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76 aRThUR speRRy peaRse the value of aquatic Preserves to fisheries (1926) From Naturalist’s Guide to the Americas, edited by Victor E. Shelford (Baltimore: Williams and Wilkins, 1926), 11–12. There are few “natural” environments for freshwater fishes in the United States. Artificially stocked streams, lakes, and ponds seldom produce such desirable fishes as are found in localities where the wilderness has not been disturbed by man. Great natural preserves like the Great Lakes and the Mississippi River should be kept as near their original condition as possible. In general the larger a fish preserve is, the better. It is highly desirable to keep the environmental complexes furnished by great rivers and lakes as complete as possible . Variety of habitats is necessary because many species do not carry on their cycles of activities in the same habitat. The bass feed largely among plants, but require bare bottom for spawning. The cisco lives in the deep cool waters of lakes, but comes into shallow water on stony bottoms to breed. Many young fishes frequent shoals, even though they live elsewhere as adults. Attempts to rear fishes in small bodies of water are often without success. In general the ecological succession in ponds eliminates the species most desirable for man. A pond left to “run” according to “nature” chokes with aquatic vegetation and becomes a swamp, populated by mud minnows, sticklebacks, and bullheads. If game fishes are desired, bare bottom is essential . Fishes confined year after year in a restricted area may be overrun by parasites . One of the trout hatcheries of the Wisconsin Conservation Commission is situated in an excellent locality and has an adequate supply of fine spring water, but is of little value because the trout are heavily infected with a parasitic copepod. Pollution may easily destroy the value of a fish preserve. Poisons may be introduced from natural sources or from the byproducts of the industries of man. Substances which use up oxygen or produce other injurious gases may be present. Minerals may be precipitated from or dissolved in the water by substances not in themselves injurious to fishes. If fishing is permitted in a preserve, it thE valuE of aquatiC PREsERvEs to fishERiEs 77 should not be so restricted as to catch certain fishes and allow others to increase unduly . If angling only is practised in a lake the game fishes are most often caught and undesirable species, like the carp, sucker, and dog fish, which seldom take a hook, become too numerous. The restricted use of fyke nets or seins for the capture of the latter fishes is desirable in such a locality. It is doubtful if the suitability of a body of water as a fish preserve can ever be judged by any single criterion. Two lakes may be of the same size and depth. The one may be “plankton poor,” have a scanty bottom fauna, contain undesirable mineral constituents, lack oxygen, and have barren shores, while the other furnishes a favorable environment in all these essentials. A river may change its whole character as a habitat for fishes on account of the introduction of factory wastes, the building of a dam, or some other apparently unimportant change in a locality. Rush Lake, Wisconsin, has abundant food and shelter and furnishes excellent breeding grounds, but is so shallow that its oxygen is used up when it is covered by ice in winter, hence it contains no large fishes. The important features for a fish preserve are: (1) sufficient size to permit variety in habitats and to lessen the dangers from contamination and rapid fluctuations in temperature, (2) adequate resources in the way of food, shelter, and breeding grounds to maintain a sufficient number of fishes to make the preserve profitable. ...

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