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

42.
fairly discrete areas.
It is-a source of food for
the puffer fish, Uranostoma richei, having been found
in the stomachs by Habib (1971).
Sepioloidea is not
present in the upper harbour around Quail Island except
when the substrate is covered with algae.
to the extent of about three per square metre.
Then it occurs'
This
species is found around most of New Zealand's coasts,
but more commonly in Northern areas (Suter 1913)
(12) Micrelenchus huttoni (Fig 15.12)
This species, a small ·blue-black gasteropod
shows a very unusual distribution existing in both sandy
and muddy sediments but, judging by numbers taken,
having a decided preference for muddy regions.
It is
a herbivore and its distribution is greatly influenced
by the appearance of the algal mat in the upper harbour.
Table 1 shows an extremely high increase in density of
from dne per square metre to 23 per square metre.
examination of this situation showed that Micrelenchus
was using the weed as a food source, for protection,
and as a site for breeding.
During the summer, therefore, Micrelenchus has
a range that covers most of Governors Bay and almost
all of Charteris Bay.
Closer
Elsewhere Micrelenchus is much less abundant,
with maximum densities of less than 10 per square metre.
It is locally abundant around the shores of Ripapa
. Island and across the mouth of Purau Bay. Directly
across the harbour there was found another localized
occurrence.
In this respect it was very similar to the
polychaete Owenia fusiformis.
found among the Chione bed.
Micrelenchus was not