FISH RESEARCH WORK

Taranaki Daily News, 18 April 1932, Page 10

FISH RESEARCH WORK

IMMATURE CATCHES THE CAUSE OF DEPLETION. SIGNIFICANT INDICATIONS. The work being done by the Fish Research Committee is set forth at length in two. reports which have just been received by the Wellington Acclimatisation Society from Mr. A. W. Parrott, biologist, and Professor E. Percival, director. The former in his report states that the total number of scale examples examined during last year was 3748, made up of 700 quinnat, 250 bullies, and 279 S trout. "The significance of this work,” remarks the report, “may be shown by taking a concrete example. The Hutt River, in the Wellington Province, will be taken by way of. illustration. This river, similar to many others, has shown clearly that if the trout are not actually being depleted they are certainly subjected .to intense fishing. Old individuals are few. Angler’s catches are composed almost entirely of two, three and four-year-old fish. Under ordinarily favourable conditions, trout four years old can only attain a length of Idin; in the Hutt River they average 144 in in length at the end of their fourth year of life. “Briefly, the history of the majority of adult trout of a particular year class (brood) is as follows: They spawn during the winter, hatch out in late winter or ealy spring, and grow as immature fish for two or three years, attaining sexual maturity in their third or fourth year of life. Each year-class or brood appears to predominate in the catch for one season, after which it falls away quickly, or in other words, is rapidly depleted. CONTRAST IN AGE'S. “It is desirable for the majority, if not all, of the fish to spawn once at least before they are captured. Over 35 per cent, of the • angler’s catches ,in the Hutt River had not spawned. The size limit at present in this river is 10in, and this length hardly protects the fish that, spawn during their second winter. The majority appear- to spawn during their third winter, by which time they range to Ilin to 14in in length. During, the previous summer they are a takeable size, and are therefore not protected by the present size limit. In contrast to the trout population in the Hutt River, we may take those inhabiting Lake Sumner. This lake is probably fished by only about 20 anglers during a, season. In Lake Sumner we find 85 per cent, of the trout examined to average four years old, against 9J per cent, in the case of the Hutt River. The fish of Lake Sumner district average 224 in in length, and 31b to 41b in weight. CAUGHT TOO SOON. “Thus our age determinations show that in the case of two localities, one heavily fished, the other hardly ever fished, the anglers’ catches in the former locality are composed almost entirely of fish under five years old, while in the Utter locality the fish caught are almost entirely over four years of age. “Further, our growth determinations show that the growth rates of the trout from these localities do not differ significantly from one another. What is more important from a conservational standpoint is that in localities which are not over-fished the fish have the opportunity of spawning once, twice, or even more frequently before being killed, thus the necessity for artificial stocking is reduced to a minimum.”

The report deals exhaustively with the growth-rate of fish and with the suitability of various streams that would serve as natural nurseries for the propagation of young fish. Professor Percival’s report deals with trout food and similar problems. Information, he says, has been gathered from different parts of the country, and from overseas in connection with the business of stocking streams and lakes. Up to the present there is no one policy which may be applied to all conditions in New Zealand, and further facts arc needed. It is still necessary to consider the financial aspect of the various methods in use, or advocated. •Specimens of smells of qninnnt salmon, remarks the report, have been received from the Monawatn River system, showing that this river, like the Wanganui, has enabled quinnat successfully to breed in its headwaters. Four sniolls have been taken this year, above Danncvirke and nt Oringi. It is necessary Unit the local anglers should make careful records during the next few years, in order to note any effects which the proximity of qiiinnat may produce in the trout fishing.