82 DEPARTMENT OF THE NAVAL SERVICE 



8 GEORGE V, A. 1918 



are approximations, it is believed to be reasonably certain that the system of storage 

 basins would have an aggregate impounding capacity of not less than five billion cubic 

 feet.^ It will be evident that the economic advantage accruing from such pools of 

 dependable character cannot be lightly esteemed. In relation to mussel life there 

 would be not only the addition of new flood areas, but also no doubt the improvement 

 of the bed of the streams back of these areas. In these lake-approximations, or river- 

 lakes as they have been called, admirable conditions should be afforded for the par- 

 ticularly valuable shell L. luteola. Not only does this shell work up well into buttons 

 but it also lends itself readily to artificial propagation on a commercial basis. Although 

 it is rare to find shells of commercial value in lakes, these river-lakes form a natural 

 habitat for the above mentioned mussel. For example. Lake Peoria, a lake expansion 

 in the Illinois R. forms at present probably the best mussel producing district in the 

 United States. As the young mussels are parasitic on fish in the early stage of their 

 life history, it would of course be necessary to construct effective fish-ways at these 

 dams. 



Further, by a study of tables 1 and 2 it will be seen that there are considerable- 

 stretches in the river where apparently suitable mussel areas obtain. If mussels are- 

 not found here in a survey, the fault will probably be due to flood conditions prohibit- 

 ing their development in these areas. If such is the case, flow-regulation should over- 

 come the unfavourable environment. . 



FOOD, A FACTOR OF THE ENVIRONMENT. 



In the discussion of favourable environments, due consideration must be given to- 

 the food problem. This is doubtless the most important factor in the environment of 

 the mussel, and it is unfortunate that no extensive work has been done along this line. 

 Actual records of stomach contents of fresh-water mussels are rare. Records of analysis- 

 show that among the microscopic forms, minute plants, diatomacese and other algae, 

 constitute a part of the food of the mussels. With reference to the food habits,. 

 Professor Clark and Dr. Wilson report in part, as follows : '' The stomach contents of 

 mussels taken from the main current of the St. Mary's, St. Joseph, and JVIaumee rivers 

 were rather noteworthy for their paucity of organic material. Through the large mass 

 of muddy matrix filling the stomach were usually scattered a few Scenedesmus, various 

 diatoms, and an occasional Pediastrum or Cosmarium." Dr. Petersen, a Danish ecolo- 

 gist and Director of the Danish Biological Station, has fully demonstrated that the 

 fine dust-like detritus forming a thin top layer of bottom deposits constitutes a large 

 part of the food of the oyster and other mollusks. Dr. Jensen, Petersen's colleague, 

 concluded after investigating the source of the detritus that its origin is primarily 

 from sea plants, broken down until it assumes the fine dust like form. It has been 

 suggested" that the "large mass of muddy matrix" referred to by Clark and Wilson was- 

 probably the kind of material described by Petersen as " dust-fine detritus." Although 

 large bivalves may not be able to avail themselves of the layer of dust-fine detritus, it 

 is no doubt taken in by water currents. Dr. Jensen also examined the water by centri- 

 fuging, and obtained material identical with the top layer of bottom deposits. In 

 Oneida lake the surface of the bottom deposits, in bays and quiet bodies of water, is 

 reported to be of precisely the character described by Dr. Petersen. It would, indeed, 

 be very interesting to establish the relationship between stomach-contents of different 

 species of mussels and the nature of the river bed in which they do, or do not thrive. 

 It would, no doubt, lead to valuable information with regard to the choice and the 

 establishment of new areas for their development. It may be found that the food 



1 Sixth Annual Report, Hydro-Electric Power Commission of Ontario, 1916. 

 - Relation of MoMusks to Pish in Oneida Lake, by Frank Collins Baker, TJniversity of Syra- 

 cuse, N.Y., July, 1916. 



