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) Selectivity Trials• in the Static-Net Fishery for Hake

Off Cornwall MAFF Commission •

. 'SeafishReportNo:402 February 1992

• MAFF R&D Commission 1991/92

© Crown Copyright 1992

•

•

SEA FISH INDUSTRY AUTHORITY

• Seafish Technology

• Seaflsh Report No.402 J Swarbrick. February 1992:

• SELECTIVITY TRIALS IN THE STATIC-NET

FISHERY FOR HAKE OFF CORNWALL

• SuMMARY

• Correctly rigged and deployed static nets are believed to be highly selective in certain fISheries. Because of the low fuel consumption of the vessels involved it can be one of the', mo'st energy efficient methods of fishing.

• SeaflSh Technology have carried out a number of trials over the last few years to improve

•

the knowledge about these nets and especially the levels of by-catch. 'There are various types of static nets in use including trammel and tangle nets and gill nets. The t= static nets by definition implies that they are anchored to the sea bed as opposed to drift nets which are free to drift with the vessel.

•

The deep water hake fIShery is a specialised fIShery mainly operated by some 30 vessels based at Padstow, Newlyn and Mevagissey. Cornwall. The high value of hake results in a relatively profitable fishery provided the hake are present during the peak season which is Swiuner-Autumn. Hake however can be found all year round.

The nets used by these vessels are generally made from120mm mesh 0.65= diameter nylon monofLIament and they are rigged each about 109m in length with a Deet or tier­consisting ofabout 15 nets (approximately 165Om). A 15m gill net vessel will fish between.

• 9 and 13.5km of nets over a 12 hour period.

• The trials were carried out on the 15.25m (overall length) .flshing vessel BRITANN1A V (FH 121). The objective was to gather data on the selectivity of the standard gear when compared to a number of alternative gear configurations and materials. The trials took place some 60 miles south of Plymouth in 50m of water.

•

• . Although catches were less than expected, all the netting variants showed a high degree of

• selectivity with little by catch and with 90% of the hake caught lying in the 60-9Ocm band which is well above the 35cm MLS. The by-catch consisted of 30cm scad, spurdog and a few crabs. No marine mammals or sea birds were taken.

• The trials demonstrated the sensitivity of a mesh size change on selectivity and an increase from 4O/.inch (l20mriJ) to 5O/.inch (140=) raised the average and maximum size ofthe fish caught but reduced the numbers of smaller (but still marketable) sizes. The mesh size has to be fmely tuned to strike a good balance. A comparison is made with the catch of a trawler· albeit working different grounds - which showed that the trawler caught hake in

• the range 25-50cm. All of these were below the sizes taken by the gill net. This type of comparison should be considered in later investigations.

• The different materials used - monofIlament, multi-monofilament and multi-fIlament showed, differences in selectivity, but since catches were small these are inconclusive. However, from an operational point ofview nylon monofIlament is preferred for hake gill nets because ofits ease in handling. The nylon monofIlament showed no untoward results in by-catch and indeed the brown crab by-catch was apparently less than those ofthe other materials. '

• The work has been funded under the 1991-92 MAFF Commission. Grateful acknowledgement is given to Skipper Freddie Turner and the crew of BRITANNIA V for' their co-operation.

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.­SEA FISH INDUSTRY AUTHORITY

• Seafish Technology

•

• SELECfIVITY TRIALS IN THE STATIC-NET

FISHERY FOR HAKE OFF CORNWALL

•

•

•

• MAFF Commission 1991-92

• Seaflsh Report NoA02 J Swarbrick

February 1992

•

I.

SEA FISH INDUSTRY AUTHORITY

• Seaf"lSh Technology

• Seaflsh Report No.402 J Swarbrick February 1992

• SELECTIVITY TRIALS IN THE STATIC-NET FISHERY FOR HAKE OFF CORNWALL

• Contents

I. INTRODUCTION I

• 2. THE FISHERY 3

2.1 What is a Hake Net? 3 2.2 Generalised Qualities of Nets Used 3

• 2.3 Mesh Size and Material 4 2.4 Seasonality 4

2.4.1 Summary of static-net fishery opportunities 4

• 3. AIMS AND OBJECTIVES OF THE TRIALS 5 3.1 Objectives 5 3.2 The Trials Variables 5

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• 4. HAKE NET CONSTRUCTION 6 4.1 The Experimental Gear 6

4.1.1 Headropes, footropes and flotation 8

• 4.1.2 Netting Panel 8 4.1.3 Dahn ropes, allchors and bridles 9

4.2 The Control Gear 10

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• SELECTIVITY TRIALS IN THE STATIC-NET FISHERY FOR HAKE OFF CORNWALL

• Contents - continued

5. THE CHARTER VESSEL 12 5.1 Vessel details 12

• 6. TRIALS PROCEDURES 13

6.1 Amounts of gear deployed 13 6.2 Normal daily routine 13

• 7. RESULTS 15

• 8. DISCUSSION 21 8.1 Selectivity of Hake gill nets 21

8.Ll Mesh size and hanging ratio 21 8.1.2 Gilling versus tangling 21

• 8.1.3 Hanging ratio 21 8.1.4 Material and mesh size 22 8.1.5 Size distribution of catch 22

8.1.5.1 Gill net versus the trawl 23

• 8.1.6 Number of hake encountered 25 8.1.7 Bycatch 25 8.1.8 Deployment 25

• 9. CONCLUSIONS AND RECOMMENDATIONS 27

REFERENCES 29

• APPENDIX I 30

• APPENDIX II 35

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• SEA FISH INDUSTRY AUTHORITY

Seaf"tsh Technology

• Seaftsh Report NoA02 J Swarbrick February 1992

• SELECTIVITY TRIALS IN THE STATIC-NET

FISHERY FOR HAKE OFF CORNWALL

• I. INTRODUCTION

• The;: Gear Technology Group ofSeaftsh has been carrying out an extensive programme of static net sea trials over the last four years. Static nets (nets that are anchored to the sea bed as opposed to drift nets which are suspended from floats at the surface and not anchored) are becoming increasingly popular as a relatively cheap and effective means of capturing

• high value species. These include monkfish (Lophius piscatoriu5j turbot (Scophthalmus maximu5j, large ftsh often associated with wrecks such as cod (Gadusmorhua) and pollack (Pol1achiuspoUachiu5j, and fast swimming, free ranging ftsh - notably the hake (MerJuccius merJucciu5j.

• Static net trials that have previously been executed by Seaftsh include investigations into bycatch reductions off the coast of North East England (Ref I), and evaluation of net selectivity in a trammel net ftshery in South East England (Ref 2) and an investigation of the performance of tangle nets used off North Cornwall (Ref 3). In the series of trials

• discussed in this report, it is the deepwater gill-net ftshery for hake offSouth West England

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that is ofconcern and the trials represented a continuation of the work to understand more about the working and selectivity of these nets. The deepwater hake ftshery in the waters around Cornwall, South East Ireland and North West France. in common with most of the static net ftsheries around England and Wales is based upon the use ofmonoftlament nets.. Nearly all the UK deepwater gill-net fleet operates from the ports of Cornwall - notably Newlyn, Padstow and Mevagissey. These vessels are the largest of the static-net deploying vessels in England, with overall lengths in excess of33 feet (10m) and power capabilities of around 350hp (261 kw). These vessels have amuch greater operating range than the smaller,

• inshore netting vessels (Ref 4). Nearly all the hake caught by the Cornish fleet is sold on Continental markets - notably those of France and Spain.

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• The deepwater hake fIShery represents a fIShery that is intensively worked by a relatively

• small number of vessels. The entire UK deepwater hake gillnet fleet numbers less than

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thirty vessels, but the revenue from the fIShery is large - individual vessels earning in excess of£30000 (1991) for a six day trip is not unusual. As the vessels involved in this fIShery are the largest of the static-netting vessels in Cornwall and the quantity of net that they work is large, the fIShery attracts a lot of attention.

MonofIlament nets of any type are now regarded as "an environmental threat" by many conservationist groups because ofalleged risks to seabirds and marine mammals. Certain specific types of monofilament static nets - notably Tangle nets - are known to have

• problems with bycatches of brown crabs (Cancer paguruS) and with fish wastage through

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prolonged immersion periods or "soak times" (Ref3). As static nets are built with a specific fIShery in mind, they tend to have performance characteristics that are peculiar to that fIShery. It would be very wrong indeed to assume that because one type of static gear may have a certain problem in its use, that all other static gears made of the same material will all have the same problem. It is essential to keep an objective mind when investigating fISheries of this kind.

• This and earlier work with static net fisheries forms part of the Ministry of Agriculture, Fisheries and Food (MAFF) commissioned programme of investigations into the performance and selectivity of these kinds of nets.

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2. THE FISHERY

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2.1 What is a Hake Net? A hake net to be effective depends upon fish becoming trapped by the opercula (gills) within the net sheet (Ref 6). It is therefore a type of gill net, and they must be rigged to fish such that the meshes are wide open. The headline of the net is equipped with floats, and the footrope of the net is weighted with lead. This ensures that the net stands vertically on the sea bed. The weight to flotation ratio is usually in the order of 4: I.

Floats used vary in design and construction, but usually have a buoyancy of about 80

• grams each. To be practical, they must be able to withstand repeated immersion in salt

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water to great depths (5Om - 150m) without collapsing. They must also be strong enough to pass through a net hauler without becoming damaged. Hollow plastic floats that are internally braced with webs, or solid, low-density plastic floats are the types used for this application.

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The leadline used along the bottom edge of the nets is usually a monoftlament based polypropylene 3~ore rope, each core containing lead pellets. The leadline is not attached directly to the bottom edge of the net panel itself. Instead, a "false fishing line" or "false footrope" is attached to the lower edge, and the leadline is suspended from strops attached to the false footrope. Thus, the net itselfnevercomes into direct contact with the seabed. Such an arrangement is termed an "anti~rab barrier" and as its name ,. implies, its chief function is to prevent crabs from becoming entangled in the net sheet. At regular intervals, a length oflight ropejoins the headline to the false footrope. These:

• prevent the net from being ripped apart along its length like a zipper if the net should becomesnagged during hauling. Any potential damage will be restricted to the distance between these "anti-rip" ropes.

• Hake nets are usually expensive because construction involves the use of heavy leaded rope, heavy duty floats and large quantities of polypropylene rope for head and footrope construction.

2.2. Generalised Quantities of Nets Used

• Nets are usually rigged so as to be about 120 yards (109m) long, and arejoined together to form "fleets" or "tiers~' ofabout 15 nets - dejJending on how individual vessels store them in the net pounds. The overall length ofa typical fleet will therefore be about 1800 yards (I 646m).'

• I

• note. the nets used in experiment were slightly shorter than 120 yards at 114 yards - see "Hake Net

Construction")

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The total amount ofnet that is fIshed varies with the size and capability of the vessel as

• can be expected. A vessel of about 50ft (15m) overall length will fIsh between 10,000 and 15,000 yards of hake nets (5.6 miles to 8.5 miles, 9.1 Ian to 13.71an). The nets are usually fIshed over a twelve hour period, then re-shot.

• 2.3. Mesh Size and Material The most co=only used mesh size for hake net construction is 40/4 inch (120=). As; indicated in the introduction, the usual material used for these nets is nylon monomament with a mament diameter of 0.65=. However, hake nets have been. made out ofmulti-monomament (I Oply) net sheets- each ofthe 10 individual maments

• having a diameter of about 0.15=. The main advantage of multi-monom. over monom. is that being much more supple it stows easily into net pounds.

• 2.4 Seasonality The majority ofCornish deep-water netters are found in the port ofNewlyn, and these vessels are often engaged in the hake fIshery all year round. The heaviest fIshing in the hake fishery appears to occur in late Summer - early Autumn. Occasionally they may

. change over to wreck fishing for prime white fIsh (cod, pollack and ling) during the late Autumn and through the Winter. Similarly, they may change over to tangle netting

• during late Spring and into the middle of Summer. It must, however, be understood that gear change-overs from one method to another are largely governed by fish occurrence in the different fisheries, and are by no means regular.

In addition to the three deep water static net fisheries outlined above, during Su=er.

• 1991 three large Cornish netting vessels undertook pioneering trips in the North East Atlantic drift net fIshery for albacore tuna.

2.4.1 Summary of static-net fishery opportnnities

• (1) Hake gill nets: All year, but peaking late Summer to early Autumn.

(2) Wreck gill nets: Late Autumn to early Spring.

• (3) Tangle nets: Mid Spring to late Summer.

(4) Tuna nets: Mid Su=er (new 1991).

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3. AIMS AND OBJECfIVES OF THE TRIALS

Following several discussions with MAFF Fisheries Laboratory, Lowestoft, it was decided that this series ofsea trials was to centre on the selectivity attribute of the fIshing gear. The short periods of time that the nets were to be deployed over (twelve hours) were expected to give very low fIsh spoilage rates when compared with those of a tangle net fIshery .. Because of this, it was decided not to monitor the quality offIsh on hauling, but subjective notes would be taken of any fIsh that appeared damaged.

3.1 Objectives

(I) To complete two voyages, each of one week duration, on successive neap tides on board a vessel engaged in the deepwater hake gill-net fIshery off Cornwall.

(2) To compare the selectivity of experimental nets with that of the vessel's own nets which were used as a cOntrol.

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(3) To determine the extent of any by-catch.

(4) To monitor any incidental mortalities (forexample, any birds ormarine mammals).

3.2 The Trials Variables

(I) Mesh sizes (two sizes): 40/4 inch (12.1cm) and 5'12 inch (14cm).

(2) Net material (three types): MonofIlament nylon (0.65mm twine diameter).

MultimonofIlament nylon (1.5mm nominal overall twine diameter, with individual 0.15mm diameter filaments).

Multifilament nylon (spun nylon yard in 210/9 weight).

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4. HAKE NET CONSTRUCflON

• 4.1 The Experimental Gear There were six variations of experimental net. For each of these six variations, six individual nets were constructed, giving 36 nets of six different types. For ease of

• handling on board the vessel, the 36 experimental nets were formed into two identical fleets, each containing 18 nets. Each net was 114 yards (104m) in length - see table, below for details:

TABLEt

• The Experimental Gear

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•

Varinnt Number

Material Type Mesh Size .Mesh

Deep

Mesh

Loog

!'and Length Hanging Ratio

Set Length ScI Depth

1 MaDam. <WJn(12Omm) 60 1515 200yds(I83m) 0.57 114yds(l04m) . 19.5f1(6m)

2 MaDam. 5'hin(14Omm) 50 1310 200yds(183m) 0.57 114yds(l04m) 18.8f1(5.7m)

3 MuJlimooofil. 4¥Jn(12Omm) 60 1515 200yds(I83m) 0.57 114yds(l04m) 19.5fi(6m)

4 Multimonofil. 5\iio(l4Omm) 50 1310 200yds(I83m) 0,57 114yds(l04m) 18.8f1(5.7m)

5 MuitifLIa.mcDI <WJn(12Omm) 60 1515 200yds(I83m) 0.57 114yds(l04m) 19.5f1(6m)

6 MullifLInmcol 5'mn(14Omm) 50 1310 200yds(I83m) 0.57 114yds(l04m) 18.8f1(5.7m)

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• All the experimental nets were rigged with a hanging ratio of0.57, achieved by hanging seven meshes on a staple offour stretched meshes in length (4/7 =0.57). This gave a net

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length of 114 yards (104m), and was the rigging method currently favoured by fIshehnen at the time of the construction of the nets (1988). More recently, hanging ratios of 0.60 are preferred - achieved by hanging fIve meshes on a staple of three stretched meshes in length (3/5 = 0.60). This gives a net length of 120 yards. "Staples'" are the loops of twine attaching the top and bottom edges of the net panel to the head and footropes respectively.

In summary, there were two fleets ofexperimental nets, I and II. Each fleet contained

• the sequence of net variants 1 through 6 three times, giving a total of 18 nets in each of the two fleets.

• 4.1.1 Headropes, footropes and flotation All the experimental nets had a double 6mm polypropylene headrope. On one of these ropes 80 gram floats were threaded. These floats were lashed securely in place by several turns oftwine at either end; in use this proved to bean undesirable feature (see Discussion). The "false footrope" attached to the bottom edge of the

• net consisted of a single 8mm polypropylene rope, from which the 12mm leaded

•

polypropylene leadline was suspended on 18inch strops of6mm rope positioned under every other float. (See Figure 1for details ofthe false footrope) ..The weight.. runnage of the leadline was 0.21 kglm (6.70zlyard). The fact that the net was· allowed to remain suspended 18 inch (46cm) over the seabed formed a barrier to the entry of crabs into the net sheet. It was considered that very few hake escape' capture by swimming under the net through the anti-crab barrier.

• 4.1.2 Netting Panel The main body of the net was constructed out of a sheet of nylon monomament mesh of 40/4 inch (12.1cm) stretched mesh size. The stretched length of the net panel was 200 yards (183m) and when rigged with a hanging ratio of 0.57 gave a set length of 114 yards (104m) by placing seven meshes on a staple length of four stretched meshes.

• The top and bottom edges of the monomament net sheet were reinforced with three rows of twine that were heavier than the main body of the net. Working from the edge of the net inwards, these three rows consisted of:

• (1) One row of double monom (2 x 0.65mm diameter). The staple loops pick up this row of meshes.

(2) One row of single monom 0.8Omm diameter.

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• (3) One row of single monofil 0.7Omm diameter.

• (4) Main body of the net (0.65= diameter).

• The 10 ply multimono nets had a similar gradation of twine weight. From the edge of the net inwards, there are three reinforcing rows thus:

(I) One row of double monofil (2 x 0.65= diameter). The staple loops: pick up this row.

• (2) One row of single 0.75= monofil.

(3) One row of single 0.70= monofil.

• (4) Main body of the net (0.15= 10 ply multi-monofilament).

The nylon multifuament nets had a single row ofheavier spun nylon twine at each edge of the net sheet for reinforcement.

• See diagram of generalised hake gill net.

• 4.1.3 Dahn ropes. anchors and bridles

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The exact method of rigging the bridles and dahn ropes, together with the choice ofend weight inevitably varied from vessel to vessel. However, it was usual to use a line-to-depth ratio of about 3:1 with the portion of line i=ediately below the dahn float of leaded rope. This reduced the chances of fouling on other vessel's propellers.

The bridles were made of 12= diameter polypropylene rope. The top bridle _" (attached to the net headrope) was4fm(7.3m) ofunleaded rope; the bottom bridle

• (attached to the net footrope and leadline) was 2% fm (4.6m) of leaded rope.

•

Where the bridles met, they were connected together into a plastic eye. From the eye, a 45fm (82m) length of 12=diameter polypropylene rope was run out. Ten fathoms (18m) from the end ofthis, a weight ofabout 60lb (27kg) was attached on a short strop. At the very end of the 45fm rope, a 44lb (20kg) 4-fluked anchor was attached. From the anchor, the dahn line ofI0=-12=polypropylene rope ran· to the surface. The top 20 fathoms (36m) of the dahn line were of leaded rope..

• - 9­

•

The dahn floats consisted ofan 18 ft (5.5m) bamboo pole with a 20kg (44lb) float

• about one third of the way up it - the lower end being weighted to ensure upright floating. A code flag was fIXed to the upper end of the pole. In addition to the dahn float, a pellet buoy of about lOins (25.4cm) diameter was fastened to the dahn line to allow retrieval of the line should the dahn float itself be missing.

• The skippers ofsome hake vessels prefer to use chain weights rather than anchors, as chain is easier to stow, and safer than fluked anchors on board aroUing vessel.

• 4.2 The Control Gear The gear normally deployed by the vessel - the control gear - was very similar to the experimental gear, but there were some differences (apart from the experimental variables) that must be noted (Table 2).

• Nets are rather like clothes - their function never changes, but through the whims of

•

fashion as well as through technological advances, their forms can and often do. At the time of construction (1988) of the experimental gear, the method of hake net rigging favoured was to put seven meshes onto a staple length of four stretched meshes (see 4.1). This meant that the commonly used 200 yard (183m) net sheets rigged this way had a hanging ratio of0.57 and a rigged length of 114 yards (104m). However, at the time of the trials (1991) it was favoured to put five meshes onto a staple length of three . stretched meshes - a hanging ratio of0.60. This meant that a 200 yard net sheet became rigged to 120 yards (110m). The vessel's gear were rigged with the latter method. The.

• 5% difference between the two hanging ratios of 0.57 and 0.60 in terms of net performance is negligible, however. (See Reference 7for further explanation ofhanging ratio).

• Any inevitable difference in overall length of the control gear when compared with the vessel's gear can be corrected mathematically for comparison purposes.

The most important difference between the experimental and control gears was that the control gear had floats which were allowed to slide freely within a staple length. This

• reduces snagging orshooting. (see 8.0). All the control gear wasconstructed ofO.65mm monofilament.

•

• - 10 ­

•

•

• TABLE 2 A comparison of the vessel's nets

(contro) nets) with the Experimental Nets

•

•

•

Attribute Vessel's Nets (40/0" mesh)

Experimental Nets (40/0" and 5'h" mesh)

Mesh Deep 60MD 40/0":6OMD,5'h":50MD

Pane) Stretched Length

200 yds 200 yds

Set Length l20yds lJ4 yds

Float Attachment sliding fIxed

Hanging Ratio 0.60 0.57

Set Depth 19ft 40/0": 19'hft, 5'h": 18.8ft

Material Type Monoftlament Monofilament Mu1timono Multifilament

•

•

•

•

•

• - 11 •

•

I.

• 5. THE CHARTER VESSEL

It was decided that the most appropriate vessel for the trials requirements was MFV "L & T Britannia V" FH 121, skippered by Freddie Turner of Mevagissey, Cornwall. The vesSel itself is based in Mevagissey and is the largest vessel fIShing from the port.

• 5.1 Vessel details

Name: MFV "L & T Britannia V" FH 121

• Built: Alexander Noble of Girvan, Scotland in August 1986

Overall Length: 15.25m (50.03ft)

Registered Length: 14.54m (47.70ft)

• Beam: 5.64m (l8.50ft)

•

Depth: 3.35m (11.65£1)

Draft: 3.IOm(lO.17ft)

Gross Registered Tonnage: 21.16 tons

•

Hull: Wood, with aluminium deck shelter added.

Engine: Volvo Penta 382 hp (285 kw)

Hauler: Tarbenson 750-500 drum hauler

•

Fish Storage: Refrigerated flShroom - boxing in ice

Navigation aids: - LORAN "C" Navigator

- DECCA system interfaced to CRT track plotter/recorder

- GPS Satellite navigation system

•

•

• - 12­

•

• 6. TRIALS PROCEDURES

•

It was decided to carry out two sets of trials in the hake deepwater gill-net fIshery on successive neap tides. This would increase the chances of taking a good catch. Fishing with static nets in deep water (over 5Om, 27 fathoms) restricts vessels to fIshing over a neap tide period. When the tide picks up towards a spring tide period the tidal flows become too great for the nets to be efficiently deployed. Ifdeployed, they would suffer damage on the

• seabed and frequently part on hauling. Furthermore, it would be difficult for the skipper to keep the vessel on station over the gear. The "safe" period for gear deployment is about two to three days either side of a neap tide, depending on the extent of the neap tide.

•

Fishing according to the proposed pattern meant a week spent at sea, a week ashore and then a second week at sea. The average duration of a hake netting trip is usually a week over a neap tide. The area fIshed during both parts of the trials was approximately 60 nautical miles South of Plymouth.

•

6.1 Amounts of gear deployed Forcomparison purposes it was decided that the vessel would deploy roughly an equal amount of its own nets alongside (or as close as practically possible) to the SeafIsh experimental nets. The SeafIsh gear amounted to two fleets of 18 nets of varying

•

construction (see Table I). Each fleet measured 2052 yards (1876m). The vessel's gear amounted to two fleets of15 nets - all ofidentical construction (seeTable 2). Each fleet measured 1800 yards (1646m). Any difference in gear length, or the number of shots· given to each of the two sets of gear can be corrected mathematically.

•

6.2 Normal Daily Routine At the beginning of a fIShing trip, the vessel would leave port and aim to be on the fIShing grounds by early evening. The skipper would then spend some time searching for likely "marks" using echo sounders. Once a suitable aggregation of fISh had been found, the nets were shot, working down the tide.

The process of shooting all the gear (two 2052 yard SeaflSh fleets and two 1800 yard fleets belonging to the vessel) would take between one and two hours. The process of

• shooting the SeaflSh nets took longer than if it were the vessel's own gear. This was

•

because the multifilament nylon twine nets easily became snagged. Nets that were stowed in the aft net pound were shot directly over the stem rail. Nets that were stowed forwards of the wheelhouse in deck pounds were shot differently. These nets were passed through a system ofaluminium "troughs" or shooting channels which led past the wheelhouse, and out over the stem of the vessel. Great care was taken to prevent the nets snagging while passing out through the shooting channel.

• - 13­

•

•

• The nets, marked with dahn floats, would be left to fIsh overnight. During this period, the vessel maintained close proximity to the nets to warn other vessels (coasters and trawlers) of their position. To this end, the vessel also displayed a yeUow flashing light in common with most of the Newlyn fleet.

• Hauling would commence at fIrst light. It was usual to pick up the down-tide end of·· the net fIrst, and work gradually up into the tidal flow. This ensured that tension was kept on the gear throughout hauling. When the vessel was fIshing its normal fuU· complement of about 15000 yards ofhake net (about eight fleets) then hauling would take about 12 hours. Fishing with a minimum of four fleets the hauling time was

• considerably less - six to eight hours being usual. Hauling involved four men - one

•

operating the hauler and removing fIsh from the nets, one removing fIsh and gutting, and two others flaking the net down into net pounds. To enable the net to be easily passed to the stem section of the vessel for stowage, a remote belt hauler was fItted. This was operated by one of the crew (engaged in flaking the net down) by means ofa remote control. The fuU hauling procedure was monitored from the wheelhouse by

•

means of remote T.V. camera units fIXed underneath the deck shelter. In addition to these, a remote T.V. camera was fItted to an outrigger overlooking the hauler and the net at its point ofemergenCe from the water. This enabled the vessel to be manoeuvred into the best position for hauling and the hauler could be slowed or stopped directly from the wheelhouse if necessary.

Reports of fIsh occurrence would be relayed by the skipper over the VHF radio. This. procedure - routine for aU the hake vessels - enabled each vessel to "home in" on the.

• best fIshing. TABLE 3

Calendar of opemtions

ShOlNo Fleet shot I Shot date I Haul date I I 30.00.91Trial I 1 21Scafuh ­ 01.10.91•

2. Scafuh 2 x vc:sscl 01.10.91 02.10.912

03.10.912. Scafuh 2 x vessc:l 02.10.913

• TriaiU 4 15.10.91hScafuh I. vcucI 14.10.91

15.10.912x Scafuh 2. vcucI 16.10.915

6 16.10.91 17.10.912. Scafuh 21 vcsscI

• note: "Seafish" fleets = 18 x 114 yards nets = 2052 yards

"Vessel" fleets = 15 x 120 yards nets = 1800 yards

• - 14 ­

•

••

• 7. RESULTS

The results are presented on the following pages in a series of two tables and four diagrams (Tables 4 and 5 and Figures 2-5). The raw data as collected at sea is contained in Appendix II.

• Table 4 Numbers of hake caught in the experimental (Seafish) nets and the control (Vessel's) nets.

Table 5 Crab occurrence in the experimental nets.

•

• Figure 2 Size distribution forcatchtakenin the vessel's nets (4.75 inch monoftlament).

Figure 3 Size distribution for catch taken in the experimental nets.

Figure 4 Catch taken in the experimental nets divided into net types.

• Figure 5 Catch taken in the experimental nets - showing relative numbers of hake

caught in each of the gear variations.

•

•

•

•

• - IS ­

•

•

• TABLE 4 Numbers of hake eaught in the experimental (Seafish) nets and the control (Vessel's) nets

Shol

No

Two Fla:u of 2052 yda: Bapcrimcnlal Nets

Two FlocU of 1800 yda: Control Nels

H.uI

date

SoakTimc (To

H.uling)Scafuh I Scafish II Vc:ascI I Vc:ascI II

TRIAL I I 23 8 - . 1.10.91 12-18 houn

2 8 14 15 (17) 17 (19) 2.10.91 12-18 houn

0­3 40 36 54 (62) 85 (97) 3.10.91 12-18 houn

TRIAL II 4 2 10 17 (19) - 15.10.91 12-18 houn

5 24 33 27 (31) 25 (29) 16.10.91 12-18 houn

6 24 17 26(30) 26 (30) 17.10.91 12-18 houn

TOTAL 239 TOTAL 290 (332)

•

•

•

Figures in brackets are control net catchescorrected for the dilTerence in fleet length •experimental fleets = 2052 yards; control fleets = 1800 yards. :. multiplication factor = 1.14. To compare the total catches, multiply the conlroltotaJ in brackets by 1219 Le. 1.33. This corrects for the difference in the number of shots.

TABLES

•

•

•

•

• ~ '..

•

Crab occurrence in the Experimental Nets

TRIAL n. SHars 4, 5 & 6

NBTlYPBNO NBTlYPB NO OF CRABS

I MODO 4.75" 0

2 MonoS.SO" 0

3 MuJtimono 4.75" 4

4 MuJtimono 5.50" to

5 Muhud 4.75" 19

6 Mullud 5.50" 16

Information collected from 3 shots. It was not practical to collect crab information from the vessel's nets due to the nature of the charter.

The variation of the positions of the different net types within each fleet, together with the 0

number of shots involved are an attempt at diminishing the effect that any natural aggregations ofcrahs may have on the apparent crah occurence in the nets.

- 16 ­

• • • • • • it it'. • • •

HAKE TRIALS 1991 - VESSEL'S NETS

All nets 4.7 Sin Monofilament

Size distribution for standard gear

NUMBERS

20 VESSEL'S NETS

"-290; mean-72

6

t I ! I!! I, J i, 1\ {, ,f \ t! t v,y, \ Io ( •• !. I I 1 !, I! , ,! I, ,! I !,!, I" ,I!' f i, ,I! 'V,''! f i, !! ! J , !! !

30 36 40 46 60 66 80 86 70 76 80 86 90 96 100 106 "110"

SIZE CLASS (em)

Six fishing daya ov..r 2x 1 w ....k trips Britannia V FH 12 1 Ar..a flsh..d: 60 mll ..s south of Plymouth ex 1800yd (1.611km) n.. t shots

• • • • • • • • • • •

5

o

10

"

HAKE TRIALS 1 991 - EXPERIMENTAL NETS

4.751n & 5.501n MONO, MULTIMONO & MULTIFIL. NETS

Showing relative performance of each gear type

NUMBERS

25 I ..

ITIl 2'

20 t- I. ~;'

18 ~f Ii

III II! - to- , 00 15

IU 12t2 12iI!fi :: ill 1f I II mIi! '" j

,o-ao 40·4" &o-ag oo·eo 70·nl 00-00 Slo·gg 100·100 "0-' 10

SIZE CLASS (em)

Six tl.hlng day. over 2x 1 week trip.

4.7 51n MONOFIL

• "-eOi mee.n-74

.. 5.501n MONOFIL

.. "-32; mean-77

iii; ;~,. 4.7 51n MULTIMONO llr~,~ II :~:I~ I; "-41; mean-7 3

Imi]tm! 5.6 Oln MULTIMONO ::::;::::::::' n-28; mean-7 8

IT!Tj.4.75In MULTIFIL ::::::: n-S8; mee.n-73

D 5.501n MULTIFIL

n-22; mee.n-74

Britannia V FH 121

•

::n .~ .....

Aree tl.hed: 50 mil•••outh ot Plymouth 12x20 52yd (1.88km) net .hot.

• • • • • • • • •

HAKE TRIALS 1 991 - EXPERIMENTAL NETS

4.751n & 5.501n MONO, MULTIMONO & MULTIFIL. NETS

Showing size distribution divided Into net types

. SIZE CLASS (em)

• • •

lilil'~liij!;~iWill~i~;t:::::::::::q:;:::j;';::: ;.;::::;;;:: ii: ::iij! I 88

I;jlliIPI::@I!i~llqijJ.II'f::;·:?:;;:;·:::::·:;:::·:':::·::3't· t·;·;:: jt j;j:': : .t·:! I 88

4.7 SIn MONOFIL

• n-SO; mean-7430-39

S.501n MONOFIL

40-49 • n-32; mean-77

'iijj\I~~ 4.7 Sin MULTIMONO 1I0-S9 !Ih!ilffim n-41; m ....n.73 ,

Ijjj;l S.SOln MULTIMONO "r1

Ie­ 80-69 ~.:;:::::~::::: n-28; mean-7S

.j>.70-79 87 I InU~jI4. 7 SIn MULTIFIL

:-;<:: n-S8; mean-73

60-89 D S.SOln MULTIFIL

n-22; mean-74

90-99

100-109

110-119

o S 10 1S 20 2S 30 3S 40 411 110 SS 80 8S 70 711 80 85 90

NUM8ERS

SIx lI.hlng d..y. ov..r 2x 1 w ....k trIp.

Ar.... lI.h"d: 8 0 mil"••outh 01 Plymouth

8rlt..nnl.. V FH 121

12x20S2yd (1.88km) n ..t .hota

• • • •

4.741nM 0 N 0 FIL !:!,l::!:I::::11i::l;::::II:;!,,::·::·I·:.·!::!:I;li'~j1,I;i:!:::~~!:!I:,.::II,::ll:I,I.!:::,I:I!II:I,,::llli"lill'~JJ:il:llf~II!lll::!il~f!II!:::I:!r~ll~illll:ll:rf~fll!IJI:!I!r!jl~!:::80

..........................................I 8.801n MONOFIL r::::<::::::(:::::::::::::::::::::::::::::)::::):::::::::::::::::::::::: 32

~!. 4.781nMULTIMONO !11:~II·~!::::ji,'J:.!··!I'I:.ill:llll::··I··:I.l:1!::II:.:I:~·I:II!I.:I:.II··:::::·~I,::··I!··!:·':!·!:111:1:':::I':::,··::I~·:·l:!·::I:·:::·::::':I::!r!:·!·:l:,l·~:.141

8.601n MULTIMONO rU?)U?:::(H:::}:::U:::H::H<:U:Hl28

4.761 n M UL TIFIL 1.:,:.:::',:1:',,·::::::::·::..::,:,:::::::::'::::',::1':!.I::I:':I::::,::,':::,'!:::,I:::,::·:::::::::,l'::11::I:::I:'::::I:I::::I·l,:!::::·:,:::::,:l:·:::::I;:::!::1:::·:I:l:I,I:I·!!.I').1:1:,·:"[1:::'1..:;:::':1 I·::i;.,::!·!::·il::~I'''lji.::~ 68

............................j 5.601n MULTIFIL 1(:»»>\>::::::::::::::::>:::: 22

, , , , , , ,

. " • • • • • • •

HAKE TRIALS 1 991 - EXPERIMENTAL NETS

4.751n & 5.501n MONO, MULTIMONO & MULTIFIL. NETS

Showing numbers of hake caught In each gear type

. GEAR TYPE

•

IlI:!i::!4.76In mnh

I>H 6.601n mnh

:!1

~

o 6 10 16 20 26 30 36 40 46 60 66 80 86 70 76

NUMBERS

Six fishing days ov..r 2x 1 w ....k trips

Area flsh..d: 80 mll..s south of Plymouth '. Britannia V FH 12 1

12x2062yd (1.88km).n.. t shole

VI

• 8. DISCUSSION

•

•

8.1 Selectivity of Hake gill nets Selectivity describes how fmely tuned a setoffishing gear is for catching fish ofa certain size range or species (Ref 3). "Selection" (the process of selectivity) is defmed as the alteration of the probability offish capture depending on the characteristics of the fish, (Ref8). "Selectivity" usually means selection bysize and "size" is usually the total length of the individual fish.

8.1.1 Mesh size and hanging ratio

• The main two attributes governing selectivity in a gill net are mesh size and

•

hanging ratio. Mesh size governs the physical size limit of hake that can become "meshed" or "gilled" in the net. The hanging ratio governs the extent to which the meshes open up and therefore the ease of fish becoming gilled. Static nets that have very slack hanging ratios - the tangle nets - rely on fish becoming entangled in the sheer volume ofnetting presented to them, rather than becoming gilled (Ref 3).

8.1.2 Gilling versus tangling

• In practice the distinction between "gilling" and "tangling" became blurred. From

•

observations made during the trials, most of the hake trapped in the nets appeared " to be tangled in the main body of the net. However, upon careful removal, it was common to fmd the hake held either by the gills or held around its middle by one mesh, suggesting that it had firstly become gilled and secondly tangled through" struggling. Another apparent catching characteristic was that of hake being held"

•

in the net by meshes caught around their teeth. Again, careful removal of the fish from the net usually revealed that it had at least one mesh around its head. MacMullen (Ref6) suggested that hake become trapped by one of1hree methods ­gilling, wedging (being lightly caught by the snout) or tangling. From observations made during thetrials under discussion it would appear that, whilst all three of these catch characteristics were observed, it was probably the gilling mode that occurred ~rrst. This was borne out by further observations; during the hauling process it was not unusual for fish to continue to run into the net. Thus,

• there were fish trapped in the net for different time periods ranging from a few minutes (alive and kicking) to the entire soak time up to the point ofhauling (dead with somescale loss). Those fish that had freshly "run to net" were nearly all gilled in the classic manner, and rarely were tangled.

• 8.1.3 Hanging ratio MacMullen (Ref 6) also suggested that widely varying hanging ratios (tight and slack netting) would not affect the size distribution of the catch, or the sizes of

• - 21 ­

•

•

• catches. Observations made during these trials reinforced this theory.The hake were hitting the nets very hard as they were occasionally held by a mesh at a point

•

behind the head - which is wider than at the gills. This could mean that, from a hake catching viewpoint. hanging ratio is ofsecondary importance as the hake run into the net at sufficient speed to become meshed regardless ofmesh opening. The hanging ratio is ofmore importance from a rigging viewpoint because it accounts. for the rigged length ofeach net - and therefore the total effective fIShing length of each fleet (200 yard net sheet rigged at 0.60 hanging ratio becomes 120 yards long; rigged at 0.57 it becomes 114 yards long). It therefore makes sense to use a hanging ratio that maximises the rigged length of each net sheet (approx. 0.60 ­

• correspondiD.g to the vessels nets).

• 8.1.4 Material and Mesh Size Figure 5, shows the number of hake caught in each gear type. Although the numbers are less than those hoped for, it can be seen that for each of the three material types. the 40/4 inch mesh size caught a greater number ofhake than the 5% inch mesh size. Of the three materials, the monofllament and multif1lament nets were comparable in performance, but the multimonofllament nets lagged behind by about 30%. Multifilament net is extremely difficult to deploy; it is made ofa

• very heavy twine which collapses when wet and easily snags upon itself. Multimonofilament has one advantage over the other two twines in that being very supple. it is much easier to stow. However, along with multifilament, it is. relatively expensive and has a higher bycatch rate than monof1lament.

• 8.1.5 Size Distribution of Catch

•

Figure 2 gives a size distribution for fish encountered in the control nets (vessel's nets) which peaks at 70-75 em length for 40/4 inch mesh size. The mean size offISh in these nets was 72cm. Figures 3& 4 show size distributions for the experimental (Seafish) nets presented in two slightly different ways for clarity.

The low number offish encountered does not allow further statistical breakdown of the information while still remaining representative of the fishery. However, a number of observations can be made from these diagrams.

•

•

As would be expected both the control nets and the experimental nets appear to have caught the same range ofhake sizes, from about 30em to about Il0cm. Both sets of gear have peak occurrences at the 70-79em group. Of the 40/4 inch mesh· experimental gears. themultimonofilament appears to be themost selective in that both the size groups adjacent to the peak 70-79em group contain less than 50% of the numbers of fISh in the peak 70-79em group. and the peak 70-79em group for both of the other variants contain more than 50% in these adjacent groups. The monofllament nets appear to be least selective in that the differences between each

• - 22­

•

••

• of the adjacent groups and the peak: 70-79cm group is less than either of the other

• variations.

• It must be bOllle in mind that these are apparent trends and not hard-and-fast conclusions.. It is difficult to comment on the relative selectivities of the three twine varian~ in 5V. inch mesh size because the numbers encountered are so low. One would expect a discemable upward shift ofthe peak 70-79cm group; only the monofilament nets indicate this. This leads to the question: what is the size distribution of hake occurring on the fishing grounds? Without this information it isveiy difficult to put this very limited selectivity information into perspective.

• However, it is likely that the hake occurring on the grounds were of similar year· classes more suited to capture by the 40/. inch mesh nets, which would explain why the 5% inch nets caught less. The skipper suggested that this was the case; indeed hake fishing grounds further to the South-West require the use of 5.50 inch mesh as there. runs of bigger hake are encountered.

•

8.1.5.1 Gill net versus the trawl Figure 6 gives a comparison between gill-net caught hake and trawl caught hake. It must be borne in mind that the two size distributions come from dilTerent areas; the gill-net fish were caught in an area approximately 60 miles South of Plymouth whereas the trawled fish were taken in an area 10 miles South West of Plymouth. Because of this, it is difficult to use the trawl data to check whether the population structure (on the gill-net grounds) is biased towards the 70-80cm length range (Ref6) most frequently encountered in the

• gill nets. It is known that large hake are rare inshore.

• _ The two gears have different selectivity mechanisms operating. MacMullen

(Ref6) proposed that the peak occurring in the size distribution for trawled fish is caused mainly by the population structure than by physical fISh-mesh interactions as in gill nets. Further, the lack of large hake in the size distribution is largely.due to the low towing speeds (2.5-3.0knots).. Hence the trawl actively selects for small hake and actively excludes larger fISh, whereas gill-netting actively excludes the younger, smaller year classes.

•

•

•

- 23­

I , Figure 6 I.

GILL NET HAKE TRIALS 1991

All nets 4.751n Monofilament 60 mesh deep

Size distribution for vessel's standard gear NUMBERS

20 ,-------------------------, 4.76a(120mm)

n"290; m8an"72

15

• 10

5

• 0w..........~~.u..lt.'U~.u.1-'-'-'-'-~ ...................~.u.L~~...L..I.bA~.u.........u.u.u

30 40 50

• Six fishing dsya oyer 2x 1 week trips Britannia V FH 12 1

Area fished: 80 miles south of Plymouth 9x 1800yd (1.65km) net shota

TRAWLED HAKE: Size Distribution (numbers)

• 90mm diamond mesh codend and extension

NUMBERS

60 ,--------------------------, 90mm MESH

n0677

• 50

40

• 30

20

• 10

0L....,.......................u............<L....~--'-'-~u.....~ ..........~~~_'_'_' .....~__.....................J

10 15 20 25 30 35 40 46 50 66 80 86

SIZE CLASS (em)

• MFVs Leysn Mor and Budding Rose, Looe SEAFISH Noy 1991

- 24­

•

80 70 BO 90 100 110

SIZE CLASS (em)

•

8.1.6 Number of hake encountered

• Table 4 gives a fleet-by-fleet breakdown ofthe numbers ofhake caught in both the

•

experimental nets and the control nets. The control net values have been raised to correct for the shorter fleets of these nets. To compare the total offish caught for the control and experimental nets, account must also be taken of the difference in number of shots between these two gear types. Thus, the total number of hake' caught in the experimental nets amounted to 239 fish; for the control nets it was a 441 fish equivalent. The reason for this near 90% difference is mainly that half of the experimental nets were constructed of 5% inch mesh which (from figure 3) appears to be less suited to the size class ofhake on the grounds than the 40/4 inch

• mesh.

8.1.7 Bycatch

•

• Bycatch in the hake nets consisted mainly of scad or horse mackerel (Trachurus

. trachurus), spurdog (SqlJ1l1us acanthias)and a few brown crabs (Cancerpagurus). Scad and spurdog were the only signillcant fish bycatches taken. Scad proved to be a constant nuisance for all variations ofhake net including the vessel's nets, but the problem wascompounded in theuseofmultifI1ament (nylon) nets, from which it was difficult to release them. The scad measured approximately 30cm and they formed the main part ofunusable bycatch. Spurdogs occurred on a very irregular basis. Spurdogs can be landed but this is economical only in large numbers. As their occurrence is usually irregular then relatively few landings ofthem are made. During the trial, about ten boxes of spurdog were caught on one day.

• Brown crabs were occasionally taken, but numbers were kept very low by means.

•

of the anti-crab rig along the bottom edge of the nets. Table 5 gives details of crabs taken in the experimental nets over three successiveshots. Theexperimental monofilament nets caught no crabs at all; the vessel's monofilament nets (control nets) caught very few. The multimono nets caught moderate numbers, but the worst variant for crab capture was the multifI1ament nets. Being a heavy net when wet, the net body occasionally came into contact with the seabed, allowing ingress of crabs.

• . At no time during the trials was there any evidence of any marine mammal interaction with the nets, nor any evidence ofany bird interactions. The nets were set in approximately 80 metres of water in an area 60 nautical miles South of Plymouth:

• 8.1.8 Deployment Using the control nets (vessel's nets) as a standard the experimental nets suffered some problems on shooting. The floats on the headline secured tightly to the rope by each end gave repeated snags and tangles if one float accidentally passed

• - 25­

•

• through a mesh or staple. The control nets had free-sliding floats within each

• staple; this small amount of"give" dramatically reduced the frequency offoul-ups

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(see Figure I and Section 4.1.1). The wet multifl1ament nylon net sheet displayed. a tendency to "whip" about on shooting. Because the multifl1ament nets were very heavy and twine diameter relatively large, they displayed a tendency to move about on the seabed to a greater degree than the other net variations; consequently they sustained some damage.

The monofl1ament nets retained sufficient resilience or "spring" in the net sheet to pass through the shooting channel (Section 6.2) or over the stem rail with very

• little danger of tangling. The multimonofl1ament nets had the advantage of occupying less space than the equivalent mono or multifl1ament nets, but the monofl1ament nets were, by far, the easiest to handle on board the vessel.

• All the control nets (vessel's nets) deployed over the course of the trial had 60 meshes to their depth. Recent times have gradually seen vessels changing to nets that are 45 meshes deep (in 40/4 inch monofl1ament). This gives the advantages of easier storage, lesS weight, and less cost than 60 mesh nets while the catching qualities of the nets are seemingly unalTected.

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• 9. CONCLUSIONS AND RECOMMENDATIONS

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9.1 The deepwater gill net hake fIShery is the most prominent of all the static net fISheries in Cornwall and one of the most important in the U.K.1t is worked by the largest of the vessels engaged in netting, and is almost exclusively an offshore fIShery.

9.2 There is evidences to suggest that the level of bycatch taken in monoftlament hake gill nets is consistently low. For the second of the two trials (shots 4, 5 & 6 on Tables 4 & 5) there were no brown crabs (Cancer pagurus) taken in the

• experimental monoftlament nets.

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9.3 Themultimonoftlament and multifilament netsexhibited a higher degree ofbrown crabs capture than in the monoftlament nets. The multifilament (or "nylon") nets exhibited by far the worst incidental brown crab capture of the three experimental gear variants.

9.4 There is sufficient evidence to suggest that the anti-crab barrier along the bottom of the hake nets is higWy effective at reducing the ingress ofcrabs to the net sheet.

• 9.5 The proper use ofdeepwater hake gill nets appear to present very little risk to birds or marine mammals. During the entire trials there was no evidence of bird or mammal interaction with any of the fIShing gear.

• 9.6 For each of the three experimental net variants a mesh size of 40/. inch (120=) caught more hake ofeach respective sizeclass than a mesh size of5Y.inch (140=) on grounds approximately 60 miles South of Plymouth.

• 9.7 From the information obtained during the course of the trials in terms of the hake total length, themonoftlament variant of the experimental gear appears to be the least selective of the three variants used. The multimonoftlament (often referred to as "nylon") variant appears to be the mostselective. However, the low numbers offISh taken during the trial make it impossible to quantify the degree ofselectivity

• further. (See 8.1.5, Size distribution of catch).

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9.8 Nylon monoftlament is the favoured material for hake gill net construction by most of the skippers of the deepwater hake gill net fIShery. This is because it is easy to handle on board the vessel, easy to efficiently deploy, lightweight and strong, does not readily catch brown crabs, it is comparatively inexpensive and is readily available. Neither multimonoftlament or multifilament satisfy all these criteria.

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• 9.9 To obtain a full and accurate picture of the mechanisms ofselectivity in hake gill

nets, it is recommended that a further set of trials be conducted in this fishery. Ideally these should take into account the more distant fishing operations requiring the use of5Y2 inch mesh (140=) as well as operations in shallower water using 40/4 inch (120=) mesh.

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• REFERENCES

• (I) Arkley, K. 'Static Fishing Nets - Experiments to reduce bycatch and bottom debris',

SeafIsh Internal Report No 1398. March 1990.

• (2) Arkley, K. and Swarbrick, J. 'Fishing trials to evaluate the relative selectivity and, efficiency of different netting yarns used in the construction of static nets used in fISheries for sole and plaice in the Eastern English Channel'; SeaflSh Technical Report No 382, Apri11990.

• (3) Swarbrick, J. 'An Investigation of the Performance of Tangle Nets used off North Cornwall', SeaflSh Technical Report No 391, Apri11991. 42pp.

• (4) Munday, K.C. 'Gill Net and other Set Net Fisheries in Cornwall', SeaflSh Internal

Report No 1400, 1990.

(5) Unpublished MAFF report, 'Gill Netting in Coastal Fisheries in England and Wales'; MAFF 1990, 19pp.

• (6) MacMullen, P.H. 'Gill Netting Trials on MFV 'Heart of Oak' of Helford'; SeaflSh Technical Report No 235, February 1984. 25pp.

(7) MacMullen, P.H. 'Set net trials on MFV 'Victory' of Helford', SeaflSh Technical Report No 203. June/July 1982.

• (8) McDonnel, A. 'Driftnets in the North East Atlantic', Greenpeace International,

November 1990. 54pp.

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APPENDIX I• Photographs

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Figure I MFV"L aDd T Bri13cnia V" LOA IS-25m (50.031\) Figure 2. - TarbensoQ 7SO-SOO d.rom hauler in operation

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FiCure 3 _Showing Q monofilament nel entering tbe shooting chnnnci from a rUidships nel pound

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Figure 4. Showing a net heine shot over tbe siern rail from tbe aft net pound

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Figure S - Showing the shoo ling cblUlDCI deploying ocl, over the stero oribe vessel

Figun: 6 . Showing tbe lkluling operation; tbe fish an:: ranovro from tbe hauler (leO) by band (centre). The oct is pulled over 8

plastic tubcnnd naked down into net pounds(rigbt)

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• Figure 7 ~ A IDrgC llOem hak.e (Mt:rfuc:ciu$ me.rlulXiui)

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APPENDIX II• Trials Data

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• 100 100 110

n= 60 32 41 28 56 22 TR1ALS TOTAL= 239 MEAN= 74 77 73 76 73 74 STD DEY= 13 13 11 12 9 15

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HAKE TRIAL OCTOBER 1991

• VESSEL'S NETS

CONTROL NETS: 43 65 69 73 78 90

FISH 44 65 69 73 78 90 ALL NETS LENGTH 45 65 69 73 78 91 MONO, 4.75"

• (cm) : 45 65 69 73 79 91 46 65 69 73 79 91 9x1800yd (1.65km) 47 65 69 73 79 91 net shots­47 66 69 73 79 94 Data coalesced 49 66 69 73 79 95 54 66 70 73 79 98

• 55 66 70 73 79 99 56 66 70 73 8.0 100 56 66 70 73 80 100 57 66 70 73 80 106 57 66 70 73 80 108 57 66 70 73 80 108

• 59 67 70 74 80 59 67 70 74 80 59 67 70 74 81 59 67 70 74 81 59 67 70 74 81 60 67 70 74 81

• 60 67 70 74 81 60 67 70 74 81 60 67 70 74 81 60 67 70 74 81 60 67 71 74 81

.",... ......61 67 71 74 81

• 61 67 71 74 81 61 67 71 75 82 61 67 71 75 82 61 67 71 75 82 62 68 71 75 82 62 68 71 75 82

• 62 68 71 75 83

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63 68 71 75 83 63 68 71 75 83 63 68 71 75 83 63 68 71 76 83 63 68 71 76 83 63 68 71 76 84 63 68 72 76 84 63 68 72 76 84 64 68 72 77 84 64 68 72 77 84 64 68 72 77 84

• 64 68 72 77 85

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. 68 64 69 72 77 87 64 69. 72 78 87 64 69 72 78 87 64 69 72 78 88 65 69 72 78 88

64 72 77 86

65 69 73 78 88 TRIALS TOTAL= 290 65. 69 73 78 88 MEAN= 72 65 69 73 78 89 STD DEV= 10

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