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

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(18) Hemiplax hirtipes (Pig 15.18)
This small mud crab was the major inhabitant
of the muddy upper harbour.
It became particularly
dense along the stretch of bottom between Governors
Bay and the wharves area. Heminlax was absent from the
t
sandy portion off Purau mouth but was present in Purau
Bay.
botto~
Normally it lives in a tunnel dug in the muddy
which must be of such a consistency that it
will not crumbl~
in. At the low tide marks the positIon
of Hemiolax is occupied by a very similar crab Helice
crassa, (Stephenson 1970). Hemiplax is a scavan rand
detrital feeder sifting through the mud for food particles.
Hemjolax is the main food of the puffer Uranostoma richei
Habib (1971) and contributes to the diet of many other
harbour fish, (personal observations).
(19) Trochus tiaratus (Pig 15.19)
Trochus is a herbivorous gasteropod feeding by
rasping algal growths off rock and shell surfaces.
is widespread over the sandy' portions of the harbour
with local concentrations near Ripapa
eastern tip of QDail Island.
land and the
It
Elsewhere sampling showed
that the ~verage d~nsities were higher in the area off
Diamond Harbour, declining northward across the harbour
(see Fig. 15.19).
The lack of rocks and other objects for al 1
attachment may be limiting the spread of Trochus into
the muddy regions.
(20) . Asterina reqularis (Fig 15.20)
This aste"roid was present in almost all samples
but reached a maximum density north of Quail
land.
rhe occurrence became scattered in the sandy regions.