If you’re trying to manage steelhead, one of the more difficult tasks you will have is getting an accurate picture of what populations are doing over a given time.
Unlike many of their brethren, steelhead don’t put all their “eggs in one basket.” Runs are timed throughout the year, often during times of high water and poor visibility. This make more traditional methods of measurement, such as redd counts, problematic.
However, through the use of modern technology, scientists are finding ways to get better data. Being big believers in good science, the Wild Steelhead Initiative and a handful of great partners have launched a series of monitoring projects using sonar technology. The first long-term monitoring stations are in progress in the Hoh and John Day rivers and more are expected to come online in the years to come.
Sonar has been used for many years to estimate run sizes for sockeye salmon in Alaska, but only recently has it been used in the lower-48. Where used it has been very successful in generating run size estimates and quantifying uncertainty by providing narrow confidence bounds around the estimate, something that is very difficult with redd counts.
So why is sonar the way to go?
Good numbers count: Accurate estimates of run size are fundamental to managing steelhead. Decisions about the status of populations, their habitat, and their fisheries are largely, if not wholly in some situations, based on the annual run size of steelhead in a given river. In short, biologists need solid estimates of run size to make informed decisions about how to best manage the fish and their fisheries. Poor or inaccurate estimates of run size may not only misinform managers about the status of steelhead populations but they may also contribute to declines and hinder recovery efforts.
Sonar excels: When water clarity is poor, sonar still gets the job done
It requires less labor: This is an important point as budgets for wildlife agencies are thin and managers are spread across several large watersheds. While redd counts may be efficient for salmon species that spawn over a one to three month period, funding and labor limitations within agencies make it more difficult to enumerate steelhead because they may spawn over an eight month period.
Redd counts have a high level of uncertainty: Redds only provide an estimate for the number of females. But sex ratios are not necessarily 50:50 and can vary widely in a given year. Nor can we assume each female steelhead digs only one redd.
Good precedent: Sonar has been used with great success on places such as the Elwha, successfully estimating run sizes for both species with a high level of certainty for the past four years.
Better science means better management: Plain and simple. It is very difficult to evaluate whether current management strategies and habitat restoration actions are working without good data.