TEMPERATURE FOR SPAWNING. 13 



destruction of the egg, and not of the fish when once 

 brought into being. Steam navigation, as 1 have said be- 

 fore, very little affects a fishery, as long as it is confined to 

 the tideway of the river. Salmon never spawn within the 

 range of the tide, if they have a free passage up to the heads 

 or clear water : for it is there they desire to deposit their 

 eggs in the shingle and clean coarse gravel. Most fish 

 prefer to deposit their eggs in gravel or sand : but some, 

 such as carp and tench, spawn among the weeds called 

 Ranunculus aquations, or water crowfoot ; and in this weed 

 the egg becomes well entangled, and secured from the pre- 

 datory appetites of other fish. 



Salmon take one hundred days, trout fifty days, and 

 many other fish forty-two days, to come forth from the egg, 

 provided the water does not change its temperature during 

 the period of breeding: so that it is not impossible to bring 

 varieties of better sorts of fish from distant countries to 

 stock our streams with, and I should say, from what I have 

 myself experienced, with success. The temperature best 

 adapted for spawning ranges from 53 to 56, and at this 

 warmth I have never found any alteration in the time I have 

 stated, which may be relied upon as correct, and the true 

 time in every case. Should this even temperature vary very 

 much, then the egg, as the water loses its warmth, is sensibly 

 retarded in its incubation. From this change of temperature 

 T have known the egg of the trout to be delayed from fifty to 



