An experimental artificial reef was constructed in the break-water of Tuticopn Harbour during July-August, 1989 at a

depth of 6 m using discarded lorry tyres. A total number of 23 modules, consisting of 69 tyres and fabricated in lhree

different designs, were used for the reef construction. The reef occupied a bottom area of approximately SO sq.m. with

a height of 0.8 to 1 m. Within a period of one month from the time of construction, autotrophic community dominated

by red algae and heterotrophic community dominated by cirri pedes, in addition to colonization by various groups of

invertebrate organisms, were observed on the reef structure. The inhabitation by fish was observed during the third

month. The behaviour of fish and shellfish" in the artificial reef was observed by SCUBA diving

Rajamani, M

CMFRI Digital Repository

TnI!' Second Indian Fisheries Forum Proceedings \fay 27-31, 1990. Mangalore, India. p.261 -263. Observations on Experimental Artificial Reef Constructed at Tuticodn M. RAJAMANI Tuticorin Research Centre of Central Marine Fisheries Research Institute Tuticorin-628 001 ABSTRACT An experimental artificial reef was constructed in the break-water of Tuticopn Harbour during July-August, 1989 at a depth of 6 m using discarded lorry tyres. A total number of 23 modules, consisting of 69 tyres and fabricated in lhree different designs, were used for the reef construction. The reef occupied a bottom area of approximately SO sq.m. with a height of 0.8 to 1 m. Within a period of one month from the time of construction, autotrophic community dominated by red algae and heterotrophic community dominated by cirri pedes, in addition to colonization by various groups of invertebrate organisms, were observed on the reef structure. The inhabitation by fish was observed during the third month. The behaviour of fish and shellfish" in the artificial reef was observed by SCUBA diving. INTRODUCTION Floating bamboo bundles and piles of stones kept on the sea bottom have long been used as fish-gathering devices by traditional fishennen in various parts of the world (Turner et al., 1969; Stone, 1982; Vik, 1982; Grove and Sonu, 1983; Chang, 1985). These objects attract fishes as they provide living space, shelter or protection from predators, thus serving as a habitat. The algae and other organisms which attach to the objects serve as food for fishes, especially for young ones. They also act as a base for attachment of eggs in some cases. Based on this principle, artificial habitats for fishes are being constructed in many countries either on the floor or on the sub-surface of the sea. Various s.t11lcrures have been designed using different materials and anificial reefs have been constructed mostly on the floor of the sea for enhancing the coastal fishery (Sheehy, 1982). Although artificial reefs are being consttucted extensively in many countries, particularly in the South-east Asian countries on a commercial scale as a Govemment sponsored programme, work on these lines is only at a preliminary stage in India. As experimental observations are required prior to large-scale construction of al1ificial reefs in the open sea, an experimental artificial reef using cheap materials was constructed at Tuticorin during the year 1989, the congregation of fish and shell-fish in the vicinity of the artificial reef was studied and the results presented in this conununication. MATERIAL AND METHODS Discarded lorry tyres were used as the reef blocks for the construction of the artificial reef. Three designs of modules were fabricated on board the Research Vessel, Cadalmin IV. Each module consisted of three tyres which were fastened together with polypropylene rope of 6 mm thickness. Design 1 was in the [onn of a tripod with the tyres standing vertically (Fig. 1). Each module of this design was provided with maximum inter-space between the blocks and the module occupied a floor area of approximately 2.3 m. A total number of !3 modules of this design were fabricated and released in the break-water of Tuticorin harbour at a depth of 6 m. during July. 1989. Design 2 was fabricated in the fonn of a cylinder with no inter-space between the blcoks, but with provision for free flow of water from one end to the other. Design 3 was in the fonn of a well with no inter-space betv·/een the blocks and the water in the module attaining more or less a stagnant condition. The bottom area covered by each module in Design 2 and 3 was less than 1 sq.m. These modules were fabricated and released in the same area during August, 1989. The height of the structure was about 1 m in the case of Designs 1 and 2 and 0.8 m in the case of Design 3. The modules were carefully released with the help of the winch of the vessel and their position on the bottom was set right by SCUBA diving. The rutificial reef thus constructed covered an area of approximately 50 sq. m. After the construction of the reef was over, observations were made every fortnight, either by snorkelling or by diving with SCUBA. The important fauna and flora associated with the reef and the congregation of fish and shellfish and thei r behaviour were studied. In order to assess the nature and extent of invertebrate colonization on the reef structures, t.yre pieces measuring a size of 100 cm2 were tied along with the modules at t.he time of construction of the reef and these were periodically removed and observed. Experimental fishing was carned out during every observation using either hook and line or a perch trap. The perch trap was made up of fibres of Acatia wood and had a length of 1 m, width of 0.5 m and height of 0.3 m. The fishes caught by the hook and line and the perch trap were sorted out, identified and their sizes recorded. In the case of fish, the total length was measured (from snout to caudal tip), whereas in the case of the crab, w:dth of the carapace was recorded. 261 .~~~ """"'-::.-~ Fig. i. Schematic diagram of the reef modules showing the inhabitation by fish in the well-type module as observed by underwater diving with SCUBA RESULTS .'ND DISCUSSIONS , -, -< , --z " oWithin a period of one month fiOm the time of construction of the artificial reef, good growth of algae was observed on the reef structures including the lyre pieces. The maximum length of the algal filament was 27 mm when observed after 15 days . This increased to 48 mm 37 days following tile constnIction of the reef. The a lgae belonged to two classes viz., Rhodophyceae and Phaeophyceae and were mainly represented by three species namely. Acanthophora sp. Graci/aria spp. and Padilla sp. In addit ion to the algae, growlh of sea grass was also obscn'ed. The animal community was represented by various groups of invertebrate organisms. However, the animals belonging to the groups Porifera, Bryozoa, Polychaet". Isopoda, Amphipoda and Cin-ipedia were found to have colonized the reef structures in large numbers. It was observed that the colonization by jjolychaetcs and c irripcdes was very rapid. Initially. the composition of both the polychaetes and cirripedes was almost in equal propol1ion. However. as the period advanced. the settlement of barnacles on the reef structures increased at a faster ratc. Underwater observations on the hiotic community of the anificial reef were carried out by SCUBA diving and the inhabitation and the behaviour of fish <md shellfish were studied . The inhabitation by fish was re~orded for the first time during the third month i.e. in October. Thereafter, the inhabi tation could be nmiced during every observation. Serrmllts sp. preferred to live within the crevices of the reef structures , whereas Lutinll11S spp. preferred to swim in (he stagnant water body of the we ll -type module without rouching the reef structures. Caram: spp. and Selar malam were observed to hover in large numbers about 2 m above the reef structures. Apparently, these fishes were taking shelter in the lee waves produced by the reef structures . The blennids, Dasson sp. and Pelroscirles lienardi were observed in the sub-surface and found to cling to the marker rope, whereas crabs (Portwllls pelagiclls) were found to live on the marker float, hiding themselves under the seaweeds grown on the float. Thlls, four distinct groups of fishes were recognized based on their attraction to the reef structu res. Experimental fishing carried out in the vicinity of the artificial reef has shown that three species of carangids namely, Caranx caran,RllS, C. Sal/Slm and Se/ar malam were taking shel ter in the mid-water column, whereas the perches, I.llfialll1S vitia, Ljll.lvij1amllla, Lethrinus IIebu/osus, Serraf/us bOell{lck and Lares calcariJer occupied the bottom area closely interacting with the reef structures. During January 1990. i.e. six months after the construction of the reef. only two spec ies viz .• C. carangus and Setal' malam w~re recorded. But, during February, two species of Caranx and three species of Llltia1!us were observed. The composit ion of the species collected from the artificial reef further increased in March when two species of crabs viz" PorfwlIIs pelagiclis and Charybdis sp. and ten species of fi,h were recorded_ The si ze ranges of the different species of fish and crabs collected during di fferent months are given in Table l. The analysis of the s ize-frequency distributions of L. lIebuioslts and L. vitta showed that the fomler ranged between 138 and 199 mm \vith a mode at 136-140 nun, and the laner from 122 to 172 111m with a mode at 121-125 mm_ Reports of artificial reefs attract ing distinct groups of fishes are available in literature_ Change (1985) observed four distinct groups of fishes in an artificial reef constnIcted at a depth of 18 m. According to Nakamura (1985), the optimum height of a reef structure to cause a lee wave is approximately 10% of the water depth. In the present investigation, the depth of the water was only 6 In and the height of the reef was between 0_8 and I m. Though the height was more than what has been recommended, congregation of fish could be observed above the structures indicating the fonnation of lee waves. Observations on the behaviour of fi sh in the vicinity of the artificial reef suggest th~1t the design of the structure plays an important role in attract ing fish. Tn the present investigation. the relationship between the reef design and the behaviour of fish was studied fro m two angles the behaviour of fish 262 Table I. Size range of fishes and crabs collected from the artificial reef Month Species Size range (mm) No. of (min) (max) specimens collected August, 89 PortUflllS pelagic/ls 25 I October, 89 Partllll/iS peiagiclis 32 33 ). January. 90 Cararu carangllS 157 252 2 Sefar ma/am t49 t92 4 February, 90 C.sal/SUlI t89 I Selar malam 1)5 t82 ) Llitianus fulvij1amma 132 I L vitta 15) t66 2 Lllljanlls sp. 240 I March, 90 Par/linus peiagiclis 44 I Charybdis sp. 76 86 2 Drusan sp. 86 Petrosc;nes lienardi 37 CaU)'odon bataviellsis 210 Siganlls orami" tl9 142 2 Saralllls boe,lQck 223 t Lelhrinus nelm/oms 138 199 II Lethrinlls sp. 139 210 18 LIlI/anlls virta 122 !72 23 IAles calcarifer 201 248 4 Chaetodontops callaris 83 towards a single unit of the reef and the entire arrangement of the reef. It was observed that out of the three designs used. the well-type des ign was more effective. Ll.llianlls spp. were found to swim within the 'well' indicating its preference to swim in stagnant water bodies. On the other hand, when the entire reef was considered. it was found to be effective in attracting the pelagic resources, particularly the carangids. It has been reported that in Japan about 150 species of fi sh exhibit dislinct response to reefs (Nakamura, 1985). "Ifnough some reports are available on the construction of artificial reef in Indian waters, infonnation on the behaviour of fish in the aI1 ific ial reef is lacking (CMFRI, 1988; Anon. 1989). The results of the present investigation clearly show that certain groups of fishes, particularly Ihe lutianids exhibit distinct response to the artificial reef, which will be very useful in designing sui table concrete structures for artificial reefs in the open sea for exploitation of this commercially important group. ACKNOWLEDGD'lli~TS The author is greatful to Dr. P.S.B.R. James, Director. Central Marine Fisheries Research Institute , for encouragement and for providing necessary facilities to carry out this investigation. He is thankful to Dr. KA.Narasimham, Officer-in-Charge, Tuticorin Research Centre of CMFRI and to Dr. D.BJames, for offering valuable suggest ions. Thanks are due to S/Shri A. Dosman Fernado, F. Soosai V. Rayan, N. Jesuraj and P. Muthukrishnan, Skin Di vers, for their valuable help in SCUBA diving operations. He is also thankful to Dr. S Lazarus for c,ritically going through the manuscript. The help extended by the crew members of the research vessel, Cadalmin IV in the construction of the artificial reef is acknowledged with thanks. REFERENCES ANONYMOUS, 1989. Synthetic fish aggregation devices! artificial reefs in India. Project Progress Report, Shri AMM. Mllfugappa Cheniar Research Centre. Madras. CHANG, K.H .. 1985. Review of artificial reefs in Taiwan: Emphasizing site selec tion and effect iveness. Bull. Mar. Sci., 37 (1):143·150. CMFRI. 1988. Anificial reef research. CMFRI Newsletter No. 41. p. 4·5. GROVE. R.S. A:-''O SONU, c.J., 1983. Re view of Japanese fishing reef technology. South. Calif Edit ion Comp. 83·RD·137. 116 p. NAKAMURA, M., 1985. Evolution of artifi cial fishing reef (:oncepts in Japan. Bul l. Mar. Sci., 37 (1):271~278. SHEEHY. 0.1., 1982. The use of des igned and prefabricated artific ial reef in the United States. Mar. Fish. Rev., 44 (6· 7):4· 15. STONE, R.B., 1982. Artificial reefs: toward a new era in fisheries enhant'elr.ent? Mar. Fish. Rev., 44 (67):2-4. TURl\ER. C.H., EBERT. E.E. A:-''O G;VEN, RR .. 1969. Man-made r~ef ecology. Calif. Fish. Game Fish Bull ., 146. 221 p. VIK, S.F., 1982. Japanese artificial reef technology, Aquabio Jnc., Florida. 380 p. 263 

Observations on experimental artificial reef constructed at Tuticorin

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Observations on experimental artificial reef constructed at Tuticorin

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