PIERRE, S.D. -- Biologists with the South Dakota Department of Game, Fish and Parks are investigating how changes in hatchery rearing techniques might improve the survival of salmon stocked into Lake Oahe, and they need the help of salmon anglers.

According to Fisheries Biologist Robert Hanten of Pierre, thousands of specially-tagged Chinook salmon have been stocked in Lake Oahe over the past three years. A small coded-wire tag, only a millimeter long and the diameter of human hair, was implanted in these fish. Although invisible to the angler, tagged fish can be identified by the absence of a tiny fin on their back.

"Untagged salmon have a small fleshy-lobed fin directly in front of their tail, but this fin is removed as part of the tagging process" Hanten said. "If anglers catch a salmon missing the adipose fin, we would like anglers to turn in the head of that salmon at a local bait shop, along with information on the fishes length, weight and the date it was caught."

The tags distinguish groups of salmon that were raised differently at McNenny State Fish Hatchery in Spearfish. "These differences could be as subtle as giving the salmon more room during rearing (growing fewer fish in the same amount of water), ‘exercising’ some fish more than others or providing one group of salmon with overhead cover compared to another group reared in the usual uncovered tanks," said McNenny State Fish Hatchery Biologist Mike Barnes of Spearfish. "We have seen indications that the number of salmon surviving to spawning size can be dramatically increased by giving them more space, and we just stocked tagged salmon this spring, some of which were grown in tanks with artificial hiding cover."

Salmon stockings were reduced in the late 1990s and suspended in 2001 and 2002 during a time when prey abundance was low and predator numbers were high. As the prey base, primarily rainbow smelt, began to recover, reduced salmon stockings were reinitiated in 2003. Salmon have been stocked every year since 2003. "We are stocking approximately one-half of the number and pounds of salmon we used to stock in the 1990s," Hanten noted. "Until the Lake Oahe water levels increase and the volume of cold water habitat increases, reduced salmon stockings will continue to maintain a fishery and provide an egg source for future years."

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