Southland Streams Now In Good Order For Anglers

Southland Times, Issue 23989, 2 December 1939, Page 16

Southland Streams Now In Good Order For Anglers

By

MATUKU

Reports from various streams show that they are now in excellent fly fishing order and good bags were got on the smaller streams last week-end. One angler who fished the Otapiri on Sunday, got a limit bag on .the dry fly and was very pleased with the average size of the fish. He reports that they were larger fish than have been caught at this time of the year in the' Otapiri for several seasons. It would be good news to sportsmen if they could be assured that the. increased size was due to the prohibition of the creeper as a bait in the Otapiri. This may be the case but it would be unwise to be dogmatic on this point. Careful students of trout problems are cautious in drawing definite conclusions as to the cause of any increase or decrease in size of fish. If, however, the increased size is maintained it will appear as n justification of the prohibition of creeper fishing. On the Orawia during the week-end limit bags were also obtained and the Orawia can now be relied on to provide good sport for the next month or six weeks. The fish in this stream are of'fair average size and are numerous and on a favourable day a limit bag can easily be got. There is no doubt that there is a large run of spawning fish from the Waiau river into the Orawia and its tributaries. HUGE TROUT NETTED Some years ago a research party from the Southland Acclimatization Society netted some pools in the Orawia near Feldwick in the winter when the spawning run was in the stream. Among the fish captured was a 171 b female in beautiful condition, obviously a Waiau fish. Two other fish captured were 91bs and 71bs in weight. It seems improbable that any of these large fish remain in the Orawia for the fishing season, but their fry from . natural spawning must be invaluable in keeping up the stock of trout in this stream. The warmer weather of the last two weeks will cause an increase in terrestrial, as well as aquatic, insects and this causes the trout to adopt a more varied insect diet. Manuka beetles and cicadas (crickets) will very soon put in an appearance and form a large proportion of the trout’s food supply. Anglers will notice that these insects are larger and less transparent than most aquatic insects and are more easily imitated by artificials. In addition a good number of bluebottle flies and spiders of various kinds get blown on to the water.

On all Southland’s streams where bush or shrubs grow on the river banks manuka beetles will be found and are blown and drop freely and float on fhe surface of the water. A small Cochybondhu on a No. 14 hook with a peacock herl body will prove a satisfactory imitation of the manuka beetle and the trout take this artificial freely when feeding on the natural beetle. On Lake Hawea and Lake Wanaka at Christmas time ‘the trout cruise along the lake margins where tutu and native shrubs grow and pick the beetles off the surface. In these places a Cochybondhu fished dry on a fine cast will prove quite successful. IMITATION OF CRICKET When the crickets are about, a fedtipped Governor will prove a successful imitation. In the up-country streams such as the Mararoa and upper Oreti a large Governor on a No. 12 or No. 10 hook is generally used. These flies can be fished in the rough ripples and do not call for the fine and delicate handling required when small dry flies are used in the small down-country streams. / . ' Another fly which is successful in the up-country streams and lakes is the Black Gnat fished dry. Some anglers believe that this artificial is taken for a cricket as it is usually successful when tire cricket is on the water. I thipk,. however, that this fly is taken by the trout for a blue bottle of which some are generally in evidence at the same time as the cricket. Whatever the trout take it for, however, the Black Gnat is a successful fly and an angler should be provided with a few particularly when visiting up-couiitry streams.

Anglers proceeding up-country should provide themselves with these flies in addition to the small- flies such as Dad’s Favourite, Greenwell’s Glory and other small flies used in the smaller streams near town.

RESEARCH INTO TROUT GROWTH We are all familiar with the angler who is quite sure he knows all the reasons for decline in trout populations and decrease in size of trout. Anyone really interested in the various angling problems will be well advised to carefully consider the articles in the last annual report of the Biological Association of the British Empire for the year ending March 31, 1939. Twenty years ago the problem of the growth of trout would have been answered by investigators with much greater confidence than is the case today. In those days it appeared to be merely a matter of food supply; feed trout well and they yzill grow rapidly and to a large size. The first doubt cast on this theory v was due to a discovery of Professor Knut Dahl, the famous Scandinavian trout expert. Professor Dahl proved, and his conclusions are now accepted as proved, that the trout’s rate of growth j for the first year at any rate was dependent on the size of the egg and was independent of the parent fish or the water from which it came. Large eggs produced large fry and small eggs produced small fry. These young fish were fed on natural plankton which was given in sufficient quantities to enable the fish to obtain as much food as they were inclined to take. FOOD THEORY It was definitely proved, however, that fry from large eggs grew rapidly and fry from small eggs grew slowly notwithstanding that each had as much food as it could eat. Thus the old idea that growth of trout was merely a matter of food supply had to be abandoned, at least as regards the first year of a trout’s life. A later theory was that alkaline waters produced large trout, this theory being based on the fact that the chalk streams of England which are strongly alkaline produce large and rapidgrowing trout. On the other hand the Scottish and Welsh'moorland burns fed with acid water from peat bogs produce dwarf races of trout.

Further investigations, however, show that this theory is not infallible and does not solve the problem. In the 1937 report of the British Fisheries Department investigations have shown that even in Britain there are acid locjis in which the trout produced are exceptionally large and fast . growing. Similarly investigations of trout in strongly acid waters in South Africa have shown rapid growth of trout. ' The -latest theory is that there is some chemical constituent, which is at the bottom of the curious incentive to rapid growth of trout in certain waters but what this chemical may be is still unknown. Lime in the soil is of value chiefly as a base for phosphate and it may be that lime in water also acts as a base for phosphate or some other chemical or chemicals whose action on growth is as yet unsuspected.

These remarks will show how complicated is the problem and how necessary it is to have trained scientists to consider and elucidate the various matters to be considered. In the report of the Biological Association mentioned above Dr Worthington, the director, quotes the programme which the association is proceeding to tackle. This programme, to quote the director’s own words, 4 consists “of an analysis of the actual rate of growth under a variety of conditions, the correlation of these growth rates with geological, chemical and biological conditions, the experimental modification of matural conditions by treatment in various ways in an effort to increase the growth rate of fish, the planning of a svstem of management designed to give the best out of any given water.”

In this connection it is interesting to learn that Mr H. K. Allen, the scientist who was responsible for some of the principal work in investigating trout growth at Lake Wintermere in England for the Biological Association of the British Empire is now a member of the staff of the New Zealand Freshwater Fisheries Research Board in Wellington. New Zealand is fortunate in having a scientist of Mr Allen’s experience and his investigations into New Zealand conditions will be awaited with considerable interest.