Fish Sampling 133 



9G 



These represent the combined experiences of Starrett and Barnickol 

 and the members of the Ilhnois Natural History Survey staff who have 

 fished with these methods for many years. 



Gill Nets. These nets are made with hnen or nylon thread, fine enough 

 so that fish, not seeing them will become gillcd or entangled (Figure 6.1). 

 Gill nets are tied to give bar measurements (one side of a square mesh) 

 ranging from 1 to 4 inches; sometimes special sampling nets are made 

 by splicing 50-foot sections of increasing mesh sizes from 1 inch up to 

 3 or 4 inches. Gill nets can be set at various depths from surface to 

 bottom. They are selective for pelagic fish such as herring and trout and 

 are seldom used in shallow lakes. 



Table 6.2 An appraisal of the efficiency of several fish sampling 

 methods commonly used in artificial lakes, as related to 

 common warm-water fishes (in part from starrett and 

 barnickol ^^) . 



^ Bluegills, green sunfish, red-ear sunfish, etc. 



Trammel Nets. A light gill net of small mesh is hung with plenty of 

 extra webbing between two walls of netting consisting of very large mesh 

 of heavy twine. A fish hitting the light net carries a pocket of this net 

 through an opening in the larger net and so becomes trapped. Trammel 

 nets are supplied with floats and weights; they are set across and/or 

 floated in a current (in a river) or set around a school of fish (in a lake). 

 These nets are selective for fish that can be frightened into hitting the net. 

 They are commonly used for commercial fish— carp, buffalo, and catfish. 



Seines. These are pieces of webbing of various mesh sizes and lengths 

 held upright in the water by floats and weights and pulled through the 

 water to encircle fish. They are somewhat less selective than most odier 

 types of gear. Seines can be used only where the water depth is less than 

 the depth of the seine and where the bottom is clear of snags. When con- 

 fined within a small area, certain fishes such as largemouth bass will jump 



