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Big brookies live in the depths of Deerfield Lake

Two of the biggest brook trout ever caught in the United States were caught at the Black Hills’ own Deerfield Reservoir last winter, according to at least one Web site.

Rapid City resident Ryan Rempfer caught a whopping state record 11-pound, 2-ounce brook trout Dec. 30, 2006. Rempfer’s fish was also the biggest brook trout to be pulled out of the ice on a fishing pole, as he broke the previous Freshwater Fishing Hall of Fame record.
His feat was nearly matched by a 10.15-ounce fish caught about a month later by Corey Dillavou of Rapid City. Dillavou caught his fish Jan. 24, 2007.

The Web site www.landbigfish.com lists Rempfer’s brook trout as the largest ever caught in the United States.
Second on the list is a 10-pound, 1-ounce brook trout caught in Wisconsin, which Dillavou’s fish eclipses by one-half ounce.
Rempfer’s fish took out the previous record 9-pound, 3-ounce brook trout caught at Deerfield in 2004. In addition, every state record brook trout in South Dakota history except for one has come out of Deerfield.

“It’s pretty phenomenal,” South Dakota Department of Game, Fish & Parks fisheries biologist Gene Galinat said. “The state record was broke in 2004 with a 9-pound brook trout and then this year, we had an 11-pound and a 10-pound come out. So there are definitely some big ones in there.”

Galinat said he isn’t sure why brook trout, which fishermen usually catch at an average size of 6 inches to 9 inches, are growing to such massive proportions in the central Black Hills lake.

Unkenholz said he was pretty surprised at the size of the two brook trout, as was fisheries biologist Greg Simpson. Calling the catches “remarkable,” Simpson said he thinks lack of predation may be enabling the fish to become larger.

The size and depth of the lake are also contributing factors, Galinat added, as is the fish’s switch from insects to a fish diet.
“It’s a cold lake and it’s got some deep recesses for these fish to take some refuge,” he said. They’re probably pretty old fish so they’ve been in the system for a while and they were able to make it.”

Galinat said brook trout are naturally occurring in Deerfield, because the GF&P hasn’t stocked any in the reservoir since 1983. The fish are probably coming from upstream Castle Creek, he said.