72 



Conservation Department 



tion by many of the Crustacea from the surface toward the bottom, 

 or in the opposite direction. As a result the species which has a 

 large percentage at the surface has a conversely low one near 

 the bottom, and vice versa. 



Again, since this zone is located in what may be termed the 

 middle of the lake there is but little contrast between the Ameri- 

 can and Canadian sides. Among the copepods, how^ever, Limno- 

 calanus still shows considerable preference for the Canadian side, 

 while Daphnia is somewhat more abundant on the American side. 

 On the bottom in this zone is the mysidacean, My sis relict a, which 

 is much larger than any of the plankton Crustacea and is freely 

 eaten by some of the larger fishes. Here also are found the 

 amphipods and the insect larvae, neither of which were found at 



Typical lacustric zone plankton community in the deepest part of the 

 lake. Station 04.15, 62 meters. Linmocalaniis macriirus, abundant; 

 Daphnia long, galeata, rare; Daphnia piilex, common; Sida crystal- 

 Una, rare; Mrsis relicta, abundant; Pontoporeia hoyi, common. 



more than one or tw^o stations, but both of which constitute excel- 

 lent fish food where they do occur. The most noticeable thing 

 about the plankton in this lacustric zone was its excej^tional abund- 

 ance; a 5 minute haul of the meter net rarely yielded less than 

 250 cubic centimeters of plankton, it often reached 1000 and twice 

 went to 2000. The few small catches were all at the surface and 

 were offset in every instance by a large catch made simultaneously 

 near the bottom. In fact, the chief production of the plankton 

 Crustacea ap])ears to start early in the season over the deeper water 

 in the central portion of the lake. It then graduallj^ ex])ands 

 until it covers the whole of the lacustric and much of the littoral 

 zones, reaching the peak of i)roduction at the height of tlie sum- 

 mer tem]ieratui'e. 



Summary. — 1. ^riie ])i-(\s('nt sur\('\' gives an excellent idea of 

 the kind and amount of macroplankloii in Lake Erie and its 



