MEETING OF THE WATERS
A journey on the marine side of Australia’s Coastal Wilderness
Part 3 –
The Invertebrates
Invertebrates – the other marine animals
The invertebrates comprise a large proportion of the marine animals found in this region. You
can see many of them by walking along the beach, checking out rock platforms and pools or
snorkeling and diving. Some are grown commercially, such as the oysters and mussels, and
they can be purchased fresh in several of the towns along this coast.
Crustaceans
Crustaceans such as the rock lobster are also seasonal visitors here, with the Eastern Rock
Lobster the most common. In other areas, lobsters lurk in crevices. But in Twofold Bay at
Eden they are flourishing in the kelp beds, hiding from predators. Another beneficial behaviour
is an association with Wobbegong sharks. Wobbegongs eat octopus, and octopus eat lobster,
so a rock lobster is often be found hiding with a Wobbegong.
Eastern Rock Lobster
Wobbegong shark
Another crustacean of interest is the prawn, whose run from estuary to sea during the summer
months attracts a flurry of fishing activity.
School Prawn
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Crabs are another common crustacean resident, with large numbers of different species on the
beaches, mangroves and estuaries and seagrass beds, as well as offshore.
Soldier Crabs
Blue Swimmer Crab
Molluscs
The molluscs are a large and geologically ancient group of animals that are very diverse in
appearance and habit, and include snails, chitons, clams, mussels, tusk shells and octopus,
squid and sea slugs.
Bivalves
The clear, clean marine and estuarine ecosystems of the region make it a hotspot for
sustainable aquaculture industries such as oyster and mussel farming.
Cleanest water – sweetest oysters
Oysters are filter feeders, so their successful growth is intrinsically connected to water quality,
which is very good in this region. Oysters from the waters of this coastline are renowned for
their freshness and sweetness. You can buy them fresh from most of the coastal towns – just
look for roadside signs.
Oysters were a major part of the diet for local Aboriginal groups for thousands of years. They
were also literally the ‘building blocks’ of early colonial Australia. During early European
settlement oysters were collected in their thousands, their shells burned to generate lime. The
lime was a key ingredient in the making of cement, and throughout the late 1800s there was a
push for as much lime as possible. Ancient indigenous shell deposits were dug up, and live
oysters were taken in their thousands. In only two decades oysters were seriously depleted
across NSW, which prompted new legislation banning the burning of live oysters. Collectors
then had to apply for oyster leases, and so began the selling of oysters for consumption. An
industry was born.
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Oysters
At the turn of the century the oysters were harvested wild from the rocks, after which
rudimentary farming was tried on moveable stone beds, some of which can still be found under
the bridge at Merimbula.
Intensive cultivation of oysters didn’t begin in earnest until after World War One, in the 1920s.
One of the pioneers who came to this part of the coast 90 years ago introduced ‘stick culture’
farming to the region, where oysters are grown on vertical wooden poles.
Racks in an oyster farm
Today, the main growing areas are Merimbula Lake, Pambula Lake, Nelson Lake, Wonboyn
and Wapengo. These sites all enjoy protected foreshores with little or no heavy industry, and
minimal human habitation. Merimbula Lake consistently produces fine oysters because of its
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topography, tidal system, water temperature and clarity, and the thick mangrove forests found
on the lake’s foreshore which promote the microscopic plankton food source of the oyster.
Mussels
Mussels are another delicacy grown commercially in the region. In the 1970s experimental rafts
were placed in Twofold Bay for catching and growing the Blue Mussel. Today, there is one
farm growing the Blue Mussel on infrastructure within Twofold Bay. The mussel spat is caught
and grown to maturity entirely within the bay in wild conditions.
The Blue Mussel is the only marine mussel species farmed in Australia. Although the Blue
Mussel in Australia is similar to and shares the same scientific name with the one from southern
Europe, it is native to Australia and has been found in ancient Aboriginal middens (piles of
discarded shells).
A meal of mussels
Other common bivalves found in the region include scallops and various cockles.
Scallops
Pippis
Cockles
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Snails (Gastropods)
Abalone
Abalone harvesting was first undertaken by Aboriginal fishermen, who have been eating the
nutritious ‘mutton fish’ for thousands of years. Early European settlers disregarded the fishery,
describing the abalone as ‘snails’.
But this began to change in the 1800s with the arrival of Chinese miners during the gold rush.
The Chinese first landed in Twofold Bay in 1855, and considered the abalone a delicacy. Local
Aboriginal men began to capitalize on this, harvesting, drying and supplying abalone to the
Chinese right along the south coast. Soon they were selling to markets in Sydney, and even to
China. So began a lucrative market.
By the late 1950s and early ’60s the industry began to gather momentum and suddenly
everyone was diving for abalone, keen Aboriginal kids. There are wonderful accounts of this
scramble for ‘mutton fish’, including a story told by a local Aboriginal elder whose father had
crafted a pair of goggles out of a tyre tube and a broken windowpane.
Like all marine resources, abalone is vulnerable to overfishing, disease and competition with
other species. Abalone and sea urchins are the two dominant species in shallow inshore reef
areas. When these two species are in balance, all is well. But in areas where abalone have
been overfished or natural urchin predators, such as the groper, have declined, the urchin can
dominate, with dire results. The urchins are voracious plant feeders and will eat right down to
the substrate, leaving behind ‘urchin barrens’ or ‘white rock’ areas that completely bare. Such
places are devoid of plant and consequently fish life, and can no longer support abalone
communities. Only the urchins remain.
Abalone depend on seaweed-rich, rocky reef environments to mature and reproduce. They are
particularly dependent on healthy areas of algal ‘turf’, where shellfish spat lands and the larvae
start to grow.
Over the past 30 - 50 years these barren habitats have increased noticeably with serious
impacts on the range of the abalone. In recent times abalone stocks were in a downward spiral
because of a combination of factors including virus, parasites, overfishing and theft. Tighter
regulation of the industry and scientific research has contributed to an increase in healthy
breeding stocks.
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Abalone shells
An abalone feast
The other sea snails of the region are well known to beach walkers and lovers of rock pools.
Some examples are:
Rib Top Snail
Pheasant Snail
Cabestana Snail
White Foot Snail
Cephalopod Molluscs
Octopus
Local encounters could include the octopuses below. Beware of the small Blue-ringed
Octopus - it as small as a golf ball but quite deadly. There is no antidote for its venom and it is
effective enough to kill a human.
Pale Octopus
Gloomy Octopus
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Southern Blue Ringed Octopus
Squid
The squid found in the region include:
Calarmari Squid
Pyjama Squid
Southern Bobtail Squid
Closely related to the squid, cuttlefish also inhabit the region’s waters. They differ from the
squid insofar as they have an internal shell (the cuttlebone). Cuttlefish ‘bones’ are often found
on the region’s beaches.
Cuttle Bone
Giant Cuttlefish
Reaper Cuttlefish
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Echinoderms
Echinoderm adults are recognized easily by their radial symmetry (usually five-pointed), and
include such well known animals as sea stars, sea urchins, sand dollars and sea cucumbers.
Echinoderms are found at every ocean depth, from the intertidal zone to the deep ocean.
Urchins
The predominant urchin species seen on the southeast coast has black, large-spines.
black spined urchin
This species is found in very large numbers in the region, often to the detriment of other species
(eg the abalone). There are a couple of theories that might explain its predominance. One
theory centres on the relationship between rock lobsters and urchins – the rock lobster is one of
the urchin’s main predators. During the 1800s and into the 1900s, rock lobster was almost
fished out. Photos from the 1920s and ‘30s show boats up to their gunnels with massive
catches. The decline of the rock lobster may have helped the explosion of the urchin population.
Another theory links the urchin plagues with climate change and the southward shift of the East
Australian Current, altering the normal range and incidence of the animal. Both these factors are
likely contributors to the success of the urchins, but there may be additional factors in the
marine environment that we don’t yet understand.
Seastars
Seastars are very common throughout the region. The photos show few examples of this
extensive group that you may come across.
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Biscuit Star
Orange and Purple Star
Granular Sea Star
Jellyfish, corals and other stingers
These animals are classified into four main groups: the Anthozoa (sea anemones, corals and
sea pens), Scyphozoa (jellyfish), Cubozoa (box jellies) and Hydrozoa, which includes the
Portuguese Man o’ War, called the blue bottle jellyfish in Australia.
Many of these groups have ancient lineages, with the fossil record extending back into the
Precambrian era, well over half a billion years ago.
Corals live in compact colonies of identical individual polyps that secrete carbonate that, in
time, creates a large skeleton which, in many species form reefs.
Although corals can catch small fish and plankton using stinging cells on their tentacles,
most corals obtain the majority of their nutrients from algae that live in the coral’s tissue.
A small number of temperate coral species can be found in the region, as well as many varieties
of their ancient cousins, the anemones and sponges.
Green Stony Coral
Small Knob Coral
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The soft coral, the sea fan is also found here.
Sea fan
You can see different jellyfish, pulsing gracefully through the water, while swimming or boating
in estuaries and in coastal waters. The ones to look out for are the small bluebottles. If they are
around you will often see lots of them washed up on the sand, and its best to keep out of the
water.
Jewel Anemone
Sea Nettle Jellyfish
Bluebottle
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Zooplankton
The zooplankton (with the microscopic plants, the phytoplankton) are the ‘engine’ of the marine
environment. They are the bottom of the food chain which is the life support system of the
marine world.
The word zooplankton is derived from the Greek zoon, (meaning ‘animal’), and planktos
(meaning ‘wanderer’ or ‘drifter’). Individual zooplankton are usually too small to be seen with
the naked eye. Zooplankton is a term more descriptive of size rather than a description of
related animals. For example, the group includes the larval stage of bigger animals and small
species of other groups such as the Crustaceans (eg krill). Important zooplankton groups
include the foraminiferans, radiolarians and dinoflagellates.
They generally feed on the phytoplankton (minute marine plants at the base of the food chain)
or other zooplankton.
Foraminiferans,
Radiolarians
Dinoflagellates
The zooplankton includes tiny crustaceans such as copepods, krill and arrow worms.
Copepods
Krill
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Arrow Worms