CX ARTIFICIAL CULTIVATION OF FISH. 



ascend the stream which feeds the pond, but having wire trays so fitted 

 that the eggs when deposited drop through into a receptacle for their 

 collection. Some observers, however, appear to think that, due to the 

 rapidity of the current, the milt is often washed away before it has 

 performed its function, and consequently a number of ova escape 

 impregnation. Rough fish may likewise be artificially cultivated, as has 

 been remarked upou (page lxvii). 



In stocking pieces of water with eggs or young of Salmonidas it would 

 seem desirable that great attention should be paid to the age and condition 

 of the parent fish, as I have observed (page lxix). I assume that care will 

 be taken that the water is appropriate, for although new stock may tend to 

 improve local breeds in suitable places, such will not be the case should the 

 food be insufficient or inappropriate. Perhaps the Lochleven race of trout 

 grows as fast as any other in these islands, especially when the eggs are 

 from seven or eight year old parents, while in the warmer south they increase 

 more rapidly in size than in the colder north. 



The introduction of exotic forms of fish into our fresh waters has been 

 advocated, a proceeding which, although it may be beneficial, on the other 

 hand may be the reverse. It should first be considered whether the stranger 

 subsists upon a vegetable or animal diet, and secondly whether sufficient 

 exists for his consumption where it is proposed to acclimatize him. 

 Anadromous forms may be beneficial, due to the small amount of food they 

 generally require when ascending the rivers to breed. Carnivorous forms 

 may be useful, in order to diminish too large a number of coarse fish in a 

 river, where they are in excess of its capabilities for supplying them with 

 sufficient nourishment ; but when they have thinned down the primitive 

 stock they may continue to deplete the fishery to too great an extent, and 

 be a nuisance in their turn. 



It is not surprising that the cultivation of fish-ponds for coarse fish has 

 decreased or almost disappeared from this country, because increased 

 facilities of carriage of fish from the sea-coast has rendered their produce 

 of but little value; and as such has become' less and less esteemed the care 

 bestowed on ponds has been diminished until at last they may be said to 

 produce fish of an earthy or muddy quality*. If left unattended to they 

 must deteriorate : they should not stand full more than two or three years 

 unless the proprietor revels in the contemplation of miserable half-starved 

 forms. The best treatment appears to be rotating crops of vegetables with 

 crops of fish, for which purpose at least three ponds are requisite, although 

 more are undoubtedly advantageous. 



The aspect of the ponds, nature of the soil and character of the water 

 are all factors to be taken into account, hard clays and gravel being generally 

 unfavourable, and a marly soil mostly to be preferred. In constructing' a 



