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Commercial Mud Crab (Scylla
serrata) Fishery Information
Mud crabs are
harvested by professional fishers. Commercial crab fishers may travel more than
100km to set their pots. Commercial mudcrab fishery information
Commercial Fishing for Mud Crabs:
There
are four species of mud crab, Scylla serrata, S. tranquebarica, S.
paramamosain and S. olivacea that are the focus of both commercial fisheries
and aquaculture production throughout their distribution. They are among
the most valuable crab species in the world, with most of the commercial
production sent as live product to markets.
Mud crabs are harvested by professional fishers
throughout the Queensland coast from Southport to Karumba, and generate almost
$10 million in wharf value to the States economy. Mud crabs are sold mostly as
an icon species to the tourist and restaurant trade.
Commercial Mud Crab Fishery in the Northern Territory
The Mud Crab Fishery is one of the key Northern Territory (NT) wild harvest
fisheries. The giant mud crab (Scylla serrata) accounts for 99% of the catch,
while the orange mud crab (S. olivacea) constitutes the remainder. There is
little byproduct and bycatch in this fishery due to the highly selective gear
used to target large mud crabs.
The fishery has been assessed by the Australian Government’s Department of
Sustainability, Environment, Water, Population and Communities (SEWPaC) against
the Guidelines for the Ecologically Sustainable Management of Fisheries. Full
export exempt accreditation has subsequently been issued under the Australian
Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The
assessment demonstrated that the fishery is managed in a manner that does not
lead to over-fishing, and that fishing operations have minimal impact on the
structure, productivity, function and biological diversity of the ecosystem. The
fishery is due for reassessment in 2012.
CAAB (Codes for Australian Aquatic Biota) Code for Mud
Crab: 28 911902
Fishing Method
The main apparatus used by commercial fishers to catch mud
crabs and blue swimmer crabs are wire-mesh crab pots and trawl-mesh (nylon) crab
pots.
The pots are set on the bottom, generally in estuarine or near-shore areas for
mud crabs and near-shore and offshore areas for
blue swimmer
crabs.
Fishers operating in offshore waters usually set their gear in trotlines of
about 10 pots per line. The trotline consists of pots attached to each other
with a buoy set at one end of the line and a flagged buoy set at the other end.
The fisher usually checks them daily or on each rising tide, hauling them by
hand-hydraulic winch, removing the catch, and then rebaiting and resetting them.
Many commercial crab fishers work from remote, rudimentary land-based camps,
although some access remote waters using mother-ships or permanently-moored
pontoons. Crabbers may travel more than 100 km to set their pots and then stay
in the same area for a number of days before returning to their base to unload
the catch.
Crab pots are baited with fresh meat or fish and set in estuarine and coastal
waters. Pots must have a float (with the unit number inscribed) attached and
must not exceed 0.5 m³ in volume or 1 m in any dimension. Pots are generally
checked on each daylight high tide. However, if tides and other conditions are
favourable, they may also be checked again at night.
Pots are manually hauled into dinghies and each crab is checked to ensure that
it is above the minimum legal size, not berried (i.e. with eggs attached) and is
commercially suitable. The last condition is an industry initiative to ensure
that no empty (i.e. low meat content) mud crabs are harvested. This condition
helps maintain the reputation and high market value of NT mud crabs and reduces
mortality during transport.
Catch
Both male and female mud crabs can be retained in the NT. The minimum legal size
(MLS) - measured across the widest part of the carapace - for commercially
harvested mud crabs was increased from 13 cm to 14 cm for males and from 14 cm
to 15 cm for females in May 2006.
Scientific Name
Scylla serrata
Location
WA, NT, QLD, NSW
Season
All year round
Size
To 3.5 kg
Australian Species Code
00 702001
Taste, Texture
Delicate sweet taste. Medium to firm texture.
Estuary General Fishery in NSW The Estuary General Fishery is a diverse multi-species
multi-method fishery that may operate in 76 of the NSW's
estuarine systems. It is the most diverse commercial fishery in
NSW and comprises approximately 600 fishing businesses
authorised to utilise 17 types of fishing gear. This fishery is
a significant contributor to regional and state economies
providing high quality seafood and bait to the community.
The Fishery includes all forms of commercial estuarine fishing
(other than estuary prawn trawling which comprises the Estuary
Prawn Trawl Fishery) in addition to the gathering of pipis and
beachworms from ocean beaches. The most frequently used fishing
methods are mesh and haul netting. Other methods used include
trapping, hand-lining and hand-gathering.
Video from Queensland Seafood showing
the Mud Crab Fishery:
Northern Territory, Australia Mud Crab
Commercial Fishery
Mud Crabs are the only crab species in the Northern Territory
(Australia) harvested for sale. The two main types of Mud Crabs found in
Northern Territory waters are the Giant Mud Crab, Scylla serrata, which
make up over 99% of the catch from all sectors, and the Orange Mud Crab, S.
olivacea, which make up the remainder.
The fishery is dependent on substantial wet season rains for a good crab season.
Heavy runoff rain flushes nutrients from the land and washes it into the rivers
where it feeds tiny animals, which are in turn eaten by bigger fish which are
then eaten by Mud Crabs. If there is not enough rain then there is not enough
food for the crab and catch numbers drop.
The amount of byproduct or bycatch in the fishery is minimal due to the highly
selective gear used to target large Mud Crabs. Many crabbers install escape
holes in their pots to allow undersize crabs to escape. This not only prevents
the smaller crabs being attacked by large crabs already in the pot, it also
reduces the amount of sorting the crabber needs to do when emptying the pots.
To assist in maintaining a sustainable fishery, size restrictions are in place
for both male and female crabs, in addition to a ban on taking females with
eggs. Commercially Unsuitable Crabs or CUCs (“empty” crabs or those with a low
meat content) are not allowed to be taken. This reduces mortality during
transport and helps maintain the reputation and high market value of Northern
Territory Mud Crabs.
Restricted bait nets catch a variety of inshore fish species which can only be
used for bait, not for retail purposes. Restrictions on where and how the nets
may be used reduce the risk of bycatch or interactions with protected species.
Here's a SUMMARY OF HANDLING RECOMMENDATIONS FOR COMMERCIAL MUD CRAB FISHERS
of above Pdf file:
- Confirm legal size and not berried as per regulations
- Confirm the crab is not a commercially unsuitable crab (CUC). Newly moulted
crabs are prone to stress and will not tolerate transport and temperature
changes. CUCs returned to the water will become “A” grade crabs within weeks
- Bury or dispose of responsibly any contaminated, badly damaged, deformed,
diseased or parasitic (loxi) crab
- Tie crab’s claws hard against the body to restrict movement as soon as
possible. This will minimise the crab’s stress, aggression and the possibility
of damage to other crabs and handlers
- Hold in clean, damp, insect proof, hessian-lined and covered crates to limit
the disturbance, minimise moisture loss and stop direct breeze and sunlight
affecting the crabs
- Avoid direct wind/breeze. Holding crabs in drafts during transport and storage
will cause mortalities. Air-conditioning will also dry crabs out, but may be
required to avoid very high temperatures
- Keep quiet. Limit any loud noises, vibration and impacts as these will cause
increased stress levels in the crab
- Disturb as little as possible. Each time you disturb the crab you are
increasing stress levels in the crab
- Handle gently. Minimise the handling movements and be careful when legs are
stuck in baskets or caught on another crab. Pulling on a leg that is stuck can
cause bleeding and increases the risk of mortality
MUD CRAB AQUACULTURE INDUSTRY IN AUSTRALIA
The mud crab (Scylla serrata) is a promising aquaculture species
due to its fast growth and good market acceptability and price. A mud crab
aquaculture operation requires significant capital input for both the breeding
and grow-out phases.
Mud crab farming requires expertise in husbandry of crustaceans, water
quality control, pond management, nutrition, processing and marketing.
Mud crabs have good export potential. The development of new mud crab
products, both for domestic and overseas markets, also creates opportunities for
farmers. One of these new products is soft-shell crab (i.e. crabs that are
harvested when they have just completed moulting). Commercial production of
soft-shell crabs has already commenced for blue swimmer
crabs (Portunus pelagicus) where the crabs are farmed in a similar manner to
mud crabs prior to being harvested for soft-shell production. The processing
technologies used for this crab species also apply to mud crab soft-shell
production.
Mud Crab Farming Methods
Mud Crabs can be raised in two systems - Grow out farming and fattening systems.
Here's a page from Roy's Farm about Mud Crab Farming. Lots of facts and
information about the two types of crab farming systems, water quality, feeding
and harvesting.
http://www.roysfarm.com/mud-crab-farming/
There
are four species of mud crab, Scylla serrata, S. tranquebarica, S.
paramamosain and S. olivacea that are the focus of both commercial fisheries
and aquaculture production throughout their distribution. They are among
the most valuable crab species in the world, with most of the commercial
production sent as live product to markets.
