EEPORT OF COMMISSIONERS OF IXLAXD FISHERIES. 137 



tinued experiments in order to bring the work up to its present 

 condition. It can now be truly said that the scheme, as now operated 

 is entirely practical and successful. The chief obstacles which had 

 to be overcome in reaching success were the serious cannibalism of 

 the larvae, the necessity of crowding them together in order to rear 

 large numbers, the difficulty of supplying them with sufficient food, 

 and the parasitic growths of diatoms and protozoa which infest the 

 early stages. 



The main feature of the scheme used in rearing consists in keeping 

 the fry in constant circulation. This is accomplished by confining 

 the fry in canvas bags which are suspended in the water and provided 

 with windows of fine mesh copper wire netting. Two bladed paddles, 

 not unlike restaurant fans, are kept revolving slowly in the bags at 

 a rate of 10 revolutions per minute. Through their motion the 

 water is kept fresh and the fry are prevented from settling to the 

 bottom. The current of water is made just strong enough to keep 

 them separated, thus preventing them from feeding upon one another, 

 and yet of sufficient strength to keep their food in circulation near 

 them. 



A 2^ horse power gasoline engine supplies the power for operating 

 the paddles. This power is transmitted from the houseboat (Plates 

 XIV and XV), in which the engine is located, to the floats ftnc*hor& a 

 fey the side of the houseboat, by means of shafting and mitred gears. 

 A specially constructed device is used for transmitting the power 

 to the constantly moving floats, and consists in a pair of toggle- 

 joints connected by a sleeve in which two pieces of square shafting 

 slide. The two floats are fastened to the houseboat, one on each 

 side, and are composed of a framework of 6 x 6 spruce, floated by 

 barrels. Each one is capable of containing five rearing bags. These 

 bags^are made of canvas, eleven feet square and four feet deep, with 

 three windows of copper netting, one in the bottom and one on each 

 of two sides of the bags. More detailed account of the various 

 constructions and operations will be given in the following para- 

 graphs. 



