35] STUDY OF SOUTHERN WISCONSIN FISHES— CAUX 35 



vegetable matter, mixed with a large amount of fine mud and silt, all of 

 which is passed through the digestive system. Algae, diatoms, desmids 

 and particles of larger aquatic plants are the principal food I have found. 

 The species is hardy and makes very good casting bait. An inhabitant of 

 shallow water, it apparently has few enemies among the fishes, though 

 many are eaten by herons and bitterns. 



24. Chrosomus erythrogaster (Raf). Red-bellied Dace. 



One of the most beautiful of our fresh water fishes. The brilliant 

 coloring of the male, together with the very fine scales, has confused the 

 species in the local minds with trout, for which it is often mistaken. It is 

 abundant only in the Ashippun river, but occurs sparingly in the Ocono- 

 mowoc and Scuppernong rivers. In the Ashippun it is found over gravel 

 bottom, in clear, running water and associated with Notropis cornutus 

 and Hybopsis kentuckiensis . Breeding occurs late in May or early in June, 

 and the male carries traces of his brilliant red belly late into the summer. 

 The food consists entirely of entomostraca, algae and particles of aquatic 

 vegetation, with an occasional Hyalella or Gammarus. 



25. Eybognathus nuchalis (Agassiz). Silvery Minnow. 



A very rare species, recorded only from the Menomonee river, and 

 therefore found only in the Lake Michigan drainage area. Three specimens 

 are all that I have taken. These came from water slightly muddy in quality, 

 over a fine silt bottom, and with only slight current. Two specimens were 

 examined for food, and showed an abundance of entomostraca, diatoms 

 and algae (mostly Spirogyra) abundantly mixed with fine silt. 



26. Eybognathus nubila (Forbes). 



Another rare species, found most commonly in the Scuppernong creek, 

 where I have taken thirty-eight specimens. The water here is dark grayish 

 brown in color due to a large amount of fine silt and muck in suspension. 

 The bottom is soft, the water eighteen inches deep and normally with little 

 current. The food seems to consist almost entirely of algae (Spirogyra, 

 Zygnema, Closterium) with occasional entomostraca and small insert 

 larvae. Nothing is known of the breeding habits. 



27. Pimephales promelas (Raf). Fathead Minnow. 



Like Eybognathus nuchalis, with which it is associated, this species is 

 recorded only from the Menomonee river, where, however, it is extremely 

 abundant. In this river it is the dominant fish species, and I have taken 

 two hundred or more in a single sweep of a minnow net. It is most common 

 in muddy water, and entirely absent from those parts of the river flowing 

 over clear gravel. It is a bottom feeder, apparently grubbing in the soft 

 bottom for insect larvae which form over 90% of its food. The species 

 breeds in June, usually rather late in the month, the nests being shallow 

 depressions near or under the banks. In this region the fish are characteris- 

 tically infected with the small black cysts of a fluke probably Diplostomu- 



