u0HG utH¡tt8lll ÐtPIflf ffto
- ,-.
/
f
/ nr ilnmo. ao[ irurowu, ilAs
soitt
D0uBrs
[Bot,I
wlilrlBilr r0 ÍoHI. ilt ilils
nt
ÂBIIÍY 0f
ilt 6SUI 2f llt
wlilr ls H0iilltcf,
ll0uBls. soft[
1999
ilt
[I Alilt
lll [IS-
RtGtRD,
dIIRITS iIITGHTII APPARTIIIIY IGRTT
AEnE.
R[GU-
nR G0ilInBufon I0 Rs[ s Grilr
I
SI0RY
HtililHt
ilG[0sn11 wn0tt
0f ilts c0ilI[ltll0lts tRI
0Í
Ht$
RÍPR0-
OUGIO HBT.
'Wotk on whitebait migration has shown
that a mixed species shoal of whitebait moving upstleam will partition itself by species
according to the nature of the tributary being
leached
whitebair ofkoaro will rarely move
into the -low pH, acidic, tannin-stained water
that comes out of coastal forest, but banded
kokopu rvhitebait do so freely. Neither of
these species will move into the rather
walmer waters derived from coastal swamps,
but demand cool water. Possibly these s[reams
also have lower oxygen levels, and otler features that dissuaded koaro and banded
kokopu whitebait from entering them. But,
inanga rvhitebait will do so freelf These differences cleally involve the Frsh getting guidance about where to go, and making decisions
to do so, but this is not the same as homing.
They are literally "following tleir noses" with-
OST FISHERS ARE
beneficiaries (a perfect
out there being any element of fìnding their
job for our ageing, unem-
r'-F
way "home"
"home" being some place that
they are familiar with because they have been
there before.
There is, from time to time, much talk of
horning in whitebait, and one aquacultural
ventllre is underway in northern New Zealand
based on the expectation (perhaps hope, or
ployable workforce?) But
whitebait have to return to
the point of release if
whitebait ranching is to become an
economically sustainable activity. Therefore the
pivotal question is: Do whitebait home?
I think there are good reasons for homing to
dream might be a better description) that
whitebait larvae released to sea to feed and
occur:
thern hemi- ¡ They a
d tlout, fìshI sphere
I es that
Theyarediadromous,spending the larval-¡ ¡ juvenile phase in the sea before retur.ning
,¡l
-å ,"
freshwater ro grow into adults. Homing
is common behaviour in diadromous fishes.
rageous ro home.
J I
,1
:)
parenli grew is
t you than any
stream selected at random. Likewise, the place
where you hatched is likely to successfully incubate your own spawn in turn. Fish that home
will have better survival overall in tìle long run,
although a good degree of straying is also
required to ensure population survival in the
lace of naturally qhanging h4biqm,
, ¡ The odds of annually repeating the prot>
I I abitiry of locating relarively very resrricred
-J areas of suitable adult freshwater habirat
rvhile 'lost' in the vastness of the ocean (particu-
larly when you are only 48mm long) would be
signifìcantly improved by evolving rhe various
behaviours required for homing. For example,
current streams of at least one knot are common around the New Zealand coasdine. Thus,
after about 150 days at sea, randomly swimming
whitebait could have been carried over 3500
nautical miles down-current from the home
river. After a few years of random returns,
New Zealand rivers should be empty. But it is
5ô Fish & Gome New Zeolond
obvious that they arg
I
¡ [ nious, universal explanation for the regJ ular annual runs of whitebait into the
alray of different rivers and streams all
around New Zealanð' Even the numbers and
species returning to each system appear in
proportion to the habitat available. If they
just selecting optimum habitat, it is logical to expect all the fish in an area to rush for
the best stream, because that would offer
each individual the best chances for survival.
Population behaviour obviously relies upon
the behaviour of the individuals comprising
were
rt.
signifr-
don't. If they do, ocean
ranching has a shot and the sustainable
restoration of whitebait fisheries becomes a
cant numbers, or they
possibility. But please note that restoration
must be both biologically and economically
sustainable.
By 1996, I had become sufficiently
to try ranching on my own resources. Support from my
past employer, the Ministry of Agriculture
and Fisheries had been offìcially nil. The
idea was ridiculed by higher-ups. In this relict
obsessed by my 1973 good idea
take off my hat to both the aquacuhure
entreprerÌeurs who are risking their morte¡
and also to the whitebait as even more arì^zing little animals than I already think rhey
are.
But I arn not holding my breath."
of the British Colonial Service, the managcri-
lot.
Homing is simply the most parsimo-
Ary*.y, whitebait either home in
grow rvill return to the release site. 1'o ¡|¡q
extent that the tvhitebait larvae have hatched
in a freshwater system, and so havr so¡s
experience ofit that could forrn the b:rsis for
a memory-based navigation back "h,rme',
homing is theoretically possible in a w;tv that
is untrue of eels. But, we need to remcr¡þs¡
that inanga lvhitebait don't acrually dcvelop
in water', but in the aiÌ aùtong the dam vegetation on the banks of tlle estuaries.
They are immersed in their "natal" ivateç
after hatching, for only a few minutes - - and
that mixed with sea water
as they are .rvspl
to sea. And they do this rvhen
only abrrut 78mm long. Though they have all of Lheir
"body palts", and can presumably smctl, it
seems to me to be little short of fal'-fetr.hed
that they have both the ability to home, and
that they are in freshwater long enouglÌ to
give them the capacity to do so when they
return to freshwater some six months larer.
Other evidence also is germane to this
question. There are, for instance, whitt'bait
runs into rivers where there is no k¡own
spawning habitat, sometimes big whitcbait
runs. If these fish are "homing", what spurvning grounds did they come from and rrhat
are they homing towards? Whitebait cl< arly
choose what water they migrate into, but I
suspect that they do so by choosing ¡rreferred water qpes, and perhaps kin recognition has a role in attracting them. If I am
wrong, and aquaculture of whitebait based
on a homing migration is feasible, then I'll
al opinion seemed to be that anything of Ncw
Zealand, origin was inherently so inferior tlrat
complex behaviour was impossible (tlris
included the staffl. Resources lvel'e put ir[o
salmon faÌming and growing Chinese car¡rs.
Respectabìe imported concepts.
And then everything changed overniglrt.
MAF became extinct. Accountants
hrrd
ascended to power and all human activiry in
New Zealand became defined as busincss
(hospitals, schools, science, you name ir).
Inefficiencies that had allowed small bits of
freedom to explore new ideas were eradicat('d
by a new regime of strict accountability.
Scientific life became a succession of fìllirrg
out funding applications.
Tring of continually having to convinr:e
people ofhow indispensable I was (and devcloping a few private doubs anyway) and having
had no better research ideas put to me sinr:e
the 1973 one, especially nothing whir h
required such massive simultaneous problern
solving, it was time to step out and ûy whire-
bait ranching. Foltunately, my family
has
been highly supportive, helping through tlre
turmoil and huge amounts of wolk demandr.d
srnce.
t)a
r'e
ta!
Iar
rn
ha
be
fe
te
tal
sh
rh
pa
rh
st(
ra
ye
w
ah
aÎ