Fish Marking: A Better Way To Dye

NEAH BAY (Aug. 25, 2004) – Some hatchey-reared Lake Ozette sockeye are getting a dye job to distinguish them from their wild cousins. The Makah Tribe is conducting a trial of a new way to mark fish that is less harmful than traditional fin-clipping. The method uses calcein, a harmless dye that glows under a special light.

“This could be cheaper for us and is better for the fish,” said Joe Hinton, Hoko Hatchery Manager for the Makah Tribe.

Though the antifreeze-green colored dye looks ominous, it is invisible after application and is harmless to fish and people. It’s also better for the fish than having their fins clipped.

“Fin clipping requires a lot of handling for young fish. It’s creates stress on the fish, it’s labor intensive and it’s expensive. Also, after adult fish have returned to spawn and die, decomposition can make it difficult to tell if the fish is fin-clipped or not,” said Hinton. The other advantage to using the dye is being able to mark very young fish that are too small to adipose clip.

Lake Ozette hatchery sockeye, which are reared from eggs taken from wild stock, also receive another special mark before release. By varying water temperature levels during rearing, a mark similar to growth patterns in tree rings is left on the fish’s ear bone or otolith. While the mark is helpful to identify hatchery fish after they return as adults to spawn and die, it can’t be used to count young hatchery origin fish as they leave the lake because it requires killing the fish to detect it. The dye, on the other hand, provides a non-lethal way to identify hatchery fish, which is an important management tool.

As a control measure, the fish will also be fin clipped until the dye performance in both smolts and returning adults is evaluated. Marking hatchery-produced sockeye is necessary because wild Lake Ozette are listed as threatened under the Endangered Species Act.

This summer, fisheries technicians marked 13,000 fish with the dye. The dye glows under a special light, particularly lighting up the fins of the fish because it binds to the bony structures. The dye can’t be seen without the $4,000 special light, which the Washington Department of Fish and Wildlife (WDFW) loaned to the Makah Hatchery.

“Our primary goal was to have a mark that would identify the hatchery juvenile fish when they left the lake,” said Caroline Peterschmidt, project biologist for the Makah Tribe. “If it lasts until they return to spawn as adults, we’re probably going to have to use a microscope to find the dye. But that’s fine. That would be a bonus to have it last that long and we could stop fin-clipping.”

“It’s allows non-lethal sampling, it clearly marks all the hatchery fish and it’s cheap,” said Peterschmidt. WDFW and other tribal restoration programs are also testing this marking technique.

For more information contact: Caroline Peterschmidt, project biologist, Makah Tribe, (360) 645-3175, Joe Hinton, Hoko Hatchery manager, Makah Tribe, (360) 963-2784, Debbie Preston, coastal information officer, Northwest Indian Fisheries Commission, (360) 374-5501