Technical reports

A world review of the fishing techniques used in association with fish aggregating devices in small-scale fisheries and potential interest for the Lesser Antilles countries

J. Prado
Fishery Industries Division
FAO Fisheries Department
Viale delle Terme di Caracalla
00100 Rome, Italy
e.mail: [email protected]

1. INTRODUCTION

There is wide experiences gained with Fish Aggregating Devices all over the world, including in the Caribbean over a period of more than twenty years. Exploitation of the aggregated fish started using traditional fishing gear and methods and, in many cases, there have not been, for many reasons, many systematic experiments to improve the related fishing technology. It is observed that in many cases the great expectations raised by the installation of FAD were not fully met. Under certain conditions, there was an, occasional, increase in fishing yield for a few fishing units but most of the time there was no definite progress for the concerned communities resulting from sustainable higher level of exploitation of all the living resources available.

2. RESOURCES AVAILABLE AROUND FAD

The resources to be fished will consist of pelagic fish if the FAD are set in deep waters or pelagic and demersal fish/reef fish if the FAD are set in shallow waters. Obviously if the FAD is set near a natural reef, more reef fish might be attracted/aggregated by this artificial structure, while more pelagic fish will be found if the FAD is set over an open sand bottom away from reefs. In relation to this, it is also worth mentioning that, based on experiences in the Caribbean, it was found that setting midwater aggregators/FAD over reefs would be a cost-effective method of enhancing reef fisheries (McIntosh Marine USA; 1984).

A distinction can be made between two categories of fish near a FAD: “residents” and “visitors”. Experience in PNG led to the following observations: residents may include: damselfishes (Abudefduf sp.), some silversides (Atherinids), sea chubs (Kyphosids), teraponds and triggerfishes (Balistids); many of them being herbivorous feeding on the fouling community attached to the FAD or planktivorous. The “visitors” include: sharks (Carcharhinids), dolphinfishes (Coryphaenids), small tunas (skipjack) and mackerels; generally, carnivorous. Another presentation makes a distinction between so called “bait fish”: round scad (Decapterus. sp), herring (Harengula and Sardinella) or pomfrets (Bramidae) and “predator species” such as amberjacks (Carangid), rainbow runner and blue runner.

In general, (according to A. Fonteneau and JP Hallier, 1992), the common situation is:

Very close to the FAD: Small fish, juveniles, molluscs and small crustacean.
A few meters away: Small pelagic fish, Carangidae; Balistidae, groupers (Serranidae)
Farther: Various predators such as different tuna species, dolphinfish, marlins and sailfish, triggerfish (Balistidae), rays and sharks (See Figure 1)

In the Caribbean, it was observed (J. Sacchi and A. Lagin; 1985), after only two days that the fish species distribution according to distance from the FAD. On surface the closest observed were: small carangidae, Exocetidae, Nomeidae and fish juveniles (e.g. of coryphaena). A bit further species such as coryphaena (adults) and balistes were observed. Still further, under the current: Cybiidae (such as wahoo and Spanish mackerel) were observed, and finally, in deeper mid-water: tunas and sharks were observed.

The same authors observe that large pelagic fish stay below the FAD as long as there are still small prey fish (Carangidae, Exocetidae, Nomeidae). If the small prey fish are harvested it will be necessary to wait for the shoal to recover before seeing a return of Coryphaena and Cybiidae.

However, more research carried out in the nineties using acoustics added more information regarding the distance of fish versus the mooring line of the FAD: in general, larger fish are not only found deeper but commonly at a distance of more than hundreds of meters (one nautical mile or more) while smaller individuals normally stay closer to the line. (See Figure 1 (b)).

From experiences in the Caribbean, drifting objects mainly attract: coryphaena, flyingfish (Hirundicthys affinis), Canthidermis sufflamen (a triggerfish of minor interest, in most of the countries, which, in addition, may bite the bait on the lines more eagerly preventing the catch of high value species), sharks (the presence of which will, in many cases, create problems during fishing, for instance, with trolling lines) and less, wahoo (Acanthocybium solandri) and rainbow runner (Elagatis bipinnulata). Tuna seems to be less attracted.

Regarding aggregation of some demersal fish, it is worth mentioning that, in India, FAD in shallow waters aggregate fish such as Lutjanides, Decapterus sp., Selaroides, Selar sp. and Trachinocephalus sp.(/lizardfish); all of which are demersal but appear pelagic in shallow waters, with a characteristic shoaling behaviour. (Sanjeeva R.; 1987)

During a certain period, squid eggs fix onto FAD elements, such as a buoy.

It was observed, also in the Caribbean, that a free-drifting object, after a few hours, generates a colony of tunas. The problem is how to catch the fish without disturbing the established colony. This is an important matter with two main questions to which only empirical evidence in the concerned fishing areas can give answers: 1) how much time necessary for an established fish colony to recover after intensive fishing?, and 2) what is the possibility for temporary transfers of fish colonies from one FAD to another to allow certain fishing operations, for example with surrounding nets in particular? Such transfers of aggregated fish are not automatic such as in the case of light attraction since it normally takes some time for a FAD to become attractive.

Normally, fish begin concentrating in the morning, peaking near midday and then decreasing in the afternoon.

3. FISHING GEAR WHICH CAN BE USED, IN PRINCIPLE, AROUND FAD

The fishing gear to be used depends, to a certain extent, on the type of FAD. Some FAD attract fish at the surface level only (consisting basically in a large raft or buoy, possibly with additional elements attached to it). These are the so called “surface FAD”. Others attract fish at different heights of the water column because there are attracting devices at several levels below the buoy, on the mooring line. These are the so called “mid-water FAD”.

The fishing gear to be used also depends on the depth since when FAD have been set in rather shallow waters, there is the possibility of catching aggregated fish not only near the surface or in mid-water but even near the bottom. For instance a boat seine can be used (as done sometimes near “Indonesian rumpon”) or a large liftnet can be layed for a certain amount of time directly on the bottom below a non-anchored FAD before lifting it.

The weather is also, to a certain extent, a selection factor, the vessel and equipment being at disposal may also justify preferences. When the weather is fine, surrounding nets are commonly used, with (purse seines in Japan) or without purse line (lampara net off Malta); in smaller scale fisheries, trolling lines are also used; when the weather is bad, surface drifting, monofilament longlines can be used.

In, general, the fishing methods which can be used include: Handlining, Longlining, Pole and lining; Fishing with trolling lines; gillnetting, the use of surrounding nets; the use of scoop nets and liftnets; fishing with mid-water fish trap.

3.1 Handlining

Handlining can be used either near the surface or more often for fishing in mid-water and deep-water.

Figures 2 and 3

The fishing operations take place up-current of the FAD. The priority is to recognize the depth at which the large fish are found in the water column. This depth, in most cases varies according to season. The initial fishing effort is usually over a range of depths where the tuna might be expected by testing several lines at different depths at the same time.

The main task is to send the baited hook as quickly as possible to the depth where the tuna or other big fish are which may, according to season, be 100 m, 200 m, 300 m or even sometimes more. For this purpose various weights are attached on the line in different ways. However, weights are not systematically fixed on the mainline in order to keep the natural aspect of the bait. A few effective methods used in the Pacific and the Indian Ocean are briefly described below (from descriptions in publications of the Secretariat of the Pacific Community).

In the Comoros, the technique, so called “drop-stone with chum” technique consists in dropping the bait to the desired depth (100-200m) using stone(s). For instance, in the Comores two stones are used between which some chum (minced fish) and the baited hook is held. When the bait reaches the desired depth, a quick jerk on the line frees the stones, which are attached to the line by a loop and a quick-release knot. The baited hook emerges in the middle of a cloud of minced fish (SPC Newsletter 3). Very often stone only is used.

In certain areas, the stone with the bait attached to it by making several wraps with the line around it are wrapped in a broad leaf, such as from breadfruit in order to prevent bait escaping too soon.

It is worth mentioning that many Fishers pay out several meters of line into the water before they release the stone + bait package, to make sure that it falls freely. It is observed that the Fishers can also measure the fishing depth by counting arm-spans as they feed out the line.

In a modern adaptation of the technique off Hawaii (Pacific), the lost stone is replaced by a flat 1-2 kg lead sinker which stays on the mainline: “Palu-ahi fishing”. See the description by SPC given in Annex.

Another version of the “stone fishing” technique used in French Polynesia is worth mentioning which is not strictly speaking handlining since it is left drifting under a buoy. (SPC Newsletter No 1)

Stones are used as in the previous method to lead the baited hook to very deep waters where the potential catch is expected. In this case, the chum consists of a piece of skipjack. The remaining line after the bait reached its fishing depth is left on a spool, just below the buoy.

Drifting handlining with live bait for tuna and Coyphenea (mahi mahi)

From La Reunion, with live bait bigeye scad is caught (Selat crumenophothalmus) at night. The fishing gear consists in a main line of very fine monofilament (dia 0.3-0.4 mm) carrying five short snoods (0.15 m of dia. 0.2-0.3 mm) with lures (with small lengths of shiny knitting wool and sometimes also fluorescent beads close to the hooks). Normally, a lamp is used over the side of the small boat to attract the fish. The handline is hand jigged while slowly brought back to the surface. Other methods around a FAD include a monofilament line as fine as dia. 0.5 mm or thicker, with a tuna hook (No 5-7/0) or swordfish hook (e.g. Eagle Claw L 9014 size 8/0). The boat is stopped up-current from the FAD. The bait is attached to the hook very carefully, either through the mouth from beneath or sideways through the nose. The forward position of the hook allows the baitfish to swim. When a fish bites, the fisherman pays out more line to allow time for the fish to swallow the bait.

Handlining at night with light attraction

In fact several means are often used at the same time for attracting, not only large pelagic fish but also small fish which are used as bait fish. The light can come either from several incandescent bulbs above the surface or more powerful lamps set underwater after the bulbs have been waterproofed (i.e. using silicon mastic). The light attracts scad, mackerel, squid and other baitfish, which will themselves attract larger fish. As mentioned above large quantities of minced fish are commonly used at the same time as bait. It is worth mentioning that this observation is also valid for the use of several other fishing methods in association with FAD.

It is important, as far as possible, to use live bait, but pieces of fish or squid can also be used. The way the bait is attached to the hook is of prime importance. The fish may often nibble the bait two or three times before swallowing it (whereas trolled hooks and lines are fast moving); so it is very important not to strike immediately at the first bite as this may scare the fish away.

When the fish has bitten there should not be too much slack in the line which would allow it to throw the hook, on the contrary, there should be some strength on the line to set the hook when the fish strikes. The strength is obtained, when the line is set from a boat, by tying the line to a strong point on the boat with a breakaway line which snaps when a fish bites. When the line is drifting strength is also obtained, by the floatability of the float or buoy stretching up the line to the surface when a fish pulls it in another direction.

When using drifting handlining, if there is strong wind or current, it is required to limit the drifting speed using oars or the engine. In many situations, handlines which fish a bit deeper in midwater catch larger tuna fish (with higher individual market prices) than surface fishing gear such as trolling or pole and line. As with most techniques targeting tunas or marlins, the best results are obtained at dawn or at dusk.

3.2 Longlining

3.2.1 Short monofilament horizontal longline (See Figure 4 also)

These gears are becoming more and more popular and have already proved their effectiveness. In addition the investment is pretty low. The same lines can be used either near the surface or in mid-water.

3.2.2 Longlining with vertical longline (See Figure 5 also)

Vertical longlining is a simple and relatively cheap way to catch large pelagic fish aggregated by FAD at several levels of the water column. The vertical weighted mainline suspended from the surface by a buoy may reaches down to a depth of 300 m or more. The branchlines or snoods with hooks are, in general, clipped to swivels which are built into the mainline at intervals aroung 10-20 m. The first branchlines with hooks are either at a certain depth (i.e. around 100 m) to fish only in the water layer where large deep pelagic fish are expected or not far from the surface and up to a certain depth if shallow water species such as dolphinfish, sailfish, marlin or barracuda are targetted in addtion to deeper waters species such as large tuna. Anyway, all parameters, length of the mainline, length of the branchlines, their number on a vertical longline and spacing on it, can all be adjusted to local conditions, from experience and, possibly, according to seasons (variations of the depth of fish, of fish species available, their concentration, etc.).

Effective vertical longlines are made from monofilament (thick enough: at least 200 kg breaking force) or kuralon (nylon) (easy to grip for hand-hauling and less liable to tangle when the line is coiled on the deck). For easy manoeuvering, the mainline can be wound onto a fishing reel on the deck of the vessel (in particular, when the mainline is made from monofilament) or it is just handle by hand.

The line is set from a boat either drifting not far from a FAD or tied to it. The setting is made from the part of the vessel, which will avoid the line and the boat being pushed together by the action of current or wind. The baited branchlines are fixed, at given intervals, to the mainline one after the other during the shooting (but, for safety reason, the clipping should never be done before the hook is in the water!).

It is worth mentioning that it is common that a vessel set several free-drifting longlines one after the other, not far one from the other (when there are other fishing units around, each drfting lines should obviously be properly marked).

3.3 Pole and lining

This technique is commonly used for small and large skipjack and small yellowfin tuna. Some bait is used, however, it will be either on the hook (live or dead) or (as common around FAD in the Maldives) just chummed, over bare, barbless hooks and in conjunction with a spray system.

3.4 Trolling line

In principle, two types of trolling can be distinguished: - surface trolling, for smaller tuna in surface schools, coryphaena or rainbow runner; - sub-surface or deep trolling, for larger fish. The strategy is normally, trolling first fairly slowly using heavier gear and passing as close to the FAD as possible. If there is no success, then the heavier gear is changed to lighter lines and smaller lures and troll a little faster for smaller tunas; if there is still no success the lighter lines are changed to monofilament traces which are used to start chasing the fish schools. Experiences in the Pacific (according to SPC) shows that the majority of the fish caught around FAD are taken on the up-current side.

Surface trolling line (Japanese Jumbo lines; SPC Newsletter No 2)

For tuna and other large pelagic species fishing off Okinawa, Japan, this technique consists of trying to keep the trolling lines out of the water and have only the lures touching the surface. See Annex for detailed description.

Slow trolling

Slow trolling is possible either with lures or dead or live bait. The lure can be a plastic squid-type lure giving it lifelike movements by pulling and releasing the line, at a distance of approx. 100 m. Dead bait such as squid or scad, can also be used. Slow trolling with live bait is very effective with predators like tuna and dolphinfish.

Sub-surface or deep trolling line (Fishing with vertical longline, SPC, 1999)

The problem when trolling the line at high speed (e.g. up to around 6 knots) is to keep the line at the desired speed. This can be achieved by the use of heavier materials (e.g. use of wire in place of nylon monofilament) and/or by fixing in-line sinkers on the line. Materials such as lead weights or a piece of chain and/or “diving lures” can be used. Artificial lures are designed to dive by having a mini-diving board on them; they can be made of wood, plastic or steel.

There are great fluctuations in yield depending on weather and sea conditions requiring the fishers to use his skill to adjust the depth of fishing, towing speed and select the right model of lure.

Potential catch in the Caribbean: dolfinfish/coryphaena, wahoo, barracuda, yellowfin or blackfin (Thunnus atlanticus) tuna^[18]

Strings of FAD with mid-water aggregators may form a “trolling alley”: i.e. two strings of FAD spaced 200-500 m apart in two parallel lines ranging from 1 to 2 km in length. An arrangement which proved effective in the Caribbean in shallow waters (30 m depth) (Deyoung, B. R; NYS Sea Grant Extension Program, USA; 1984)

On the same trip, in many cases, it is wise to take on board material for trolling for both deep-water and the surface. This practically means having on board both heavy duty lines rigged with large lures or bait and lighter lines rigged with small plastic octopus or other lures since it might be necessary to change between one type of gear and the other during fishing.

It is worth mentioning that in places where there has been some competition between trolling and handlining on the one hand, and pole and line fishing on the other, the former is said to disperse the schools of tuna making them more difficult to catch with the latter (see Figure 6 also)

3.5 Gillnetting

With the use of drifting gillnets there is a possibility of catching a lot of fish if set in correct position: depth and orientation to the current, while the necessary investment can be relatively heavy, The use of gillnets for catching small pelagic fish (bait fish/prey fish) can be effective but there is obviously a risk of the net webbing entangling on the FAD mooring if the gear is set too close. This is a risk which, considered seriously by the fishers, may prevent use of this gear.

Encircling gillnet can also be use, while this is less common.

3.6 Surrounding nets (Purse seine or Ringnet, with purse line to close them; lampara net, without purse line)

There are two main ways of operating surrounding nets in association with FAD. One way involve setting the net near the FAD, which is not itself encircled or setting the net around the FAD, which means that before closing the lower part of the surrounding net (before pursing and before hauling the net) the FAD has to be pushed out of the enclosure.

Another method is that when the vessel nears the FAD, an appendage is carefully detached and temporarily fixed to another buoy (which the vessel has brought with it, e.g. an empty oil barrel). The upper part/the attracting section of the FAD is therefore detached from its anchor line for the duration of the operation. If the FAD is furnished with a side buoy, the whole raft is detached and no extra buoy is needed. This unit is then left to drift away from the anchoring line, taking with it the fish aggregated in the appendage. After a while the appendage has drifted far enough and the purse seine is set out in the normal manner. After closing the net and while hauling it in, the buoy and the appendage are kept on board the vessel. After the catch is recovered, the appendage is attached again to the anchoring line. In respect to this operation, it is worth mentioning that disengaging a FAD buoy from its anchor rope can severely disturb the fish, which is aggregated around it. It is therefore common to have two or even three buoys. The first one (or two) carry the anchor rope and remain attached to it, while the third one carries the appendages and is easily detachable (see Figure 7 also).

Surrounding nets are also used, in some places, in association with small/light FAD which can easily be removed and are used as sorts of lure, e.g. traditional method in Malaysia.

Some vessels use an annex boat during the night before fishing operations to play the role of temporary aggregating device for small pelagic fish either as target species or to attract predators. The light boat is moved aside from the FAD with the fish originally aggregated around it, being then surrounded by the seine.

There is no uniformity of opinion as to whether fish stay preferably up-stream/wind of a FAD or down-stream/wind (this probably depends on species, age and environmental conditions). It is worth mentioning that the effectiveness of surrounding nets might be affected by water clearness.

In general, surrounding nets allow the harvesting of a large portion of the colony of fish which has been aggregated by a given FAD (in one set). This aggregating device needs some time to “recover” to attract new fish, i.e. a period during which there should be no massive harvesting. For this reason, to ensure daily fishing operations, a seiner must have at its disposal several FAD around which it can fish.

Among traditional fishing the “Kannizzatti” fishery using ring-net type of surrounding nets, in Malta, Mediterranean Sea, can be mentioned, which takes place around anchored floats constituting surface FAD for dolphinfish (Coryphaena hippurus) and pilotfish (species known for having a commensal relationship with carnivorous large fish such as shark and ray). Regarding this fishery it is worth mentioning the traditional practice of setting a series of FAD, from the coastline to up to eighty miles, with intervals of 1 mile between FAD.

The same method with surrounding net is used around bamboo rafts attracting dolphinfish in the coastal waters of Japan; in this case, the bamboo rafts are anchored in series, with about a mile between them. In Malaysia, a series of light FAD/lures for attracting small pelagics are set along a straight line towards the sea with its bearing in relation to a given land mark. In connection to this it is also worth mentioning that the aggregations around several light neighbouring FAD are, when possible, grouped to get a shoal large enough to be worth surrounding with a seine.

3.7 Scoop nets

Scoop nets or similar larger nets as drive-in-nets are frequently used in association with surface FAD. An example is “Fishing flying fish with lure”, a traditional method, used for instance in south India: bundles of branches and leaves are set out; flying fish gather to deposit their spawn on the branches and leaves; then dip-nets are used to scoop up the fish. The same method known as “with Brushwood” is found in many other places using scoop nets to catch the aggregated fish.

3.8 Liftnet

In this category, it is worth mentioning, in India, large lift bagnets operated from four catamarans working together which are set on the bottom in shallow waters under floating attracting devices. (see Figure 8)

3.9 Mid-water fish trap

The use of such mid-water traps hung under a float or raft, which attracts small pelagic fish, is a traditional method in several countries in Asia. In the Pacific, SPC tested the effectiveness of mid-water traps suspended under FAD. Light, large rectangular traps, 2 x 1 x 1 m dimension, wooden frame and cover with chicken wire mesh, without bait, were suspended 4 m below the FAD. The above mentioned experience proved a certain effectiveness for catching small pelagic fish (see Figure 9 also)

3.10 Previous to the use of various types of fishing gear: Fishing for the bait near to FAD

In shallow waters, FAD will often aggregate small pelagic/bait fish making capture easier. Capture can be achieved in the daytime using a surrounding net, a liftnet or with a midwater trap attached below the FAD in shallow water (as in PNG). Another capture method involve a pole, line and lure with drive-in-nets (as in the Maldives where several divers herd the fish into a large net set on a coral head)

Bait is also captured at night using light attraction and jigging lines, and possibly floating anchor. If lines (very fine) are used for fishing baitfish at night, the rigging usually includes small fluorescent octopus or multicoloured silver woolflies. It is worth mentioning that if the live bait is caught with hook, its removal from the fish should be done very carefully because wounded live bait die very quickly.

The species of small pelagic fish being aggregated may change according to season and time of day; some might be more effective for catching large fish around FAD; such considerations may affect the fishing strategy being adopted by Fishers at a certain time/season. For catching the bait: in daytime with surrounding net or at night with light attraction and jigging lines, possibly floating anchor. In certain areas, bait raised in aquaculture, tilapia or mullet, has been used (see Figure 10 also).

To keep baitfish alive on board, water tanks with water circulation can be used. When a small boat is used, a cheap solution is to keep the bait fish in a woven basket attached to the outside of the canoe. Baitfish can also be stored for several days in a large floating fish trap. In respect to bait utilization, it is worth mentioning that specific skills are required, first for catching the bait, then for keeping it alive.

The options in term of fishing gear are summarized in the table below:

Finally, it is rather common having near to FAD competition between small-scale methods and larger scale ones; the benefit of small boats fishing near to a FAD installation with lines would, in many cases, stop with the arrival of a larger vessel with purse seine. There is, in many areas, a strong need for management measures for fishing operations on FAD: i.e. specific regulations, possibly with some time allocated to small-scale fisheries.

4. POTENTIAL PERFORMANCE OF FISHING GEAR

It should be kept in mind that even with a FAD, there are normally fluctuations in yield (for many reasons), whatever fishing gear is used. In general, there is a higher yield with all fishing gear at sunrise (for this reason, some boats prefer to stay out during the night near to the FAD to be ready for fishing at sunrise when boiling of hungry tuna is frequently observed). Generally, the yield is less at sunset when fish schools are feeding.

Certain fishing techniques and specific methods for certain tuna species are more appropriate than others around FAD making those, in principle, more effective. FAD affect the expected performance of certain fishing gear and may guide fishing practices (e.g. shoals of tuna are often larger near FAD and the risk of escapement before complete closure of the purse seine is reduced; more chance when setting at dawn; more mixed species within a shoal)

The profit from a specific fishing method in small-scale fisheries will greatly depend on the distance of the FAD from the coast (fuel cost for sailing to and back); ratio between fishing time and sailing time.

A grouping of small shoals of fish aggregated to several light FAD within a large shoal is, in many cases, worth before setting a large surrounding net.

The effectiveness of any fishing near a FAD will depend on the sea conditions and current; it will also depend on the quantities of bait fish aggregated by the FAD and availability of them for the fishing operation.

It is not known whether fishing effectiveness, trolling in particular, depends on the position of the FAD versus the coast or versus other aggregating devices (Feigenbaum, D, Friedlander A. and Bushing M, off Puerto Rico; 1987)

When there are many boats around a FAD competition will reduce the individual yield. A lone boat arriving first at an offshore FAD with a shoal of fish around it will obviously make a better catch. The relative positions of the FAD to each other should be decided carefully and fishing activities around the FAD should, as already mentioned above, be properly managed in respect to fishing effort (number of vessels at the same time), time or season, etc.

In shallow water, the experience shows that optimal conditions consist in the association of FAD and benthic artificial reefs (in this respect, for the Caribbean: see the experience on 30 m deep bottom by Beets, J. off the US Virgin Islands, 1987). At the same time, the yield from artificial reefs could be increased by the addition of a series of small FAD: “midwater aggregators would be a cost-effective method of enhancing reef fisheries” (McIntosh Marine USA; 1984).

In general the profit made in artisanal fisheries with the use of FAD is more for fishing units for which fuel consumption is an important component from an economic point of view. If there is (for any reason) no substantial increase of the yield when fishing near to FAD, at least, the aggregation device allow a decrease of expenses for fuel by a reduction of the sailing time and for searching the fish.

5. POTENTIAL MEDIUM TERM IMPACT ON FISHERIES COMMUNITIES

As already mentioned there may be competition for fishing around FAD. This may lead - to conflict between fishing gear which cannot or will have difficulties cohabiting; - to excessive landings making the fish price drop on the local market leading to stronger and stronger competition; - to the disappearance of the less effective fishing gear; - to excessive investment in fishing equipment.

A FAD affects the species distribution in a given area. There is, in general, no evidence that FAD enhance the total fish resource in a given area. In areas with limited fish available it will be scarce in the neighbouring area if it is concentrated around the FAD. In the areas where the fish is scarce, less fishing methods are effective (e.g. trolling).

6. SITUATION AND POTENTIAL IN THE CARIBBEAN

6.1 Situation

Published in 1996, the FAO Fisheries Technical Paper No. 357 describes fisheries and related research for tuna and other large pelagic fish in the Western Central Atlantic as follows:

Regarding the evolution of the fisheries, the following observations are reported: In several countries of the region (St. Vincent, Grenadines, St. Lucia, Trinidad and Tobago, Barbados, Venezuela) longlining has been developed for large pelagic fish and trolling vessels have been converted for longlining over the last twenty years. Larger vessels mean more power and number of hooks per day resulting in increased fishing capacity were introduced in the fisheries. Increased fishing capacity was also observed with fishing methods other than longlining such as trolling (e.g. in Trinidad and Tobago where the capacity of the troller was doubled), on pelagic fish other than tuna (e.g.flyingfish), with boats making several days fishing trips.

Besides the fishing capacity/effort of small boats, fleets of larger vessels from inside and outside the region have been competing for the same resources. The larger vessels include longliners from Cuba and Venezuela, industrial purse seiners from Venezuela (the capacity of which was multiplied by 6 in the 1980' s), and longliners from USA,.

In the same FAO document, regarding tuna and other large pelagic fish stocks, it is worth observing, from the following list, that several of the main stocks are estimated to be either over or at least fully exploited:

Northern bluefin tuna: considerably overexploited;
yellowfin tuna: at or near MSY;
blackfin tuna: unknown;
albacore: Probably near full exploitation;
bigeye tuna: at or above MSY;
Atlantic sailfish: according to ICCAT, in 1996, at least fully exploited, if not overexploited;
blue and white marlin and swordfish: overexploited;
mackerels and dolphinfish: unknown;
skipjack tuna: still being discussed
wahoo: unknown

6.2 Opportunities

Experience (in other parts of the world and in the region) shows that progress regarding fishing gear and methods could be made in particular for small-scale Fishers to be more effective beyond the surface in deeper waters. For example blackfin tuna are known to shoal in midwater and improvement of fishing methods for fishing in mid-waters would probably allow an increase in catches of this species. More swordfish could also be caught in mid-water. Other species of tuna, such as albacore (Thunnus albacora), are met in waters deeper than those exploited now by artisanal fishers locally, such as bigeye tuna (Thunnus obesus) and bluefin tuna (Thunnus thynnus).

As already mentioned, getting live bait is often a problem for Fishers, so there would be a particular interest in techniques which do not require it. Another potential is fishing with traditional methods near the surface at night as certain mid-water species migrate to the surface during the night. In this respect, it is worth mentioning the recent development of night fishing off La Réunion and Comoros, in the Indian Ocean, with traditional techniques, normally used in daytime, which gave promising results.

At the same time, the capacity of vessels needs to be improved: larger motorized, decked vessels able to sail farther offshore for more than one day. Regarding existing opportunities in mid-water, equipping vessels, including smaller ones, with echo-sounders would improve performance. Consideration should also be given to the fact that, in many cases, there are fluctuations in the availability of large pelagics, even around FAD. Therefore the artisanal fisheries near FAD might be seasonal (reflecting to a certain extent the actual fishing season from December to June) so the boats must be in a position to use alternative methods off-season.

At the same time it would be worth making efforts to improve the potential value of certain species which are attracted. This means first of all improving fish handling on board (keeping it fresh, in shade, with use of fresh sea water) then either progress in the processing of the fish or market development (to increase the interest of potential consumers) or both. In the region, for instance, a potential exists in this respect with bigscale pomfret (Taractichthys longipinnis).

7. CONCLUSION

However, while FAD have been experimented in the region for more than thirty years, it is worth remembering that a key element is still (there as everywhere else in the world) finding a way to extend the life of the anchored FAD. In particular this can begin by reducing the destruction of the FAD by local fishers themselves. This draws attention to the importance of intensive extension work to explain and justify FAD to potential beneficial professional groups. Regarding life duration of the FAD, it is also worth reporting that in French Polynesia, fishing gear tangling with the mooring line, in particular with mid-water techniques, was found to be the main cause of FAD loss (up to around 70-80%).

At the same time, more research work is required on the attracting power of drifting objects.

Note: It is worth mentioning that SPC, the Secretariat of the Pacific Community, based at Noumea, in New Caledonia, published some very useful material concerning FAD which includes in particular: - “Vertical longlining and other methods of fishing around Fish Aggregating Devices”, a Manual for Fishers; 1998; - “Trolling techniques for the Pacific Islands”a manual for Fishers, 1987; - “Fish Aggregating Device (FAD) Manual” of South Pacific Commission; 3 volumes + a floppy disk regarding planning FAD programmes. Most of the illustrations in this paper are taken from these documents.

Figure 1a The marine life related to a floating object

Figure 1b: Typology of aggregations around fish aggregating devices: (a) "deep-scattered fish"; (b) "intermediate scattered fish" and (c) "shallow schooling fish". For each type of aggregation, a schematic histogram of TS values distribution observed is represented. (Josse et al., in Aquat. Living Resour. 13(2000) 183-192)

Figure 2 Handling in deep water live-bait

Secretariat of the Pacific Community (SPC)

Figure 3. Handling in deep water

Secretariat of the Pacific Community (SPC)

Figure 4. Horizontal longline

Figure 5. Vertical longline

Secretariat of the Pacific Community (SPC)

Figure 6. Fishing with trolling lines

Secretariat of the Pacific Community (SPC)

Figure 7. Fish Aggregating Device with detachable aggregating device to allow encircling by a surrounding net

Figure 8. Liftnet, drive-in-net

Figure 9. Floating trap attracting and retaining small pelagics

Figure 10 Fishing for bait with handline

Secretariat of the Pacific Community (SPC)