Biological Survey — Erie-Niagara Watershed 73 



horizontal distribution, with important suggestions as to its ver- 

 tical and seasonal distribution. The last two factors, however, 

 require additional investigation before they can reach an equality 

 with the first three. 



2. The amount of animal plankton in the lake is amply 

 sufficient, not only for the fish it now contains, but also for all the 

 fry with which it can be stocked from the hatcheries situated 

 around its shores. And this fish food is as exceptional in quality 

 and size as it is in quantity. 



3. The marginal zone, since it is the place to which many of the 

 newdy hatched fish fry resort, is w^orthy of more careful examin- 

 ation than could be given to it during the present survey. It can 

 be most conveniently reached by automobile trips around the lake 

 shores. 



4. We should also know the rate of reproduction of the 4 or 5 

 more important species, the average length of their life, and their 

 seasonal distribution. This is especially true of the two largest 

 copepods, Epischura and Limnocalanus, with reference to which 

 no data are available. 



5. Insect larvae probably form an important food factor in the 

 marginal zone, and should be included with the plankton Crustacea 

 in any further study of that zone. 



6. Whatever depth may be considered as forming the boundary 

 line between shallow and deep lakes, Lake Erie wdth its maximum 

 depth of 62 meters would fall in the latter class. But the deep 

 area is so small compared with that of the entire lake, and there 

 is so much shallow water that the plankton is decidedly inter- 

 mediate in character, especially in its cladoceran species. 



7. Not merely the animal but also the vegetable plankton is 

 very unevenly distributed throughout the lake both horizontally 

 and vertically. And this is as true of the separate species which 

 combine to make up the plankton as it is of the total bulk of the 

 latter. 



8. In the horizontal distribution three zones may be accurately 

 distinguished, which may be designated as marginal, littoral and 

 lacustric. In each zone the macroplankton differs from that of the 

 other two zones in the kind and number of its constituent species, 

 as well as in their numerical proportions. 



9. During the present survey there were identified 19 copepods, 

 29 cladocera, 1 amphipod, and 1 mysidacean, a total of 50 species. 

 Of these, 5 copepods and 7 cladocera were found in all three zones, 

 1 copepod and 1 cladoceran were present in two zones, 2 copepods 

 were parasitic upon fish and hence cannot be assigned to any zone, 

 while the remaining 34 species were confined to a single zone. 



10. Through the cooperation of other members of the working 

 staff, especially Dr. Sibley, it has been possible to designate in the 

 following list of species the kinds of fish for wdiich each Crustacea 

 serves as food. This makes the value of the macroplankton for 

 fish food specific rather than general, and adds greatly to the 

 usefulness of the present report. 



