Of the 25,000 species of fish in the world, none arouses more interest among American anglers than Micropterus salmoides, the largemouth bass. Unlike his cousin Micropterus dolomieu, the smallmouth bass, and trout, the largemouth is present in ponds and lakes in every state except Alaska. He is, by a combination of sheer weight of numbers and extent of range and fight, the most popular American gamefish.
The man who knows the most about the ecology of the largemouth bass is Dr. George W. Bennett, chief of the Aquatic Biology Section of the Illinois Natural History Survey in Urbana. And what he has to say may come as a surprise to many anglers and a number of state fish and game commissions. For instance, Dr. Bennett thinks there should be no closed season on largemouths. "I don't see how any honest biologist could back up that closed season business," he says. "Every fishery biologist knows that it's a lot of baloney. Why penalize the fishermen? You take away the best period there is, the spring. The fishermen are just paying the penalty for something not based on any fact at all."
Bennett also thinks there should be neither creel limit nor minimum legal length because it is virtually impossible to fish out a bass pond. Bennett's research has proved that the moderately fertile largemouth pond or lake supports about 50 pounds of bass per acre. This poundage averages out to about 100 bass of all sizes, with 25 of them 10 inches or more. The most successful fishermen can catch only 60% of the bass and, if other species are present to compete for the available food, the danger is too many fish rather than too few.
Now 55, Dr. Bennett has been studying fresh water gamefish, particularly bass, for more than half his life. A strapping, soft-spoken Nebraskan (he sounds like Gary Cooper playing Wild Bill Hickok), he received his B.A. at Doane College, a small liberal arts school of which his uncle was president, his M.A. at the University of Nebraska and his Ph.D. at Wisconsin. In 1938, he joined the Illinois Natural History Survey. In 1941, he took charge of the newly opened Ridge Lake laboratory for studies of largemouth bass in Fox Ridge State Park, seven miles south of Charleston in the east-central part of the state, and his findings are based on a 22-year study conducted there and at ponds and lakes elsewhere in Illinois.
Dr. Bennett has written any number of scientific papers, and his book, Management of Artificial Lakes and Ponds, which Reinhold published last year at $8, is an invaluable work on the art and science of producing the maximum annual number of wild fish. Dr. Bennett is a Fellow of the American Institute of Fishery Research Biologists and a former president of the Upper Mississippi River Conservation Committee. Besides his work at Ridge Lake, Dr. Bennett is involved in a couple of other major projects. At Dundee, in the northern part of the state, he has 15 experimental ponds stocked with largemouths, smallmouths, bluegill sunfish, bullheads and perch for a study on population dynamics. At Havana, on the Illinois River, he is attempting to reestablish lakes that were drained by the U.S. Army Corps of Engineers in a turn-of-the-century flood control project. Before the army constructed levees and upriver reservoirs, the Illinois used to yield the greatest crop of fresh-water fish in the country, 24 million pounds a year.
Ridge Lake is to aquatic biologists what the Institute for Advanced Studies at Princeton is to scholars. Eighteen acres in extent, it was especially built for the Illinois Natural History Survey by the Civilian Conservation Corps. When it was finished, Dr. Bennett stocked it with 435 largemouths. All the largemouths that have come out of that lake—and there have been 27,000 of them so far—are descendants of that original stock.
Since 1942, Ridge Lake has been open to public fishing on a highly controlled basis. Every fisherman is logged in and out of the red brick laboratory that stands on the shore of the lake. The fisherman may fish only from a boat which the survey provides free of charge, and he is required to keep every fish caught, no matter how small. Upon his return to the dock, a laboratory assistant notes, on a special yellow card made out in the name of the fisherman, the number of hours fished, the kind of fish caught, the length (to the nearest 10th of an inch), weight (to the 100th of a pound) and the bait used. The assistant also notes any fins that were clipped during periodic censuses of the lake. In addition, he takes 15 to 20 scales from each bass. These are later studied to show age and growth patterns. Fish scales can be read in much the same manner as the annual rings on a tree stump; each ring on the scale designates one year. A fish keeps the same scales throughout its life, and they grow in size as the fish grows. The annual rings on the scales are laid down in the spring, when the fish, after a dormant period, begins its yearly growth. The growth rate of the fish determines the space between the rings. When the fish grows rapidly, the space is wide; conversely, when the growth is slow, the rings are close together.
Besides all the data collected on fish from Ridge Lake, there have been innumerable studies on the lake itself. For example, biologists have investigated such phenomena as rainfall, thermal stratification, aquatic plants, plankton and bottom fauna and water transparency. In short then, Ridge Lake, under Dr. Bennett's direction, has been studied upside down and inside out. It is a fishery biologist's dream, or, as Dr. Bennett puts it, "a great toy."
One of Dr. Bennett's first projects in the early years at the lake was a study of the factors that controlled the size and poundage of a largemouth population. At the time, most fishery biologists believed that the largemouth population depended on the number of other fish, usually bluegill sunfish, on which the bass could prey for sustenance. The normal ratio was considered to be three or four bluegills for every one bass, and it was thought that if the bluegill population dropped, the bass would suffer accordingly.
But studies at Ridge Lake showed these assumptions to be invalid. Dr. Bennett discovered this in the following way. Up until 1943, Ridge Lake contained only largemouths. A drainage census of the lake that year revealed that each acre averaged 48.2 pounds of bass, just about what the lake should produce. In 1944, Dr. Bennett stocked the lake with 129 bluegills, and when he drained the lake the next year in 1945, the bass poundage had dipped to 39.6 pounds per acre, while the bluegills averaged 8.4 pounds per acre. He returned both bass and bluegills to the lake and, two years later, he drained the lake again. This time the bass poundage had slumped to 31.5 pounds per acre, while the bluegill poundage had jumped to a startling 193.3 pounds. All told, at the time of this census—this was in 1947, only three years after the stocking of the 129 bluegills—Ridge Lake contained the astonishing total of 67,700 bluegills. Dr. Bennett removed 66,000 of these permanently, returning only 1,700. As a result, the largemouth population once again started to increase.