RIVER ANGLING

Evening Post, Volume CVII, Issue 56, 9 March 1929, Page 17

RIVER ANGLING

SLOW DETERIORATION

AN INEVITABLE DECLINE?

IUIJSr.S AND EEMEDIES

Every angler of morethan .a few. years'experience .knows (hat the (rout fishing hi '.New'Zeaiand'rivers is slowly deteriorating. ,' Big fish are , not- found,.,in . streamti where they were twenty, years, ago, and in many'rivers their;jnck'is not made up for by numbers-'of "smaller ■,'. but equally game trout. . It w.<is.: a. foregone conclusion .that the tremendous- weights reached by the.early'trout liberated inf'NeW Zealand, the average Jar ~.above that,.of trout in either America 'or' Europe,• would not be maintained whenr.the .lavish' food 'supplies .were :depleted; rlnteresting flights were . thrown on the": question 1 of-food supply by the recent- conference' of Hatchery curators, .where .it" .tAvas...siib>vn that" the balance: :6f : Nalture jia.d been so upset by the. introduction -of < trout, that; to regain it. .was impossible;;.'.. .:■:■".:.' ARTIFICIAL CAUSES: . Added Jp_tjie_dete.rip.ratiou _qf.Jhe. bait food supplies, the ruin of'"many rivers for trout through:artificial causes;received considerable a'tteutiouiV/l'he denudation of forest, resulting in the turning of deepvooletl .rivers; iiifol jj'iere. storm : channels of shifting shingle, theabsorbtion (in the .Canterbury'Trive^.of', large quantities of the normal flow by- -water races, the draiuiug-of-swampsj- and '.the ■pollution of streams, had . alii" :if - was ■ stated, affected not only, the condition."-and spawning of trout, butliad-also wiped out or decreased the natural food, supplies, particularly the tiny shellfish, or water.snails, upon which trout largely. :feed..: ,■...... ■'.':. The increasing pollution of streams was regarded: by; the conference ;as the. .most serious- menace '■ tpUthe.-- much, advertised "finest tiont/ishiug in.'tiie world." Apart from poisonous- effluents .-from- factories, there was the loss caused -by "the ;discha'rge of. sawdust, flaxihill.-refuse,. :'and: other sediments, which,-.,settling . down in- the gravel,-' smothered- the. hatched fry,"- and perhaps,.more: important still,-' 1 affected the insect: fo6d supply. '.Sulphuric acid;'■•"and. caustic, soda/'iised" in washing. dow;ii-dairy factories;^skini 'inilk-'-discharged into ■streams,'"chees_el'a<2l6i'y; effluent,-hot water and ■■ effluent' from"' boiling' down'"Works, and drainage from.-artificially manured lands; were all mentioned,! instances being given where fish had died in hundreds from these -'causes'.' While • pollutidu: of streams would, kill off ■■'trout ■in time;,it would more, speedily., destroy the' insect lad-in .the streams. Detegafe".' noticed a diminution of the. larger insects.; Biieli as crickets and ■•.grasshoppers", ' due,- it was thought, to .(.lie .iiHrodiictioii. of insect.eating birda such• as",the starling. "There did. not .seem-to be the' same:-unanimity of opinion that .there had been' a notable decrease of smaller insect life. so. far. HEAVIER FOODS DEPLETED. ■ It was (.lie opinion of ■ the conference that the decrease in the we&hW of trout was due to the diminution''in: the supply of i the "heavier, feed, " such.-" as inanga twhether.as ' whitebait or in .its adult stage], bully, smelt, 1 or "silvery," koura or freshwater crayfish, and the shrimps at one time so plentiful in tlie streams. Here again the changed character of the streams was held to have a part, as there was-no cover for shrimp'and inauga in shingle streams which were once chaius of pools or Jugooiis fringed with cress or -raupo. It was stated that trout,grow, to eight inches loiig in a few weeks,•on. whitebait* iv the old days, but whitebait were now,-as-the price of them showed,:very-much less plentiful. It'was true that; 2!) tons of whitebiiit; were .brought \to Christehuch from Westland during the last season, but this was said to be the result of a raid on the last stronghold: of the delicacy, in South Westland, --,-f/he,;bridgiug ,of ...remaining strea-nis giving motor access to hitherto unexplored rivers. .''Big- trout were now found, it was said,,chiefly at the.mouths of rivers, where there were run's, of bait of various kinds, and one suggested means of briging trout back to their .former-size was the breeding, and liberation of various form of bait food. An instance was given ■of a yearling trout having reached a pound weight amongst,, a.; xba.tch .of. yearlings, through cannibalism,.and i 'this, was-'ohe of the. arguments 'adduced,- -sfor .■&■■_. plentiful supply* of lfeaYy. buit ..food: to^secuie- big fish. . If trout - throve indefinitely .on an 'unadulterated .-cannibal diet, there would soon be no problem of too many .small fish, but the.habitual cannibal when adult soon acquires" a-Jean land hungry dook, all fins, tajl, .gills, and;jaw. It may.well be that the deterioration in the quality of trout in'bo many streams,! apart from size, is'due to excessive cannibalism j-induced through .lack-'of sqlid .natural food, . ' , TOO MANY FISH LIBERATED? The conference dealt at, length with tlie question of iish culture'imd- the' liberation of eyed ova and .fry,- and -in -this connection Mr. Evans (South'Canterbury).raised a new. and valuable-point that the washing of gravel before the eggs were artificially planted '.gave the' hatched/fry a better -, chance, as if removed sediment, which 'he liad found -".cue of 'the .most frequent causes of killing of eggs naturally deposited by trout.' '.. .'■■ ,-. The theory has already been advanced by Captain J.S. Phillips,'the Wellington Acclimatisation Society's- -freshwater biological student, that far .^qo many, fish are behig put :out'into tlie rivers:by the societies, in relation -to.the'--depleted food supplies- availabler- '■ lf--trout.; increased:! uudrecked, Hike rabbits "oh a'li..-. island, undoubtedly .in tirii.o they would eat themselves out,-but they-.have-many natural enemies, including, .eels: While eels --prey upon' trout .iiji'.'to".several.,pounds, according tp the size-of .the eel, .trout" tail, cat. wil-y.-itliG- young eels,. and 'as the latter spawn iii'the -deep.sea, trailt. ca'niiot;harry lluv eel'spawning; beds,..us. .'the .eels'"'do, thoirs. The 'buiry and inauga ..supplies, under ;flie.combined .ceT.aiid' troiji . 'at"tacks';'are'likely to' diminish -still further. With trout reduced to ground feed, ..such.' as tiny .shellfish', caddis, creeper, and an occasional -worm,.-with-' surface 'msect 1 feed;

only available in_quantities frpni Christ; man until the autumn, English"-proportions will be more aud more'rexer.t'ejtl.to. : f-_

It was stated that a difference in the spawning dates between the rainbow.;aud brown (rout gave opportunities for one .to. cat tlie. other's 'eggs. -From- the; evidence it; certainly seemed as though ..the. .two. varie: ties do not- thrive-in 'the -same Waters. C'piklilions: .at 'I'liiipo..- are: di.tTcreni' .from; .those in most New Zealand : streams, but even : there the. ra.inbcny. trout liiivo'; shown •'sign's of gradually 'iallini; v back ; in. weight, if not iv numbers. V .

The moral of the evidence'placed 1 before the. .conference; appears: tp. bo that -while trout to acertain extent :need. insect food, ithey thrive'better when they can fatten iiipoir smaller iislies, such .aS bullies' '::and inanga; after the 'sajd; smalfer "lighes -havij ;fatte.ued:.npon tlje '.in'sfects, thaii- _they do when tlicyhave to collect the insects-for themselves.- Now : that- the.'.trout-., have thinned out the smaller .-fishes'to- such, an. extent that they can no longer ;grow to.tiniusual sizes on this feod;. it remains to bo :seen whether they will, not in time,' as .the bait food' gets, lic.iivce'r, go-back to thVsbse of the English trout, .averaging perhaps half: a pound,.with ■a:...thr.ee-poj!ndeiv.-.a5:..-a. rarity. -" ' . ;'