68 FISHES OF PENNSYLVANIA. 

along the shore, and in some cases it ascends rivers for the purpose of 
spawning. It is believed also that when the feeding grounds of the 
whitefish are polluted by mud the fish temporarily seek other localities. 
There appears to be a spring and summer migration also from lake to 
lake. Spawning takes place during October, November and December, 
upon shoals or occasionally in rivers. The female is larger than the 
male. According to the observations of Mr. George Clark, the two 
sexes, in the act of spawning, frequently throw themselves together 
above the surface, emitting the spawn and milt with the vents close 
together. Spawning operations are most active in the evening, are con- 
tinued at night, and the eggs are deposited in lots of several hundred at 
atime. The number of eggs in a fish of seven and one-half pounds was 
66,606; the average number being nearly 10,000 for each pound of the 
female’s weight. The period of incubation depends on the temperature. 
The usual time of distribution of the young isin March and April. The 
very young are described as swimming near the surface and not in 
schools. They are very active and soon seek deep water to escape 
from their enemies. Their food consists chiefly of smail crustaceans. 
The adults subsist upon the same food with the addition of small 
‘mollusks. 
Growth.—The only means of determining the rate of growth of the 
whitefish is by artificial rearing. Mr. Samuel Wilmot had young fish 
which were five inches long at the age of four months. The growth 
under natural conditions must be even greater than this. Mr. Wilmot 
himself has seen whitefish measuring seven inches in December in his 
ponds. 
Enemies and Diseases.—The eggs of the whitefish are destroyed in 
immense numbers by the lake herring (Coregonus artedi). 'The water 
lizard (Menobranchus) also consumes vast numbers of the eggs. The 
young whitefish are eaten extensively by the pike perch, black bass, 
pike, pickerel, and fresh water ling. The lake trout also feeds upon the 
whitefish. A leach parasitic on the whitefish proves very troublesome 
to that species, and the scales are liable to a peculiar roughness which 
has been observed late in November or during the spawning season. 
There is also a lernzean which fastens itself to the gills and other por- 
tions of the white fish. 
Uses and-Capture.—The excellence of the flesh of the whitefish is so 
well known as scarcely to require mention. Its commercial value is 
great. In Lake Erie, in 1885, according to statistics collected by the 
United States Fish Commission, 3,500,000 pounds of whitefish were 
caught, over 2,000,000 of these by fishermen from Erie alone. In this 
year Erie county had 310 persons employed in the fisheries. The capital 
invested in the business was nearly $250,000. ‘The wholesale value of 
the fish products was upwards of $400,000. The whitefish was the third 
species in relative importance; blue pike ranking first and the lake her- 
