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

with Hope that some trout follow whitebait ancl smelts in from the sea, thrrs
bringing them within reach of the angler. It is the experience of many ar.rglels
at the mouths of large east and south coast rivers that trout enter ilr substantial
nrrmbers during the angling season only when *hit"b"it or smelts are running.
The \Mater of Leith offers evidence that a stock of large mature trout may exist
in rthe sea and that few components of it come into fresh water except i¡ the
spawning seaso11. Therefore, in considering certain of these fisheries, it is necessary
to lieep in mind the possibility of changes over the years in the proportion
of the stock frequenting fresh ar-rcl salt water. To such an extent as the indrrcer¡ent
of fish to come within range of the anglel has lessenecl, there may appear to have
been a cleterioration of a stock.
SELECTION AND PRESENTATION Otr DATA
New evidence is available which goes some way towards showing to what
extent the average size of trout has been maintained in a series of important
angling waters since, in some cases, a few years after streams were first openecl
to angling. This evidence is taken largely from diaries of anglers and official
recorcls of trout weighed in in contests conducted by angling clubs. It is arirplified
by the inclusion of data from Arthur and Spackrnan, where it appears that typical
rarther than exceptional catches have been lecorded, and where such data are
sufiñciently specific as to locality of capture, or lure employed, to warrant colrrparison
with data equally well described from some later period.
Except at Lake Taupo, where there are rnainly rainbow, clata relate
solely to brown trout,. the only important exotic species founcl in all
waters uncler consideration. Perch are present in small nurnbers in some of the
waters. Qtrinnat salmon (O. tsch,azuytscltø) are present in substantial quantities
in the Rangitata and in less quantities in the Opihi ancl Ashburto¡ Rivers. Trout
enter these three rivers from the sea. Salmon became established in the Rangitata
between 1910 and 1920 and in the Opihi and Ashburton in the follorving ten
years.
Conrparisons of the results obtaine