements using a USGS Price Pygmy Current meter. These two datasets were used to generate rating curves for estimates of continuous streamflow.”
The team also collected stream temperature data by deploying a continuous temperature logger in each of the studies reaches. In the early morning hours of each survey, the researchers collected dissolved oxygen data from each pool using a handheld DO logger. They also took measurements of length, average width, and average depth to estimate pool volume for each habitat unit.
The researchers also estimated survival, using tracking technology and models.
“We used an individual-based mark-recapture approach using passive integrative transponder (PIT) tags (the same microchips that are used to track pets),” Dr. Obedzinski describes. “We inserted PIT tags into individual coho salmon, and then we tracked them in the stream over the summer using a portable PIT tag detection wand that we could wave through the water. For survival estimation, we used the robust design in Program MARK which allowed us to include environmental factors as covariates and test their relative influence on survival.”
The monitoring team discovered that low streamflow during summer’s dog days is among the greatest barriers to coho recovery. Once hatchery fish are released, they, naturally, migrate to the ocean. The dried out waterways prevent their return for spawning as adults.
“When working at such low streamflows, measuring discharge accurately was extremely challenging,” remarks Dr. Obedzinski. “Identifying whether pools were connected or not was a useful alternative metric to streamflow that turned out to be even more important for fish survival than absolute streamflow. To document the time of disconnection in a given riffle/pool complex, we found game cameras aimed at the riffle/pool complexes to be very useful.”
Band-aid solutions and long-term change
Because low water levels threaten the survival of the fish, relocating fish to areas with more water is one of the strategies that the experts running the hatchery employ. It’s a time- and effort-intensive process but has been essential to keeping the species out of greater danger.
Retrieved August 27, 2018 from https://www.fondriest.com/news/small-amounts-of-water-enable-juvenile-salmon-to-survive.htm