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Five reasons sonar is super cool

(Above: Upstream from the future sonar site on the South Fork of the John Day)
When trying to manage steelhead, one difficult task is getting an accurate picture of population size in any given year and over time. Traditional methods of estimating the number of adult steelhead that return to a river, such as counting redds (nests) are not reliable because of poor water clarity, high water, lack of manpower and the fact that redd counts don’t provide critical information about the number of males versus females, which is important to accurately estimate the number of adult fish.
As believers in good science, the Wild Steelhead Initiative and some great partners 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 salmon in Alaska, but only recently has it been used in the lower-48. Where used it has been very successful in generating accurate run size estimates and quantifying uncertainty.
1. Good numbers count: Accurate run size estimates are fundamental to management. Decisions about the status of populations, habitat, and their fisheries are largely, 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 regulate fisheries and hatcheries. Poor or inaccurate estimates of run size can be a big problem, particularly when they overestimate run size and too many steelhead are allowed to be killed in fisheries.
2. Clear picture: When water clarity is poor, sonar still gets the job done.
3. Less labor: Fish management budgets are thin and manpower very limited. Sonar collects needed data without the need for ground surveys and does so throughout the year, which is important because steelhead typically enter rivers over a span of many months..
4. Counts males and females: Redds counts only provide an estimate for the number of females. But there can be large imbalances between the number of males and females. Also, a female can dig more than one redd, so the number of redds may not accurately reveal the number of females. Steelhead digs only one redd.
5. Proven accuracy: Sonar has been used with great success in places such as the Elwha River, successfully estimating run sizes for both species with a high level of certainty for the past four years.