For pollock surveys in Alaska, things are looking upTo help estimate fish populations, scientists experiment with seafloor-mounted sonar systems that monitor fish in the water column above

摘要

Shelikof Strait, in the Gulf of Alaska, is an important spawning area for walleye pollock, the target of the largest - and one of the most valuable - fisheries in the nation. This year, a team of NOAA Fisheries scientists went there to turn their usual view of the fishery upside-down.Scientists have been conducting fish surveys in the Shelikof Strait for decades. They do that in part by riding around in a ship and using sonar systems - basically, fancy fish finders - to see what's beneath them. But in February of this year, scientists moored three sonar devices to the seafloor and pointed them up toward the surface. The devices have been recording the passage of fish above them ever since.