The benthic ecology and community structure in Lyttelton Harbour ...

37.
(3) Chion~ stutchbutyi (Fig 15.3)
Th cockle common throughout New Zealand"
in sheltered inlets and on mudflats (Morton and Miller,
1970, Ralph and Yaldwyn, 1956). It usually grows in
large beds where conditions suit its establishment.
This is the case in Lyttelt6n Harbour with very dense
beds, almost pure stands of Chione, are found around
the coas ts of Quai I Is land and extend ing eas twar"d from
Quail Island along the path of the flood tide. Smaller
patches "Jere found elsewhere in the midd 1e harbour but.
none were dense and the individual animals were smaller.
To the west and northwest of the Quail Island beds, and
extending to the low water mark, there was a region of
juvenile Chi6ne. They reached a maximum diameter of
. 9 millimetres, most being less than thi~. It appeared
that they could not survive above this size outside
the main bed. Presumably spat fall very widespread
over the upper harbour and initially juveniles survive
and grow outside the main bed. Conditions for surviv~l
past this stage must be met only where the present
popUlation is found. There does not seem to be any
evidence of migration of Chione within the harbour.
(4) Myadora striata (Fig 15$3)
This species show a similar distribution trend
to that of Chione. Myadbra does penetrate the Chione
bed but reaches its maximum around the perimeter of
the beds. Comparing Fig 15.3 and Fig 15.4 it may be
seen that Myadorapenetr~tes slightly further out into
the muddier sediments from the shores of Quail Island.
The distribution down the middle harbour again was
basi~ally
similar to that of Chione but the impression
was that!::1,ya.dora showed a greater tolerance of ne