December, 1958 



Bennett: Aquatic Biology 



175 



the warmouth was later published as an 

 article of the Natural History Survey 

 Bulletin (Larimore 1957). 



During the summer of 195(J Larimore, 

 with the help of Leonard Durham and 

 others, began an intensive investigation 

 of the fishes in Jordan Creek, a small 

 spring-fed, upland stream in V^ermilion 

 County. This project marked the be- 

 ginning of upland stream investigations 

 as a continuous program of the Section 

 of Aquatic Biology. Through the use of 

 the electric seine and other special equip- 

 ment developed for stream work, it has 

 been possible to make both intensive and 

 extensive studies on the ecology of stream 

 fishes in the central Illinois region (Lari- 

 more, Pickering, & Durham 1Q52). The 

 smallmouth bass, Micropterus doloniieui 

 Lacepede, was found to be the most im- 

 portant anglers' fish in these streams. 

 The fry of this bass were particularly 

 vulnerable to floods on streams when the 

 floods were accompanied by sudden 

 changes in water temperatures. The adult 



bass showed well-developed homing in- 

 stincts as did some other species (Lari- 

 more 1952). Tests of the value of plant- 

 ing 6- to 8-inch smallmouths in a 

 stream already containing a population of 

 smallmouth bass demonstrated that it 

 was possible to build up numbers of these 

 fish only temporarily. Minnows removed 

 from a stream with an electric seine were 

 replaced by other minnows through mi- 

 gration and reproduction within a period 

 of a few months (Larimore 1955). Ap- 

 parently streams are quickly repopulated 

 even when fish are killed by drought con- 

 ditions, heavy winter ice, or temporary 

 severe pollution. 



In studies of ponds and lakes, by 1945 

 evidence had accumulated to substantiate 

 the idea that a lack of fish predators was 

 an important problem to be faced in the 

 management of these waters. Obviously, 

 fishing was no substitute for natural pre- 

 dation, and much of the task of the fish 

 manager was that of functioning as a 

 predator of small fishes (Bennett 1947). 



Fisheries technicians of the Illinois Natural History Survey using fish shocker for sampling 

 the population of a stream. The shocker is a recent development that has been used successfully 

 in both streams and lakes. 



