Evening Star Newspaper, June 9, 1929, Page 95

THE SUNDAY STAR, WASHINGTON, D. C, cience Aids The "Hook And Liners” Fishing Fish Facts From the K 1sconsin Lakes—Haphaz- ard Methods Are Gone and Scrence Shows How to Make Bigger Catches—IFish Stories T hat Are Really True. BY GEORGE DACY. HEN scientists go a-fishing, they carry along special thermom- eters, water samplers, devices o determine sunlight penetration as well as plankton nets and technical traps—and they always bring home the bacon, or rather the overflowing creels of fish. Fishermen, modern and amiable Ananiases, have been telling fishing fables ever since Jonah explored the internal workings of the whale, These amazing tales, fabricated chiefly from fiction, are now devoid of spectacular features when compared with the astounding fish stories which filter from the research labora- tories of the Wisconsin Geological and Natural History Survey, directed by Dr. E. A. Birge, president emeritus of the University of Wis- consin, For more than 30 years Dr. Birge has been engaged in fishing fish facts from 323 Wis- consin lakes—the most studied group of lakes in the world. This scientist has sought to solve inland lake secrets, even as experts study soils and ascertain their adaptabilities for the pro- duction of varicus crops. The stocking of lakes with breeding fish has been a hit-or-miss proposition ever since the dawn days of such conservation activities. Science did not know what varieties of fish were adapted to certain lakes, nor did it ap- praise the available fish-food contents of such bodies of fresh water. These were but a few of the riddles which Dr. Birge began to study when bicycles were still in style. To produce, in each lake, the maximum amount of game fish that it is capable of de- veloping is the gcal of this research. The ex- tensive investigation involves careful study of the biology, physics and chemistry of various lake waters which, combined, provide valuable data in determining the fish best adapted to each body of water. No two lakes are exactly alike. Each Wis- eonsin lake has its individual characteristics. Some are ideal for trout, while others are best adapted for bass and pike. To locate the most suitable varietics of game fish in the proper lakes where the essential supplies of fish food are most abundant is the aim and ambition of Dr. Birge's tircless work. HY is it that ciscos grow only one-half as fast in Northern Wisconsin lakes as in Lake Erie? Why do the lakes of Southern Wis- consin provide more fish food than those of the northern sections of that State? How can science take accurate fish censuses in inland lakes? Why is it that, in cold-water lakes, the oxygen supply is so deficilent at lower depths that only such upper-water fish as bass and sunfish can exist in these lakes during the Summer season? How does the penetration of sunlight in lake waters influence the growth of aquatic plants and dictate fish population? The scientific fishing experiments are answer- ing these and many similar questions which previously have challenged all attempts at so- lution. This interesting research, which is laying the foundation for the scientific conservation of lake life, collects data on water temperatures at various depths, surveys the algae, plankton, crustacea and aquatic plants growing in the lakes, makes chemical analyses of water sam- ples lifted from different levels, and generally keeps tab on all conditions which affect the maintenance and multiplication of fish schools. Thousands of fish have been caught in order to obtain samples of fish scales from which the ages of the finny swimmers may be determined. Whenever the scientists lowered lines or nets, it was not long until they raised representative catches. First of all, they made dependable tests to locate the most favorable sections of the lake, where the finest fish would congregate. There- upon, they lowered their baited hooks or nets to exactly the right depth. They used the most desirable bait, and never had to wait long for “strikes.” ‘This style of scientific fishing is in- fallible in securing record strings of champion fish. The age of a fish can be determined ac- curately from the microscopic study of the scales. This information is important in as- certaining the species of fish best adapted to any given lake or stream. Knowing the age and weight of the fish, it is a simple task to compute the rate of growth. Logically, fish grow most rapidly under most favdrable con- ditions. URING the last Summer Wisconsin sports- men supplied the State scientists with 50,000 samples of fish scales from their suc- cessful catches. They have also co-operated by providing dependable data about the weight and length of each fish, the number and va- rieties caught in various lakes, the time period of each angling trip and similar facts and figures. Dr. Birge and his assistants have determined the ages of all their fish from the scales. Just as the forester counts the annual rings in a certain cross-section in determining the ages of trees, the limnologists compute the groups of rings on fish scales in sleuthing out the total birthday parties which fish have cele- brated. , % o JUNE 9, 19 cosRT 1920—PART 7. Dr. Birge using a micrscope to identify tiny form of fish food taken from the Wisconsin lakes. Each fish scale contains many concentric rings. Observing with the microscope, the in- vestigator finds that the spacings between these rings vary. Fish that live in cold water breathe more slowly, eat less and do not grow as rapidly as those that inhabit warm waters. The rings produced during the Winter or cold-water sea- son are spaced more closely together as com- pared with faster growing Summer season re- sults. The Wisconsin experts count the closely spaced rings on fish scales—each represents the growth of one Winter—and thus arrive at the accurate age of unknown fish. By more detailed study, science finds out the rate of growth of the fish during any one year. It also ascertains the season of year when the fish were caught from these interesting fish- scale records. The rate of growth of a given species of fish from one lake is compared with the development of the same species in other lakes and streams, and in this manner the best lakes for certain fish and the most suit- able fish for individual lakes are discovered. AN extraordinary electrical centrifuge which can be operated at a peak speed of 50,000 revolutions a minute has been devised to sep- arate the myriads of bacteria and other forms of life from the plankton specimens recovered Special electric light detector originated by Wisconsin’s technical fishermen for determining sunlight penetration in lake waters. Sunlight controls aquatie plant h, which in turn regulates the food supply of minute animals. The latter are the food of game fish. from different depths in various lakes. Ordi= narily, the centrifuge is run at a speed of 32,000 revolutions a minute, the water sample being fed slowly into the separator, with the result that the organisms are churned from the water, and are deposited on the sides of the special steel bowl, from which position they are removed subsequently for scientific indentifica« tion and study. ‘The quantity of organic matter in the plank= ton of Wisconsin lakes ranges from 700 to 6,000 milligrams per cubic meter of water. The remarkable centrifuge is the only type of ap= paratus capable of separating the minute or= ganisms from the water where they live. It permits of recovering and identifying from onee third to one-half of all the invisible bacteria in a lake-water sample, as well as 97 per cent of the larger forms of life. Special water bottles—adjustable metal con- tainers—which collect from one to three liters of lake water at a time—are used. Their con=- struction is such that they can be lowered to the desired depths in the lake. A trip trigger is then pulled which opens the bottles anad closes them again as soon as they are filled with water. The organic content of the lake can be estimated from these specimens, while material is also obtained for fish-food studies. The number of water samples taken varies with the size and depth of the lake. Such food as water fleas as large as pinheads—the favorite food of game fish—are studied in each lake, as well as the particular plants upon which these fleas feed. SAMPL!‘S of water are analyzed chemically to ascertain the amounts of phosphates and nitrates present, as well as the content of oxygen, carbon dioxide, chlorine and other ma- terials which influence fish life. Temperatures of the water at various depths are taken with special thermometers, while scientific surveys of the algae growing in the different lakes ara also made. The extent of tiny animal life in these lakes is determined. There is an intimate correlation existent between the plant and small animal life and the fish content of each lake. Small fish, for example, cannot prosper unless plenty of crustacea occur, while the population of large game fish depends proportionally on the abune dance of small fish which the former consume. As a result of fish research of this kind, one expert estimated the fish population of a cere tain Wisconsin lake 26 miles in circumference at 10,000,000. Lake trout, whitefish and ciscos prefer to live in the cool lower waters of an inland lake, while bass and sunfish thrive in the warmer surface waters. Many of the Wisconsin lakes studied are practically virgin territory, far removed from the beaten paths of civilization, and hence free from the pollution which usually develops when the shores of such bodies of fresh water are populated to capacity. It is thus possible to make conclusive comparisons of uninhabited and habited lakes to ascertain the long-time effects of man’s presence on fish increase, ane nual growth and well-being, The rate of sunlight penetration has been studied by means of special apparatus developed expressly for that purpose. Large aquatic plants which are essential in the successful life cycle of game fish depend upon sunlight for growth., Some lakes are stained with peat and other dark-colored sofls, while others are dise colored by falling leaves and wind-blown vegee tation. Dr. Birge reports that 1 per cent of the sun’s energy will penetrate to a depth of 65 feet in a clear, sparkling, fresh-water lake. In dark and discolored lake water, a similar Continued on Ninth Page.