GOING FISHING with Kotare

Press, Volume CXIV, Issue 33514, 20 April 1974, Page 11

GOING FISHING with Kotare

C a d d i s-wise, hold everything. Trichoptera larvae, those small succulent grubs that trout are so fond of, probably all go through one-year life-cycles, not two. With K. Radway Alien’s later findings to substantiate my earlier story of the horny-cased caddis’s two-year cycle, I felt it safe enough to suggest that anglers could fish imitations of the Cased adult Olinga larva — one of the most popular foods of trout — at all times of the year. As a matter of fact the suggestion is still valid, but not because of the hornycased caddis’s two-year life-cycle. Although we cannot discount the possibility of a two-year cycle, Olinga probably undergoes the normal one-year cycle of its relatives, according to a specialist in the New Zealand Trichoptera, Mr A. G. McFarlane, of Christchurch. I wrote to Mr McFarlane before my earlier column on the caddis was published, knowing that so many things remained unsaid, and hoping that Mr McFarlane might allow me to use answers to questions I wanted to put to him. This may sound tremendously scientific and all that, but it’s not really. Work it out. Some 98 per cent of the food eaten by trout is taken below the surface. Cased caddis, especially the horny-cased (Olinga) and stony-cased (Pycnocentrodes) species, which browse chiefly on the beds of rivers, comprise important proportions of the food taken by trout. Imitations fished by anglers of the cased larvae

themselves, which amble slowly around; pupae hatching at the surface; and the hatched sedge flies themselves, must increase a fisherman’s chances of taking trout from water in which the natural caddis is present in some numbers.

Which is in most New Zealand rivers and streams from North Cape to the Bluff, says Mr McFarlane. K. Radway Allen, during his intensive study of the Horokiwi stream near Wellington, noted the presence of adult cased Olinga feredayi larvae all through the year. He didn’t say so in the scientific paper he published, but in a later “popular” version of his findings he hinted that the reason for the presence of the larvae could be a two-year life-cycle. Now, that was a hint of great significance to any fly-fisherman knowing anything at all about the food trout eat. Allen found that Olinga featured largely on the trout's diet all year round, so clearly an imitation could also be fished logically all the season, and with expectations of success.

Alien’s partial conclusion from the constant presence of adult larvae may be incorrect. He apparently may not have realised that many caddis species, including Olinga, commonly undergo a period of quiescence, known as a diapause, during their development. In answer to another of my questions, Mr McFarlane says that it would appear that the colour of Olinga larvae is as uniform

from Southland to North-' land as the colour of any species of insect, although it does vary a little from stream to stream. So it looks as though an imitation of that almost fluorescent light green of the larva .itself — sometimes so bright as to show through the case — would be appropriate virtually throughout the country. Possibly, however (and this is my thought, not Mr McFarlane’s), s the colour of those familiar homy cases might vary from district to district. Local species Anglers interested in fishing imitations will obviously check on the colour of their local Olinga species, as well as the size of the largest larvae they find. Imitations fished in fast or flood-coloured waters need only represent the insect in a general way but in streams or reaches of moderate flow, where Olinga are found grazing naturally, and where trout have more time to ‘“study” the artificial, more true-to-life imitations may be necessary. I have caught trout in coloured water after a fresh, on a “half-and-half” — that is, a natural Olinga case pushed down the shank of an old thin-bodied wet fly, and a few dark hackles teased out behind the head both to represent the legs of the caddis and to stop the case itself working its way up the cast.

Normally, of course, trout take the Olinga

caddis when it is browsing on diatoms — species of algae which give the stones of our rivers and streams their brown colour. They would be familiar with the fluorescent green of the insect itself, hence my earlier mention of the body-colour. It would seem important for imitations to carry at least an eighth of an inch or so of that colour behind the head.

It is certainly important for the base of the body to be built with copper or lead wire, to give sufficient weight to the artificial to trundle it along the bed of the stream.

Olinga artificials can be fished with confidence throughout the season. And where local regulations permit angling in some waters all year round, the imitation will be just as effective through the winter. Fishermen having access to waters unpolluted by aerial top-dressing phosphates will find larger populations of diatom-browsing caddis species there than elsewhere.

Aerial top-dressing has sounded the death-knell for the Olinga species that Allen found most abundant in the Korokiwi. The chemically enriched water, in years, has encouraged excessive grow’th of filamentous algae. These have shaded the stones on which diatoms formerly grew. Diatoms cannot tolerate shade.

So the caddis dependent on them have practically disappeared, reports Mr McFarlane. So much, once again, for progress.