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

Environment Improvement-Physical
LIMITATIOI{S
The great expanse of river u¡aters in New Zealand, the fact that such waters
are not owned by fisheries authoritics, ancl the lack of revenue sufñcient to pav
for substantial moclifications of natural rivers for fisheries pLlrposes make iurpossil¡le
the consideration of schernes of stream itlprovement on a scale sufÊcient
to have any very wide and appreciable effects. The position may change graduall1'
as populatioll grorÀ's. There is still so much water per angler and so much lightlyexploited
water, that, except rvhere outside aicl may be forthcoming, consideration
may at'present be lirlitecl to waters rvhere unusual cor-rclitions reuder stream qr
lake in.rprovement especially easy or especialll¡ necessary.
Such major physicâl changes; as lnay in future be brought about in natural
',r,'aters seem likely to result, not fror¡ the efforts of ar.rglers, but fror¡ the damming
of rivers for hydro-electric purposes ancl fror¡ tl-re activities of Catchment Boarcls
establisl-recl under the Soil Consr:rvation ancl Rivers Control Act, 1941. Generaily,
the activities of such boarcls, in sc¡ far as they aim at controlling run-off in hill
areas of precipitation, should be beneficial if they tend to goverrl the rate of flou''
of stleams and to increase the stability of their l¡eds. The further activities
of such boards in straightening and conflning streatls in lowlancl areas are not
capaltle of general assessment, l¡ut it seen.rs possible that they r,vill often be
harmful.
The probability of the activities of Catchrnent Boards affecting the nature and
carrying capacity of streams suggested the need for the establishment of a liaison
ltetweel local bodies and locai fisheries authorities; this has been arranged.
Such liaison also exists between the Marine Department, as the central fìsheries
authority, and the Soil Conservation and Rivers Control Council. There is need
that fisheries autl-rorities, which are themselves powerless to effect substar-rtial
changes in the character of an)¡ appreciable nutnber of streams, sirould ensut'e that,
rvhen moclifications of streanrs are plannecl for the benefit of any section of the
conurnlrit1-, the possible effects; on fisheries sl-rould be assessed ancl taken into
consideration.
Some such projects ruay, r,vith slight modifications, lte made beneficial or less
harmful to fisheries withor,rt hu:rt to the principal encl they are designed to serve.
'Ihe Karapiro clam project on the Waikato River affordecl an excellent instatrce
of concessions willingly made to fisl-reries interests. These involved tire provision
reparecl channels to provide
spar,r,ning facilities to con-ìpensate for the destruction of spar,vning areas previously
used.
Ilereafter consideration will be limitecl to possibilities of effecting iurproveureuts
to environments 'n'hich may be rvithin the capacity of Acclimatization Societies
to carry out.
STREAM IN{PROVEMEI{TS
There is to-day a considerable literature on methods of so-called strearn improvement,
but the amount of detailed descriptive u''riting on how to effect supposed
Fisheries bulletin (N.Z. Marine Dept.) no. 9 (1948)
[ 133