FISHES OF DOUGLAS LAKE, MICHIGAN. 227 



parts of the lake, but it is more likely that it has made its way thither from Maple 

 River. 



NoTROPis CAYUGA Meek, Cayuga minnow. — Three specimens only have been taken 

 in the lake at locality 11, on stony shoals at the west side of North Fishtail Bay at the 

 entrance. The slopes bordering these shoals are sparsely grown with plants, and they 

 are so much protected from wave action that there is a thin crust of algal marl uniting 

 the superficial sand particles. 



NoTROPis HUDSONius (De Witt Clinton), spot-tailed minnow, and the common 

 shiner are the most abundant of the Douglas Lake minnows and the most widely dis- 

 tributed. On July 29, 107 specimens of the spot-tailed minnow were taken with the 

 seine on the sand shoals of South Fishtail Bay in about 2 feet of water. They were of 

 nearly uniform length and averaged 2.8 inches; 64 were females and 24 males. These 

 were immature fish and were in schools together with young of the yellow perch and 

 common sucker. Two hundred and sixty-seven immature individuals were seined in 

 the same place on September i, 1911. On the 20th of July, 1912, 9 mature individuals 

 2,% to 3^6 inches long were seined at Bryant's dock (locality 9), together with mature 

 Pimephales notatus and .S. atromacidatiis . Mature individuals 4 to 6 inches long are found 

 in many places in the lake where there is abundant vegetation on the slope. Here the 

 fishermen seek them for bait and take them with the baited minnow hook by casting, 

 as one casts for trout with the fly. They are taken in company with the common shiner 

 and in about equal abundance. The fishermen locate these schools by the disturbance 

 of the water's surface due to their rising, and often visit several patches of vegetation 

 before they find them. Hence it appears that the fish may travel together in schools 

 from one patch of vegetation to another. 



The alimentary canal of one of the immature individuals taken on the sand shoal was 

 found to be filled with Cladocera, apparently of the genus Chydorus, the form that makes 

 up the bulk of the food of the young perch and suckers taken in the same habitat. The 

 Cladocera were apparently as numerous as in the young perch, but there were no other 

 Crustacea such as occur in the perch. The short, slender, close-set gill rakers with the 

 narrow gill openings make an excellent apparatus for the capture of these small Crus- 

 tacea. The roof and sides of the mouth and the tongue have many short papilla; set in 

 curved longitudinal rows, and these may serve to hold the Crustacea while permitting 

 water to pass backward. There are no records of the stomach contents of the adults 

 of this species in Douglas Lake. Elsewhere (Forbes and Richardson, 1908) it is known 

 to feed on insects, crustaceans, and vegetation. 



NoTROPis coRNUTus (Mitchill), common shiner, is taken on the hook in the same 

 manner as A^ hudsonius and in company with it in patches of vegetation in nearly all 

 parts of the lake. It is very abundant. Three taken in South Fishtail Bay in August, 

 191 1, measured, respectively, 3.5, 3.75, and 4.06 inches in length. These were in fine 

 condition, the mesentery heavily laden with fat. The contents of the alimentary canal 

 were as follows for the three specimens : 



1. About two-thirds Cladocera, apparently Chydorus; one-third insects, apparently 

 larval. 



2. Remains of insects and a small quantity of Cladocera. 



3. Some fragments of broad, green leaves on which were brj'ozoan tubes; some 

 Gloitrichia: a large number of detached bryozoan branches, some of them with state- 



