WHAT TROUT EAT

Hokitika Guardian, 16 October 1929, Page 8

WHAT TROUT EAT

BAD EFFECT OF CLEARING. CONCLUSIONS OF RESEARCH STUDENT. WELLINGTON, October 13. For some time expert fishermen liavb 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 £4O. 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. It is worth noting that to-day many other acclimatisation societies have adopte>. similar systems, but all credit for originating the idea must go to the Wellington Society.

DISCOWRIES IN THE WATER

Until this research was carried out little was known of the food supplies of trout lioeiated in New Zealand rivers. During the preliminary period when the rivers and streams round Weellington were being examined by Captain Phillips, ■ numerous aquatic organisms were discovered that wene 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 botin-. tiful source of food supply not to the trout but to birds. Besides, amongst other things, the increased scouring has) swept away other types of foou supply and incidentally removed the shelter so beloved of trout.

CONTENTS OF STOMACHS OF , FISH. 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 spot the Vbanks aie bare. Only a few pnapjietising .pupae and larvae were discovered. In the Belmont stream itself, with its willow-lined banks, such proved favourites as the caddis larvae, May fly larvae, and creeper were caught in enormous numbers.

• In fact, a careful examination o) 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. But for the arrival of the whitebait at a most opportune moment the trout would be in a very poor condition at the beginning of the fishing season.

TROUT EAT SAND FLIES

Beetles, far from forming an article of diet, are, with miinor 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 most audacious manlier. 1 Sand flies, Captain Phillips declares, undoubtedly form 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.