WHAT TROUT EAT

Taranaki Daily News, 14 October 1929, Page 7

WHAT TROUT EAT

BAD EFFECT OF CLEARING. > STUDENT’S CONCLUSIONS. For some time expert fishermen have suspected that many of the trout rivers of New Zealand, particularly in the Wellington district, have been failing to support as many, trout as might have been expected. In order to investigate the. matter the Wellington Acclimatisation Society made an annual grant of £4OO a year, two years ago, to pay the expenses of a qualified research student. Captain J. S. Phillips, the student selected, has now made a report on the subject of very considerable interest to fishermen (saya the Dominion). Until this research was carried out little was known of the food supplies of trout liberated in New Zealand rivers. During the preliminary period when the rivers and streams round Wellington were being examined by Captain Phillips, numerous aquatic organisms were discovered that were still unknown to science. Even to-day their life history is a matter of conjecture. After carefully investigating the food supplies of the trout it has been proved conclusively that the removal of riverside bush has had decidedly adverse effects. Not only is there lack of cover for the flying stages of aquatic insects, but those that contrive to survive have formed a bountiful source of food supply not to the trout, but to birds. Besides, amongst other things, the increased scouring has swept away other types of food supply and incidentally removed the shelter so beloved of trout.

As an example of what the effect of the removal of riverside bush can do sample catches of trout food were taken in the Hutt River 200 yards above its junction with Belmont stream. At this epot the banks are bare. Only a few unappetising pupae and larvae were discovered. In the Belmont stream itself,, with its willow-lined banks, such proved favourites as the caddia larvae, Alay fly larvae, and creeper were caught in enormous numbers.

In fact, a careful examination of the stomachs of a large number of trout has shown most clearly that caddis and May fly form between them something like 90 per cent, of the food eaten by trout. Just after spawning, however, when a rich, plentiful spring diet is vitally important, these articles of diet are at their scarcest. Bui- for the arrival of the whitebait at a most opportune moment the trout would be in very poor condition at the beginning of the fishing season. Beetles, far from forming an article of diet, are, with one minor exception, a distinct disadvantage. Besides feeding on caddis fly and other trout food, they have been known even to capture young trout fry in a moet audacious manner. Sand flies, Captain Phillips declares, undoubtedly fofm quite an appreciable diet of the trout. Many fishermen will take comfort from this, but will agree nevertheless with Captain Phillips when he remarks that there is no need to encourage or even protect this abundant form of trout food.