Aquatic Biology 



GEORGE W. BENNETT 



THE research in aquatic biology that 

 was so much a part of the endeavors 

 of the staff of the Illinois State Labora- 

 tory of Natural History and later the 

 Illinois Natural History Survey vi^as in- 

 itiated by Stephen A. Forbes. From the 

 very beginning of his active period in 

 Illinois, Forbes showed great interest in 

 fishes and he began collecting specimens 

 for species records, distributional records, 

 and food habits studies. He wrote ar- 

 ticles on Illinois Crustacea and food of 

 Illinois fishes for the first volume of the 

 Bulletin of the Illinois State Laboratory 

 of Natural Historv (Forbes 1876, 1878^, 

 1880^, 1880^-, \^iU, 1883c). In the pe- 

 riod 187^1888 he collected 1,221 fish of 

 87 species, 63 genera, and 25 families; 

 these he used to study their diagnostic 

 characteristics, their distribution in the 

 state, and their food habits. Forbes' inter- 

 est in aquatic biology was broad, and he 

 himself worked on or arranged for others 

 to work on crustaceans, leeches, proto- 

 zoans, rotifers, and aquatic insects, as well 

 as fishes native to Illinois. 



BEGINNING OF AQUATIC 

 ECOLOGY 



Many of the early publications of the 

 Illinois State Laboratory of Natural His- 

 tory dealt with the taxonomy and distri- 

 bution of aquatic animals new to science, 

 or additions to the known distribution of 

 named animals. Forbes was familiar with 

 these subjects and also with the ecology 

 of aquatic organisms at least as early as 

 1887. In that year his "The Lake as a 

 Microcosm" was first published in the 

 Bulletin of the Peoria Scientific Associa- 

 tion; later it was republished in volume 

 15 of the Bulletin of the Illinois State 

 Laboratory. In this short but epoch- 

 marking paper, Forbes (1925) described 

 a lake or pond as an environment in 

 which the animals and plants were 

 largely isolated from the surrounding ter- 

 restrial animals and plants but were very 

 much interrelated and interdependent 



among themselves; each organism was 

 producing more new individuals than the 

 environment could support, so that many 

 of them served as food for other types of 

 animals, and competition was very keen. 

 Forbes had observed the biological phe- 

 nomena associated with fluctuating water 

 levels — with floods following excessive 

 precipitation and low waters following 

 droughts — and described them as follows: 



Whenever the waters of the river remain for 

 a long time far beyond their banivs, the breed- 

 ing grounds of fishes and other animals are 

 immensely extended, and their food supplies 

 increased to a corresponding degree (Forbes 

 1925:538). 



As the waters retire, the lakes are again de- 

 fined ; the teeming life which they contain is 

 restricted within daily narrower bounds, and 

 a fearful slaughter follows; the lower and 

 more defenceless animals are penned up more 

 and more closely with their predaceous en- 

 emies, and these thrive for a time to an 

 extraordinary degree (Forbes 1925:539). 



Forbes recognized that periods of bio- 

 logical expansion and contraction were 

 normal and, without the introduction of 

 abnormal forces, would tend to hold 

 "each species within the limits of a uni- 

 form average number, year after year." 

 Every organism had its enemies that 

 seemed to be balanced against its repro- 

 ductive potential and, although every 

 species had to "fight its way inch by inch 

 from the egg to maturity," yet no species 

 was exterminated. 



Apparently the Illinois State Fish 

 Commissioners, assigned the duties of 

 protecting the fisherit- resources of the 

 state during this period, either had not 

 read Forbes' "The Lake as a Microcosm" 

 or did not understand it, because their 

 main activity for the 20 years following 

 1890 was the rescuing of fishes from the 

 land-locked, drying backwaters of the 

 Illinois and Mississippi rivers and the 

 returning of these fishes to the open wa- 

 ters. 



Perhaps the Commissioners should not 

 be condemned severely, because their be- 

 liefs and activities were in no way dif- 



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