a fishing industry guide

to offshore operators

Fisheries and Offshore Oil Consultative Group

A FISHING INDUSTRY GUIDE

TO

OFFSHORE OPERATORS
CONTENTS

1. Preface 1-2

2. Profile of the UK Fishing Fleet 3

(i) Demersal or Bottom Fishing Methods 3-14

(ii) Pelagic or Midwater Fishing Methods 14-17

(iii) Static Gear 18-21

3. Addendum 22

4. Table 1 23
Summary Statistics for the UK Over 10 Metre
Fleet as at 31 December 1998

5. Table 2 24-25
Summary of typical gear component sizes and
Towing speeds for various fishing methods

6. Annex 1 26-28
Useful Addresses
 PREFACE

1.1 This booklet has been prepared by the Scottish Executive Rural Affairs Department at
the request of the Fisheries and Offshore Oil Consultative Group (FOOCG) in conjunction
with the Fisheries Research Services - Marine Laboratory Aberdeen (FRS-MLA) and the
Ministry of Agriculture, Fisheries and Food.

1.2 Since the previous version was published in 1976 both the UK Fishing Industry and
Offshore Oil Industry have undergone substantial changes. In particular the loss of distant
water fishing opportunities means that most vessels concentrate on home water grounds on
the UK Continental Shelf and adjacent slopes, areas where interaction with offshore oil and
gas installations and their related infrastructure are most likely to occur. It is however to be
applauded that the two industries have managed to co-exist in this often unpredictable,
violent and dangerous environment throughout this period. There are many examples of co-
operation and mutual support that testify to the good working relations that continue to
evolve between the two industries.

1.3 Some areas are more important than others to fishermen and are therefore more
intensively fished. The booklet 'Fisheries Sensitivity Maps in British Waters' published in
1998 provides valuable information on the spawning locations and nursery areas of several
commercially important species along with a range of fishing effort maps. That booklet was
prepared by the FRS-MLA in conjunction with the Centre for Environment, Fisheries and
Aquaculture Science (CEFAS) Fisheries Laboratory, Lowestoft using their own data along
with further information provided by the Scottish Fishermen’s Federation and National
Federation of Fishermen’s Organisations. The United Kingdom Offshore Operators
Association (UKOOA) published the booklet in a paper version in limited numbers for
essential users during the summer of 1998. An electronic version can however be found on
their website at:

www.oilandgas.org.uk/issues/fisheries/index.htm.

1.4 Over the past twenty years new fishing methods such as demersal pair trawling and
seining have evolved, together with twin rig trawling and the growth of fishing for many high
value deep-water species which now find a ready market. As a result of these developments
fishing vessels and the gears that they carry have generally become larger, heavier and
stronger over the years. It follows then that in the event of fouling underwater obstructions,
such gear is less likely to part under load or be torn free. In addition to a brief description of
the gears currently deployed by the UK fishing fleet this booklet also includes details of the
typical (mean) and maximum sizes of rigging components such as warps, bridles and otter
boards which could conceivably make contact with installations on or near the seabed.

1.5 Details of the various types of static gear used in UK waters to catch diverse species
of finfish and shellfish are also included because of the risk of damage to such gear from
offshore oil and gas related activity particularly seismic surveying. The physical presence of a
seismic survey vessel and its equipment has the potential for disrupting fishing operations. In
the open sea, a seismic vessel towing streamers prefers to maintain its course and speed in
order to obtain seismic data. Notwithstanding, due to the number and length of the streamers,
these vessels are hampered in their ability to manoeuvre. As such, other vessels not similarly
hampered in their ability to manoeuvre are required to keep clear of a seismic vessel. In areas

1
where static gear is deployed, seismic operations involving towed streamers or deployment of
bottom cables may require the temporary removal of static gear to enable access to the area.
Account needs to be taken of the effort required by fishermen to remove and eventually
reinstate such gear.

1.6 Safety is of primary concern to both industries. It has been recognised that not only is
there the ever present threat of gear becoming snagged on underwater obstructions, that may
or may not be related to offshore operations, but also that there is the potential for fishing
gear to cause damage to subsea equipment and pipelines. It is therefore hoped that the
information given in this booklet will prove useful to both industries in the calculation of
loads likely to be encountered in the event of contact between fishing gear and subsea
installations. It is also hoped that this booklet will have a wide distribution both offshore as
well as among those persons on barges, drilling rigs and supply vessels who have a
responsibility for ensuring the safety of operations at sea.

Scottish Executive Rural Affairs Department

March 2001

2
 Profile of the UK Fishing Fleet

2. In 1998 UK vessels landed just over 924,000 tonnes of fish and shellfish into the UK
and abroad with a first hand sale value of £662 million. The number of active vessels of 10
metres and over totalled 2,150, with approximately a further 5,000 inshore vessels under 10
metres in length fishing mainly with static gear. A detailed breakdown of the composition of
the over 10 metre fleet is given in Table 1. In addition to the number of vessels, the
minimum, mean, median and maximum values for overall length, gross tonnage and main
engine power are included for each category. It should be noted that these figures apply only
to fishing vessels registered in the UK; foreign vessels using different gears also operate
within British Fishery Limits. A description of the methods of capture with the relevant
information on gear components is set out below, together with a summary for common
fishing gears.

(i) DEMERSAL OR BOTTOM FISHING METHODS

Demersal Trawl (Otter Trawl)

2.1 This is by far the most commonly used towed gear in UK fisheries. Both finfish and
shellfish species found on or near the bottom are taken by this method. A diagram of the gear
deployed in fishing mode is set out in Figure 1. The trawl net (a) is cone or funnel shaped
with wings extending forward to guide fish back into the funnel and ultimately the cod-end,
the rearmost and narrowest part of the trawl where the catch is collected. Otterboards or
trawl doors (b) are heavy metal devices designed to keep the gear on the bottom and provide
hydrodynamic spreading forces to open the gear horizontally. Details of some types in
current use can be found in Appendix A/Otterboard performance and Behaviour, Commission
of the European Communities. The otterboards are connected to the towing vessel by steel
wire ropes known as trawl warps (c), and to the net with wire or combination ropes called
bridles (d) or sweeps. The weighted groundrope, constructed of wire or chain strung through
rubber discs, rockhopper or metal bobbins, serves two purposes. It protects the lower mouth
of the trawl net from sea bed damage and is weighted sufficiently to ensure good bottom
contact is maintained. Floats are attached along the headline or upper part of the net mouth to
open the trawl vertically. The entire assemblage is towed by the trawler at a speed of 3 knots
(min 2, max 4). Warp length/water depth ratios range from 4:1 or more in shallow water
(25m) to 2:1 in deep water (1000m) with 3:1 the norm on the majority of fishing grounds on
the continental shelf (50m -200m). Bridle/sweep lengths between otterboards and net also
vary considerably, from a few metres to 180 metres depending on target species and nature of
sea bottom. On smaller vessels, combination (polypropylene/steel) wire may be used as
sweeps and on larger vessels mid-link chain may form part of the rig.

3
Typical (and maximum) values for above components:- Trawl warp (c) wire diameter 20mm
(28mm); Bridle/sweep (d) wire diameter 20mm (32mm or 19mm chain); Otterboard (b) size
and weight 5.3 square metres x 1400 kg (8 square metres x 3000 kg).

4
Twin Rig Demersal Trawl

2.2 The essential elements of twin rig trawl gear are set out in Figure 2. This gear is
generally used for target species tight on the bottom, such as angler, flatfish and Nephrops.
By towing two nets side by side the effective swept area, and hence catch, is increased. As
with the single demersal trawl above otterboards (a) provide the horizontal spreading forces
and floats and groundropes the vertical forces. The obvious difference in rigging is the third
wire or central warp (b), which runs from the vessel to the clump (c), a heavy weight which
can consist of short lengths of chain cable shackled together or a custom made device
(Figure 3) designed to roll rather than be dragged along the bottom. Warp length/water depth
ratios are similar to those used with the single demersal trawl and bridles/sweeps (d) can be
steel wire, combination wire, chain or a mixture of all three. Normal towing speed used is
2.5 knots (max 3.5 knots).

5
Typical (and maximum) values for above components:- All three trawl warps wire
diameter 20mm (24mm); Bridle/sweep (d) wire diameter 16mm (26mm combination,
19mm chain); Otterboard size and weight 2.84 square metres x 600 kg (5.4 square
metres x 1500 kg); Clump weight 620 kg (2000 kg).

6
Demersal Seine Net

2.3 Scottish seining, also known as flydragging, uses long lengths of seine rope
constructed from either leaded polypropylene or combination wire to herd fish into the path
of the net as the gear is hauled. Up to 3 kilometres of rope a side (14 coils) may be shot in a
triangular plan (Figure 4) with the dhan, or marker buoy, supporting the end of rope first shot
to which the vessel returns to complete the set. Both ropes (a) are then led to the winch and
the vessel steams slowly ahead, gradually increasing winch speed as the gear closes to keep
the net moving steadily forward. Combination sweeps (b) allow the floats to open the net
vertically and the footrope, generally rigged much lighter than that of a trawl, is sufficiently
weighted to keep the lower edge of net mouth in contact with the sea bed. Starting from a
stationary position a seine net may reach a forward speed of 2 knots during the later stages of
the haul before it leaves the bottom. Virtually all whitefish species are taken by this method,
which is for the most part confined to grounds on the continental shelf (200 metres
maximum), but is seldom utilised in the harvesting of shellfish. This technique generally
fishes most effectively during the hours of daylight when rope herding capabilities are
optimised.

Typical (and maximum) values for above components:- Seine net ropes - leaded 28mm,
combination 28mm (leaded 34mm, combination 32mm); Sweeps - combination 16mm
(24mm).

7
Demersal Pair Trawl

2.4 In two-boat or pair demersal trawling (Figure 5) each vessel tows only one warp and
by keeping station at a set distance apart (0.2-0.3 nautical miles) provides the horizontal
forces required to spread the gear, rendering the need for otterboards unnecessary. This
means that two vessels of relatively modest engine power can between them tow a
comparatively large trawl, increasing between 50% to 100% the volume of water swept per
vessel. Shackled between warps (b) and bridles (d) a heavy wire sweep (c) ensures good
bottom contact. In all other respects the net (a) is similar to a single boat trawl, with floats
and heavy rockhopper groundrope providing the vertical forces around the net mouth. Warp
length/water depth ratio is around 3:1 with activity confined mainly to the continental shelf
(200m). Heavy sweep wire lengths can range from 100 to 400 metres, depending on bottom
conditions and vessel capabilities. Towing speeds between 2.5-4.0 knots can be encountered,
with around 2.8 knots the norm.

Typical (and maximum) values for above components:- Trawl warp (b) wire diameter 21mm
(24mm); Heavy sweep (c) wire diameter 26mm (30mm); Bridles (d) wire diameter 20mm or
16mm chain (19mm chain).

8
Demersal Pair Seine

2.5 This method of fishing was originally developed by single-boat flydraggers teaming
up to tow a single seine net between them using up to 13 coil (2860m) of seine net rope (see
above) in place of the wire warps and heavy sweeps of the pair trawl gear. These vessels
towed up to 0.5 nautical miles apart and increased considerably the area of sea bed swept by
the gear. However this technique requires large areas of clear ground to function efficiently
with the risk of snagging on rough bottom or underwater obstructions ever present so a
hybrid method, a cross between pair seining and pair trawling, evolved. By introducing
3-4 coil (660-880m) of seine rope between the heavy sweep and bridles of the pair trawl rig
the area swept by the gear was considerably increased without the need to deploy long
lengths of rope warps (Figure 6). Distance between vessels was reduced to around
0.28 nautical miles and towing speeds range between 2.2 to 3.5 knots, the normal rate being
towards the lower end of this range (2.5 knots). Like the pair trawl this gear is generally used
in water depths under 200m and targets white fish species only.

Typical (and maximum) values for above components:- Trawl warp (a) wire diameter 19mm
(22mm); Heavy sweep (b) wire diameter 22mm (26mm); Seine ropes (c) combination
diameter 32mm (40mm); Bridles (d) combination diameter 16mm (24mm).

9
2.6 Due to the nature of demersal trawling, twin rig demersal trawling, demersal seine net
and demersal pair trawl, and the restrictions they can put on vessel manoeuvrability, it is not
always possible for fishing vessels to respond positively to requests to move out of the way of
other vessels which are similarly hampered in their ability to manoeuvre eg seismic vessels.
To overcome the problems associated with restricted fishing vessel speed and
manoeuvrability it is recommended that early communication be established if access is
sought across an area being fished.

Twin Beam Trawling

2.7 Beam trawls are used to harvest whitefish, mainly flatfish such as sole, plaice or
megrim together with angler and other species found hard down on the sea bed. Each net is
fished from an outrigger boom, one on each side of the vessel (Figure 7), and towed from
here on a single warp (a) shackled to a three chain bridle (b) attached directly to the beam (c)
which holds open the mouth of the trawl. The beam, 9-12m in length, is constructed from
heavy steel tube and supported on each side by rugged steel trawlheads (d) which slide over
the sea bottom. Ahead of each groundrope tickler chains (e) or chain mats are often used to
disturb fish, causing them to rise up and be taken by the trawl following immediately behind.
Towing speeds are generally higher than otter trawling, reaching 6 or 7 knots on clean ground
with ticklers, whereas on rough ground stone mats are towed at 4 knots. On the most
powerful modern beam trawlers the weight of each fully rigged beam is almost 10 tons.
Furthermore such vessels can tow this gear at 7 knots. Beamers usually operate on the
continental shelf (200m) with warp length/water depth ratios of between 2.5 or 3:1. Some
vessels have switched to a double wire system (z) to facilitate the hauling procedure, and
consequently impose a doubling of the load applied to an obstruction before warp failure may
occur.

10
Typical (and maximum) values for above components: Trawl warp single (a) wire diameter
26mm (34mm), double (z) wire diameter 24mm (26mm); Chain bridles (b) 19mm diameter
mid-link (22mm); Assembled trawl weight (c+d+e) = 7.5 tonnes (10 tonnes).

Scallop Dredging

2.8 Dredges are used mainly in UK waters for scallops. Ships rigged for beam trawling
deploy dredge arrays from outrigger booms in the manner of beam trawls. Each dredge (a)
consists of a ruggedly constructed triangular steel frame and tooth bearing bar or sword,
behind which a mat of linked steel rings is secured. The toothbar may be spring-loaded to
reduce gear damage (Figure 8). A heavy netting cover or back is laced to frame, sides and
after end of this mat to form a bag in which the catch is retained. Scallops, which usually lie
recessed in sand and fine gravel, are raked out by the teeth and swept into the bag. Several
dredges are shackled to a hollow steel tow bar (b) fitted with chain bridles (c), one for each
dredge. The entire assembly (Figure 9) is towed on a single wire warp (d) and larger vessels
generally tow two bars, one on each quarter. The number of dredges used varies with towing
power and handling capabilities, with fourteen (ie seven on each side) a fairly typical number,
but on the largest vessels 24 x 2' 6" (760mm, which is the length of sword) dredges, or 12 a

11
side, is not uncommon. Most vessels use 2' 6" dredges although 2' (610mm) dredges are also
still found in this fishery. Warp length/water depth ratio is generally around 3:1, but in bad
weather or strong tides more wire may be paid out to keep the gear on the bottom. Normal
towing speed is around 2.5 knots, with an effective maximum of 3 knots, as the gear does not
perform as efficiently at higher speeds.

Figure 8. Scallop dredge

12
Typical (and maximum) values for above components:- Individual dredge (a) weight
75 kilograms (100 kg); Tow bar (b) weight - 750 kg (1500 kg), length - 6 metres (10m);
Chain bridles (c) - 16mm (19mm) mid link; Warp (d) wire diameter - 20mm (26mm). Total
weight of one side of gear as set out in Figure 9 - 1400 kg (2800 kg).

13
 (ii) PELAGIC OR MIDWATER FISHING METHODS

2.9 Pelagic gears are used principally in the capture of shoaling species such as herring,
mackerel, scad, blue whiting and sprats which may be found close to the surface, in mid-
water or just off the bottom. Of particular note are the mackerel fishery throughout UK
waters but especially off the South West of England and to the north and west of the Scottish
Islands, the North Sea and Irish Sea herring fishery, the blue whiting fishery off North West
Scotland and in the Northern North Sea and, the west coast horse-mackerel fishery. Pelagic
gear is also used for a number of small seasonal fisheries such as that for hake in the Clyde
and North Channel, the bass fishery in the English Channel, certain cod and haddock fisheries
in the Irish Sea and various targeted North Sea fisheries.

Single Boat Pelagic Trawl

2.10 Like demersal trawls single boat pelagic trawls are towed using a wire rig (Figure 10)
which incorporates otterboards (a) to provide horizontal spreading forces. Both net and doors
are much larger than their demersal equivalents, but of much lighter construction as neither is
designed for bottom contact. The otterboards, usually of high aspect ratio and aerofoil
section, are towed by the vessel using two steelwire warps (b), and connected to the net by
four-wire bridles (c). Unlike demersal trawls pelagic trawls are towed on the headline, and
solid steel or lead weights (d) provide the vertical forces required to open the net in a
downwards direction. As these weights are slung on the lowest point of the gear they will
inevitably make contact with the bottom when fishing hard down, even although both doors
and net may not. Pelagic trawls are towed at the appropriate level in the water column to
intercept target shoals with gear depth being controlled by altering towing speed and/or warp
length. Electronic equipment such as sonar, net and catch monitors have greatly improved
the precision of this method of fishing. Normal towing speed is in the region of 3.75 knots,
but may be increased to as high as 5 knots when fishing mackerel. Pelagic trawlers can be
found in all NE Atlantic waters, both on and off the continental shelf.

14
Typical (and maximum) values for above components: - Otterboard (a) size and weight -
11 square metres x 1500 kilograms (16 square metres x 2500 kilograms); Trawl warp (b) wire
diameter - 32mm (38mm); Bridle (c) wire diameter- 26mm (30mm); Weight (d) - 1.1 tonnes
(5 tonnes).

15
Pelagic Pair Trawl

2.11 As is the case with demersal pair trawlers, the absence of otterboards allows the two
vessels to deploy a much bigger net than would otherwise have been possible to tow at an
effective speed. Target species and fishing techniques are similar to those set out above, with
the additional requirement that both vessels have comparable towing power available and
must at all times act in concert. The main difference in gear rigging is that two towing warps
(a) are deployed from each vessel, one to the upper bridles, the other to the sinker weight (b)
ahead of the footrope (Figure 2). The lower bridles (c) connect the weight to each side of the
footrope. Towing speeds are high, normally 4 knots but up to 5.5 knots on occasion. Smaller
vessels (<20m) fish for herring, mackerel and sprats in coastal waters but larger vessels
search for shoals far offshore.

Typical (and maximum) values for components: - Trawl warp (a) wire diameter - 26mm
(34mm); Bridle (c) wire diameter - 26mm (28mm); Weight (b) - 1.1 tons (5 tons).

16
Purse Seine

2.12 Purse seiners capture large aggregations of pelagic fish that shoal in midwater or near
the surface by surrounding these concentrations with a deep curtain of netting which is
supported at the surface by floats (Figure 12). Small lead weights on the underside of the
curtain ensure that the leadline quickly sinks and the net is then pursed under the shoal by
heaving on a wire or purseline (a) which runs through steel rings attached to the lower edge
of the net. When the gear is closed and fish can no longer escape the netting is hauled
lengthways using a mechanised power block until the fish are packed tightly in the bunt, or
last remaining section of the net to be hauled. The fish are then pumped or brailed aboard the
vessel. A large purse seine can be as long as 1 kilometre and 200 metres deep. Purse seiners
generally try to avoid bottom contact as the small mesh nylon netting is easily damaged. A
purse seine is not strictly speaking a towed gear but the purseline wire, being probably the
strongest subsurface component, could possibly foul and cause damage to underwater
installations. Typical (and maximum) values for pursing wire diameters are 26mm (28mm)
of 6/24 fibre core construction although 6/26 dyeform compacted wires with both fibre and
steel cores are also used.

17
 (iii) STATIC GEAR

Pots and Creels

2.13 Traps in various forms of cages or baskets are used throughout the UK for the capture
of crabs, lobsters, crayfish, nephrops, shrimps, cuttlefish and several other species. These
pots differ in shape, size and construction materials according to the target species, and local
practices. They are usually baited and set on the seabed singly or in strings attached to dhan
buoys at each end, which act as location markers and support for the recovery lines. Vessels
working this method of fishing need to have a large open deck area to enable them to carry
large numbers of pots. They are fitted with a powerful creel hauler winch specially adapted to
take the main rope with pots being lifted clear as they pass the winch. Some vessels are fitted
with a chute to guide the pots over the side when shooting the gear. The pots are usually
raised each day to allow the catch to be removed and fresh bait to be set.

Figure 13 Selection of Pots and Creels

18
Baited lines

2.14 Bottom set and drifting lines (long lines) are ropes, up to several kilometres in length,
carrying a large number of baited hooks on branch lines which are supported in the water
column at the required depth by buoys. Given the length of the lines the attendant buoys may
not be visible over a large proportion of the submerged line and where a buoy is visible the
surface mariner may be unable to determine if the buoy is connected to a line of pots or a
baited long line.

Figure 14 Baited Lines

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Drift nets, gill nets, tangle nets and trammel nets

2.15 Fixed or anchored nets have been used as a means of catching fish for centuries and a
wide variety of traditional nets have been developed to suit local conditions. The various
types used are covered in greater detail below. There is considerable confusion over the terms
used to describe fixed nets. Any net that is held stationery rather than being towed by a vessel
or allowed to drift in the current can be called a fixed net. Usually such nets are attached to
anchors but in shallow water they may be fixed to posts or other suitable objects driven into
the seabed. Typically the nets consist of a wall of netting. Floats are attached to the headline
with the number and spacing depending on the floatation required. The footrope is designed
to rest on or just above the seabed and is weighted either with individual lead weights or a
continuous lead line consisting of lead pieces threaded on fine twine and held within a
continuous braided sheath. Supported in this manner the nets hang vertically in the water
column.

2.16 The procedure when fishing fixed nets is similar irrespective of whether gill, tangle or
trammel nets are being used. The nets are usually fished in groups or 'fleets' and bridles attach
the end of each fleet to a heavy weight or anchor on the seabed. Each weight or anchor is
secured to a marker buoy or dhan flag on the surface by a length of rope equal to about 1.5 to
2 times the depth of the water. Depths of water fished in this manner typically range from
15m to 140m with some fisheries going as deep as 1800m eg deep water monkfish caught in
tangle nets.

2.17 Lengths of nets can vary from between 50m to 200m and lengths of fleets from
between 300m and 3000m. The amount of netting being fished, whether deployed in the
water column or set on the seabed, at any one time can range from between 2km and 30km.
Soak times, the time that a fleet is left on the seabed to fish, can range from a 6 hour tidal
soak up to 72 hours. These figures are dependant on which species are being targeted and
whether the area is also subject to trawling which may be in direct conflict with fixed net
fisheries.

2.18 The nets are normally shot whilst steaming into the tide and are fished along the
direction of the tidal stream rather than across it. This reduces the chance of the nets being
swept over or tangled in the strong tidal conditions found in many sea areas around the UK.
The dhan is thrown overboard and the vessel steams away paying out the rope until it reaches
the anchor attachment, which is then dropped overboard. The fleet of nets follows until the
full length has run out and the second anchor and dhan follow. Retrieval of gear is carried out
in a similar fashion with first the dhan and anchor then the nets followed by the remaining
dhan and anchor. Virtually all boats now use net haulers to help them retrieve their gear.
They have a basic design consisting of a rotating drum covered with a rubber surface, which
is driven by a hydraulic system run off the main engine. This creates friction between the net
and drum allowing the hauler to take the strain and pull in the net.

2.19 Drift nets are generally used for pelagic and migratory species such as herring,
mackerel, pilchards, sprats, bass, salmon and sea trout etc. they are normally rigged to form a
curtain in the water and generally down-wind, with the vessel at the leeward end of the gear.
The net is set out in a straight line and drifts with the current. Fish on passage swim into the
net and are 'gilled'. The fishing depth of the net can be adjusted by adding weights to the
bottom of the sheet and altering the float line. Single sheets of net are usually 50 or 100
metres in length. Varying numbers are joined together to form a 'fleet' of nets. The length and

20
depth of the nets can vary considerably depending on the target species of fish and the nature
of the seabed or depth or depth of water being worked.

2.20 Set nets and gill nets are sometimes used from the shore and in water too shallow for
most seismic vessels. They are, however, also used from vessels at sea and are then marked
by surface dhan buoys. When used offshore, the fishing vessel is usually in attendance. Dhan
buoys are laid at intervals but it is not always possible to see 2 buoys at once. It is therefore
difficult to be sure of the direction in which the nets are set. On fine ground the nets can
extend to around 1500 metres in length. The practice of surrounding wrecks - 'wreck-netting'
is also increasingly prevalent.

2.21 Tangle nets are single walled nets used to catch species such as monkfish, turbot and
ray. While they resemble gill nets in their design they have a greater amount of slack netting
and less flotation at the headline and a smaller vertical height of netting. The result is a much
more loosely hung net, which effectively entangles species with protruding spines.

2.22 Trammel nets are three walled nets which can be used to catch a much wider variety
of species ranging from cod and monkfish to plaice and sole. The net consists of three walls
of netting in which a small fine meshed inner net is sandwiched between two outer walls of
larger mesh netting. The three sheets of netting are attached to the floated headline and
weighted footrope so that all three hang vertically in the water. Slack netting is ensured by
setting the net loosely on the headline and footrope and by having the inner net depth
measuring approximately twice the outer net wall depth. This ensures that there is always
plenty of slack net for the fish to become entangled.

21
Addendum

3. The information from which many of the above descriptions were distilled was
supplied willingly and in good faith by a number of sources including several net
manufacturers and gear suppliers. The data are presented here in similar spirit. This booklet
is not, nor can it be, a definitive statement of absolute values, but is essentially a snapshot of
the fishing fleet, gear and methods currently in use. The continuing evolution of fishing gear
and techniques will ensure that the booklet is out of date by the time it is published.
Nevertheless it is felt that, given this qualification, a realistic appraisal of modern fishing gear
and components is offered.

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 Table 1

SUMMARY STATISTICS OF OVERALL LENGTH, GROSS TONNAGE AND

POWER FOR THE UK OVER 10 METRE FLEET AS AT 31 DECEMBER 1998

Method of Number Overall length

(metres) Gross tonnage Power (KW)
Capture of
vessels
Mean Med- Mean Med- Mean Med-
Mi Max Min Max Min Max
ian ian ian
n
Pelagic Gear 50 15 51 51 86 32 959 745 6210 216 1598 1321 2422

Beam trawl 119 11 30 29 45 23 202 149 3195 172 798 596 709

Demersal trawl, 1309 10 19 18 44 1 84 54 1920 36 280 223 803

seines & nephrops
Lines and Nets 179 10 19 14 44 4 85 30 1177 23 251 172 492

Shellfish: Mobile 210 10 16 14 34 5 48 33 746 0 215 186 257

gear
Shellfish: Fixed 269 10 12 11 40 1 22 13 746 33 138 96 319
gear
Distant water 4 52 57 58 61 1146 1476 1444 2462 1800 2225 2319 1871
(external waters)
Distant water (EU 10 39 52 45 98 381 1152 597 4854 1264 1865 1268 3229
waters)
Mussel dredgers 2 14 21 21 29 30 40 40 447 90 269 269 449
(Non MAGP)
Total Vessels 2152

23
Table 2. Summary of typical gear component sizes and towing speeds for various fishing methods
Sinker/Clump wt
Warp diameter Otterboard area Otterboard weight
2
mm Bridle/sweep diam kg kg m kg Towing speed knots
mean max mean max mean max mean max mean max mean max
Single boat Wire 20 28 20 32
demersal trawl Chain 19 mm chain n/a n/a 5.3 8 1,400 3,000 3 4
Twin rig demersal Wire 20 24 16 26 comb
trawl Chain 19 mm chain 620 2,000 2.84 5.4 600 1,800 2.5 3.5
Demersal pair Wire 21 24 26 30
trawl Chain 16 mm chain n/a n/a n/a n/a 2.8 4
Demersal pair Wire 19 22 22 26
seine Combination wire 32 comb 40 comb n/a n/a n/a n/a 2.3 3.5
Demersal seine 28 leaded 34 leaded
net 28 comb 32 comb 16 comb 24 comb n/a n/a n/a n/a n/a n/a
Single boat pelagic
trawl 32 42 26 30 1,100 5,000 11 16 1,500 2,500 3.75 5
Pelagic pair trawl 26 34 26 28 1,100 5,000 n/a n/a 4 5.5
24
 Towing speed Warp diameter Chain bridle diam Beam weight Beam length Beam height
knots mm mm per side kg m m
mean max mean max mean max mean Max mean max mean max
Twin beam trawl 3.5 7 26 34 19 25 7,500 10,000 9 12 0.6 0.8
Individual Dredge No dredges per Total weight (kg)
weight side per side
Bar length
Bar weight kg m mean max mean max mean max
Scallop dredge 2.5 3 20 28 16 19 750 1,500 6 10 75 100 7 12 1,400 2,800
Warp construction: Mostly 6 x 19, with 6 x 26 for beamers
Older vessels and beamers use fibre core; newer vessels with auto-winches use steel core (dyeform, etc)
25
 Annex 1

USEFUL ADDRESSES

(i) Government Departments/Agencies

1. Scottish Executive Rural Affairs Department

Freshwater Fisheries, Aquaculture and Marine Environment Division
4th Floor
Pentland House
47 Robb's Loan
EDINBURGH
EH14 1TW
Tel 0131-244-6233 Fax 0131-244-6313

(The Secretary of the Fisheries and Offshore Oil Consultative Group (FOOCG) is also
located at the above address.)

2. Ministry of Agriculture, Fisheries and Food

Rural and Marine Environment Division
Nobel House
17 Smith Square
LONDON
SW1P 3JR
Tel 020 7238 3000 Fax 020 7238 5881

3. Department of Trade and Industry

Oil & Gas Directorate
1 Victoria Street
LONDON (Exploration and Licensing)
SW1H 0ET
Tel 020 7215 5000 Fax 020 7215 5142

4. Department of Trade and Industry

Oil & Gas Projects Office
Atholl House
86-88 Guild Street
ABERDEEN (Field Development, Environment & Decommissioning)
AB11 6AR
Tel 01224 254000 Fax 01224 254019

26
5. Fisheries Research Services
Marine Laboratory
PO Box 101
Victoria Road
ABERDEEN
AB11 9DB
Tel 01224 876544 Fax 01224 295511

6. Centre for Environment, Fisheries and Aquaculture Science

CEFAS Laboratory
Burnham-on-Crouch
Essex
CM0 8HA
Tel 01621 787200 Fax 01621 784989

7. Scottish Fisheries Protection Agency

Pentland House
47 Robb's Loan
EDINBURGH
EH14 1TW
Tel 0131 244 6094 Fax 0131 244 6471

8. Sea Fisheries Inspectorate

Ministry of Agriculture, Fisheries and Food
Fifth Floor
Nobel House
17 Smith Square
LONDON
SW1P 3JR
Tel 020 7238 5815 Fax 020 7238 5814

27
 (ii) Sea Fish Industry Authority and National Fishermen's Organisations

9. Sea Fish Industry Authority

Seafish Technology
Seafish House
St Andrew's Dock
HULL
HU3 4QE
Tel 01482 327837 Fax 01482 223310

10. Scottish Fishermen’s Federation

14 Regent Quay
ABERDEEN
AB11 5AE
Tel 01224 582583 Fax 01224 574958

11. National Federation of Fishermen’s Organisations

Marsden Road
Fish Docks
GRIMSBY
North East Lincolnshire
DN31 3SG
Tel 01472 352141 Fax 01472 242486

(NB There are in addition numerous other smaller or locally based associations. Details of these can
be obtained from either the local Fishery Office or the National Federations)

(iii) Offshore Operators and Seismic Contractors

12. The Director

Operational and Technical Affairs
United Kingdom Offshore Operators Association
9 Albyn Terrace
ABERDEEN
AB10 1YP
Tel 01224 626652 Fax 01224 626503

13. International Association of Geophysical Contractors

c/o IAGC EAME Manager
4 St. James Road
SEVENOAKS
Kent
N13 3NH
Tel 01732 743025 Fax 01732 740623

28
ISBN 0 7559 0162 2

Designed and produced on behalf of the Scottish Executive by Astron. B17532-06-01