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Alaska Department of Fish and Game

Alaska Fisheries Sonar

Yukon (Pilot) River
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To detect fish, the Pilot Station sonar site deploys two types of sonar transducers into the river. The tranducer pictured above is a DIDSON tranducer and is being deployed off the river’s left bank. The Pilot Station sonar site consists of two counting stations located across from one another on the banks of the lower Yukon River. From the perspective of a boat floating downstream, the site’s main camp is located on the river’s right bank. The sonar site’s crew fish inriver gillnets so that sonar-detected fish can be seperated by species. Because large numbers of many species of fish migrate up the lower Yukon River, the Pilot station sonar site would not be able to produce estimates without the species information provided by the inriver gillnets. At the fish camp, natives dry and smoke strips of chum salmon and other subsistence-harvested species such as sheefish. The Yukon is Alaska’s largest river. Between the site’s two sonar-counting stations the river is 3,280 feet wide. Fish camp near the sonar site. Sonar site camp. Gillnetters release fish as quickly as possible to minimize the number of fish that die after being caught in the net. Large quantities of debris can sometimes make sonar site deployment and operations very challenging early in the season. All gillnet-captured fish are also measured and identified by species. A small tissue sample is also collected from from king and chum salmon and deposited into vials for genetic analysis. Site technicians view fish-detection data from the two types of sonar systems on computers in a variety of formats. An unofficial fish-count tally is kept in the kitchen tent in camp. During spring breakup lots of debris floats down stream, including large rafts of trees. Debris from spring breakup along the sonar site's north shore. In addition to DIDSON, the site also uses a type of sonar technology known as spilt-beam sonar. South bank sonar tent. Fish that die before they can be released from the gillnet are donated to the nearby native community of Pilot Station. An airplane arrives weekly to pick up the genetic samples so they can be analyzed in a lab. Split-beam sonar data display echos bounced off fish as fish traces. View of Yukon River upstream of and from a hill above the sonar site. When king salmon are caught gillnetters collect scale samples, which are used to determine the age of the fish.