244 FISH. 



water type and the stagnant water type. The flowing water type 

 differs from the stagnant water type chiefly in the amount of vegeta- 

 tion and mud which is present. In the former the vegetation is con- 

 fined to the flags and rushes along the margin and the filamentous algae 

 in the slack water pools. The streams are all more rapid in their upper 

 than in their lower com-ses, and the lower parts, being nearly on a level 

 with Saginaw Bay, show transitional conditions between the stream 

 and lake. Pigeon River (PI. Xb, Xlb) exhibits these conditions very 

 plainly. The upper part is shallow and rapid, but near the lake there 

 is a stretch of slowl}^ flowing water about a half-mile long and eight to 

 ten feet deep. Mud Creek and the county drain near Bayport drain 

 the same general area. They carry only a small amount of water at 

 any season, and still less during the driest part of the year. Dming 

 the dry times they consist principally of scattered pools, but the lower 

 portion, which is at the lake level, contains about two feet of water 

 throughout the year. 



The stagnant water habitats associated with the streams are char- 

 acterized by conditions intermediate between those of a flowing stream 

 and those of a lagoon lake. They have quite clear water with a mud 

 bottom and an abundant aquatic flora. The oxbow pond at Caseville 

 is an example of this type. It was originally formed by the artificial 

 cutting off of the bend of the river to straighten the course of the latter, 

 but it has now become a typical ox-bow pond. (PI. XIa.) The bottom 

 has become covered with mud and the waters are now filled with aquatic 

 vegetation, with an abundance of duckweeds (Lemnaceae) and fila- 

 mentous algae near the surface. It lacks a current during the greater 

 part of the year, but retains a connection at one end with the lower 

 part of Pigeon River. 



Another habitat that deserves special mention is found in the bays 

 along the coast. The principle one of these studied is Tm-tle Bay 

 (PL Xlllb), on the south side of Sand Point, the largest of the partially 

 inclosed bodies of water along the shore. It is cut off from Wild Fowl 

 Bay by a sand spit, but still opens at one end by a narrow, shallow 

 passage which is gradually being filled. The water within is clear and 

 the bottom muddy. The vegetation is abundant and varied — cat- 

 tails, bulrushes and arrow-leafed plants grow along the shore, and pond- 

 lilies, pond weeds, etc., in the deeper waters. 



The waters of Saginaw Bay north of Sand Point offer a very uniform 

 environment. (PI. la). The water is shallow and the bottom uni- 

 formly sandy. There is no vegetation over this area and no shelters, 

 except a few artificial ones. The fish of the deeper waters outside the 

 shore area could not be examined in detail, but they were investigated 

 to some extent by following the catches of the commercial fisheries of 



