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Artificial Reefs and Fish Aggregating Devices Experienced fishermen realize that fishing is often better in the vicinity of submerged objects such as rock outcroppings, shim wrecks, reefs, and logs, than in areas where the bottom is flat and barren. Many fish are attracted to the submerged objects on which marine plants and animals may grow. These communities serve as a basis for a marine food chain that provides food for larger predators. Submerged objects also provide shelter and spawning grounds for some fish and invertebrates (figure 3.1~. Artificial reefs are man-made or natural objects specifically placed to attract fish, provide or improve fish or shellfish habitat, and increase fish biomass locally. Extremes range from traditional designs frequently made from local scrap materials to modern Japanese-style artifical reefs that are highly sophisticated modules built of concrete, fiberglass, or steel. The extent to which artificial reefs increase fish biomass or redistribute existing stocks of fish is not clear. However, even if they do not substantially increase fish production, they can be used as effective fisheries management tools. The increased standing fish crop around artificial reefs reduces fishing effort and, therefore, saves time and fuel. Fishermen in developing countries often must limit their efforts because of high fuel costs. Furthermore, artificial 85
86 FISHERIES TEClINOLOGIES FOR DEVELOPING COUNTRIES Water Surface ~ I Floating Water Column Benthic High Profile Mld-Water I l Reefs I ~ . .__ _ _ . 1 Benthic ' Low Profile Bottom lo= FIGURE 3.1 Depending on the marine environment and the target fish, high- or low-profile benthic reefs, or coating or midwater fish aggregating devices may be used to attract fish and facilitate their capture. (J. McGurrin, Artificial Reef Development Center) reefs can be used to create fishing grounds for artisanal fishermen who use traps and hook and line gear. Fish aggregating devices (FADs) are structures located at the surface or at midwater depths to take advantage of the attrac- tion of pelagic fish to floating objects. FADs called paycos have been utilized for centuries in the Philippines to attract migrating tuna. Like artificial reefs, FADs can also reduce fishing effort and conserve fuel. ARTIFICIAL REEFS Many types of fish live around reefs, plants, and corals. Arti- ficial reefs function like natural reefs providing shelter, spawning,
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 87 and nursery areas for reef fishes. Additionally, the algae and inver- tebrates that rapidly colonize the submerged structures provide a food source for some species. Two approaches are possible for an artificial reef program, depending on available resources. Commonly available materials can be used for reef construction where funding ~ limited. Even these materials must be prepared to withstand extreme weather conditions, however. The second approach is to fabricate specially designed, essentially permanent, structures. This usually requires well-funded programs, steel and concrete for construction, and large vessels for placement. The U.S. National Artificial Reef Plan provides general guide- lines for the placement of artificial reefs. If possible, the site should be near fishing villages to simplify the logistics of installation and to minimize time, travel, and fuel consumption before the fish can be processed on land. An artificial reef should not be placed in commercial fishing areas unless it is specifically intended to close an area to these operations. Recent research suggests that the reef site is more important than the design. The artificial reef should be located at least 60~ 1,000 m from natural reefs; otherwise, the fish will tend to swun from one to the other. Sites with strong tidal currents should also be avoided because these currents will cause erosion around the reef, unless the bottom is hard. Mouths of rivers where siltation may bury the reef should also be avoided. A constant current quite acceptable and is favorable to benthic filter feeders inhabiting the structures. The long axis-of the reef should be perpendicular to the prevailing current and along fish migratory patterns. The depth of the reef must be appropriate for the target species. A firm sand or shell bottom is most suitable for an artificial reef to prevent subsidence. The bottom profile should be flat or gently sloping. Soft clay, silt sedunents, and areas that are already biolog~cady productive should be avoided. High wave energy locations and areas with seasonally shifting sands should not be considered. The Japanese national program suggests that artificial reefs should have a hierarchal arrangement where modules form sets, 10-20 sets form a group, and several groups form a reef complex. They advocate minimum effective sizes of 400 m3 for a set and 50,000 me for a group, with at least a 1-km separation between each group. This approach In developing countries would be far
88 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES beyond the means of artisanal fishermen; it would require strong national assistance. Many locally available materials can be effectively used as artificial reefs. They should provide an appropriate habitat, be structurally sound, and firmly secured to the bottom. The ac- tual choice of material will be based on what is readily available and economically feasible. Bamboo, rattan, and stone are typical materiab that have been used. Bundles of Brush Tn all areas of the world, fishermen have used simple bundles of brush to attract fish into hiding places and thus facilitate the catch. Bundles of brushwood are tied to lines to capture crabs, shrimp, and small fish in Japan, the Philippines, Indonesia, and Vietnam. The fish are harvested by shaking out the bundle into a scoop net. In Central Africa, boxes full of leaves are placed on lake or estuary bottoms. Fishermen lift the boxes out of the water and shake them to collect the small fish. Ivory Coast fishermen place coconut palm fronds in shallow water to attract shrimp. While one person drags the frond to shore, another follows with a scoop net and gathers the fleeing shrimp. In the protected areas inside the keys on the south coast of Cuba, fishermen are still using "mangrove fisheries." These structures are located in 4~5 m of water, usually in sea grass (Thallasia) beds. To build these strcutures, one needs a notched tree trunk about 1 m tall, two smaller branches nailed transversely, and a bundle of mangrove boughs, 4~5 m long, whose ends are placed into the two openings of the tree trunk. The bundle may have a diameter of almost 5 m and a height of 3 m. The structure may be fished about 15 days after installation and, thereafter, at intervals of 15-45 days. It usually lasts about 1~12 months. One small boat may fish up to 150 mangrove fisheries. Brush Parke In the Philippines, SEAT! (Samar Sea-Ticso Pass Fisheries Development Corporation) has developed several Brush parks to provide shelter ant] spawning areas for fish. Each unit In the
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 89 park is a tripod made of ipil-ipi! wood (Leucaena leucocephala, a fast-growing tropical tree). The tripods stand about 3.~5.0 m tall. Horizontal crossbeams lashed on with nylon twine hold the tripod together. Villagers hang fallen coconut palm fronds from the horizontal beams. The units are placed in calm, shallow coastal waters and are held down with stones. The palm fronds have a useful life of about 3 months while the frames last about a year. Preliminary results from SEAT! indicate that a Month har- vest of the brush units with nets yields between 10 and 20 kg of fish per unit. Croaker, squid, rabbit fish, barracuda, and anchovy are among the species caught. The algal and invertebrate growth on the structures is a food source for many species of fish. Others enjoy the safety of the structure's interior. A brush park near San Jacinto Island, Masbate Province, Philippines, includes about 4,000 units. A trap net, constructed of bamboo, has been built in the center of this underwater forest. The final section of the trap net is regularly hauled. The undersized catch is returned to the sea to avoid depletion of the stock. Lobster Shelters Lobsters prefer a living space only slightly larger than the size of their bodies. Traditional Cuban artificial reefs have been developed based on this behavior. The shelters are usually constructed of mangrove branches that are about ~12 cm in diameter. The two thickest sticks are placed parallel to each other at a distance of 1.5-~.8 m. Two other parallel branches are placed above and transversely to the first layer. The two layers are nailed together or fastened with galvanized mire. A third layer or roof of branches is added to the structure. These additional pieces of wood are fastened to the second layer with some space between branches so that light can enter. Another level may also be added. The finished sandwich structure measures about 2-2.5 m on a side (figure 3.2~. These lobster shelters are used in shallow waters (~6 m) that do not have strong currents. The number of shelters occupied is high, especially when the structure has been in the water for some time and supports algal communities. Shelters must be checked and repaired annually. The lobsters are caught by several methods. Fishermen in a boat may shake the shelters with a hook and catch the lobsters
90 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES 1 1 In He A, L;j~t,~,~,~~~,~j~ rid 7~C~~3~ ~!L~'t'-It'd Or. i i . [. ~ ~~ _ _ . . .. .. _ ~ . ~ _~ ~ - an 1. 1 ~ ~.~S-~ ~ ~ W ~ ~ ~ ~ . , , . ~ . ~ ~ . ~ . ~ ~ ~ ~ . ~ ~ ~ ~ ¢ . , ~ ~ ~ ~ ~ ~ ~ ~ ~q~J.~f,jj,.~, ~~ ~ -~ Ad~~;~-~-~-~- ~-:~-~ < ~. FIGURE 3.2 A traditional Cuban lobster shelter is used at 4-6 m depths to attract lobsters and facilitate their capture. with a scoop net as they escape. Divers may also facilitate capture and trap the lobster in nets as they scurry away. In the Gulf of Batabano on the south coast of Cuba, fishermen from local cooperatives have placed some 120,000 lobster shelters and annually harvest 7,000 tons of lobster from them. Shelters are increasingly being constructed of ferrocement, since it is illegal to cut mangroves. Moreover, ferrocement has a longer life than wood. The ferrocement shell is mounted on two wooden branches that may sink into the sediment, leaving space for the lobsters under the shelter. In the Mexican state of Quintana Roo on the Caribbean, fishermen have operated an extensive artificial habitat for spiny lobsters (Panulirus argue) since the late 1960s. About 10,000
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 91 1.5-m2 shelters have been installed in a back-reef and bay area. The shelters are constructed on a frame of the trunks of the thatch palm (figure 3.3~. Originally, the roof was also made of this palm, but newer styles use a variety of materials including barrel lids, corrugated roofing material, and ferrocement (figure 3.43. The shelters are known by a number of different names including casitas, sombras, and casas Cabanas, the latter designation in honor of the fishermen who introduced their use. The shelters are assembled on shore and then ferried to areas of shallow water where they are sunk. They are positioned about 20-30 m apart, and are reported to last for ~8 years. Rubble and Rocks The traditional Japanese artificial reef involved simply placing shore or quarry rocks at shallow depths as a way to enhance fishing grounds. In northern Japan, fishermen have placed rocks to enhance kelp production since the late 1600s. In the 1870s, fishermen from Toneichi, Twate Prefecture, transported more than 100,000 rocks (40-50 cm in diameter) for the cultivation of seaweed. Currently, rock reefs are used in Japan to enhance seaweed production and to create habitats for abalone, snails, sea urchins, crayfish, and sea cucumbers. The size and arrangement of the rocker depend on the target species. A single layer is sufficient as a seaweed substrate. Imrna- ture sea urchins and abalone prefer crevices, and for these species a layer of rocks 0.4-0.6 m high is ideal. Higher piles of rocks are useful for attracting fish. Since rocks may be moved or buried by storms, they are often placed in an enclosure called a futon cage because it has the shape of a Japanese floor mattress. Futon cages are now made of synthetic fiber nets. They measure 4 x t.2 m and are about 0.5 m in height. The rocks used have diameters of 2~50 cm. Because of their weight, futon cages are quite stable on the sea bottom. The cages are placed in a solid area or in a line with 2 m between cages. Alternatively, they may be arranged to form a 10 x 14 m rectangle. Thousands of futon cages are employed in northern Japan.
92 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES FIGURE 3.3 Mexican fishermen construct a lobster shelter similar to those used in Cuba. (D. L. Miller, World Wildlife E`und)
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 93 FIGURE 3.4 Ferrocement slabs can be used to make a more durable lobster shelter. (D. L. Miller, World Wildlife Fund) Tires In many developing countries, old tires have a high economic value and, therefore, may not be appropriate for artificial reefs. However, tires do not disintegrate in seawater and are fairly easy to handle. Scrap tires are somewhat problematic as reef materials be- cause of their low density and tendency to trap air. Regardless of the number of tires that are secured together in a bundle, the struc- ture will move with currents and wave motion unless adequately ballasted. In Virginia and New York (USA), slit tires have been imbed- ded in a Tom concrete base for use as a reef module. A steel rod or cable is passed through the tires for additional reinforcement. Once placed, these units may subside slightly, but have shown no tendency to move or deteriorate (figure 3.5~. Researchers at Oregon State University (USA) have investi- gated the underwater stability of various types of complex tire configurations. Among these are rows, triangles, rosettes, and even one tire stuffed into another (figure 3.6~. All the tires were ballasted with concrete to increase the submerged weight. This
94 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES study tested the feasibility of a 500,00~tire reef planned for waters near Winchester Bay, Oregon. Thailand's Department of Fisheries sponsors numerous arti- ficial reef projects at Rayong in the Gulf of Thailand In order to develop fishing grounds for artisa~al fishermen. Automobile tires are among the materials used In these projects. The tires are tied with wire into quadripod modules, each containing 8 tires (figure 3.7~. Each artificial reef project employs between 50 and 560 mod- uTes of water depths between 4 and 18 m. Another program near the National Institute of Coastal Aquaculture at SongkhIa uses structures of 40 tires tied together in 2 rows of 20. The units are placed in water depths of ~7 m. An experimental artificial reef constructed of old tires has been placed near Haifa, Israel. The Fisheries Technology Unit of the Israel Ministry of Agriculture sponsored this project. Since the eastern Mediterranean Is very unproductive and h" a flat, sandy bottom, it offers little refuge and few spawning sites for fish. The artificial reef succeeded in increasing the fishery yield. The principal unit had a concrete base that was 3.3 x 3.3 m. FIGURE 3.5 Scrap tires can be used to make artificial reefs, but unless firmly ballasted, they will be swept away by waves, currents, or storms. (D. Feigenbaum)
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES (A) 6$ 55 (B) ~ .68 tot Configu- Dimensions (inch) Tsteffed .~' EN v. ( D ~ I. O ) ~ W4.i 4: In,, 1.7SX~05 Top ~ °.~} -I Elev. 2.72 rosette ~ - ~ '2 at 82 . , ro5etIB ~ ~ 1 5 65 ~ 7-~6 0-~! 20 T'res t~- (D8I.3') :( _ __ (tt2) v(ft3) .5 x ~.] fez ,.. .34 (A) $: 1.68 (8) ,_~ 2.53 80.2 1.5 X ~ . 22e 2.22 S.78 4.91 .Bt) x to "W ", 2.29 1 15~ 1 LIZ} ~ . 95 10x 91t ~ L as x 8.89 20 X ~ L .., FIGURE 3.6 Scrap tires can be combined in many ways for various-sized reefs. Tires were connected to the base by a framework of steel bars (figure 3.8~. In an effort to increase the spaces and surfaces of the tires, some of them were placed vertically, some horizontally. The 3-m high structures were constructed on land and Towered into the water with a crane.
96 FISHERIES IECNNOLOGIES FOR DEVELOPING COUNTRIES ... , .~.~.~.~.~ A- -- ~! . . ~ .-. in ':-. ~ ~.~j~...9 2:.:. (,.,.".., .,~ .:- .2.'2",.~.~ - FIGURE 3.7 In Thailand, automobile tires are assembled for an artificial reef. (J. Munro) Cement and Concrete Structures Although too costly for most artisanal fisheries cooperatives, concrete artificial reef modules could be used In a national fisheries plan to benefit small-scale fishermen. These materials are durable, of sufficiently high density so as not to be displaced by bottom . . .. currents, and can effectively close an area to trawling. The Japanese are leaders in this technology and have devel- oped hundreds of types of concrete modules to improve fishing grounds. The simplest structures are open concrete cubes with sides measuring 1 m, although larger varieties also exist. A vari- ant has an algae-covered mesh on the cube's top surface. Other structures are cylindrical and box-shaped with many variations in the size of the openings. An igloo-shaped unit has given encour- aging results in the Chesapeake Bay in the eastern United States (figure 3.9~. Damaged concrete pipes have been used for artificial reef con- struction in Hawaii. The pipes varied from less than 0.3 m to as much as 2 m in dia~neter and from 0.3 to 4 meters in length. Many
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98 FISHERIES TECHNOLOGIES FOR DEVELOP~G COUNTRIES FIGURE 3.9 An igloo-type structure is fabricated for deployment in the Chesapeake Bay, USA. (D. Feigenbaum) tons of concrete pipes have been placed on the flat and sandy bot- tom in 23 m of water off the western coast of Oahu. Standing fish crop estimates were 5-10 times higher than the pre-reef counts. Juvenile fish grew to maturity on the reef, indicating that pro- ductivity can be improved for more sedentary species. Pyra~nids of 6 pipes, 0.6 m In diameter and 3 m in length, hare also been evaluated in Virginia (figure 3.10~. In Taiwan, concrete blocks have been used on sandy bottoms for over 10 years. Recent efforts have centered on placing concrete modules on the bottom under floating fish cages and longline oyster cultures. The blocks have a volume of 1 m3 and are placed in 12-15 m of water. The inner space is designed as a shelter for such reef fish as snappers and groupers. The primary objective of the artificial reef program in the Gulf of Thailand is to enhance fishing grounds for artisanal fishermen. Rayon g was the site of the first reef, which was constructed in 1978. Seventy concrete framework cubes measuring 0.5 m on a side and 50 quaciripod modules of 8 tires each were dropped in 18 m of water over an area of 1,200 m2. Additional reefs have
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 99 FIGURE 3.10 Damaged drainage pipes are widely used as artificial reefs. (D. Feigenbaum) been constructed annually since 1978. All were situated on sandy bottoms near fishing villages. Concrete modules have been placed throughout In the 50~km2 project area. If the area is trawled, the trawl nets will be damaged by the concrete modules. The hypothesis is that the artisanal fishermen's catch using traditional fishing arts will increase in areas where trawlers are excluded. In other areas, trawler exclusion modules are also being combined with groups of artificial reefs. The artificial reef at SongkhIa, which was constructed in 1982, covers 2,500 m2 of sandy bottom. Different types of modules have been used in this project. Twenty Entire units were placed at ~7 m water depth during the first year. One hundred twenty open concrete cubes measuring 0.8 m on a side followed in 1983. Juvenile green sea mussels were attached to the cubes before placement to increase biomass at the site. Evaluations of the fish catch at the Rayong reef have been inconclusive. A definite change in composition of the catch has been noted, however. Predeployment catches indicated a typi- cal soft-bottom community dominated by croakers and catfish.
100 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES Catches at the reefs show a high proportion of valuable groupers and snappers, which normally are not found on muddy bottoms. An additional artificial reef site is near the Phuket Marine Fisheries Station in the Andaman Sea, Thailand. In that area, 10 reefs have been constructed of tire modules, concrete cubes, and pipes (figure 3.11~. The reefs were placed in parallel rows, perpenclicular to the trawling path to hinder trawling. Fiberglase-Remforced Plastic Although most fabricated artificial reefs are produced from cement and scrap tires, fiberglass-reinforced plastic (FRP) has also been used. In the United States, ribbons of FRP have been bonded into open-mesh cylindrical shapes (about ~ m in diameter and 5 m in length), and then joined in arrays of 2-10. The raw materials for these units are readily brought to shore areas and are relatively easy to assemble and float to the desired area of use. Cement ballast is used to anchor the units (figure 3.12~. In a Florida trial, ah of the components for the FRP reefs were shipped from Japan and assembled at dockside. The units were : ~~_~ FIGURE 3.11 Concrete cubes are fabricated for an artificial reef in the Andaman Sea, Thailand. (J. J. Polovina)
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES _ .. .... . , ~ - ~ . . __ - - ~~ . ~.~.~ ~ ~~ ~ ~~ .. ... ~ ~ ~ ~~ It T:: S~ -hi ~~ ~~ ~ ~ ~ ~~ ~~ ~~.~ ~ ~ ~ -if if_ .::- :2~:'~'~"~:~:~2~'~.~ :'' ''-?- ~~ ~ ~~ ~ :~ :~ ~ ~ I_ :, . :; .,,,.,.'.': :''.-,,- I. ~~: :~ ~ ~ I.- ~ :: . ~~ ~ ~ ' ' -2~ ~2~'.~ i'- ~ ~-~'"~'-'~'~ I'm ~ ~~?¢~ ~~ ~ ~ ~~ ~ ~ ~~ ~~ ~.~ ~ ~ i.: -_r ~ jaw :~ Air' ,",.2~'~"~''~: "'', ~'~,~,1~'~ ,~ ~~l~d~ ;~ 441~,>~, ~ T~ ~ ' ~ i' ~ ~ ~~ ~ ~ ~ ~ ~~ ~~ ~ ~ ~ ~ ~ ~~ ~~ ~~' ~ - ~~ ~ ~~ At'"" '.~ "'W':iL:N':~i~i~ I' 'Nazi ~ 'a ''"' ~'~ ~~ . ~ ~.~- ~- ~. hi. ~.~i~i~i~.~:~i~$: item: -iii~i if i: :~r~iji~ij~ ~ ~:ii:i~:.i:~: ~ - i::- :i ~~:~j~j~:~ j~.~.~ ~ i. ,. i, i:. ~.~.~ ~ ~.~..~ i, ~j~ ~ ~~ Jo jj~j~j. I~ ~ ~ ~ jive iii ~ ~~jjjj j:' j jjj~ j~j~ ~ j j I ~ :: ~ ~ ~ : ~ : i:: A ~~ jig :: ~j~j~ ~j~j j ~~j,j~.~j-j~.~- ~..~.~ -. ~~j~j~jI~-~ jj~jj~jjj~j~jj~'jj~j~j.~.~jjj~j~jjjj Wi :j~j:.- ~~ :j-~ ~~j~:~ j ~~ jig jjj~j~ i~i~.~.~i-.~,~ ~~,-.~.. . -. . -..~-.~.i~.~-iiii:~i~iii~ i~i~i~:~i~iiii~:ii~i~i~i:i I ~~ ~ j ., :~ , j Age: ~~ ~ jjj~j~j~ . ~j~j~.~..~.~..~...-~-..~:~.~.~ ~:~j~j~j::~:~:~:~: j~i:i:i~:~:~:~::i:~ ~ ~::::~: ~:~ .: ::- :::i': ::i i~:~i:~:. ,,, i ; , ?~ Jim Ott --I. ,~'..~j ~~-i.j-. .~ :~j, j.,, -a,..., if:: ~',''.:?~.~'~.~'-':,.~.~.'~:~'~ ~ i, ~ ~~ ~ j ~~,.~ ~.:~ ~ i,:?, I.. j.~ :~: ::: j j:j:j:j:j:j:~:j~:j:~ i:: ~ :::~: ~.?~ ::::: :i.~i~: :. i. 101 ~ ~.~ ~.~:~ :. -.-.- ~~.~, ~~ ~~; ~~ ~~'~"-'~'~'~'~.~'~'~'~'~'~.-.~'.::':i.,?.~..~',~:~'Y'~ ~~.~.~.~-..::,~ ~.,~ i.:. hi Alibi.... ~~.:i::i i ti :~ ~ ~~ ' ."'. L ~ :::: :. :...: FIGURE 3.12 A fiberglass-reinforced plastic (FRP) reef is loaded on a barge in Hawaii for deployment at a depth of 120 m to concentrate snappers. (R. Moffitt) ballasted with cast concrete, and reusable airbags were employed to float the units to the placement site. As the airbags were deflated, the reef sank, and the flotation devices were recovered for reuse (figure 3.13~. A concrete culvert reef with approximately the saline size and volume as the FRP unit was constructed at the same site, and a control area in the same vicinity was identified. Research surveys of these three areas were then conducted every 2-4 months. Preliminary analysis of the survey data for the first 18 months indicates that the FRP reefs appear to attract and retain a sig- nificantly greater total abundance and diversity of fish, and have much richer epibenthic communities than the culvert reefs. In particular, the FRP reefs have been more effective for larger mid- water predators such as the greater amberjack and king mackerel, and seem to have a larger number of the bait fish and juveniles on which these predators feed.
102 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES ~ ~~--~ -I - -. At. ~~ -age. :~ :,i,~-~.- - -I- ~~ ~~.~ ~.- ~.~. I - ~ ~~-.- ~.~ ~. ~~ .~.~.~.~.~ ~, ~.~ ~.~ ~,~ ~ ~.~.~.~ FIGURE 3.13 An FRP reef module is positioned for placement off the coast of Florida; (A 1981, Aquabio, Inc. Drilling Rigs When offshore oil and gas drilling rigs become obsolete, they can be used as artificial reefs in some cases. In the United States, Tenneco Oil has clismantIed a drilling rig and moved sections of its steel towers to locations to serve as artificial] reefs (figure 3.14~. =YC!~ ~ ^~^ Ar"Tl~T~ I ~ 1~ Alar - ~~ - An AM ~ JJ~ ~ I Pelagic fish, such as tuna, billfish, yellowtail, mackerel, sar- dines, sharks, and dolphins, are attracted to floating objects from which they seem to obtain some spatial reference. Surface and midwater attractor reefs or fish aggregating de- vices capitalize on this behavior. These may be used alone or in combination with benthic artificial reefs. Although recent FAD designs are made of durable materials, less durable traditional structures have been used for centuries. As a management tool, FADs should be accessible to the target population of fishermen and located in an upwelling zone or along
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 103 Sd`etinnn 86 Ft. Sections of ~ I Towers Hi ~-~ AUanUc Ocean :> - x Clean Floor . FIGURE 3.14 When drilling rigs become obsolete as oil producers, they can become fish producers. Tenneco Oil is relocating steel towers from such a rig for use as artificial reefs off the Florida coast. (R. Brownlee, Miami Herald) a migratory pathway. A combination of artificial reefs with FADs could enhance several different types of fisheries in the same area. FADs might also be used to shift a fishery closer to market or to a safer location. Landings of migratory pelagic species could be increased by locating FADs in areas where bottom-dwelling fish are overexploited, providing an alternative catch to preserve the livelihood of artisanal fishermen. Traditional l?ADs Japanese fishermen still use rafts made of bamboo bundles (1 m x 8 m) to attract dolphin fish (Coryphaena hippurus) and tuna. The fish hiding beneath the rafts are caught by encircling nets.
104 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES DIAGRAM OF KANNIZZATI FLOAT Cork-wood . ~ Marker-nag Corl(-wood .~IS ~X: 1 so cm Anchor ~~ it' 4 mm. SlsaJ Rope \ FIGURE 3.15 Maltese fishermen use these cork floats to attract dolphin fish and pilot fish. Encircling nets or hooks and lines are used for capture. In the Mediterranean, near Malta, dolphin fish and pilot fish appear from August to December. Both of these species seek shelter under floating objects. Maltese fishermen take advantage of this behavior by anchoring cork floats at intervals of about 1 mile to as much as 80 miles from shore. The floats, a signal flag, and a Innestone anchor are linked with sisal rope and are deployed at depths ranging from 150 to 800 m. Fish attracted to these floats are captured by encircling nets, surface long lines, or trolling. This gear is described locally as a kannizzati fishery (figure 3.15~. In the Philippines, payaos (bamboo rafts) are used to attract tuna (figure 3.16~. Fishermen anchor payaos with rocks in very deep water. These rafts are approximately 1.5 m wide, tapered at one end, and about 4 m long. Coconut palm fronds are suspended about 20 m below the surface. The paycos are fished by purse seiners and have produced catches of up to 200 metric tons per set. A very similar technique is used in Malaysia. A lure line is sum ported by a bamboo raft and is anchored in position. The fishing
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES ~ ~ i 2 2 2 ~ ~ ~ ~ . T: .. . ~ ~ ~; ~ . i: ~ ~ ~~: ~ ~ ~ of;':,: ~~ ~~''~ ~ ~ ~ ~ ~~ ~~ ~ ~ ~~ ~ ~? ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ . ~ ..~ ~, ~.~ ~,~.~.~-~.~ ~ ~~ ~ , ~ ~~ ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ ~ :. ~~ ~ I-' ~:~,_..3 I:' : ~ . . :: ~ ~ ~~ ~ ~~ ~ A,.; ~ ~ ~ ~ ~ L.,,.' ~ ~ : :~ ~~ T T~ :~ ~ ~ ~ I,. ~ ~~ ~ ~ ~~ ~~ ~~ ~~ ~~ ::~ ::::: :: : ~ : ~ : :~ :::: :N :: - :: : ::~: :: : : : : : : : :: - . Or :: : : : :: : I:: ::::: :::: :: f ~ ~ it? ,< : god.: ~ : : it.: .. ,_ : ~ ~~' . A ~ ~ hi ~ hi.'': ~1: ' 'f' ~ :~, ~ In An' - ~1 : :: ~ :: `` ~ ::: ~ ~ ~ F ~ `>,, 1 ''' :: Em. ~ ~ ;' :: ., - ~ ,' - A'' ,'',' ~ ~ ~ ~ I: : :: 105 ::::::: ~::~:~: ~:~ :: :: : ~~:~ : ::: ::::::: : :: ~ ~ ::::: :: ::: :: :::::: :::::: :::: ~ :: : : FIGURE 3.16 The top photo shows bamboo raft (payao ) anchored in deep water in the Philippines to attract tuna. (W. Matsumoto) Payaos are about 4 m long and taper from about 0.5 m to 1.5 m wide (bottom). Palm fronds are suspended about 20 m below the raft. (E. O. Murdy, ICLARM Newsletter)
106 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES line, called roempon, is prepared by attaching palm leaves or bun- dles of grass along the line (figure 3.17~. Dip nets or surrounding nets are used to catch the fish attracted to the device. In the equatorial western Pacific, floating branches, trunks, and trees attract large quantities of tuna and other pelagic fish. Diverse, vertically stratified marine populations develop around these logs and trees. Directly beneath the floating timber are communities of smaller fish collectively serving as bait for preda- tors below. Organisms growing on the log provide food for the bait, and the log itself serves as shelter. Sharks occupy the next lower niche and feed on the bait. Tuna occur at greater depths with mixed schools of skipjack and small yellowfin appearing above the large yellowfin and bigeye. Bigeye tuna remain at depths of 50 m or more during the day but move toward the log at night. Skipjack and yellowfin tuna are often seen on the surface during the day, downwind of the log. In addition to the fish, a number of turtle species, sea snakes, sea birds, and marine mammals occasionally visit the log communities. Several characteristics unprove the likelihood of log coloniza- tion: a minimum size of about 2 m in length by 0.1 m in diameter, the presence of submerged branches or roots, and time enough at sea for barnacles and algae to become establishecI. To be most effective, such floating logs should be no closer than 5 km from each other. The catch around such logs can be impressive. Purse-seiners have landed 150 t from the sea beneath a- 2-m log. A Am tree yielded a 1,500-t catch over a 2-week period. For village fishermen, the use of logs or trees as FADs may be a worthwhile approach. Available funds can be devoted to providing a mooring system for essentially free FADs. Modern FADs Recent innovations in FADs improve on the durability of the traditional structures by using plastics and artificial fibers. Used mainly to attract migrating pelagic species, these midwater or surface FADs consist of the main fish attractor, a mooring line, a concrete or sandbag anchor, and a surface or subsurface buoy to suspend the FAD. One type of midwater FAD is constructed from a metal or plastic frame covered with nylon fabric, plastic film, or canvas
107 r3 , . ~n , ,.~\ ~~F '^ ! ~ ~'1 .j! At. j) he,`; , R Con To q, ~ Cal I,: oo 0 - ~ ,£' d o w oo - ._ w ·~ - r3 J Cal C) · CO W ~ O 1_ ~
108 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES ,,,,,., ,,,,, ~ r~:~:~ - -., -, , ~:~::~:~ , -,-., ,, .,.:,.- . ..~. :~ JO ~ ...... ~ ~ ~~ ~ ~~ FIGURE 3.18 Midwater FADs made from plastic rods and nylon fabric have been widely used in the Caribbean. (McIntosh Marine) (figure 3.18~. McIntosh Marine of Florida has designed a large parasol FAD to use in deep water with strong currents. Four plastic rods radiate from a metal alloy cone, and nylon fabric covers them to form a pyramid. These structures measure 5.2 m high by 8.2 m diagonally at the base. The metal cone is attached to the mooring line at chosen depths in the water column. In strong currents, the pyramid contracts slightly due to the force of the water against it, thus reducing drag. A smaller version of this parasol FAD, the mini-FAD, measures about 1.8 m in height. McIntosh Marine has deployed its m~ni-FADs throughout the Caribbean to serve different needs. In St. Kitts, Barbados, and Trinidad and Tobago, midwater fish attractors have been placed to improve landings of pelagic fish for artisanal fishermen and fish- eries cooperatives. In Barbados, a project is being designed to shift the fishing effort from demersal species in an overfished traditional fishing area to migratory pelagic species farther offshore. In recent years, more than 300 surface FADs have been de- ployed in the central and western Pacific and Indian oceans Much of the development work for these structures occurred at the Southwest Fisheries Center Laboratory in Honolulu, Hawaii.
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 109 Tire Buoy 5_ tire filled with ~,~ polyurethane foam \ polypropylene line " chain Single-Sphere Buoy Pentasphere Buoy -a 333 _:_ chain with steamers Cable Not Drawn to Scale \ \:ypropylene Propylene enchain \ chain I; FIGURE 3.19 In Hawaii, several different designs for FADs have been tested. The most successful is the single-sphere buoy. Most of these FADs consisted of two 208-l steel of} drums filled with polyurethane foam and held together in an iron frame with about 13 m of polypropylene rope netting draped from the floats. These FADs are anchored to concrete blocks in water depths of 400-2,300 m. They have been successful in recruiting skipjack tuna {, Katsuwanus pelamis) in quantities sufficient to warrant commer- cial fishing with pole-and-line vessels. Other work in Hawaii has involved FADs with several different designs (figure 3.19~. Tire-based FADs were made from discarded sugarcane truck tires filled with polyurethane foam. These were unwieldy at sea and were replaced by pentasphere FADs. The pentaspheres, made from surplus steed buoys welded together, generated considerable drag under strong current conditions and broke their mooring lines. Single-sphere FADs were then constructed and tested. These produced less drag than the previous designs, and currently all new and replacement FADs have this design. The total catch at 29 FADs over three-and-a-half years was
110 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES _ _ _ ~ surface marker buoy (28"-diameter buoy) 1/2" chain (10 ft.) 1 1 60 feet I 1" polypropylene rope NO CURRENT CONDITION 58"-diameter buoy 3/8" wire rope 1/2" chain TAUT MOORING A_ 3,000-lb surplus anchor FIGURE 3.20 A sub-surface FAD ~ also being tested in Hawaii. estimated at 4 million pounds. The major species captured were yellowfin tuna, skipjack tuna, marlin, and dolphin fish. These comprised 96 percent of the total reported catch. The principal fishing gears used were pole and line, hand line, and trolling. An experimental subsurface FAD (figure 3.20) is also being tested in Hawaii. It consists of a 28-inch diameter marker buoy at the surface attached to a 58-inch diameter buoy at a Fathom depth; the buoy is connected to the anchor line. It is believed that this configuration will better tolerate strong surface currents and storm waves.
ARTIFICIAL REBUS AND FISH AGGREGATING DEVICES RESEARCH NEEDS 111 Although they have been used for centuries, artificial reefs and FADs have not been subject to rigorous scientific analysis. Liter- ature on artificial reefs tends to be descriptive and speculative, not quantitative. Efforts have centered around reef construction and design, but little ~ known of the basic biology involved or the impact of the reefs on the fish stocks. The relative importance of attraction versus production must be addressed. This will require collection of catch and effort data from a wide variety of artifical reef sites before and after deployment, and must include adequate controls. Improvements can be made in reef designs. The optimal reef size, configuration, and design should be determined for various environments and purposes. Experiments should be designed to include both controls and replicates. Cost-effectiveness should be determined, especially for developing country applications. Specialized reefs for fish recruitment, growth, and spawning need to be developed. The use of artificial reefs as stocking sites for juveniles from a land-based hatchery should be explored. Little ~ known of the social benefits of artificial reefs and FADs. Conflicts between users must also be explored and reduced. [IMITATIONS Although in practice artificial reefs and FADs have enhanced fisheries in certain areas, they are not a panacea for Al problems in fisheries. Since the deployment of artificial reefs has generally resulted in substantial aggregations of fish, the use of such devices without careful planning is not recommended. Prior to use, careful thought must be given to possible long- ant! short-term effects on the general environment in which they are deployed. Increased ease of capture also increases the danger of overexploitation. User conflicts may result over the commercially valuable catch at the reef site or from a decreased stock in adjacent fishing grounds. Reef construction costs vary widely with location and type of construction material. Caution must be taken to avoid toxic materials that may contaminate the environment. For ex- ample, oil and gasoline should be removed from vessels or vehicles before they are deployed as artificial reefs.
112 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES SELECTED READINGS Artificial Reefs and ]?ADe Alevizon, W. S., V. C. Gorham, R. Richardson, and S. A. McCarthy. 1985. Use of man-made reefs to concentrate snapper (Lutzjanidae) and grunts (Haemulidae) in Bahamian waters. Bulletin of Mannc Scicnec 37~1~:3-10. Bailey, K. 1985. Loge as Fish Aggregation Dances in the Equatonal Wc~tcrn Pa- cific. Fisheries Research Division, Ministry of Agriculture and Fisheries, Wellington, New Zealand. Bohnsack, J. A., and D. L. Sutherland. 1985. Artificial reef research: a review with recommendations for future priorities. Bulletin of Mannc Science 37~1~:11-39. Boy, R. L., and B. R. Smith. 1984. Design Improvement to Fish Aggregation Device (FADJ Mooring Systems in General UP in Pacific Island Cour~tries. South Pacific Commission, Noumea, New Caledonia. Bergstrom, M. 1983. Review of E~pericnec~ With and Present Knowlcdgc about Fuh Aggregating Dc~nec`. Bay of Bengal Programme, BOB P/ WP/ 23, Madras, India. Campos, J., and H. Gusman. 1986. An artificial reef for artisanal fisheries enhancement in Costa Rica. ICLARM Newsletter 9~2~. Chang, K.-H. 1985. Review of artifical reefs in Taiwan: emphasizing site selection and effectiveness. Bulletin of Mannc Scicnec 37~1~:143-150. De la Torre, R., and D. L. Miller. 1985. Update on the Mexican Caribbean's artificial habitat-based spiny lobster (Paru~lirw argue) fishery: the eval- uation of design, material, and placement optimums. Proceedings of the 88th Gulf and Caribbean Fuberic~ Ir~titutc Annual Meeting, Martinique. D'Itri, F. M., 1985. Artificial Reefs. Lewis Publishers, Chelsea, Michigan, USA. Doulman, D. J., and A. Wright. 1983. Recent developments in Papua New Guinea's tuna fishery. Mannc Fi~hencs Review 45~10-12~:47-59. Feigenbaum, D., C. H. Blair, J. R. Martin, and M. Kelly. 1985. Virginia's artificial reef study: description and results of year I. Bulletin of Mannc Scicnec 37~1~:179-188. Feigenbaum, D., C. H. Blair, M. Bushing, L. Parker, D. Devereaux, and A. E`riedlander. 1986. Artificial Reef Study. Technical Report 8~. Department of Oceanography, Old Dominion University, Norfolk, Virginia, USA. Galea, J. A. 1961. The "Kannizzati" Fishery. Technical paper No. 7. Fisheries Department, Malta. MacLean, J. 1986. Who's working on artificial reefs? ICLARM Newsletter 9~2~:22-23. Madbu, S. R., and M. Bergstrom. 1985. Fish aggregating devices. Appropriate Technology 12~3~:22-24. Matsumoto, W. M., T. K. Kazama, and D. C. Aasted. 1981. Anchored fish aggregating devices in Hawaii waters. Marine Fubcmce Rctnew 43~9~:1-13. Matsumoto, W. M. 1982. Structured flotsam as fish aggregating devices. NOAA Tcchrucal Memorandum NMFS, SWFC-22. NOAA, Washington, D.C. USA. Miller, D. L. 1983. Shallow Water Mariculturc of Spiny Lobster (PanuliruJ arywJ in the Western Atlantic. Department of Geography, SUNY College at Cortland, Cortland, New York, USA.
ARTIFICIAL REEFS AND FISH AGGREGATING DEVICES 113 Mottet, M. G. 1982. Enhancement of the Marine Environment for Fisheries and Aquaculture in Japan, Technical Report No. 69. Department of Fisheries, State of Washington, Seattle, Washington, USA. Nakamura, M. 1985. Evolution of artificial fishing reef concepts in Japan. Bulletin of Manne Science 37~1) :271-278. Parker, R. O. Jr., R. B. Stone, C. Buchanan, and F. W. Steimle, Jr. 1974. How to Build Marjorie Artificial Reefs. Fishery Facts 10, NOAA, Washington, D.C., USA. Patton, M. L., R. S. Grove, and R. F. Harman. 1985. What do natural reefs tell us about designing artificial reefs in Southern California? Bulletin' of Madeira Science 37~1~:279-298. Sato, O. 1985. Scientific rationales for fishing reef design. Bulletin of Marine Science 37~1~329-335. Scott, P. C. 1985. Fish aggregating buoys in Brazil. ICLARM Newsletter (April):11. Sheehy, D. H. and S. F. Vik. 1982. Japanese ArtificialReef Technology. Aquabio, Inc., Annapolis, Maryland, USA. Silva, A. F. 1975. Observaciones sobre arrecifes artificiales usados pare pescar en Cuba. Serif Ocear~ologica, No. 26. Sonu, C. J. 1983. Review of Japar~e~e Fishing Reef Technology. Tekmarine, Inc., Sierra Madre, California, USA. Sonu, C. J. and R. S. Grove. 1985. Typical Japanese reef modules. Bullet of Marine Science 37~1 ) :348-35 5. State of Hawaii. 1984. Environmental As~cs~mcut and Negative Declaration Hawaii Fish Aggregating Decree System. Department of Land and Natural Resources, Hawaii, USA. Stone, R. B., C. C. Buchanan, and F. W. Steimle, Jr. 1974. Scrap lores as Artificial Reefs. Report SW-119, EPA, Washington, D.C., USA. Stone, R. B., H. L. Pratt, R. O. Parker, Jr., and G. E. Davis. 1979. A comparison of fish populations on an artificial and natural reef in the Florida Keys. Manne Fisheries Review 41~9~:1-11. Stone, R. B. 1985. National artificial reef plan. NOAA Technical Memorar~durn, NMFSOF-6. NOAA, Washington, D.C., USA. Valdes, E., and A. F. Silva. 1977. Alimentacidn de los peces de arrecifes artificiales en la plataforma suroccidental de Cuba. Informe Oientif~co- Tecruco, No. 24. Instituto de Oceanologia. Weisburg, S. 1986. Artificial reefs. Scicr~cc News 130~43:59-61. RESEARCH CONTACTS Artificial Reefs and FADs Aquabio, Inc., P.O. Box 4130, Annapolis, MD 21403, USA (D. Sheehy). Artificial Reef Development Center, 1010 Massachusetts Ave., N.W., Suite 100, Washington, D.C. 20001, USA (J. McGurrin). Council for Agricultural Planning and Development, 37 Nan Hal Road, Taipei, Taiwan 1007 (J.C. Lee). Department of Biological Science, Florida Institute of Technology, Melbourne, FL 32952, USA (W. Alevizon).
114 FISHERIES TECHNOLOGIES FOR DEVELOPING COUNTRIES Department of Oceanography, Old Dominion University, Norfolk, VA 23508, USA (D. Feigenbaum). Division of Aquatic Resources, Department of Land and Natural Resources, 1151 Punchbowl St., Honolulu, Hawaii, USA (E. Onizuka). Fisheries Technology Unit, Fisheries Department, P.O. Box 1036 Ministry of Agriculture, Halfa, 31009 Israel (S. Pizanty). Geography Department, SUNY, Cortland, NY 13045, USA (D. Miller). ICLARM, South Pacific Office, Box 1531, Towneville, Queensland 4810, Australia (J. L. Munro). Institute of Zoology, Academia Sinica, Taipei, Taiwan 115, (K.H. Chang). McIntosh Marine, 621 Idlewyld Drive, Ft. Lauderdale, FL 33301, USA (G. McIntosh). Ministerio de la Industria Pesquera, Barlovento, Santa Fe, La Habana, Cuba (S. Vauj~n). National Marine Fisheries Service, F/Mll, Washington, D.C. 20235 USA (R. Stone). Sea Fish Industry Authority, Industrial Development Unit, St. Andrew's Dock, Hull HU3 4QE, England (J. E. Tumilty). SEATI Corporation, 119 Maginhawa St., Diliman, Quezon City, Metro Manila, Philippines (R. Macapagal). Southeast Fisheries Center, NMFS, 75 Virginia Beach Drive, Miami, FL 33149, USA (J. Bohnsack). Tekmarine, Inc., 37 Auburn, Ave., Sierra Madre, CA 91024, USA (J. Sonu). VANTUNA Research Group, 5504 8th St., Fallbrook, CA 92028 USA (M. Patton).
