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4 Panel Cod-end
By constructing a cod-end using 4 panels it allows the cod-end to remain more open when compared the more standard two panel cod-end. This improves the flow of water through the trawl helping to maintain the quality of the catch and allow the smaller fish more time to escape through the meshes. This style of cod-end is often made using square mesh or at least include sections of square mesh.
A device that emits an acoustic signal to deter cetaceans from approaching fishing gear. Sometimes referred to as ‘pingers’.
SDN - Anchor Seine
A net shot in the open sea using very long ropes to lay out the net and ropes on the seabed prior to hauling from a boat at anchor.
A bag net has a long vertical wall of netting, often several hundred metres long, running at right angles to the shoreline that is intended to interrupt the natural swim of the fish and direct them along it away from the shore and into a series of traps.
A net shot by hand or from a small boat in a circular shape then drawn ashore by hand from both ends. To target fish living close to the shoreline.
Beam Trawl - Chain Mat Gear
A trawl that is towed on the seabed where the net is held open by a wood or steel beam. The chain mat gear is designed to be towed over fairly rough ground.
Beam Trawl - Open gear
A trawl that is towed on the seabed where the net is held open by a wood or steel beam. The open gear has series of tickler chains towed ahead of the net.
Beam Trawl - Pulse trawl
The pulse trawl is a development of a standard beam trawl as a method of targeting bottom living species but in particular Dover sole. Using the standard beam and beam shoes the ticker chains and heavy ground gear has been replaced with a series of wire electrodes that pass an electrical pulse onto the seabed to stimulate the fish to rise up and fall back into the trawl. The beam if often replaced with a hydro dynamically shaped Sum wing beam arrangement to further reduce seabed impact.
Beam Trawl - Shrimp beam trawl
A trawl that is towed on the seabed where the net is held open by a wood or steel beam. Usually a lighter weight gear using small mesh netting to target shrimp.
Beam Trawl - Sumwing
A trawl that is towed on the seabed where the net is held open by an aero foil shaped bar that is skimming just of the bottom.
Benthos Release Panel
A benthos release panel is a panel of larger mesh or square mesh netting fitted into the lower panel of a trawl, usually a beam trawl to release any benthic material and seabed debris before it passes into the codend
A selective box trawl is a trawl that is made up of 4 panels, a top panel, a lower panel and two side panels with these 4 panels carried right down to a 4 panel cod-end. A 4 panel net will natural take up a more open cross sectional shape compared to a 2 panel net and cod-end. This allows the catch more space to swim freely in thereby more time for the smaller ones to escape through the diamond meshes. It also gives more opportunity to include other selective devices to further improve either size selectivity or species selectivity.
Bridle Angle and Wing End Spread calculations
Calculations for the wing end spread and Bridle angle of a single trawl using a calculator.
Calculating the Sweep Angle and Wing End Spread of a Single Demersal Trawl. (auto)
An easy to use calculation for wing end spread and sweep angle of a single trawl.
A coverless trawl has the top panel of the net cut back to allow the release of fish rising in front of the footrope.
Demersal Trawl - General
A cone shaped net that is towed on the seabed to target demersal fish species. The mouth of the trawl is held open by a pair of trawl doors (Otter Boards)
Demersal Trawl - Nephrops hopper trawl
A nephrops trawl towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors) designed and rigged to be towed over rough seabeds to target nephrops
Demersal Trawl - Nephrops trawl
A low demersal trawl towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors) designed to target nephrops
Demersal Trawl - Rockhopper trawl
A trawl towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors) designed and rigged with a rock hopper footrope to enable it to be towed over hard rocky seabeds
Demersal Trawl - Scraper net
A long low demersal trawl towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors) designed to target fish or shellfish that live on or very close to the seabed
Demersal Trawl - Sole Trawl
Trawl towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors) designed and rigged to target Dover sole.
Diamond Mesh size
Most drift nets, gill nets, trawls and seine nets etc are made of netting with a diamond shaped mesh. The size of mesh used can range from 40mm right up to meshes many metres in length in the larger pelagic trawls. It goes without saying that by using larger mesh there will be larger gaps between the netting twine that will allow more of the smaller sized fish to escape from the net. Increasing the mesh size is one of the easiest way to improve the size selectivity of any gear and reduce by-catch of immature fish. However much depends on how the meshes are orientated (square mesh, T90 mesh or T zero mesh) and on how much the meshes are allowed to open when the gear is fishing. As an example, in a lobster trap the netting is stretched tight over the frame therefore the mesh opening is set and stays constant, in a trawl the opening of the mesh is dictated by the towing speed and the tension in the netting and both these will vary during any fishing operation.
This type of gill net that is suspended in the water, usually just below the surface, but can be worked anywhere from the seabed to the surface to target pelagic species. The depth below the surface can be set by rigging the floats on the rope strops attached to the headline. As with other gill nets the mesh size is chosen to suit the size of the target species. The main difference with this type of gill net is that it is not anchored, but allowed to drift with the tide usually with one end attached to the boat. The soak time will also be much shorter than that for bottom set gill nets.
Gaps of set size that are fitted into traps to allow the escape of the target species that are too small to land.
Fish stimulation as a selective device is still a relatively new concept. Stimulation is being trialled using a light, sound or electric pulses. So far there is some evidence that light does have an effect on fish behaviour. The Pulse trawl has shown that different species can be stimulated with different strengths and frequency of electric pulses.
Flip Up Ropes Construction
The design and construction of a flip up rope for fitting into a demersal otter trawl.
A fyke net is a type of fish trap. It consists of long cylindrical netting bag usually with several netting cones fitted inside the netting cylinder to make entry easy and exit difficult. This net is then mounted on rigid rings or other rigid framework and fixed on the sea bed by anchors, ballast or stakes It also has wings or leaders to help guide the fish towards the entrance of the bag. They are commonly used in estuaries or inshore shallow water.
This is where there is complete change of fishing gear to change the catch composition thereby reducing discards. This could be things like changing gear from trawling for nephrops to targeting them using creels to minimise by-catch.
By simply reducing the physical size of the whole gear or just part of the gear, it is sometimes possible to reduce unwanted bycatch and be able to handle the gear more efficiently.
A gill net is a single wall of netting anchored on the seabed to catch fish that swim into it.
The commercial hand line fishery is exactly what the title says, fishing using a rod or hand held lines as a commercial venture in a similar manner to recreation angling. It covers several different methods of fishing such as jigging, bait fishing and trolling usually done from a small inshore boat usually single handed but some boats do work with two people on board. They will land small quantities of fish on a daily basis in pristine condition.
Usually this is a trawl or static net that has been design to keep the headline (top of the net) very low, probably below 1 metre in height to prevent the capture of high swimming species.
It is working on the principle that different species of fish live or move at specific heights off the seabed or below the surface. this can be at different times of the day (often daylight or dark)or even on a seasonal basis. the gear is designed just to target this reduced area in the water column that they swim in.
Inclined Netting Grids
The inclined grid is fitted in the trawl at an angle so that it allows certain species to pass through and into the codend and directs other species or size of fish out through an escape hole in the top of the trawl.
Inclined Separator Panels
An inclined separator panel has the leading edge of the separator panel set back from the fishing circle of the trawl. the front of the panel is inclined down to set the height of the panel.
Jigging is a method of fishing that has evolved over many centuries, using hooks with artificial lures fitted to attract and capture fish. The lures are designed to resemble small fish that the target species would normally feed on. They are usually operated in a rhythmic up and down motion to simulate the movement of small fish, but often particularly if the fish are feeding well, the very movement of lowering the jig to the required depth is enough for the fish to take the jog and be caught.
Catching fish on hook and line can be traced back to the days of the cave man when hooks were fashioned out of bone and line was fashioned from any twisted strands that were available. The use of multiple hooks on one line (longline) probably did not start to come into its own until the late 1800s when the construction of hooks became more mechanised. The next major step would have been in 1950-1970 when automated line systems were introduced to bait, shoot. haul and stow the lines. Prior to this, every hook would have been baited by hand before shooting. Though these hand baiting techniques are still used in some fisheries today.
Multi Rig Trawl - more than four nets
A method of towing several otter trawls side by side. As many as 12 trawls has been experimented with by some fishermen in Denmark. This method is used to target bottom living species and nephrops.
Multi Rig Trawl - nephrops triple rig
A method of towing three otter trawls side by side using four warps and two sets of trawl doors
Number of Dredges
In some scallop dredge fisheries the number of dredges used is regulated to ensure fishing effort remains within manageable limits.
Off Bottom Trawl
This is a trawl that, by the way it is rigged and towed, swims clear of the seabed but close enough to target some of the demersal species.
Similar to a pair trawl but towed using a greater length of ropes/wire on the seabed
Trawl towed between two boats, either on the seabed or in mid-water, held open by the distance apart of the two vessels.
Pelagic Pair Trawl
square-mesh-panel-2One trawl towed in mid-water by two vessel to target pelagic fish. The height of the net in the water column can be changed by altering vessel speed and length of wire out. The nets can be very large as big as 240 metres wide and 160 metres deep but the mesh size in the mouth of the trawl are huge sometimes as big as 50 metres across.
Pole and Line
One of the main fisheries using pole and line fishing is the tuna fishery in tropical waters where the individual fish have high value. It can be a fairly basic type of fishing, with a minimum of gear, that consists of a long pole usually made of bamboo, wood or nowdays fibreglass, with a short line attached. On the line is a single barbless hook. This can be just a bare shiny hook or a simple feathered lure. Combining their experience with modern technology, the skipper will locate a school of tuna, or any other target species. They will then attract the fish close to the boat by scattering some form of small fish, such as sardines or pilchard, on the surface as bait. This is called ‘chumming’ and is done in conjunction with spraying water on the surface to create the illusion that there is a large shoal of small bait fish just below the surface. This will then send the tuna into a feeding frenzy and they will go for anything shiny that they see, such as a barbless hook.
Pots and trap - nephrops
Small lightweight, usually D shaped with two hard eye entrances designed to target nephrops
Pots and Traps - Brown crab
Rigid structures usually either inkwell shaped or D shaped with entrances designed to target brown crab
Pots and traps - Cuttlefish
Lightweight rigid structures usually with two entrances designed to target cuttlefish.
Pots and traps - general
Structures into which fish or shellfish are guided or enticed through funnels that encourage entry but limit escape.
Pots and traps - lobster
Rigid structures usually either inkwell shaped or D shaped with entrances designed to target lobster
Pots and traps - Velvet crab
Rigid D shaped structures covered with small mesh netting designed to target velvet crab
PS - Purse Seine
A large net used to surround a shoal of pelagic fish, the bottom of which is then drawn together by a ‘purse line’ to prevent escape of the fish.
Queen scallop Dredge
Rigid structure with a collection bag towed on the seabed to catch queen scallops. Generally towed with several dredges side by side.
LA - Ring Net
Net operated by surrounding a shoal of pelagic fish with a ‘wall’ of netting sometimes operated by two boats.
Similar to a purse seine but without the running purse line. Usually on a smaller scale as well.
The ring size of scallop dredges can be used as a selectivity measure to release scallops below a certain size. Most of the small scllops released will survive
DRB - Scallop Dredge
Rigid structure with a chain mail collecting bag, towed on the seabed to target king scallops. Generally used by towing several dredges side by side behind the vessel.
SSC - Scottish Seine
A progression from the anchor seine where the net is hauled against the vessels own power rather than an anchor
A trawl that is towed very close to the seabed with the trawl doors making no contact with the seabed. The trawl may be on the seabed or swimming clear of it.
This fishing method is similar to longline fishing but adapted to suit the smaller inshore vessels. The ‘small lines’ are made up of a long length of heavy twisted twine or thick monofilament twine usually between 100 – 500 metres long. Short lengths of lighter twine called snoods with hooks on one end are attached to this line at regular intervals. Each line may have as many as 200 baited hooks on it to attract fish and an anchor at each end to keep the gear stationary on the seabed.
Sort X grid
The Sort X grid was developed in Norway in the early 90’s as a measure to reduce the numbers of small fish being caught when targeting cod in the Barents Sea.
This grid works on a different principle to most grids in that it depends on the fish natural escape behaviour and ‘co-operation’ from individual fish in finding the escape area between the bars. there is some belief that the change in light penetration and water flow between the trawl and grid section help to guide the smaller fish through the grid.
Square Mesh Cod-ends
. For the release of small undersized round fish square mesh on top and / or lower panels in the codend and/or extension is one of the most effective escape devices available
Square Mesh Panels
Square Mesh Panels The square mesh panel is one of the most common used and well known selective devices. In this the diamond mesh is turned through 45 degrees to the water flow thereby ensuring the meshes in the panel remain fully open throughout the fishing operation, allowing for the release of small fish. It is sometimes referred to as T45 mesh.
A stake net has a long vertical wall of netting held up by a line of strong wooden poles sticking up wards from the beach, running at right angles to the shoreline , often several hundred metres long,that is intended to interrupt the natural swim of the fish and direct them along it away from the shore and into a series of traps.
In this design the cod end mesh is turned through 90 degrees into T90 configuration. This is when normal diamond mesh is turned through 90 degrees to enable the meshes to stay more open while the gear is being towed.
Very similar to a gill net that it is a single wall of netting, but in this rig the netting is hung onto the ropes to create a greater amount of slack netting. Tangle nets will usually have less floatation on the head rope and will not stand as high when fishing, as the average gill net. The loose netting is more effective for catching many of the bottom living species such as flatfish, monkfish and shellfish that, due to their body shape, would bot easily be meshed by a standard gill net, but will get entangled in the slack netting. As with other types of gill net, tangle nets will be rigged with a mesh size and the amount of slack netting to suit the particular target species .
Three Warp Twin Rig - Shortening the Centre Warp
These information sheets provides figures to advise skippers towing three warp twin rig trawl gear how much to shorten the centre warp by to keep the gear square
This concerns towed gears. In some situations a change in towing speed can dramatically change the composition of the catch. It may be worth looking at as an easy option for reducing bycatch.
TRA - Trammel Nets
Trammel nets are similar to a gill net but are made up of three layers of netting
Trawl Door Spread
The distance between the trawl doors is an important piece of information for any trawler skipper to know at all times.
These are basic lines that are towed behind a boat, close to the surface or at a set depth to suit the target species. Each line will have one or more hooks with a natural bait, or what is more common, an artificial lure. trolling can be used by small open boats using one or tow lines, while many of the larger vessels will be fitted with lightweight out-rigger style booms to enable them to tow multiple lines behind one vessel. These are rigged in such a way to allow each line to be hauled individually when a fish is caught. It is usually a daylight fishing operation used mainly by French and Spanish vessels and occasionally by some vessels from SW England for targeting tuna along the Atlantic coasts. Some of the smaller vessels in Southern England will use this method, but with fewer lines to target bass.
Twin Rig Trawl - Mixed species twin rig
A method of towing two otter trawls side by side to target mixed demersal fish.
Twin Rig Trawl - Nephrops twin rig
A method of towing two otter trawls side by side to target nephrops. The nets are usually smaller than an equivalent single net but are designed to sweep a wider area of seabed using less fuel.
Twin Rig Trawl - Sole twin rig
A method of demersal trawling where two sole trawls are towed side by side.