The Thames Salmon Association, which was founded as a society
in 1898, have had very little space to make their trials in, for it naturally took some time to settle the "how" and the "where." But they are as fortunate in their place as they are sensible in their methods. It was their object to get the fish into the river as low down as possible, in order to diminish the risk to the smolts from Thames pike. Owing to the fishery rules at present in force, by which small pike are protected, the Thames swarms with these little sharks, to the great damage of the fishery, and the certain destruction of bold little salmon parr. But once in the tideway, they are safe from all danger but poison, for in the Thames estuary there are not thousands of voracious pogges such as wait at the mouth of the Tweed and devour smolts by the score; and few or no large gulls, like the lesser black-backs and herring gulls, which kill tens of thousands of smolts at the mouth of the Findhorn. Bad water is the main danger. Fortunately, a very kind offer was made by Mr. William Crosbie Gilbey, the owner of a fish hatchery on a little tributary of the Lower Coble, which is itself a good trout stream above Rickmansworth, and in parts below that town. This tributary is the Misbourn, a pretty little chalk stream coming originally from a spur of the Chilterns. It is highly aerated natural trout water, and, like most chalk streams, has an even flow in winter and summer alike. It rises near Amersham, but the hatchery is at Denham, two miles north of Uxbridge. Eyed ova have been presented not only by various public-spirited owners of hatcheries in Scotland and Ireland, but also by the Norwegian Government, which only asked for the cost of the carriage. The ova lie for a month in the Denham hatching troughs, under running water, when the young fish hatch out. For three weeks they are nourished by the yolk sack, and then after these very anxious seven weeks the tiny fish are fed three times a day, and as they grow are placed in ponds and conduits, full of Misbourn water, in Mr. Gilbey's gardens. It would hardly be believed how many enemies spring up, like dragons' teeth, against them, even in so quiet a neighbour- hood, and so near London, as the grounds of a house on the Uxbridge Colne. People who have cleaned out ponds often wonder how it is that in a short time they are full of young pike, young gudgeon, and the like. Mr. Boulton thinks that the spawn trickles down in any water that enters. Where the tanks are fed from a river this is inevitable. Young pike which have "started fair" with the very small salmon fry cannot easily be distinguished from them until in no great time they begin to eat the salmon. Eels and dytiscus beetles are other enemies ; so are rats and herons. Herons which breed at Ossulston Park come to the hatchery on the Colne, but they can be frightened away by night-watchers. Not so the kingfishers. It is a tribute to the results of preserving kingfishers on the Thames and in Middlesex that they soon discovered the hatchery, and came in such numbers that they were "an absolute scourge" until the pools were netted over. Even now they carefully watch for any bole, and get inside. No one who has not seen it would credit the great audacity which protected kingfishers develop. They are highly thoughtful and clever little birds, and far more inquisitive than would be believed. The owner of a hatchery in Yorkshire had some pans in a shed, with a door made in two halves, one above the other, like a stable-door. The top half being left open, he looked in, and saw a kingfisher feeding on the ova. It flew out past his head. In the same hatchery it was found that water-shrews had got up the pipes, and were also feeding on the trout eggs.
When the parr (the name usually given to the trout-like young salmon when still in fresh water) are some five inches long and two years old, they show by remarkable changes that they are ready to go to the sea. Over their brown and spotted "parr" skin they begin to grow scales of silver, and so assume a perfectly different appearance. It was Hogg, the " Ettrick Shepherd," who first identified the silvery " smolts " with the striped "parr." Some which he handled had their silver scales rubbed off—perhaps they were not very firmly attached—and rubbing off some more, he found, on the principle of gratters le Busse, that the parr was contained in the smolt's skin. But the young salmon undergoes another most wonderful change to prepare it for its journey,—one which is not usually mentioned, though the assumption of the new scales, possibly to guard its skin against the effects of salt water, is. In its " parr " stage the young salmon has a trout-like tail, strong enough and long enough for river locomotion. But for the seaward journey it develops what is practically a new tail, broader, longer, and stronger than the old one. Mr. Gilbey's efforts have been perfectly successful in bringing the young salmon to this " smolt " stage. They change their scales, and grow their new tails. The experiment has thus shown that salmon eggs can be hatched in the waters of a Thames tributary,—just the kind of place where the breeding fish in old days would run up to, if they did not stay to spawn on the gravels in the main river. Probably they did both, just as on the Cumberland Eden scores of fish will stay to spawn near Corby Castle, while others run up the small becks towards Cross Fell, or ascend right into the lake mountains, up the Lowther to Haweswater.
Having proved that the Thames Valley waters will still breed salmon, the Association then proceed to put the young fish, in their travelling dress, into the main river at the bead of the tideway under Teddington Weir. They are liberated in batches from the spring to the early autumn, according to their state of growth. The total amount of money available is only about 2200 a year, contributed by some thirty subscribers. Yet the experiment is so well managed that it seems deserving of much more support. Practical anglers have entertained great hopes that some of the fish would be seen back at Teddington this autumn ; and two correspondents of the Association write to say that they have seen fish jumping in the big pool at Sutton Courtney, not far from Abingdon. We wish that we could think that they were correct ; but the canalisation of the river from 1788 to 1812, which was the real cause of the destruction of Thames salmon, makes the possibility of the fishes' ascent very doubtful. The present writer has seen large barbel jumping in the evening in these upper pools in such a way that they were constantly taken for big Thames trout, and this may possibly account for the fish reported. The first place where they would probably be visible is at Teddington Weir. It would be a useful test to enclose some of the smoke which
are about to be turned out in a large cage, and lower them for a few hours into different parts of the river below the Pool. The experiment would not be conclusive, but if the smolts lived it would be strong evidence that the London Thames is not too foul for the young fish to go down. If so, it would certainly be clean enough for them to ascend when they had reached the estate of salmon.
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