N.Z. MARINE DEPARTMENT-FISHERIE,S BULLETIN No. .į

accomplish the purpose, for with the increase of stock the mortality rate coulcl be
expected to rise.
In the light of tlre foregoing it is clear that a system of fisheries maintenance or
development which clepends mainly on artificial stocking cannot hope to achieve
rnuch. The question then arises of how funds ancl resources can best be used. This
is not a question which is near being finally answered. Yet knowledge has grown
sufficiently in recent years to shorv conclusively that the bulk of the funds available
has been spent to little purpose and also sufficiently to inclicate the general
character of a more promising future policy. Any future policy should be regarclecl
as provisional and subject to periodic re-examination and modification as knowledge
arises from continuing research.
Because the present factual justification for different possibilities of fisheries
improvement varies greatly, an attempt will be made to indicate in broad terms to
u'hat extent different mea"sures are warranted by available evidence. Such an
atter-npt should be regar:cled sirnplv as a progress assessment which must from time
to time be rnoclified, as rvith the growth of knou'ledge mahagement is able to
operate in a progressively less speculative fashion.
DEVELOPMENT OF' NEW FISHERIES
Present knowledge does not indicate the likelihood of there being a second great
clevelopment of inlancl sport fisheries comparable with that which followed the
introduclion of brown and of rainborv trout. The establishment of salmon of
diffe¡ent species has been attempted in a great number of waters in the North and
South lslancls. Two species provide angling in a limited number of rivers entering
the east and south coasts of the South lsland. Possibilities of establishing further
species of the Pacific series seem substantially limited to waters where they would
have to compete with quinnat salmon ancl brown trout. Past experience raises no
lropes of establishing Atlantic salmon as a sea-running fish in New Zealand.
The superimposing, as it were, of a second fisherv on an established one is a
l-razardous venture, if the two species come into competition for some essential
environmental needs. The establishment of rainbow trout in Lakes Rotorua and
Taupo, after brou'n trout hacl becorne established, appeared to lead to a recluction
of the earlier stocks to relatively insignificant proportions. Fontinalis throve in the
Tahuna-atara Stream until rainbow were releasecl. Fontinalis were extensivell'
propagated before 1900 for release in many waters where brown trout ü/ere already
established, and almost everywhere failed (Thomson, 1922).
Although the brown trout affords excellent angling in tnany lakes of the South
Island, there are certain lakes in which this species proves too difficult for most
anglers to câtch. In Lakes Te Anan ancl Coleridge, the introduction of rainbou'
trout, after brown trout were well established,.proved useful as the brown trout
were extrernely difficult to capture and the rainbow were relatively easy. In Lakes
Rotoiti and Rotorua in Nelson rainbow showed up for only a short time after
release in water where brown trout had long been present. IJnsuccessful attempts
have been made to establish rainbow trout in waters where brown trotrt are alreacly
established in very many streams in both the South Island and the southern portion
of the North Island.
Both experience and common sense suggest it as a sound rule of fisheries
tt2l
Fisheries bulletin (N.Z. Marine Dept.) no. 9 (1948)
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