AN ECOLOGICAL STUDY OF THE FISH FAUNA OF THE 



DOUGLAS LAKE REGION (AIK/HIGAN) WITH SPECIAL 



KEFERENCE TO THE MORTALITY OF THE SPECIES. 



KOV J. COLBERT. 



In this study of the fish fauna of the Douglas Lake (Michigan) region 

 special attention was given to the mortality of the various si:)ecies 

 found and it is thought that the data collected in this connection have 

 a direct bearing on the general ecology of the species involved. In 

 order that the data on the mortality might be more easily understood, 

 records of species frequency were taken for several typical habitats and 

 a general survey of the intra-lake distribution of the .species made. 

 The collection of fishes from which the data were gathered includes 

 several hundred specimens taken during the summer sessions of 1913 

 and 1914 at the University of Michigan Biological Station at Douglas 

 Lake. 



Opportunities for procuring data on these i)articular problems were 

 especially favorable. Douglas Lake affords an ample variety of aquatic 

 habitats which are easily accessible for study. The shores of the lake 

 are covered with their natural growth of vegetation and timber, and as 

 yet neither the inlets nor the outlet, Maple River, have been dredged 

 or changed to any large extent. The lake and its adjacent waters 

 may be divided into the following units for the purpose of this study: 

 North Lake, that part of Douglas Lake west of Fairy Island and Robert's 

 Point; North Fishtail Bay; Bessey Creek region together with the 

 other small inlets of the lake; and Maple River (See map, Fig. 2). 

 Each of these regions has a condition or set of conditions distinguishing 

 it from the others and encouraging the predominance of certain species 

 of fish. 



The prevailing winds of the region bloAv from th(> west and north- 

 west, hence North Lake, the part of Douglas Lake west of Fairy Island 

 and Robert's Point, is seldom disturbed by heavy Avinds and waves, 

 and the aquatic vegetation, especially MyrioplniUum and Pototnoijeton, 

 has a better chance to grow. This is particularly true immediately 

 west of Fairy Island. In this region the pike-pickerel, Esox luciiis, 

 and the rock bass, AniblopUtes rupestris, are very common, and along 

 the marshy shallows of the west shore the cat fish, Amieurus melas, nest 

 and are found in great abundance. 



North Fishtail Bay affords two somewhat tlifferent habitats. The 

 north portion is a quiet bay surrounded l)y a thick pine and cedar 



