12 



NATURALIST'S GUIDE TO THE AMERICAS 



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 habi- 

 tats 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 suc- 

 cession 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 es- 

 sential. Fishes confined year after 

 year in a restricted area may be over- 

 run by parasites. One of the trout 

 hatcheries of the Wisconsin Conserva- 

 tion Commission is situated in an ex- 

 cellent 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 oxy- 

 gen 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 should not be so restricted as to catch 

 certain fishes and allow others to in- 

 crease 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 constit- 

 uents, lack oxygen, and have barren 

 shores, while the other furnishes a 

 favorable environment in all these es- 

 sentials. 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 pre- 

 serve are: (1) sufficient size to permit 

 variety in habitats and to lessen the 

 dangers from contamination and rapid 

 fluctuations in temperature, (2) ade- 

 quate resources in the way of food, 

 shelter, and breeding grounds to main- 

 tain a sufficient number of fishes to 

 make the preserve profitable. 



3. THE IMPORTANCE TO GEOG- 

 RAPHY OF THE PRESERVATION 

 OF NATURAL AREAS 



BY STEPHEN SARGENT VISHER 



At least four of Geography's several 

 sub-divisions will be aided by the pres- 

 ervation of natural areas. These are 

 (1) Descriptive Geography, (2) His- 

 torical Geography, (3) Ecological Geog- 

 raphy, and (4) Economic Geography. 



Descriptive geography is concerned 

 not alone with describing relief features 

 and the cultural additions. It con- 

 siders likewise the vegetation and 

 the characteristic animals. Preserved 



