Statement issued Tuesday:
ARCOLA – Although state fisheries biologists reduced the number of unwanted gizzard shad in Lake Everett two years ago, how successful they will be in restoring good fishing to the 43-acre Allen County natural lake remains to be seen.
Biologists from the DNR Division of Fish and Wildlife (DFW) will return to Lake Everett in June to determine the number of shad still present in the lake and assess whether fishing for popular sport fish has improved.
Throughout the last decade, the number of shad increased sharply in Lake Everett. By 2004, shad had become the dominant fish captured during routine fish population surveys. Shad composed 43 percent of the number of fish and 54 percent of the weight. By 2008, shad accounted for 63 percent of the weight of fish surveyed.
Because gizzard shad, a slender, silver-colored fish of little interest to anglers, compete for food with bluegill and other popular sport fish, overall fishing quality at Lake Everett had declined.
Biologists also speculated that gizzard shad, because of their abundance and diet of tiny zooplankton, indirectly increased the amount of algae in the lake and reduced water clarity.
To selectively reduce the number of gizzard shad in Lake Everett, 21 gallons of rotenone were applied throughout the lake in September 2008. When used in low amounts, rotenone, a natural fish toxicant, primarily kills shad.
Once adult shad were reduced at Lake Everett, the DFW restocked 4,300 largemouth bass to increase predation on any newly hatched shad that may appear in later years.
"Based on results from our sampling last year, we estimate that 90 percent of the adult shad were killed in 2008," said Jed Pearson, a DFW biologist who has monitored the lake over the past 25 years. "Although some shad survived the rotenone application, we hope that they will not rebound to nuisance levels."
Pearson also noted that water clarity at Lake Everett was better in 2009 after the shad kill than in any previous year.
"Water clarity increased nearly three-fold in 2009 compared to the average from 2004 through 2008," Pearson said.
To evaluate ongoing benefits of the shad kill, Pearson and sampling crew will return to the lake in early June to conduct a fish population survey.
"What we hope to find this year is an increase in the number and size of bluegills, an increase in the number and size of bass, and very few gizzard shad," Pearson said. "Our biggest concern is that we might find lots of 1-year-old shad that were produced last summer."
Based on results of the survey this June, the DFW will determine if any additional fish management actions are needed at the lake.