Surveys show stark contrast in fish populations

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Surveys show stark contrast in fish populations

6/30/08

No two northern Indiana natural lakes are the same - and the results of two recent fish surveys conducted by the DNR Division of Fish and Wildlife show just how different they can be.

While sampling at Skinner Lake in Noble County in late June, biologist Jed Pearson captured 787 bluegills in only 45 minutes with his electro-fishing (shocker) boat.

That number translates to 262 bluegills per 15 minutes, or three times the average number of bluegills collected during a typical survey at most lakes in the area.

In contrast, biologist Neil Ledet, during the same time, caught only 63 bluegills in one hour of electro-fishing at Big Long Lake in LaGrange County. Ledet's catch rate of only 16 bluegills per 15 minutes was less than one-fourth the normal catch rate.

"Based on these numbers, the density of bluegills in Skinner Lake is 16 times greater than the density of bluegills in Big Long Lake," Pearson said. "That's quite a stark difference."

But the two lakes also differ in bluegill size.

"Of the 63 bluegills we caught at Big Long Lake, 35 percent were over 8 inches long," Ledet said. "Although bluegill numbers are low, they are certainly quality-size."

According to Ledet, bluegill anglers consider Big Long Lake to be one of the better fishing lakes in his area, despite their overall scarcity in numbers.

"What Big Long Lake lacks in number it makes up in size," Ledet said.

Not so at Skinner Lake. Although 787 bluegills were sampled there, only three bluegills were larger than 7 inches and none were 8 inches long.

"Ninety-two percent of the bluegills we caught at Skinner Lake were 5 and 6 inches long," Pearson said. "The biggest one was only 7.2 inches long. What Skinner Lake has in number it lacks in size."

A lot of area anglers, according to Pearson, do not fish at Skinner Lake because the bluegills are too small.

So why is there such a marked difference in bluegill populations between the two lakes? Neither Pearson nor Ledet knows for sure, but the number and size of largemouth bass may be the key.

Ledet captured bass at a rate of 87 per 15 minutes of sampling at Big Long Lake. Most of them, however, were only 8 to 11 inches long.

"Although bass were everywhere we sampled, we could hardly find any legal-size (14-inch) bass," he said.

Pearson, meanwhile, had trouble catching bass and caught only 14 bass per 15 minutes at Skinner Lake. The largest was 18 inches but 15 percent were of legal size.

That's a six-fold difference in bass catch rate between the two lakes and a significant difference in bass size. These differences might explain why their bluegill populations vary so much.

Bass typically eat bluegills. Where bass are abundant, they help keep bluegill populations in balance by thinning out small bluegills. If bass are scarce, too many bluegills survive and out-strip their food supply.

Ledet said he thinks the high number of small bass in Big Long Lake is keeping its bluegill population in check. This allows bluegills to grow rapidly. In contrast, Pearson thinks not enough bass are present in Skinner Lake to reduce its high number of bluegills. This prevents its bluegills from growing bigger. Ironically, both lakes have a 14-inch minimum size limit on bass.

Meanwhile, bass anglers have a different opinion of both lakes.

"If you're a bluegill fisherman, you're going to want to go to Big Long Lake," Ledet said.

"But if you're a bass fisherman who wants to catch a large bass, you might want to try Skinner Lake instead," Pearson said.

Both biologists will summarize the full results of their surveys later this year and use the information to consider options for future management at each lake.

"We want to maintain good bluegill fishing at Big Long Lake," Ledet said.

Pearson said he wants to find a way to improve bluegill fishing at Skinner Lake.

Media Contact:
Jed Pearson (260) 244-6805; Neil Ledet (260) 829-6241; Marty Benson, public information officer (317) 233-3853, cell (317) 696-9812
 

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