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Scallops in Bass Strait are collected in dredges which are towed along the seabed by vessels traveling at four to six knots. The dredges are strong wire mesh boxes with a mouth of about three metres wide and .3 metres high. |
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Each dredge has depressor plates which help keep the dredge in the seabed while it is being towed. After each tow the dredge is winched aboard the vessel, slid onto the cradle which tilts the dredge and thus empties it of all the scallops and collects on the tray. This method of operation speeds up the process and allows fishing to continue in rough seas.
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In Victoria southern rock lobsters and giant crabs are caught in bee hived shaped pots made with a steel frame and covered with wire mesh or netting and the entrance is a plastic funnel. |
Pots are typically 75 cm in diameter and weigh about 20 kg. The pots have escape gaps which allows for undersized fish to escape. The pots are baited with fish heads and then tied to buoyed lines. They are place 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.
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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 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 the side of the boat) through which nets are hauled aboard. Purse seining is used to catch tuna, but the practice has been criticised because dolphins which follow the schools of fish are also being caught. Purse seining is used for Port Phillip Bay to catch schools of pilchards which are used for pet food, bait and human consumption.
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Diving is a traditional means of collecting molluscs. Divers collect abalone and sea urchins ( Heliocidaris erthrogramma ) in Victoria . Divers wear 7mm or 9mm neoprene wetsuits. The wetsuits protect the diver from exposure of low temperatures and provide extra buoyancy. To offset the buoyancy, divers wear lead weight belts to help them reach the seabed. Compressed air is supplied to the diver through a plastic hose from the support boat. The diver uses the air as required by breathing in and out through a regulator. This is called hookah diving. Divers can also carry a small air tank for emergencies. Divers also wear facemasks and flippers.
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Abalones are searched for over rocky reef areas. Once found they are lifted off the reef with a rounded spatula-like tool and placed in a mesh bag. Sea urchins are picked up using long metal tongs. As the catch bag fills with abalone the diver inflates a small bag attached to the side of the catch bag to make it easier to lift. When the bag is full the diver fully inflates the side bag, sending the catch to the surface. The crew member onboard the support boat measures and packs the catch into sealed bins.
Support boats are modern high-speed boats. They measure between 5 and 10 meters in length and are able to be towed on trailers. The boats are powered by twin outboard motors with a total power of 230 to 450 horsepower.
The vessel with the diver working below is not anchored but is allowed to drift. This allows the diver to cover more area without the need to surface as often. Divers work in water depths from 2 to 40 metres.
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A mesh net is a panel of netting that is held vertically in the water. They are also called gill nets. This is probably one of the oldest forms of net fishing. In Victoria mesh nets are used to catch inshore fish like rock flathead and black bream in Bays and Inlets and offshore to catch sharks. |
When set, the meshnet of 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 10cm to 13cm.
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The most common method of beach seining is to lay out a net, with long ropes at both ends from a boat. The starting point is usually close to the shoreline and the nets travel a semicircular course.
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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 fish are then release into the shallow waters. The ropes are up to one kilometre long, have floats on the top and weights at the bottom so the net hangs vertically in the water.
The target species for this fishing method are King George Whiting, snapper, flounder and bream. Small boats are commonly used with one or two fishermen.
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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.
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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 roughly 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 .
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Longline fishing is one of the most environmentally friendly and cleanest catching methods. Longlining is a static hook and line fishing method. The gear is rigged to suit the species targeted and the area being fished. Longlines are used to catch sharks and blue-eye trevalla in offshore waters and snapper in bays and inshore coastal waters. Longlines involve setting out a length of line, often several kilometres long, to which short lengths of line carrying baited hooks are attached at intervals. The fish are attracted to the bait, then hooked and held by the mouth until they are brought onboard the vessel.
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Longlines can be set horizontally just below the surface or along the seabed and vertically. Vertically set longlines are called drop-lines or trotlines.
To begin setting a longline, the first buoy (and anchor) is put overboard. The vessel travels along the desired track while the line runs out over the stern. Tubs containing baited hooks around the rim are set out in series. The hooks are attached to the mainline using snap-on devices; a bit like safety pins. The hooks are attached at regular intervals. Longlines used in Port Phillip Bay have a maximum of 200 hooks and are spaced about every 10 metres. Drop-lines only have hooks attached to the lower section.
When all the gear has been set, the boat will travel back to the start and will then wait for the hooks to have soaked for the required length of time. In bays this is one hour.
When ready to haul the gear, the vessel approaches the leeward (sheltered) end of the set and retrieves the first marker buoy, anchor and end of mainline. The line is hauled in over a roller or side of the vessel. The branch lines are unclipped and if a fish is attached it is brought aboard using a landing net or gaff. The hook is removed from the fish's mouth and placed in storage bins. If hooks are lost they are replaced immediately before storing. The branch lines and hooks are placed on storage racks, while the mainline is coiled into a large tub.
Small longline operations are labour intensive. Large operations are often mechanised.
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