48 DEPARTMENT OF GAME AND FISHERIES No. 9 



the available food supply or forage of the finer varieties of fish ; in other words, 

 from the standpoint of the economy of any lake, the relationship of one species 

 to another must be determined. The harmful characteristics of each species 

 must be weighed against its useful or good characteristics. 



Cat, or Finger lake, located in the township of Blair, county of Parry Sound, 

 was closed indefinitely in 1930 for the purpose of bass propagation after a 

 biological survey indicated that such a step was feasible. 



In order to reduce competitor fish, steps were taken to remove the pike, 

 maskinonge and pickerel from the lake. These operations extended from June 

 13 to June 22, 1931, pound nets being used to capture the fish. The catch 

 recorded over this period was as follows: bass 62, pike 19, maskinonge 10, 

 suckers 4. sunfish 2. The pike and maskinonge were removed and planted in 

 the French river. The studies revealed that bass predominate, but the removal 

 of large predatory pike and maskinonge should improve conditions for bass 

 as regards food and survival. 



4. Mortality of Fish 



Investigations concerning the causes of fish mortality in Manitou creek 

 (Manitoulin), Weslemkoon lake (Lennox and Addington), lake Semple (near 

 Midland) and Rice lake were investigated and reported upon by officials of the 

 Branch. 



5. Operations of Commercial Nets and Hooks 



Before nets are licensed for new areas, the Branch biologists investigate 

 and report thereon. During the past year three inland water areas were studied 

 from this angle. 



An investigation of the use of hooks and bait nets by commercial fishermen 

 in the Georgian bay was commenced in 1930 and was continued in 1931. Gangs 

 of hooks and bait nets were examined periodically. The studies reveal : 



(1) In bottom line fishing 20 per cent, of the trout taken are of illegal 

 size and weight. 



(2) The floating line takes only a small percentage of illegal trout, but 

 its use should not be encouraged, since the reserve supply of trout which 

 cannot be captured in nets is attacked by such a contrivance. 



(3) Vertical movements of trout are quite apparent as the water 

 temperatures rise, deeper water being sought. In the fall they appear in 

 10 to 20 fathoms and after the spawning season is over, they appear near 

 the surface. Smaller trout under two pounds in the round seem to prefer 

 about 20 to 45 fathoms of water, the greatest number being taken at these 

 depths. 



(4) The proportion of whitefish and herring species taken in bait nets 

 is roughly as follows: bloater (L. hoyi) 70 per cent.; lake herring (L. artedi) 

 2 per cent. ; tullibee 2 per cent. ; round whitefish 1 per cent. 



Bloaters or L. hoyi are used extensively by many fishermen whole 

 and with the swim.-bladder inflated. Lake herring (L. artedi) and tullibee 

 are cut into several pieces when used as bait. There does not appear to 

 be a diminution of the supply of the bloater. It is not important as a 

 marketable fish on account of its small size and watery flesh, but it enters 

 extensively into the diet of lake trout and for this reason its wasteful use 



