At Tuticorin and Minicoy observations were made on the

experimental artificial reefs constructed by the Scientists of CMFRI

during 1988-'92, whereas at Vizhinjam the artificial reefs constructed

by the local artisanal fishermen were monitored by the

Scientists of the Institute. Good congregation of fishes was observed

in the vicinity of the artificial reefs at all the three Centers. In the

experimental artificial reef constructed at Tuticorin, four distinct

groups of fishes were recognized based on their mode of attraction

towards the reef structures. At Vizhinjam, an increase in the landing

offish was noticed in the commercial catches. At Minicoy, settlement

of pearl oyster spat and growth of several species of seaweeds were

recorded

Lazarus, S

Pillai, P P

Rajamani, M

Yohannan, T M

CMFRI Digital Repository

Marine Research and Management Editors V.N. Pillai and N.G. Menon Central Marine Fisheries Research Institute (Indian Council of Agricultural Research) Tatapuram P.O., Cochin-682 014 Kerala, India 2000 43 Artificial reefs M.Rajamani, S.Lazarus, P.P.Pillai and T.M.Yohannan ABSTRACT At Tuticorin and Minicoy observations were made on the experimental artificial reefs constructed by the Scientists ofCMFRI during 1988-'92, whereas at Vizhinjam the artificial reefs con-structed by the local arlisanal fishermen were monitored by the Scientists of the histitute. Good congregation ofjishes was observed in the vicinity of the artificial reefs at all the three Centers. In the experimental artificial reef constructed at Tuticorin, four distinct groups of fishes were recognized based on their mode of attraction towards the reef structures. At Vizhinjam, an increase in the landing offish was noticed in the commercial catches. At Minicoy, settlement of pearl oyster spat and growth of several species of seaweeds were recorded. Introduction Artificial reef technology is being used in many countries mainly for enhancing the marine fish production. The technology is well advanced in some of the Southeast Asian countries, particularly in J apan . There are two types of artificial reefs viz. (i) set on the bottom and (11) floating on the surface or at sub-surface of the sea. Depending upon the structure^the artificial reefs may be classified into three categories, namely primitive, semi-scientific and scientific. In the first category, the reef is constructed mostly in shallow waters by dumping branches of trees, boulders or rocks, scrapped boats , junked cars, discarded building materials, etc. The artificial reef constructed this way lasts for a short period and fish aggregation also is poor in such areas . The semi-scientific method of construction involves using of s t ructures having definite size and shape e.g. old automobile tyres, well r ings, large cement pipes, etc. Here the s t ructure remains stable for a considerable period and the fish aggregation also is reasonably good. In the scientific method^artlficial Marine Fisheries Researcli and Management reef is constructed with s t ructures designed to at tract a part icular group of finfish or shellfish based on the observations made on the behaviour of the group concerned under laboratory and field conditions. It may be mentioned here that in J a p a n about 150 species of fishes have been recognized as exhibiting distinct responses to reefs (Nakamura, 1985). In India, the first method has been in vogue for a very long time in certain place along Tamil Nadu and Kerala coasts (Sanjeeva Raj, 1989 a, b, 1990; Kurien, 1996). Although the method is categorised as primitive, the ingenuity with which the art isanal fishermen have used their experience in such constructions over the years has formed the basis for further development of the artificial reef technology in India. The various types of artificial reefs and fish aggregating devices used by the traditional fishermen of India have been reviewed by Bergstrom (1983) and Fernandez (1996). The primitive method of artificial reef construction adopted by the traditional fishermen was developed into semi-scientific method during 1980's when a few voluntary organizations and private agencies took keen interest in this line of work and started collaborating with fisherfolk in Improving the methods already adopted by them. Fish aggregating devices were fabricated from High Density Poly-ethylene (HDPE) pipes and discarded automobile tyres and were installed along Madras coast (Raja, 1996). Concrete well-rings were used in large numbers for the construction of artificial reefs along Madras and Trivandrum coasts and very recently t r i angula r modules have been used for artificial reef construction along Trivandrum coast (James and Lazarus, 1990; Sanjeeva Raj, 1996; Philipose, 1996). All these s t ructures have been found to be effective in at tracting a variety of fishes. The scientific method of artificial reef construction Involves designing of species-specific s t ruc tures and using such s t ructures for specific purposes such as creation of aquacul ture ground, creation of propagation ground, etc. It is in this direction the Central Marine Fisheries Research Institute initiated a project on artificial reefs during 1988 at three of its Research Centres at Tuticorin, Vizhinjam and Minicoy and the resul ts obtained are presented in this paper. Materials and methods At Tviticorin, discarded lorry tyres were used for the construction of artificial reef in the break-water of Tuticorin Harbour at a depth of 6 m. Three "670" Artificial reefs designs of modules were fabricated, each module consisting of three tyres which were fastened with polypropylene rope of 6 mm thickness . Design No. 1 was in the form of a tripod with the tyres standing vertically. A total number of 13 modules of this design were fabricated and released during July, 1989. Design No. 2 was in the form of a cylinder whereas Design No.3 was in the form of a well. Five modules each of Design No.2 and Design No.3 were released during August, 1989. The artificial reef thus constructed covered an area of 50 sq.m. 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 finflsh and shell-fish and their behaviour were studied. In order to assess the na ture and extent of invertebrate colonisation of the reef s t ructures , tyre pieces measuring a size of 100 cm^ were tied along with the modules at the time of construction of the reef and these were periodically removed and observed. Experimental fishing was carried out during every observation using either hook and line or perch t rap . The perch t raps were made up of fibres of Acacia wood and had length of 1 m, width of 0.5 m and height of 0.3m. The fishes caught by the hook and line and perch trap were sorted out, identified and their sizes recorded. At Vizhinjam, the artificial reef constructed by the traditional fishermen was monitored. Different kinds of materials were used initially. Granite stones, discarded tyres and coconut s tumps were some of the common materials used by the fishermen. These materials were later replaced by concrete rings, concrete filled worn-out tyres and a variety of s t ructures made out of concrete. The chamber-type concrete module which has been Introduced very recently along Trivandrum coast is notable among all the s t ruc tu res used by the fishermen previously. The artificial reefs were built at a depth of about 30 m. The fish catches landed from the reef a s well as the non-reef a reas were recorded. Also, underwater surveys using SCUBA were under taken to assess the fish congregation In the vicinity of the artificial reef. At Mlnlcoy, an artificial reef was constructed with the primary objective of concentrating tuna live-baits. The s t ructure consisted of 2 m diameter, three inch thick RCC slab base on which twelve vertical MS rod holders of 10 mm thickness and 1.9 m length were fixed at regular Intervals. Fourteen discarded car tyres arranged In five rows and 15x10 cm size wooden block separators were interlocked by these vertical bars . The total number of wooden pieces used to maintain the gap along the Inner periphery of the tyres was Marine Flsherie» Research and H/Ianagement sixty two. The s t ruc ture t h u s fabricated had a total height of 1.2 m. It was installed in the area between Tunda Point (southern end of Minlcoy) and Viringih during November 1988. Results and discussion In Tuticorln, good growth of algae was observed on the reef s t ructure within one month from the time of construction of the artificial reef. When observed after 15 days the maximum length of the algal filament was 27 mm which increased to 48 mm after 37 days. The algae which belonged to Rhodophyceae and Phaeophyceae were mainly represented by Acanthophora sp., Gracilaria spp. and Padina sp . In addition to algae various groups of invertebrate organisms were found to have colonised the reef s t ruc tures . The animals belonging to Porifera, Bryozoa, Polychaeta, Isopoda, Amphipoda and Clrr ipedia were observed in large n u m b e r s . It was observed t h a t the colonisation by polychaetes and cirripedes was very rapid. Initially, the composit ion of both the polychaetes and cirripedes was almost In equal proportion. However, as the period advanced, the settlement of barnacles on the reef s t ruc tures increased at a faster rate. Experimental fishing carried out in the vicinity of the artificial reef has shown that three caranglds namely, Caranx carangus, C. sansun and Selar malam were taking shelter in the mid-water column, whereas the perches Lutjanus vitta, L. fulvijlamma, Lethrinus nebulosus, Serranus boenack and Lates calcan/er occupied the bottom area closely interacting with the reef s t ructures . During January 1990, le. six months after the construction of the reef, only C. carangus and S. malam were recorded. But during February, two species of Caranx and three species of Lutianus were observed in the catches. The composition of the species collected from the artificial reef further increased in March when the crabs Portunus pelagicus and Charybdis sp. and ten species of fishes dominated by L. vitta (35.4%) were recorded. During April, Lethrinus nebulosus, Lutjanus rivulatus, L. vitta, Diagramma sp. , Platex teira and Siganus oramin were collected from the artifical reefs. L. nebulosus was the dominant species constituting 62% of the total numbers collected followed by Diagramma sp. (14%), Platax teira (8%), L. rivulatus (6%), L.vitta (4%) and Siganus oramin (4%). In the case of L.nebulosus the size ranged between 133 and 300 mm in total length, with the modal size at 156-160 mm. During J u n e , six species offish were collected in addition to two species "672" Artificial reefs of crabs. L.nebulosus was the dominant species as in April forming 61.9% of the total number of fish collected from the area. Other species collected in J u n e were Acanthurus mata (14.3%), Scolopsis vosmeri (9.5%), L.vitta (4.8%), Serranus boenack (4.8%), Tetradon immaculatus (4.8%) and the crabs Atergatis integerrimus and Charybdis sp. The size of L.nebulosus during J u n e ranged between 142 and 218 mm, with the model size at 156-160 mm as in April. During July, L. nebulosus, Lates calcarifer, Serranus merra and Tetradon sp. were collected. In the case of L.nebulosus the size ranged from 163 to 212 mm. During August Callyodon bateviensis, L.nebulosus, Ostracion nasus and Serranus sp . were collected. Sixtyseven L.nebulosus collected from the artificial reef were tagged and released back into the same area in order to find out whether they permanently reside in the same area or migrate to some other area. Out of 67 tagged and released, two were recovered on 12th April, 1990 i.e. 27 days after they were released into the artificial reef area. In addit ion to experimental fishing, underwater observations us ing SCUBA were carried out In the vicinity of the artificial reef and the inhabitation and behaviour of various species of flnfish and shellfish were studied in detail. The presence of fish was recorded for the first time during the third month after the construction of the artificial reef. Thereafter, they could be noticed during every observation. From the underwater observations four distinct groups of fishes were recognized based on their mode of at t ract ion towards the reef s t ruc tures : (i) Serranus sp . - preferred to live within the crevices of the reef s t ruc tures attaching a major part of its body to the object; (ii) Lutjanus spp. - preferred to swim within the stagnant water body of the well-type module without touching the reef s t ruc tures ; (iii) Caranx spp. and S. malam were observed to hover in large numbers about 2 m above the reef s t ruc tures . It appears that these fishes were taking shelter in the lee waves produced under the influence of the s t ruc tures placed on the floor of the sea; (iv) the blennids, Dasson sp . and Petroscirtes lienardi were observed in the sub-surface water d in ing to the marker rope and P. pelagicus was found to live near the marker float hiding themselves under the seaweeds grown on the float. Also, it was observed tha t the fish Platax tetra ranging in size from 42 to 44 mm were swimming around the marker rope in the sub-surface water whereas the larger ones of the same species (205 -208 mm) were swimming close to the reef Marine Fisheries Research and Management s t ruc tures . Thus, it appears that the larger fish are directly influenced by the reef s t ruc tures . At Vizhinjam, underwater observations revealed the congregation of large shoals of small fishes such as Apogon novemfaciatus, Amphiprion spp. and Dascyllus s p p . Larger o n e s l ike Eplnephelus corallicola, Lutjanus argentimaculatus, L.lineolatus, Pterois antennata, Spillotichthys pictus and Heniochus acuminialus were found in small numbers . The reef building polychaetes Sabellaria spinulosa and S.spinulosa var gravieri were collected from the site of the reef in large numbers by SCUBA divers. These polychaetes served as important source of food for demersal fishes. It was also observed that the cuttlefish Sepia pharaonis congregated around artificial reef for at taching its egg mass . It is interesting to note that fishes like Carangoides plagiotaenia, Lethrinus harak, Selar kalla, C. malabaricus and Selaroides leptolrpis were recorded only in the reef region at a point of time. A slight increase in the landings at Valiathura was noticed after the establ ishment of artificial reef in that area. From 669.0 t in the year 1988-•89 the landing increased to 857.5 t during 1989-'90 and then to 1442.8 t during the subsequent year. It was observed that out of the two types i.e. the tubular and well-type arrangements of the concrete rings, the first one was found to be more effective in at tracting the fishes. The hut-type bamboo modules and three-dimentlonal chamber type concrete modules were found to be more effective than the semi-circular concrete module. The sunny days from November to April appear to be the best period for fishing by hook and line in the artificial reef area. In the lagoon of Minicoy, filamentous algae belonging to Ectocarpus spp. were found to have grown on the tyres and wooden separators within three months of the installation of the artificial reef. A large concentration of mysids belonging to Neomysis spp. was observed during the fourth month. From seventh month onwards encrusting types of brown algae replaced Ectocarpus spp. Epizoites were found to concentrate on the inner sheltered sides of the artificial reef by the end of the first year. The settlement of pearl oyster spat on the reef platform was observed after a period of fifteen months . The seaweeds, Halimeda gracilis, Dictyota dichotoma, Turbinaria ornata, Gelidiella acerosa and Ceramium sp. were also found to have grown on the platform around this time. '674" Artificial reefs The following species of fishes were found to have colonised the artificial reef constructed in the lagoon of Minicoy: Abudefduf sexfaciatus, Caesio pisang, Dascyllus aruanus, D.trimaculatus, D.reticulatus, A.bengalenis, Thalassoma umbrostigma, Arotheran sp. and Heniochus sp . in their order of abundance . It was observed tha t the tidal variation Inside the lagoon influenced the quanti-tative distribution of fishes around the artificial reef with lesser numbers during the low tide period. Future research priorities and conclusion These investigations by the Central Marine Fisheries Research Inst i tute at three different Centres have clearly shown tha t artificial reefs can play an Important role in marine fisheries development by increasing the production. The variety of algae growing on the reef s tructures, provides an excellent feeding ground for various species of flnfish and shellfish, particularly for their young ones. Further , It has been observed at all the three Centres that the artificial reefs form the base for the development of various invertebrate organisms. The biological productivity Is t hus higher in the reef area a s compared to the barren sea since 'ecological succession" takes place in the former. Hence it is suggested tha t the construction of artificial reefs along Indian coasts may be taken up on a large scale as a Government-sponsored programme involving fisherfolk, research institutions and voluntary agencies with the main objective of increasing the marine fish production. As it h a s been observed that fishes exhibit distinct responses to reef s t ruc tures , the studies on the behaviour of various species of flnfish and shellfish in the artificial reefs may be intensified In order to design and fabricate suitable s t ruc tures with the specific purpose of at tracting a part icular group offish or shellfish. As many species of flnfish and shellfish congregate around artificial reefs mainly to feed on the algae that natural ly grow on the reef s t ruc tures , it is suggested that selected species of algae may be t ransplanted at the time of construction of the reef so as to augument the na tura l algal production. It may be mentioned here that a direct relationship between the production of red algae. Gelidium sp . and the production of spiny lobsters has been well es tabhshed in J apan . Hence, in order to increase the production of spiny lobsters in our waters , culture of red algae in artificial reefs may be taken up on a large scale. Marine Fisheries Research and Management As the design and dimensions of the artificial reefs depend upon the purpose of the reef as also on reef si te charac te r i s t i cs s u c h as bot tom topography, current pattern in the area, etc., the work on artificial reef should be carried out as an Inter-dlsclplinary one involving scientists from various branches of science. As local scour is one of the Important phenomena connected with the sinking of artificial reef s t ruc tures when they are constructed on the sandy or muddy bottom, basic research on this line may be intensified in the laboratory and sea in order to design suitable s t ruc tures which will withstand such conditions for many years. References Bergstrom, M. 1983. Review of experiences with and present knowledge about Fish Aggregating Devices. Bay of Bengal Programme. BOBP/WP/23. Madras. Fernandez,"J. 1996. Artificial Fish Habitats - A community programme for Bio-diversity conservation. Bull. Cent. Mar. Fish. Res. Inst. 48: 42-55. James, P.S.B.R. and S.Lazarus 1990. Artificial reef for artisanal fisheries enhancement - An attempt off Trivandrum Coast. Mar. Fish. In/or. Serv. T&E Ser., 104: 1-6. Kurien, J. 1996. Collective action for common property resource rejuvenation: The case of People's Artificial Reefs in Kerala State. India. Bull. Cent. Mar. Fish. Res. Inst, 48: 24-36. Nakamura 1985. Evolution of artificial fishing reef concepts in Japan. Bull. Mar. Set. 37 (1): 271-278. Philipose, K.K. 1996. Artificial reefs habitat enhancement and increasing fisheries potential. Bull. Cent. Mar. Fish. Res. Inst. 48: 4-7. Raja, G. 1996. Fish Aggregation Devices and Artificial Reefs. Ibid., 48: 8-10. Sanjeeva Raj, P.J. 1989 a. Modified artificial fish habitats on the Tamil Nadu Coast of India. Bull Mar. Set. 44 (2): 1069-1070. 1989 b. Artificial fish habitat technology for small scale fish workers. National Workshop on Technology for Small Scale Fish Workers, Trivandrum. 1990. Mapping the Inshore floor of India. Seq/bodExport JourRoI, 22 (2): 11-14. 1996. Artificial reefs for a sustainable coastal ecosystem in India involving fisherfolk participation. Bud. Cent Mar. Fish. Res. Inst, 48: 1-3. 

Artificial reefs

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Artificial reefs

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