parks victoria technical series marine natural values study vol 2 ...

Parks Victoria Technical Series No. 79
Flinders and Twofold Shelf Bioregions Marine Natural Values Study
Figure 37. The introduced screw shell Maoricolpus roseus in high densities on deep soft sediments in
Cape Howe Marine National Park.
The introduction of marine pests threatens the integrity of marine biodiversity and may
reduce the social and economic benefits derived from the marine environment (Parks
Victoria 2003). Most marine pests known from Victorian waters are limited to Port Phillip Bay
(Parks Victoria 2003). Two introduced species or marine pest has been recorded Point Hicks
MNP, the screw shell Maoricolpus roseus (Holmes et al. 2007a; Figure 37) and the New
Zealand sea star Astrostole scabra (Edmunds et al. 2010b). It is presumed that the
introduced green meany or green shore crab Carcinus maenas occurs on the intertidal reefs
of all the MPAs, except Ninety Mile Beach which has no intertidal reef. Other species of
particular concern include the Northern Pacific seastar Asterias amurensis, European
fanworm Sabella spallanzanii, Japanese kelp Undaria pinnatifida and broccoli weed Codium
fragile (subsp fragile) (Parks Victoria 2003).
The screw shell Maoricolpus roseus is a 5 cm long gastropod that was introduced to
Tasmania from New Zealand in the 1920s (Bax et al. 2003). It has now spread out to the 80
m depth contour off the eastern Victorian and New South Wales coast (Patil et al. 2004). In
New Zealand it is found from soft sediments to exposed habitats. This habitat flexibility
means there is a higher potential for greater ecological and environmental impacts over
larger areas than introduced species restricted to specific inshore environments (Patil et al.
2004). The dense beds of this invasive species change the benthic structure with unknown
(and unexamined) effects on ecosystem services (Patil et al. 2004). It can cover soft
sediments with its hard shell, and once dead, its shell provides abundant homes for a
particular hermit crab that can use its heavy tapered shell, thus potentially shifting the preinvasion
food web (Bax et al. 2003). Dense beds of this burrowing filter feeder may have
adverse impacts on native filter feeders, with native turritellids numbers declining with
increasing M. roseus numbers (Patil et al. 2004).
A virus affecting abalone called abalone viral ganglioneuritus has been slowly spreading
east along Victoria’s west coast. This virus can kill a large percentage of abalone in an area
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