44 



Usinger: Introduction 



Improvement of streams and lakes. — Stream and lake 

 management for the production of fish-food organisms 

 was first developed in England (Mosely, 1926) where 

 private trout streams have been maintained for cen- 

 turies and close attention could be given to methods 

 for the production of fish-food organisms. Many of 

 the techniques advocated for British streams, such 

 as collecting eggs of mayflies to introduce into a 

 barren stream, are totally impractical here where miles 

 of unimproved waters exist. However, some practical 

 techniques have been developed in this country (Hubbs 

 and Eschmeyer, 1938) and abroad, mainly applying 

 to the fish alone but in some cases with definite 

 advantages from the standpoint of fish-food production. 



Certain practices have been found to be effective 

 in increasing fish food in lakes. These include: (1) 

 management of water level by dams so as to maintain 

 maximum littoral productivity and, in small lakes, to 

 prevent drying up with consequent mortality; (2) 

 stabilizing banks by plantings to avoid excessive 

 silting; (3) regulating the abundance of fish and 

 balance of kinds of fish so that fish populations can 

 maintain themselves at optional densities in relation 

 to food supplies; (4) improving the shelter for both, 

 aquatic organisms and fish (intro. fig. 59); and (5) 

 managing the growth of aquatic plants. Other meas- 

 ures such as fertilizing and dredging or filling have 

 been done in small artificial impoundments but are 

 not practical or .even desirable in most natural lakes 

 of the state. 



In streams fish need pools for protection and riffles 

 for food production and spawning. Therefore stream 

 improvement seeks to provide both types of habitat 

 in the proper proportions, usually in a ratio of about 

 1:1. Riffles are maintained by clearing trash and 

 logs and by fencing to prevent trampling by stock. 

 Pools are created by small dams or by deflectors 

 strategically placed (intro. fig. 60). Banks are stabi- 

 lized by plantings to prevent erosion. In burned-over 

 areas shade is restored by reforestation so that water 

 temperatures in trout streams can be maintained 

 below 70°-75° F. 



It is very difficult to measure the results of stream 

 improvement because of the lack of precise sampling 

 methods. Tarzwell (1937) attempted an evaluation in 

 Michigan by determining the average production for 

 various types of bottom and then calculating the 

 potential volume of food production on the basis of 

 the area of each bottom type before and after improve- 



Spring 



Boulder Retards 



Stone Deflector 



Brush— -, 



Stone Deflector 

 Stak 

 Log Cover 

 Planting-(l3)0! 

 Deflector -&[l 

 Brush- 



Section C— c 

 of Deibler Dam 



Intro, fig. 60. Summary of some stream improvement 

 techniques (Lagler, 1952). 



ment (table 6). The results showed a threefold in- 

 crease after improvement. 



More general methods for improving the health of 

 streams include the following: 1. Pollution is pre- 

 vented whenever possible. 2. Check dams are installed 

 in large drainage areas primarily for flood control 

 but also to maintain some flow throughout the year 

 in otherwise intermittent streams (flow maintenance 

 dams, Cronemiller, 1955) thus permitting the survival 

 of organisms with long life cycles and creating a 

 perennial population of fish food organisms; 3. Stream 

 flow is equalized below large dams by judicious 

 management to avoid the scouring effects of flash 

 floods and the mortality caused by drying parts of 

 the bed; 4. Finally, efforts are being made in a few 

 places to control the ratio of predators to bottom- 

 feeding fish so that optimum productivity of fish food 



TABLE 6 (Introduction) 



Volume of food production in a stream before and after improvement, calculated on the basis of 

 average production of various bottom types and increase in area of each bottom type 





Average production 

 on 4 sq. ft. (in oo.) 



Before improvement 



After improvement 



Bottom type 



Area of each bottom 

 type in sq. ft. 



Total calculated 

 production (in oo.) 



Area of each bottom 

 type in sq. ft. 



Total calculated 

 production (in oc.) 



Sand 

 Muck 

 Gravel 

 Gravel riffle 

 Plant beds 

 Total 



0.27 



3.99 



22.76 



12.48 



5.32 



76,105 



4,942 



17,791 



98,838 



5,137 

 23,397 

 12,276 



22,355 



48,995 



23,397 



14,719 



7,142 



4,585 

 98,838 



3,307 

 23,397 

 10,156 

 22,283 



6,098 

 65,241 



