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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
This beam trawl is similar to other beam trawls in that its held open by a steel bar with shoes on each end. However the chain mat gear is rigged with a matrix of chains across its mouth to prevent stones entering the trawl and enable the gear to be towed over fairly rough ground.
Beam Trawl - Open gear
This is a Beam trawl that is rigged to target flat fish on soft sand and muddy sea beds. The open beam gear has series of tickler chains towed ahead of the mouth of the net designed to stimulate the fish out of the mud and over the footrope of the trawl.
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
The beam trawl used to target brown shrimp is much lighter than that use to target flat fish in the North Sea. It also uses small mesh netting that leaves it prone to high levels of by-catch of benthic organisms.
Beam Trawl - Sumwing
In this fishing method a beam trawling the beam is replaced with ‘wing’ style of beam without any beam shoes at the ends. The aero foil shaped beam creates lift as it is towed through the water similar to an aeroplane wing. It is designed to skim about 600mm above the seabed with a standard beam trawl net behind it. This gear is often combined with the pulse trawl system.
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
Best Practice Guidance for Assessing the Financial Performance of Fishing Gear
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 so that the headline and footrope are of similar length. This helps to allow the release of fish rising in front of the footrope.
Demersal Trawl - General
A demersal trawl is 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
The rockhopper , or hopper trawl, as it is commonly known as, is a trawl that is towed on the seabed, with the mouth held open by a pair of otter boards (trawl doors), It is designed to be towed over hard, rough seabeds and rigged with a rock hopper footrope to minimise damage when being towed over these 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. this is the type of trawl favoured by many of the twin rig vessels in NE Scotland
Demersal Trawl - Sole Trawl
This is a 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. Generally these nets are fairly small and low with the trawl doors very close to the wing ends of the trawl.
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 is a 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.
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.
Gill net is also collective name for many different styles of nets as well as being a style of net in itself. Many of these nets will be referred to differently in different fisheries. (Gill nets, Tangle nets, Wreck nets, Drift nets, Trammel nets etc)
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, where hooks attached to artificial lures are used 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 jig and be caught
Long lining can be used to target both pelagic and demersal fish with the lines being rigged and set at a position in the water column to suit the particular species. A basic long line consists of a long length of line, light rope or more common now is heavy nylon monofilament, the ‘main line’, this can be many miles in length depending on the fishery. To this main line, multiple branch lines with baited hooks on (snoods) are attached at regular intervals. This rig is set either on the seabed (demersal) or in midwater (pelagic) with a dhan bouy at either end, and allowed to fish for a set period.
Multi rig - Quad rig
A method of towing four otter trawls side by side. The idea of multiple nets is to target a wide area of seabed with no increase in gear drag. This method is used to target bottom living species and nephrops.
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. The idea of multiple nets is to target a wide area of seabed with no increase in gear drag. This method is used to target bottom living species and nephrops.
Multi Rig Trawl - nephrops triple rig
This style of multi rig originated in Denmark. In this rig three trawls are towed side by side using four trawl warps. two pairs of trawl doors are used to spread this rig. The outer pair being standard trawl doors, the inner two being smaller but with added weight as they partly act as a trawl door and partly as a clump weight.
Multi Rig Trawl - Sole triple rig
This is a method used by smaller vessels to target Dover sole. It involves towing three small trawl side by side. The rig is spread using a set of trawl doors on the outside wings and a pair of steel frames in the inside wings. The trawls are very close behind the trawl doors as it is known that sweeps and bridles have very little effect on herding Dover sole.
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.
Out rig trawling is a method of multi rig trawling where two small otter trawls with the nets close behind them, are towed from the ends of outrigger derricks in a similar way to how a beam trawler tows its gear.
In this fishing method a net similar to a demersal trawl is towed by two boats simultaneously, one towing each side of the trawl and held open by the distance apart of the vessels.
The gear and way of operating a pair seine differs very little from a pair trawl except that the pair seine has a much greater length of rope and wire on the seabed, sweeping a much greater area of seabed.
In this fishing method a demersal trawl is towed by two boats simultaneously, one towing each side of the trawl and held open by the distance apart of the vessels.
The design of a pair trawl differs very little from a single trawl that would be used by an individual vessel apart from being larger.
Pelagic Pair Trawl
This fishing method is where one trawl towed in mid-water between 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 long.
In this fishing method one trawl, designed to catch pelagic fish is towed in mid-water by one vessel. The trawl is spread horizontally be a set of pelagic trawl doors. The horizontal opening is dictated by a clump weight on the lower wing ends of the net and the rigging of the bridles between the net and trawl doors.
By altering the vessel speed and / or changing the length of trawl warp between the vessel and the trawl doors, the position of the net in the water column can be altered to suit the depth where the shoal of fish are swimming at. The nets can be very large as big as 200 metres wide and 150 metres deep but the mesh size in the mouth of the trawl are huge sometimes as big as 50 metres long.
Pole and Line
This is a basic rod and line fishery using barbless hooks and live bait. One of the main fisheries using pole and line fishing is the tuna fishery in tropical waters. The tuna are attracted around the vessel by bait fish that are carried by the vessel and thrown into the sea to attract the shoal close to the boat. The crew, sometimes as many as 25, cast their rods and barbless hooks into the water, the are attracted to the shiny lure and hook, once hooked the fisherman swings the line overhead and lands the tuna on the vessel deck where the fish releases itself from the barbless hook. The fisherman carries on fishing and casts his rod again while the fish are guided down into the vessels fishroom.
Pots and trap - nephrops
Nephrops creels or prawn creels as they are generally called, are of the basic D creel design but of much lighter construction than that of a lobster or crab pot.
They usually have the standard two entrances in the side and almost always have plastic rings fitted to the entrances to keep the entrance open. These are known as hard eyes and they make entry into the creel easy for the Nephrops. They are usually worked in long fleets of up to 100 creels.
Pots and Traps - Brown crab
Two main shapes of trap are used to target brown crabs. One is the inkwell shaped trap, with a plastic funnel entrance, that is favoured by the larger vessels and the other the standard D shaped with entrances on each side or in the top. Different design of traps are favoured by fishermen in different parts of the UK. The D shaped creel with a parlour section is popular with some of the larger vessels, particularly on the East Coast of England.
Pots and traps - Cuttlefish
Cuttlefish traps are usually larger than most other traps but of lightweight construction. Most of them have two entrances made up of a circle of plastic ‘fingers’ designed let the cuttlefish enter the trap easily but difficult for them to escape from. Most of the fishing for cuttlefish with traps is done on the south coast of England, usually on a seasonal basis.
Pots and traps - general
Pots and traps are generally rigid structures into which fish or shellfish are guided or enticed through funnels that make entry easy but from which escape is difficult. There are many different styles and designs, each one has been designed to suit the behaviour of its target species. Many designs have evolved over many years to suit the coastline and seabed where it is used only changing to make use of modern materials.
Pots and traps - lobster
The D shaped creel with two entrances is the favoured trap by many lobster fishermen. Lobsters will also be caught as a valuable by-catch in many of the crab fisheries using inkwell style pots. In some areas the fishermen use parlour pots that have a separate section to retain the catch in. Lobster gear is handles and shot in a similar way to other traps and pots.
Pots and traps - Velvet crab
Traps or creels, used for velvet crab are similar to those used for lobster. They are also D shaped but are usually made slightly smaller and have two smaller entrances, one in each side. Many fishermen will use the same creels for velvet crabs as they do for lobster, just shooting them on different grounds and at different times of the year. They will be robustly constructed to be able to cope with the rocky grounds close inshore where the velvet crabs are found.
FPO - Pots and traps - whelks
Plastic drums with a netting entrance set on the seabed for targeting whelks. There tends to be one or two static gear vessels pursuing this fishery in each port around the UK nowadays.
PS - Purse Seine
A purse seine is a large net used to surround a shoal of pelagic fish. Once shot, the bottom of the net is drawn together by hauling in a long wire called the ‘purse line’ to form a huge cup shape of netting just below the surface of the water with the targeting fish inside. The net is gradually hauled onboard the vessel and the catch taken onboard the vessel.
Queen scallop Dredge
The dredges used to target queen scallops are wider and higher than a traditional Newhaven scallop dredge. They do not have tooth bar across the front, instead they have either a metal grid, or tickler chains to get the scallops to lift up off the seabed and swim into the dredge. The scallops then fall back into a bag made of metal rings. Some fishermen are replacing the tickler chain and metal grid with a strip of rubber matting across the front of the dredge.
LA - Ring Net
A ring is a long net that is shot to surrounding a shoal of pelagic fish with a ‘wall’ of netting. It can be operated by a single vessel or by a pair of vessels.
It is similar to a purse seine but without the running purse line. Also it is usually on a smaller scale.
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
In the Scottish seine the gear is shot on the seabed in a rounded triangle shape with very long weighted ropes attached to each end of the net. The net is gradually hauled in with the vessel maintaining station using its engine power rather than an anchor as in anchor seining.
A trawl that is towed on or very close to the seabed with the trawl doors swimming several metres off the seabed. Some times the trawl as well is rigged to be skimming just clear of the seabed. In some fisheries a pelagic style of trawl is used in this scenario to target demersal fish.
A separator panel is a horizontal panel of netting fitted in a trawl to divide the trawl into two sections one above the other. The idea is to be able to separate certain species that swim higher in the water column or rise ahead of the trawl into the upper chamber and the fish and shellfish that live close to the seabed into the lower chamber. This gives the possibility to then have different selective devices in each chamber each one better suited to those species in that particular chamber.
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, are attached to this line at regular intervals. Each line may have in the region of 200 baited hooks on. The lines will have a small anchor at either end and in some cases intermediate anchors to minimise movement of the line 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.
Tangle nets are a particular design of a gill net where the netting is hung onto the ropes to create a greater amount of slack netting. This gear will usually have less flotation on the head rope and will not stand as high when fishing, as the average gill net.
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. In UK waters they are generally set on or close to the seabed to target demersal fish. In some overseas fisheries they may be set in mid water or just below the surface to target pelagic fish.
Trawl Door Spread
The distance between the trawl doors is an important piece of information for any trawler skipper to know at all times.
Trolling is a method of fishing where the boat tows a line or lines with one or more hooks with a natural bait, or what is more common, an artificial lure on to target fish swimming in the upper layers of the water column. In England some of the inshore vessels target bass using this method. Overseas trolling with multiple lines is used to target tuna.
Twin Rig Trawl - Mixed species twin rig
This method uses two trawls side by side to target a mix of bottom living species and demersal round fish. It uses three trawl warps with standard trawl doors to spread the gear with a clump weight in the centre. Often the nets are scaled down versions of a rock hopper trawl.
Twin Rig Trawl - Nephrops twin rig
This is 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. This rig was really the start of the boom in Twin Rig in the UK
Twin Rig Trawl - Sole twin rig
This is a method used by smaller vessels to target Dover sole. It involves towing two small trawl side by side. The rig is spread using a set of trawl doors on the outside wings and a single steel frame attached to the two inside wings. The trawls are very close behind the trawl doors as it is known that sweeps and bridles have very little effect on herding Dover sole