1927 GAME AND FISHERIES 5 



application must be considered on its merits. As it was impossible to make 

 a thorough study during the past two summers of all the waters requested to be 

 restocked, before making recommendations many applications were disposed 

 of on the strength of the information given by the applicants, and also on the 

 basis of a knowledge of existing conditions in the neighbouring waters of the 

 same system. 



Limnobiological studies were carried out on twenty-one inland waters 

 during the summer of 1925, and on fifty-eight during the summer of 1926, with 

 a view to determining their possibilities for fish production. The programme 

 of the studies carried out on these waters with certain modifications for streams, 

 included three fairly well-defined, and yet correlated lines of investigation: — 



(1) Fish fauna of the waters and their relative abundance. 



(2) Plankton on which either directly or indirectly fish depend for their 

 food supply was collected from various depths for quantitative and 

 qualitative studies in the laboratory. The quantity and character 

 of the plankton are good indications of the productivity of any body 

 of water. (Observations were made on the available macroscopic 

 food supply, for example, molluscs, crustaceans, insects and insect 

 larvae.) 



(3) A study of the physical and chemical properties of the water. 



(a) Physical properties, namely, depths, colour, transparency and 

 temperatures. 



(b) Chemical properties, namely, dissolved gases (oxygen and 

 carbon dioxide), bicarbonate, alkalinity and hydrogen ion con- 

 centration. 



The above factors determine very largely the abundance of the plankton. 



The biology of the fishes of Lake Simcoe was gone into more intensively, 

 and to this end eleven gill-nets, each fifty yards long and five feet deep, and 

 with mesh ranging from one and one-half inches to five inches were emplo^'ed. 

 By this means data were obtained on the relative abundance, distribution, 

 rate of growth, food and spawning conditions of the various fishes inhabiting the 

 lake. Extensive seine hauls were made over ecologically different areas in order 

 td obtain data on the young fry and minnow population. 



By means of an Ekmann dredge covering an area of eighty-one square 

 inches the life on the bottom of the lake was collected and preserved. Mr. 

 Donald S. Rawson, B.A. is making a special study of this material in the Depart- 

 ment of Biology, University of Toronto. 



Determining the suitability of any body of water, in advance of stocking, 

 and in the light of the present day knowledge of the criteria to employ for the 

 purpose, is one means of preventing undue loss in planting fish. However, 

 applicants may render most important service by following the instructions 

 issued with each lot of fish sent to them. The most important points to 

 remember in this regard are — firstly, to plant where the natural food supply is 

 adequate, and secondly, to plant out of the reach of enemies. Instructions are 

 issued to applicants having these two important principles in view. It should 

 be borne in mind that planting points vary according to the life history and 

 habits of the species planted, and the life history and habits of its enemies. 

 By means of propaganda these facts may be driven home to applicants. 



By biological surveys, legislation and education, steps are being taken by 

 the Department to preser\e the game fish in waters not already depleted for 

 the perpetual use of the |)ul)lic. compatible with chaneini.' conditions in nature. 



