As an example of a modern pond for the breeding of fish for commercial uses (and these are the kind of ponds that we have the greatest need to erect at present), we subjoin a rough pen-and-ink plan of the salmon nursery at Stormontfield, on the River Tay, in Scotland:—
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A. Lade (mill stream). |
L. Pipe to empty Pond. |
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So far as it goes, the Stormontfield suite of ponds is admirably adapted for the purpose of salmon-breeding. The water-source, a mill-race, runs parallel with the River Tay; and the breeding-boxes are laid down on a gentle slope, which is nicely sheltered by a clump of trees. The expense of constructing the Stormontfield ponds was only 500l., and it is greatly to be regretted that the proprietors of the Tay fisheries did not sooner complete the series by adding another fish reservoir. That is now, however, about to be done. As explained in our paper on “Fish Growth,” only one-half of the salmon hatched are ready to migrate at the end of a year from the date of their birth; the other moiety remains another year in the ponds. Now, to secure an annual hatching, it is necessary that there should be two reception-ponds at Stormontfield; otherwise the tiny fry of the new hatching would stand a good chance of being devoured by the old stagers of the year before. It has been greatly against the commercial success of the ponds on the Tay that they have hitherto been only able to yield a hatching every alternate year; but, even as they are, they have added largely to the income from the fisheries. Another benefit in such a series of ponds would be a depôt for the gravid fish. It is frequently the case that salmon cannot be found, just when wanted, in the precise condition that would be suitable for manipulation; but if they could be detained for a few days, they would then be ready for the process of artificial spawning. Thus, three ponds would be absolutely necessary in a perfect hatching establishment. A splendid salmon-river like the Severn might have its natural powers of production immensely aided by a series of ponds, where artificial spawning and protected breeding on a large scale could be carried on. One million of eggs could easily be hatched in a suite of breeding-boxes three times the size of those at Stormontfield; and were the ponds in proportion, and were there enough of them, a hatching might be effected annually with great ease, and much to the profit of all concerned.
Another suite of salmon-breeding ponds has been constructed on the River Ugie, in Scotland. Forty boxes have been laid down at a suitable place on this stream, and each of these will contain a thousand ova. These ponds have been constructed on the model of those at Stormontfield—Mr. Peter Marshall, the manipulator at the latter place, having supplied the plans. The piscicultural system is likewise well known in Ireland, salmon having been introduced into Lough Mask by the Messrs. Ashworth of the Galway salmon-fisheries, who propagate annually (or, rather, hatch by the artificial mode) 300,000 salmon-eggs!
As showing what can be done in fish-breeding, when it is properly gone about, we may state that the extent of new water taken in by the Messrs. Ashworth, in the district of Loughs Mask and Carra, comprise an area thirty miles in length by ten in width. In a communication with which we have been favoured by Mr. Ashworth, we are told that as many as 659,000 salmon-ova were collected, impregnated, and transported for the purpose of stocking the new salmon-water—that is to say, the waters that communicate with Loughs Mask and Carra, the purest streams of the rivers at Tourmakeady, Robe River, at Hollymount, and other streams. These loughs will speedily become highly productive. Salmon being once introduced into a good stream, and properly protected, will go on propagating themselves ad infinitum. We may here quote from Mr. Ashworth’s communication a brief description of the process of artificial spawning, which is an operation of a very simple kind, and perfectly harmless to the fish which are manipulated. When a female salmon with ripe ova is taken, it is held in a tub full of clean water, and the ova-bag is gently pressed till the eggs fall into the tub. The milt is squeezed in a similar manner from the male salmon, when an instantaneous change becomes observable in the eggs, which, bright and clear before, at once become florid. The spawned fish are as soon as possible returned to the river, when they dash away with apparent delight, agreeably relieved of what must have been a heavy burden; indeed, the spawn is a fourth part of the fish’s entire weight.
Venturing now into the sea itself, we can give our fishermen a “wrinkle” which is worth their