GAME AND FISHERIES FOR 1929 19 



net portions of rivers, and into larger lakes while immature, but they return to 

 the smaller streams to spawn, hence the necessity of keeping such streams free 

 from obstructions. 



On the other hand, providing the upper reaches of a system are well supplied 

 with speckled trout and are separated by an obstruction, natural or otherwise, 

 from the lower warmer reaches containing only coarse fish, it is not feasible 

 to run the risk of infesting the trout waters with the coarser varieties of fish 

 by opening up a fishway through the obstruction. 



Fish Measurements: 



Considerable work is being done in connection with measurements of 

 fish, particularly commercial varieties, in order to convert "legal weight" into 

 terms of "legal length." It is necessary to take thousands of measurements 

 for each species at different periods of the year, their age, sex, sexual maturity, 

 etc., in order to arrive at a fair and undisputed standard. In this connection, 

 it has been found that a standard length used for a species in one of the Great 

 Lakes, or, in one inland lake where commercial fishing is carried on, is not true for 

 the same species of the same age in a different lake. In other words, the rates 

 of growth of the same species differ in different lakes. 



Fish Tagging: 



Six hundred and thirty-five Lake Erie fish have been tagged including 

 steelhead trout, whiefish, herring, white bass, yellow pickerel, blue pickerel, 

 and small-mouthed black bass, in order to study their movements, distribution 

 and rates of growth. 



The tag, which is non-corrosive metal No. 3, is stamped on one side with 

 the letters O.D.G.F. "Ontario Department (of) Game (and) Fisheries" and on 

 the other with a serial number. 



During the tagging process, the fish, which is preferably of illegal size, is 

 retained in fresh water in a tank of convenient size in which to work on board 

 boat. The tank has the bottom or sides, or both, marked off in inches and 

 fractions thereof in order that the length of the fish tagged may be easily obtained 

 and also its depth in inches. In order to determine the age of the fish tagged, 

 two or three scales are removed from that portion of the body ventral to the 

 dorsal fin, and the area from which the scales are removed is bathed with a 

 solution of potassium permanganate. The weight of the fish is determined and 

 it is then released. 



By means of a circular letter the Canadian fishermen on Lake Erie have 

 been informed regarding the methods to be adopted in making returns to the 

 Department. A few returns have been made, but it is too premature to make a 

 pronouncement regarding the results of these experiments. 



Pollution: 



Studies in connection with pollution require more specialized and intensive 

 work. During the past year very little was done in this direction excepting 

 investigations of local disturbances at Lindsay, Bridgeport, Owen Sound, and 

 general observations made in the Spanish, Mattagami and Wabigoon rivers, 

 during biological surveys. However, preliminary surveys help appreciably in 



