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Staff Accomplishments

Fluorescent fish help researchers test the fish friendliness of dam passage routes

June 2005
Researchers at Pacific Northwest National Laboratory have come up with a novel way to evaluate the health of young salmon that pass through hydroelectric dams on their downstream journey. They dunk the fish into a nontoxic dye that glows under a special light to expose the not-so-obvious injuries like scrapes and cuts migrating fish may receive. The new dye detection method developed by PNNL has shown exceptional promise as a more sensitive and objective measure of external fish injury than the unaided eye. That's good news for the fisheries biologists who are collecting fish injury data to help design more fish friendly passage routes and hydroelectric turbines. And it's good news for the several million juvenile salmon that migrate each year through the federal and privately owned dams on the Snake and Columbia rivers and their tributaries enroute to the Pacific Ocean. By using the PNNL dye technique in conjunction with laboratory tests and field tests, biologists can measure and quantify the injuries likely from the different routes that salmon can use to get from one side of the dam to the other. "The increased sensitivity may enable us to do more specific and more accurate testing using fewer test fish," said PNNL researcher Russell Moursund. Fisheries biologists studying the dams can tell quite a bit about passage conditions from the injuries they see on fish coming out of the dams, in terms likely to make you hungry for sushi or somewhat nauseous depending on your sensitivities. Chopped heads, sliced tails, missing eyes, and pulled gills are all obvious signs of either mechanical injuries, being struck or pinched by the blades or smacking into parts of the dam, or hydraulic forces, shear, turbulence and pressure from the moving water. Fortunately, typically over 95% of the fish survive their ride through the turbines without such severe and obvious injuries. The dye dunking technique developed by PNNL gives biologists a more sensitive, and more objective, way to measure subtle injuries like scraping and descaling. Descaling, while not immediately lethal, can hasten a fish's death by scraping off the fish's protective coating of slime and scales, increasing its susceptibility to disease and parasites. Descaling has typically been measured by holding the fish up and, with the unaided eye, trying to guess at the percent of injured surface. "The problem," said Moursund, "is scraping is not that obvious, especially on parts of the fish like the fins, eyes, head, and gills, which don't have scales. So descaling has always been a pretty subjective measure of injury that hasn't been able to tell us very much about what fish are experiencing in the dams." The PNNL dye technique, which is easy to use in the field and nontoxic for fish, can immediately reveal those injuries invisible to the naked eye. In a series of laboratory tests funded by the U.S. Department of Energy's Hydropower Program, PNNL found that at higher turbulent conditions several injuries were apparent with the dyed fish that were not visible to the unaided eye, including large amounts of scale loss and damage to the fins and head. PNNL's evaluation of the dye technique showed the amount of injury was objectively measurable, the amount of injury was proportional to the amount of exposure for both turbulent and shear tests, and injuries appeared in different parts of the fish depending on whether it was exposed to shear conditions or confined turbulent conditions. By highlighting these subtle differences in injuries, the dye can provide some of the missing clues to link those injuries to specific hydroplant operating conditions that plant operators can control. This information can help dam operators like the U.S. Army Corps of Engineers to choose safer turbine designs, passage routes, and operating conditions to further decrease the likelihood of significant injuries to higher proportions of migrating fish. For more information contact: Charlie Brandt, Resource and Ecosystem Management product line manager, or Russ Moursund, project scientist.

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