Uiiiitlii Lake I'islics 427 



the fish are usually small, mostly from alM)ut six to ten inches in lcnj;th, and from 

 the collections made at these depths in CJneida Lake this same relation between 

 size of fish and depth of water was noticed there also. At these ilepths the water is 

 usually clear enouj;h to make fish visible, and rarely are any as much as a foot long 

 seen; while in dee])er water (thirty feet or soj lar{;e I'erch may be taken, some- 

 times in (|uantities. There are. however, many exceptions to this general rule. In 

 some lakes all the I'erch are small, rc>;ardless of size and depth «>r other api«rent 

 conditions, while in (jthers they run larjje. I'earse and Achtenberjj ('20, p. 299) 

 note such size differences in lakes near Madison, Wisconsin, and Dymond ('26, p. 

 S^) dcscrilx'S similar instances in lakes of Ontario, while Bensley ('15, p. 46) finds 

 the small size of I'erch in deorgian Hay unexplainable when compared with larger 

 fish of other waters. Lucas ("25, p. t>4> gives instances from Massachusetts. A 

 fully satisfactory explanation for this diversity of size in different bodies of water 

 has not been made. X'ery probably the same explanation will not answer for all 

 instances, and the condition is not peculiar to the Perch (Titcomb. '21, p. 12). but 

 may be found with regard to trout and other si)ecies. Superabundance of Perch 

 ill a body of water seems to be correlated with the small size of the fish. Here the 

 struggle for existence is so intense among the Perch that none grows large, and 

 possibly there are other factors. Titcomb (I.e.. \). 13). however, does not assign 

 nnich iniportance to inbreeding for he sees no reason for this stunting of the fish 

 and has observed that when the.se small I'erch are transferred to larger b<Klies of 

 water they Iwconic larger. When ponds are raised so as to cover two or three 

 times the ])resent areas, he would expect the Perch in two or three years to average 

 nnich larger than before the increase of the water area. Small size then seems to 

 Ik- due to enviroiunental rather than hereditary factors. Pearsc and .\chtenlRTg 

 ("20, p. 339) conclude from studies of the fish in two lakes in Wisconsin where 

 there is a difference in size of the Perch, that various adverse conditions prevent 

 growth, but foo<l does not apjK-ar to be as important as other f.ictors. such as 

 shallowness and ex]K>sure to the wiixl. 



Pearse and .Xchtenlx-rg have made the most thorough studies of the Iwbitat of 

 Perch that have as yet been ni.nde. and have reached M>me interesting and iini>ortant 

 conclusions. These undoubtedly apply to fish in regitms having conditions similar 

 to those in the l.ikes they investigated. It was found that Perch are able to live 

 under a greater variety of conditions than can any of their assiviates (p. ^Ti^i), and 

 to invade all habitats, going Ih-1ow the thermix-line and even into water without 

 oxygen where they can remain for as long as two hours (I.e., p(>. ^\j\, ?3i»i. 



( )ther observ.itions ami generalizations concerning the habitat of the Perch 

 iii.icic by Pearse an<l .Vchtenlierg ("20) are as follows: 



When Perch invade water which tlocs not contain sufficient oxygen for 

 !)realhing they apparently "Iraw on the su|)ply in the swim bl.idder (p. 32(1). 



In winter most ..f the Perch are in deep water. As soon as the lake is free 

 from ice there is a migration inshore for spawning, but the Perch so<in return U> 

 deep water and remain till lack of oxygen drives them into the shallower region.s ; 

 but as soon as the oxygen is renewed in the overttirn of the water in autumn, the 

 Perch return to the depths of the lake (p. 320). 



The nature of the f<HMl and the cbar.uter of collections ma<le in the lakes 



