264 FISHES OF ILLINOIS 



being 2.35 as compared with .32 for each of the other sections. We 

 have taken it most frequently from the smaller rivers, about half as 

 commonly from creeks, and somewhat less commonly from the clear 

 upland lakes of the northeastern part of the state. It has occurred 

 but rarely in our collections from either the larger rivers or from low- 

 land lakes and sloughs. Its avoidance of such situations is espe- 

 cially illustrated by the fact that it is recorded but five times in 546 

 collections examined by us from the Illinois River at Havana and 

 Meredosia ; that is, only 5 per cent, of the collections of this species 

 have been made from these Illinois River localities, from which 35 

 per cent, of all our collections came. Its very marked preference 

 for a swift current and a clean bottom is a matter of common 

 observation, and is shown also by the data of our collections, accord- 

 ing to which it has come from swift waters more than three times as 

 often as from a quiet current, and from a bottom of rock and sand 

 nearly twelve times as frequently as from one of mud. 



These preferences bring about a wide separation between this 

 bass and the closely related species of the same genus — the large- 

 mouthed black bass. These two species inhabit the same general 

 area, may often be found in the same streams, and feed on the same 

 food, differing only, so far as known, in respect to the ratios of the 

 principal elements. Nevertheless, they avoid competition by a dif- 

 ference in the situations preferred. These closely allied species have, 

 according to our data, an associative coefficient of 1.08, while the 

 small-mouthed black bass and the rock-bass, differing in characters, 

 habits, and food, have a coefficient of 6 . 24. In other words, the 

 latter two unlike. species are brought by a similarity of local prefer- 

 ence into each other's company about three and a half timies as fre- 

 quently as the like species of black bass. The differences of local 

 preference are not so great, however, but that the two species are 

 frequently found together. According to Jordan and Evermann, 

 "Some small lakes that are rather shallow, whose bottoms are chiefly 

 mud and whose water is warm, are found to be well suited to the 

 straw bass [large-mouthed] and to be entirely without the small- 

 mouthed black bass. But small lakes of considerable depth, cool 

 water, and with bottom partly of mud and partly of sand and gravel, 

 such as Lake Maxinkuckee, seem equally well adapted to both 

 species." 



The small-mouthed bass is found wide-spread throughout the 

 country, from Lake Champlain and the River St. Lawrence to the 

 Muskoka lakes in Ontario, and southward to Arkansas, northern 

 Mississippi and South Carolina. It is abundant in suitable situa- 



