A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

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CHAPTER TWO
MATERIALS AND METHODS
2.1
l:'ield Idork was confined to a short pe:ci,od (1--2 hours) before
and after low tide when the sea I"as calm.
At Kaikoura work ~-)as
largely _>::'estricted to the lowest tides in each month I
but at southeast
Otago all tides could be worked so long as calm condH:ions
prevo_iled. The main difficulty was that the sea is rarely calm
for more than three or four consectltive days on the outer coast.
Projects were invariably interrupted by periods of rough seas lasting
3-30 days.
Diving, bo'th free ,wd w'i th SCUBA, at high tide was unsatisfactory
for most field work, except perhaps for collecting lamina samples
or plant,s. and even these tasks were better accomplished at
low tide. In many areas the sea is never calm enough to dive amongst
Du:rvillaea at high tide. Study areas were selected on different
sides of Kaikoura and 'rautulm Peninsulas to try and reduce the times
when all study areas were simultaneously inaccessible because of
rough seas.
Compounding the problems D'l1posed by tides cmd wea ther ~"as that
caused by the sheer bulk of DuY'villaea specimens. Fully-grown D.
antarctica and D. willana weigh up to 40 kg.
Cutting and recovering
large samples of in the short time at low tide often proved to
be an exhausting task for one person.
Sampling techniques \l1ere devised to give as coulple'te, as
possible, information on such features as popUlation scructure,
standing crop. density, phenotypic variation, rep:r:odllctive periodicity
and effects of harvesting. Half of the samples Vlen':: confined to one
localii.:y (Tautuku Peninsula) so that seasonal variation in some of
these features could be- measured. 'I'he other samples came a
wide diversity of shores around New Zealand in an effort to
some information on geoqraphic variation as \Olell as obtai
a t(lean
measure of standing crop.
GrcMth, mortality and longe\ii ty we:ce
studied by monito'(ing marked specimens of both species,