The Effects of Supplemental Feeding and Fall Drawdowns on the Largemouth Bass and Bluegills at Ridge Lake, Illinois

Abstract

1.—After a draining census in 1963, Ridge Lake was restocked with 2,386 largemouth bass, 4,492 bluegills, 1,335 warmouths, 11 channel catfish, and 1,020 lake chubsuckers, making a total of 9,244 fishes weighing 510.6 kg (1,125.5 pounds). This was 78.8 kg per hectare, or 70.3 pounds per acre. In the census preceding this restocking this lake was found to contain 287 kg per hectare, or 256 pounds per acre, almost four times the weight of fish returned to the lake. In 1969, 2,000 additional channel catfish were stocked.

2.—The population of fishes was allowed to expand for two growing seasons (1963 and 1964) without drawdowns or supplemental feeding but with the usual controlled public fishing during the summer months. The hook-and-line catch in 1963 and 1964 was below the average for the preceding 20 years.

3.—Beginning in late May 1965, and continuing each year during the 3 summer months, 1965 through 1969, the fish were fed daily on a commercial pelleted fish food (32 percent protein) at the rate of 2 pounds per acre per day. Food was spread in the shallows in all parts of the lake. The food cost was within the range of $27.80-$30.12 per hectare per season ($11.25-$12.19 per acre per season).

4.—Each year, beginning in September 1965, the lake level was lowered: 4.6 meters (15 feet) in 1965, leaving a surface area of 2.12 ha 3.0 meters (10 feet) in 1966, leaving a surface area of 4.5 ha 3.0 meters (10 feet) in 1967, leaving a surface area of 4,5 ha 4.6 meters (15 feet) in 1968 leaving a surface area of 2,12 ha 4.3 meters (14 feet) in 1969, leaving a surface area of 2.76 ha The level was maintained until the water temperature in the lake was about 13° C, (57° F.) in October, when the lake was allowed to refill,

5,—In March 1970, the lake was drained to make a census of the fishes. The lake contained 2,420 bass, 9,546 bluegills, 556 warmouths, 1,477 channel catfish, 232 lake chubsuckers, and 3 fishes of other species, a total of 14,234 fishes weighing 1,440.0 kg (3,175.3 pounds).

6.—The catch of largemouth bass during the seasons 1965-1969, inclusive, was composed mostly of small fish. The f-d program resulted in the production of excessive numbers of small bass but generally did nothing to improve bass fishing.

7.—The fishermen's catch included more than twice as many large bluegills (152 mm or longer) as it did smaller ones during the 1965-1969 period. Blue gills of desirable sizes averaged 127 grams (0.28 pound) each.

8.—Neither warmouths nor channel catfish produced large hook-and-line yields because their numbers were always small. Channel catfish produced a small year class in 1963 or 1964, and this year class appeared in the catch in 1966-1969, inclusive. The catfish stocked in 1969 were too small to appear in the 1969 catch.

9.—During years when the water level in Ridge Lake remained fairly constant, bluegill numbers increased to 50,000 in one 2-year period and to 66,000 in another, to 86,000 in one 3-year period, and to 93,000 in a 4-year period. Annual fall drawdowns of 4.6 meters reduced the bluegill population to 7,500, those of 3.0 meters to 17,000 bluegills, and the 4.3- meter drawdown reduced the population to 9,500 bluegills. These drawdowns apparently had little effect on largemouth bass numbers.

10.—The average hook-and-line yield of bass in the 5 f-d years was only 18.0 kg per hectare (16.1 pounds per acre). This yield was below the average for 3 drawdown years (1952, 1954, and 1955) and 3 stable water level years (1957, 1958, and 1959). The average bluegill yield under the f-d program was 71.6 kg per hectare (63.9 pounds per acre), higher than the catch in any other period.

11 .—The average index of condition of largemouth bass in the f-d period was slightly below normal. Average bluegill condition was "fat" in June of all f-d years except 1965 and 1969. Usually the average bluegill index of condition was lower in July and August, which followed a previously observed condition cycle for that species. The condition of bluegills in 1954-1955 with fall drawdowns, but without supplemental feeding, was "fat" in June of 1954 but only reached "high average" plumpness for July and August of 1954 and for all of the summer of 1955.

12.—Largemouth bass growth was slower during the f-d period than during the period of biennial lake draining and culling of the fish population. Bluegills grew somewhat faster during the f-d period than they did during the program of drawdowns without feeding. They appeared to live longer during the f-d period and therefore attained larger sizes. They grew much faster under the f-d program than they did when water levels were stable.

13.—The pelleted food for the f-d program cost about 12 cents per acre per day, or about $11.25-$12.19 per acre per season. Fishermen were enthusiastic about the program because they were able to catch larger and fatter bluegills, and they believed that the pelleted food improved the flavor of these fish. Feeding bluegills without fall drawdowns would probably be wasteful because the bluegill population would expand faster than the food supply.