Commercial Fishing Methods in Victoria
Note number: FN0105
Published: April 1998
Introduction
The kind of method used to harvest fish and shellfish from Victoria’s estuarine and marine waters depends on the species habitat. For example, abalone are prised from rocks by divers, scallops are caught in dredges, rock lobsters are caught in beehive-like traps along rocky reefs and fish are caught with hooks on sandy seabeds
Different Methods for Different Fish
Scallop Dredging
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| Figure 1. Scallop Dredging |
Each dredge has depressor plates which help keep the dredge on the seabed while it is being towed. After each two the dredge is winched aboard the vessel, slid onto a cradle which tilts the dredge and thus empties it of all the scallops. The scallops collect on a sorting tray. This method of operation speeds up the process and allows fishing to continue in rough seas.
Southern Rock Lobster (crayfish) Fishing
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| Figure 2. Southern Rock Lobster (crayfish) Fishing |
In Victoria crayfish are caught in beehived shaped pots (1.5 metres wide x .05 metres high). There is a short narrowed entrance at the top of the pot made from woven cane or moulded plastic through which the crayfish enter. The pots have escape gaps which allows undersized fish to escape.
The pots are baited with fish heads and then tied to buoyed lines. They are placed on reefs close to the shore and to a depth of 130 metres. Each morning the pots are retrieved by winching up the buoy line. Many pots are made of steel frames covered by wire mesh. The more traditional ones are made from sticks woven between wires.
Purse-Seining
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| Figure 3. Purse-Seining |
Purse seining is used to catch pelagic species, that is, those swimming near the surface in schools. The purse-seine method of fishing is quite simple in theory. Fishermen surround a school of fish with a wall of net and then pull the bottom together to form a purse or pouch around the fish. Floats keep the top of the net from being pulled together.
The purse is pulled smaller until the catch is alongside the vessel and can be scooped out (brailing) or removed by the use of a fish pump. Often an auxiliary vessel will pull the net from a larger boat to encircle the school of fish. A crucial piece of equipment for a purse-seine vessel is a power block, (a winch which hangs from a davit over side of the boat) through which the nets are hauled aboard.
Purse-seining is used to catch tuna, but the practices has been criticised because dolphins which follow the schools of fish are also caught. Purse-seining is used for Port Phillip Bay to catch schools of pilchards which are used for pet food, bait and human consumption.
Abalone Fishing
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| Figure 4. Abalone Fishing |
Abalone is a mollusc (shellfish). It lives on rocky reefs from the shore out into the sea to depths of 30 metres. Abalone is collected by divers who use a chisel-like, iron bar to prise it from the rocks. The divers can stay under water for long periods by using hookah gear (they breathe air supplied to them through an air-hose connected to an air compressor on their support vessel). Commercial divers do not use SCUBA gear.
Meshnetting
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| Figure 5. Meshnetting |
When set, the meshnet which may be several kilometres long, is a high wall of netting usually just above the seabed. The nets are anchored in position and marked at each end with a buoy on the surface so that they can be collected easily. The fish are either trapped by their gills while trying to swim through the netting or they become entangled. As in beach seining, the net is rigged with a floatline at the top and a weighted bottom line. The size of the mesh may vary from 10 cm to 13 cm.
Mesh netting is practised by the southern shark fishery in Bass Strait. A shark fishing boat sets several 6000m nets and retrieves them over the bow of the boat by winding them on to a large spool on deck.
Meshnets used in Victorian waters not be confused with driftnets (used in ocean waters), which are much longer (35-50km long), hand much deeper in the water, have a smaller mesh size and are made from much finer material. Driftnets are not anchored and float near the surface. They are illegal in Australian waters.
Beach Seining
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| Figure 6. Beach Seining |
The most common method of beach seining is to lay out a net, with long ropes at both ends from a boat. The stating point is usually close to the shoreline and the nets travel a semicircular course. Both ropes and then ends of the net are winched in so that the area enclosed by the net continually decreases until it is small enough for the fish to be removed. Undersized and unwanted fish are then released into shallow waters. The ropes are up to one kilometre long, have floats on the tope and weights at the bottom so the net hangs vertically in the water. In shallow, protected areas which have find sandy bottoms like Port Phillip Bay, Western Port and Corner Inlet, long warps are often attached to the ends of the ropes to increase the area being encircled.
The target species for this fishing methods are King George Whiting, snapper, flounder and bream. Small boats are commonly used with one or two fishermen.
Trawling
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| Figure 7. Trawling |
A trawl net looks like a large sock being towed behind the vessel. The design of a trawl net and the method used for trawling depend on the species of fish being targeted. A trawl net is widest at its mouth and tapers towards the foot or "codend". While being towed the mouth of the net is oval and can be 30 metres across and measure 2-7 metres from the upper edge (headline) to the lower edge footline of net. The lower edge of the net is weighted with a chain while the headline has floats, which keep the net's mouth open at a pre-determined depth.
The fish are herded into the mouth of the net (and eventually to the cod-end) by side panels of net called "wings". These wings are forced outwards by otter boards or doors attached at an angle designed to provide the outward force needed to keep the net's mouth open. These doors are made of wood or more commonly steel and vary greatly in size and design.
The net is towed behind the boat for one quarter to three hours and at a speed of 2-5 knots depending on the species of fish targeted. The net is retrieved by winching in the long towing cables (warps) and then the net. When the cod-end has been hauled aboard, it is untied and the catch is unloaded on deck.
In Victoria trawling along the seabed is used widely along the coast for catching bottom-dwelling (demersal) species. Deep sea species such as orange roughy are caught by trawling around rocky pinnacles in deep water. Trawling is not permitted in bays. Trawl fleets work out of Lakes Entrance and Portland.
Danish Seine
Danish seine vessels fish in a similar method to beach seine netters however the net is hauled back into boat and not on to the beach. The net is towed along the seabed and relies on the herding effect of the towing ropes to direct the fish into the wings and then the bag (bunt) to catch fish. The depth fished will determine the species caught. Naturally the length of the hauling rope determines the depth that the net will fish. The net is laid out in a pear shape, and the ends slowly winched into the boat as the boat moves forward. These two actions draw the net wings together and forward until the fish are concentrated the bag (bunt) of the net.
Lakes Entrance has the largest Danish Seine fishery in Australia with Flathead and School whiting being the main species targeted and caught.
Hook Fishing
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| Figure 8. Hook Fishing |
Unlike many other methods of fishing, this method depends on the fish seeking out prey and not just moving or forming schools. One of the most common hook fishing methods used in Victoria is longlining. The basic method is to set out a long length of fishing line, often several kilometres long, to which short lengths of line carrying baited hooks are attached. The longlines are hauled up periodically.
The gear is often set on the bottom where it is held by anchors. The start and finish of the long-line is marked with buoys and flags. Longlining is used to catch snap-per, school shark and gummy shark. A longline set below the surface is used where the target species is pelagic. The line is suspended at the required depth by using regularly spaced buoys along the longline. This method is catching tuna off the eastern Victorian coast. A variation of hook fishing is droplining in which a longline is suspended vertically. This method is used in the blue-eye trevalla fishery.
Acknowledgements
This Information Note was developed by John Tomkin on April 1998.
