42 PISH CULTURE. 



Of course a great deal depends upon tlie temperature 

 of the water : if that can he kept down, much more 

 can be done with it ; hut contingencies, and not the 

 most favourable results which we are perhaps likely 

 to obtain, must be calculated. 



Spawn is obtained from November until rebruary. 

 To the end of January the weather is certain to be 

 cold enough, often too cold, for our purpose — so 

 much so that artificial warmth is rather required ; 

 not so always February and March. Of late years, 

 particula,rly, we have often had a warm February 

 and March, or a warm March and April. February 

 and March are most important months for the pisci- 

 culturist, and much depends on them. If they are 

 warm the temperature of the water, which has 

 perhaps been vibrating about 38° and 40°, often 

 jumps up to 46° or 47°, and the same stream of 

 water which could be safely employed at 38°, through 

 from ten to twenty trays wOl not answer at 48°. 

 Moreover, as it travels from tray to tray it gets 

 warmed by the atmosphere and by exposure, until 

 there wiU frequently be a difference of 3° or 4°* 

 between the temperature of the water in the first 

 tray and the last one. A raised temperature quickens 

 the development of the egg considerably ; with 

 salmon a difference of 10° or 12° in the temperature 



