TROUT STREAMS

Hokitika Guardian, 17 May 1927, Page 4

TROUT STREAMS

WjHY THEY FAIL,

LACK OF FOOD BLAMED

(Lyttelton ‘Times.”)

With the exception of the Selwyn River and other streams that run into Lake Ellesmere, the rivers of Canterbury have deteriorated to a marked degree as trout streams. Mr D. Hope, curator for the North Canterbury Acclimatisation Society, lias formed the opinion that the cause of the failure ot tlic trout is the destruction of the whitebait. Greater and greater quantities of whitebait are taken from the rivers each year, and with this destruction of their natural food, said Air Hope, the trout had gradually faded from the rivers.

About forty years ago said Air Hope, tho rivers were full of iiuinga. ‘‘When trout were introduced into New Zealand they were an extraordinary success. Everyone knows that they have become famous. There was a special reason for that, I have proved conclusively that it is food, and nothing but food, that causes growth. If they were such a success here there must have been some special food we possessed that suited them. In the early days our rivers wore absolutely teeming with whitebait. Immense shoals went up the rivers. 'There were the same immense numbers of inanga, and there was good trout fishing right from the source of the rivers to the sea. The trout always followed the shoals of whitebait up the streams.”

Rapid growth was one of the characteristics of the whitebait, said Air Hope. They quickly arrived at the inanga. stage, and they provided food for the trout all the time. There was no need for the trout to shift out ol the pools because the food was always there. They grew to sizes much greater than they do to-dav. Enthusiasts, expecting small fish, used to be surprised at the size of their catches. “But,” said Air Hope, “nobody seems to have studied the tiling out to see what was the special cause of their splendid growth ” NYitli the growth of population there arose a greater demand for whitebait and more and more people each year went to the rivers fo the purpose of securing this table delicacy. “Whitebait. and inanga that had gone out to sea to spawn, were taken in millions and millions and the destruction ol these meant the destruction of the stock. Now there are so many taking up whitebait fishing that the greater muni or of fish are caught as they enter the streams. Practically none now get up the streams to grow into inang,i. Year by year they are diminishing, with a resultant lack of food for the trout. 'the result is that the trout Inv-e gone from the upper waters. ami you will find them only near the mouths where there is food in the

shape of bullies and silveries that cntei to spawn. They will be in the river: two months and then go to sea again mid the trout will follow them out The result is that all our brown troll practically are going to sea and be coming sea trout.”

Air Hope pointed out that the Ashley used to be. one of the favourite whitebait rivers. But the number ol set nets in the Ashley had increased to such an extent that now practically no whitebait ("scaped at all. As a result no whitebait got up-stream and there were no trout. 'I he question of shingle also had a bearing on the question as far as the Ashley was concerned. 'The aggregations of shingle had filled the pools, and where there were no large pools t.-out could not be expected to attain good sizes even ii other conditions were favourable. Dealing with the suggestion that an expert should he employed to go into the question of breeding Hies for the purpose of improving the fish, Air Hope said lie was satisfied that (lies had never been responsible for our good fishing It was the whitebait that had made our fish what they were. The remarkable giowth made' by the whitebait to the inanga stage was illustrated by Air Hope in an experi-

ment which he carried out. “I enclosed some whitebait in a small, secure pond.” be said, “and noted their growth. 1 preserved a specimen on August 17, the date 1 placed them in the pond. At three weeks’ intervals I took specimens up to fifteen weeks. At twelve weeks they were three and a

half inches long ami of corresponding girth. They were ample size to be used as bait’and afforded flue food lor trout.”

“To prove that my theory is correct,” said Air Elope, “you have only to take the fact that the fish have deteriorated in all our rivers in Canterbury except the Selwyn and other streams that run into Lake Ellesmere.

At the present time Lake Ellesmere has an abundance of fish food in the way of bullies, silveries aiul inanga, if you care to open trout taken there rip to Christmas you will not find a single fly in their stomachs. Later in the season—in February, Afarch and

April—they will take the fly, especially in the latter two months.” To show that the bait food had a good deal of hearing on the subject. Air Hope said that the fish caught in the Selwyn amounted to tons for the season. The whole of them would average four and a half pounds, which was the finest brown trout fishing in the world. “There is no place I know of,” he said, “that supplies the weight and number of fish as the Lower Seluyn. With the great number of anglers who fish in the Selwyn every night in the week it would he fished out in no time hut for the wealth of food.

Speaking of the relative sizes of tin fish caught now and those caught in the early days. Air "Hope said that individual fish of large size were takei to-day. “But it is simply a matter of food,” he added. “There were les? fish in the early days and there was plenty of good food for them. As an instance of how they will grow I can quote another experiment I carried out. I stocked Victoria Lake with rainbow fry. T also stocked my pond with a portion of the same fry. In three years the largest fish taken in Victoria Lake was half a pound. The fish I had in my poml and which I fed artificially on meat weighed three pounds. It was simply a matter, ol food—a difference of two and a half pounds in the same period. It should he remembered, too, that the fish in my pond were not fed on their natural food. For preference, trout feed ou bait. They are cannibals by instinct. From a month old the fry will eat one another. Failing inanga trout will prey on the smaller of their own species, and of course, that also helps to reduce the stock.”

One reason why Air Hope considered that there was little to hope for from the importation of an expert was that the experts, lie considered had failed in their own countries. “I find,” he said, “that the fish at Home do not average above about half a pound. An American told me quite recently that if they got a three-quarter pound fish they thought they had a good one. Is it reasonable to expect an export to come out here and improve our fishing when they cannot improve the fishing in their own country? A\ e lui'c the proof of practical experience that we have at the present time in the whitebait the finest trout food in the world. Why not take steps to conserve what we have instead of bringing out something that may prove injurious when brought out here?” The New Zealand whitebait Mr

Hope said, was m;iijiie. There was whitebait in South America, but not

enough to he of nnv use. At Home they had what they railed a whitebait. hut it was a mixture of smelt and herring and was of no practical use at all as a fish food. 'I he solution of the trouble in the Canterbury rivers, he said, was to discontinue the destruction of the white’ait, thus leaving in the rivers the stocks of natural food that had made them such famous fishing places in the old days.