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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.

Selective Device

Acoustic deterrents

A device that emits an acoustic signal to deter cetaceans from approaching fishing gear. Sometimes referred to as ‘pingers’.

Selective Device

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.

Gear

Bag net

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.

Gear

Beach Seine

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.

Gear

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.

Gear

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.

Gear

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.

Gear

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.

Gear

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.

Gear

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

Selective Device

Best Practice Guidance for Assessing the Financial Performance of Fishing Gear

Technical Information

Box Trawl

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.

Selective Device

Bridle Angle and Wing End Spread calculations

Calculations for the wing end spread and Bridle angle of a single trawl using a calculator.

Technical Information

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.

Technical Information

Coverless Trawls

A coverless trawl has the top panel of the net cut back to allow the release of fish rising in front of the footrope.

Selective Device

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)

Gear

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

Gear

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

Gear

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.

Gear

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

Gear

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.

Gear

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.

Selective Device

Drift Nets

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.

Gear

Escape Gaps

Gaps of set size that are fitted into traps to allow the escape of the target species that are too small to land.

Selective Device

Fish Stimulation

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.

Selective Device

Flip Up Ropes Construction

The design and construction of a flip up rope for fitting into a demersal otter trawl.

Technical Information

Fyke Net

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.

 

Gear

Gear Operation

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.

Selective Device

Gear Size

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.

Selective Device

Gill Nets

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)

Gear

Hand Lines

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.

Gear

Headline Height

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.

Selective Device

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.

Selective Device

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.

Selective Device

Jigging

 

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

Gear

Long Line

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.

Gear

Multi rig - Quad rig

A method of towing four otter trawls side by side

Gear

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.

 

 

Gear

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

Gear

Multi Rig Trawl - Sole triple rig

A method of towing three sole trawls side by side.

Gear

Number of Dredges

In some scallop dredge fisheries the number of dredges used is regulated to ensure fishing effort remains within manageable limits.

Selective Device

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.

Selective Device

Out-rig Trawling

A method of towing two small otter trawls from out rig derricks

Gear

Oyster Dredge

Rigid structure towed on the seabed to oysters

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Pair Seine

Similar to a pair trawl but towed using a greater length of ropes/wire on the seabed

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Pair Trawl

Trawl towed between two boats, either on the seabed or in mid-water, held open by the distance apart of the two vessels.

Gear

Pelagic Pair Trawl

One 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.

Gear

Pelagic Trawl

Trawl towed in midwater by one vessel to target pelagic fish

Gear

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.

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Pots and trap - nephrops

Small lightweight, usually D shaped with two hard eye entrances designed to target nephrops

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Pots and Traps - Brown crab

Rigid structures usually either inkwell shaped or D shaped  with entrances designed to target brown crab

Gear

Pots and traps - Cuttlefish

Lightweight rigid structures usually with two entrances designed to target cuttlefish.

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Pots and traps - general

Structures into which fish or shellfish are guided or enticed through funnels that encourage entry but limit escape.

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Pots and traps - lobster

Rigid structures usually either inkwell shaped or D shaped  with entrances designed to target lobster

Gear

Pots and traps - Velvet crab

Rigid D shaped structures covered with small mesh netting designed to target velvet crab

Gear

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.

Gear

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.

Gear

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.

Gear

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.

Gear

Ring Size

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

Selective Device

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.

Gear

SSC - Scottish Seine

A progression from the anchor seine where the net is hauled against the vessels own power rather than an anchor

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Semi-Pelagic Trawl

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.

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Small Line

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.
Environment

Gear

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.

Selective Device

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

Selective Device

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.

Selective Device

Stake Net

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.

Gear

T90 Cod-ends

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.

Selective Device

Tangle nets

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.

Gear

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

Technical Information

Towing speed

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.

Selective Device

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.

Gear

Trawl Door Spread

The distance between the trawl doors is an important piece of information for any trawler skipper to know at all times.

Technical Information

Trolling

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.

 

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Twin Rig Trawl - Mixed species twin rig

A method of towing two otter trawls side by side to target mixed demersal fish.

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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.

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Twin Rig Trawl - Sole twin rig

A method of demersal trawling where two sole trawls are towed side by side.

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Wreck Nets

Wreck nets are types of gill or trammel nets that have been rigged to shoot over wrecks or areas of hard ground on the seabed.

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