I08 BULLETIN OF THE BUREAU OF FISHERIES. 



The depth of water below which waves would reach them is apparently a factor in 

 determining the habitat of many species of mussels in lakes (Headlee, 1906, p. 308 — 

 Winona Lake; Muttkowski, 1918 — Lake Mendota). In large bodies of water like Lake 

 Michigan the action of the waves is said to extend to 8 meters below the surface. The 

 zone of wave action is a region in lakes comparable to the rapids and riffles of streams, 

 where there is maximum circulation and aeration and a solid bottom suitable for 

 such mussels as can withstand the violent action of waves and undertow currents. 

 The species occupying this zone are given by Headlee for Winona Lake as the spike, 

 Unio gibbosus, and the fat mucket, L. luteola. Baker (191 6) says of this habitat in 

 Oneida Lake : 



The shore may be free from vegetation. It receives the full force of the winds and waves from the 

 open lake. The water is from i to 3 feet in depth and the bottom is heavily and thickly covered with 

 stones and bowlders, many of the latter being of large size. Animal life is abundant, the clams living 

 between the stones and on the sand between the stones. 



The mussels he reported are as follows: Elliptio complanatus , common; Lampsilis 

 luteola, rare; Lampsilis radiata, common; Lampsilis iris, rare; Margaritana murgari- 

 tijera, rare; Anodonta cataracta, common; Anodonta implicaia, common; Anodonta 

 grandis, common; Strophitus edentidus, rare. Some of these are very thin shelled and 

 doubtless survive the force of the waves only through the protection afforded by the 

 large rocks. No doubt the thorough aeration of the water, resulting from wave action, 

 is a favorable factor in this zone 



On the shores of Lake Pepin one of the authors has often picked up live mussels 

 that had been thrown up by heavy wave action. The mussels thus most frequently 

 encountered were Unio gibbosus, Lampsilis alaia, Anodonta corpuknta, Strophitus eden- 

 tulus, Lampsilis ventricosa, and Lampsilis luteola in about the order named. They were 

 usually immature examples. Occasionally after a storm had subsided one could see 

 mussels that had not been entirely stranded on the beach near shore and in the act of 

 making their way back again into deeper water. Headlee and Simonton (1904, p. 175) 

 recorded similar observations. 



While the data available are sufficient only to suggest how depth may affect the 

 haoitat selection of mussels, it is of interest to note some of the obser\'ations on this 

 relation. A maximum depth of 22 feet for mussels in Winona Lake is given by Headlee 

 (1906), who ascribes the control of distribution to bottom characters chiefly. Baker 

 (191 8) found that in Oneida Lake twice as many mussels occurred in water deeper than 

 6 feet as within the 6-foot contour. (See quotation, p. 103, above.) He records three 

 species as limited to a depth of i K to 8 feet, three as living at varying depths between 

 iK and 18 feet, and one subspecies as occurring only between Sand 18 feet, the greatest 

 depth which he explored. He reports an interesting case of bathymetric distribution of 

 two races, Lam,psilis radiata, occurring at i J^ to 3 feet, and a subspecies, Lampsilis radiata 

 oneidensis, living only at 8 to 18 feet, the two forms showing a distinct difference in 

 habitat. For Lake Mendota the optimum depth for mussels of the genera Anodonta 

 and Lampsilis is given as from 2 to 3 meters (6 to 10 feet) (Muttkowski, 1918, p. 477); 

 they were, however, found abundantly between 3 and 5 meters and rarely at greater 

 depths than 7 meters (23 feet). 



Wilson and Danglade (1914), in reporting a reconnoissance of mussel resources in 

 Minnesota waters, give depths of the lakes, but without detailed data on the distribution 



