76 PHYSOSTOMI. 



principally breed, is thorouglily impregnated : he likewise remarked that the milt 

 kept in water retained vitality for three days. Should the male by any accident 

 be killed during the time the female is spawning she consoles herself with another 

 mate, and it is possible that even a parr would be snfficient in order to render the 

 ova fertile. In January, 1837, Shaw took a female salmon 14 lb. weight from its 

 spawning bed and a male parr IJ oz. in weight, impregnating some of the eggs of 

 the former with the milt of the latter, and the young were similar to those raised 

 from two adult salmon. The male as a rule keeps guard near his partner, 

 probably for the purpose of keeping other males at a distance, and it is recounted 

 in the Zoologist (1847, p. 16.50) that two had an encounter in the spawning 

 season between Glenferness and Dulcie Bridge, apparently for the possession of 

 a female, and at last one floundered dead to the surface, the victor having torn 

 off the flesh along the back from the head to the tail, and down to the very bone. 

 It has been held by some that during the breeding season there is an excess of 

 male fish over females ; others account for this by the males being in a more 

 exhausted condition than those of the feminine-gender, consequently more of 

 them are taken : females likewise appear to be more crafty. 



Salmon eggs, though apparently tough and elastic, are nevertheless exceedingly 

 delicate, and Mr. Nichols tells us how Mr. Ramsbottom was carrying three soda- 

 water bottles containing some salmon ova, slung in a handkerchief to prevent 

 concussion, one slipped from the hand and fell to the earth, and not a single 

 ovum out of this bottle was hatched, while those in the others taken at the same 

 time did well. Even pouring water on eggs in a careless manner has been known 

 to kill the ova, and the like result is recorded due to using a nail instead of 

 a screw in fastening a small box of ova. It has been shown that the nearer 

 the eggs are to hatching the better will they bear transmission. 



It has been calculated by Stoddart and others that if salmon eggs are left to 

 nature the produce is about four or five fish fit for table for every 30,000 ova 

 deposited, whereas the same number are obtained from every 800 eggs artificially 

 protected. Although these figures are founded upon calculations some of which 

 may be fallacious, still it is abundantly obvious that the number of reared fish 

 from eggs left to nature is far less than what obtains in those artificially 

 propagated. In the Tay the augmentation in the number of fish was as much as 

 10 per cent., an increase not apparent in rivers in which this mode of fish 

 cultivation was not carried on. Consequently' a plan commenced being adopted of 

 obtaining the ova from the fish and rearing them artificially. The number of eggs 

 thus removed is but a small percentage of those in the stream, and it has been 

 ascertained that eggs still retain their vitality in a female salmon that has been 

 dead two hours or even more, and that they have been successfully vivified from 

 the milt of a live male. 



The mode in which fish are stripped varies ; should the examples be very 

 ripe, slight pressure will occasion eggs to pass from the female and milt from the 

 male, or a little extra pressure may be necessary. Some add the milt to the ova 

 when the latter are in water, others prefer omitting the use of water. The eggs 

 are now removed to a place prepared for their hatching and rearing the youno- 

 fish, and where a constant supply of water, at a required temperature, is artificially 

 kept up. 



During iacubation these eggs should be kept dark and the opaque ones removed, 

 or they contaminate others in their vicinity. Too great a temperature affects 

 the eggs as already observed (page 65). Sir J. Gibson-Maitland has remarked 

 that the eggs taken early in the season are the most fruitful and produce the 

 strongest fry. The young begin to pine when the thermometer marks many 

 degrees above 55° : they require an increased flow of water and conceal them- 

 selves under any available shade as the light affects them. Other fish, some 

 mammals, birds, Crustacea, and insects seek them out as food, irrespective of which 

 they are liable to gill fever or a fungus due to uncleanliness may appear upon the 

 back of the weaker fish. The young, after the absorption of the umbilical sac, 

 are fed upon various animal substances, care being necessary that such food is 

 wholesome, and that the supply does not exceed the demand. 



