Widespread degradation of coral reefs in recent years has been reported as a result of both natural and anthropogenic disturbances (Hatcher et al., 1989). Artificial reefs have been used successfully worldwide to increase catch rates of fish on areas of damaged coral. Artificial reefs provide spatial heterogeneity and refuge for fish from predators, and also provide a source of food due to the settlement of other benthic organisms.

There are few examples around the world where artificial reefs have assisted ecosystem rehabilitation (Pickering et al., 1998). Studies to date imply that they could be used as an effective coastal management tool, not only to attract fish into areas of reef degradation, but to also provide a suitable substrate for the settlement of corals and other invertebrates.

Studies, which have recorded colonisation of artificial structures deployed in tropical coastal areas, have shown that structures such as concrete pillars (Chou & Lim, 1986) can provide suitable surfaces for coral settlement and growth. Clark and Edwards (1994) demonstrated from three 50 m² concrete artificial reef structures in the Maldives that within a year each reef supported approximately 35 fish species (150-300 individuals). Structures were initially colonised by filamentous green algae (7 days), then barnacles (14 days), after 2 months a diverse invertebrate community was established. The first coral recruits (Pocillopora damicornis) were observed after 6 months, and within 11 months P. verrucosa, Acropora spp. and Porites spp. had recruited to the largest and most complex artificial structures. Some of the recruits developed a 20-30 cm diameter colony within 3 ½ years. Tyre reefs have also proven to be extremely successful in catch rates of fish in Australia (Branden et. al., 1994). They have also been extremely successful in the settlement of corals and other benthic reef fauna and flora.

Last summer artificial reefs were constructed to aid in the rehabilitation and conservation of Sampela reef, Kaledupa, SE Sulawesi. Sampela reef has been adversely affected by damaging fishing techniques, coral mining and sedimentation. The local Indonesian Baju community who inhabit an area directly behind the reef system have noticed a serious decline in fish catch in this area. The introduction of artificial reefs into this area was to help the recovery of fisheries, thereby improving the catches landed by traditional Baju fishermen engaged in artisanal fishing activities, as artificial reefs serve as nursery and breeding grounds for fish and other marine organisms.

Artificial reefs had not been used in this area before, three tyre reefs and three coral rubble and concrete reefs were constructed and colonisation of each structure was monitored. The use of coral rubble in the construction of artificial reefs has not been documented before, and because it is a natural substance the settlement of corals to such structures may be better than the use of man made structures. All structures were extremely successful and fish rapidly colonised each structure. After two months there was also evidence of coral growth. Each reef proved to be important nursery grounds for fish as well as providing shelter for larger pelagic species.

• To determine the success of the artificial reefs in terms of fish and benthic fauna and flora colonisation.

• To monitor growth rates of corals and other benthic invertebrates on artificial reefs.

• To monitor leachates from tyres into the marine environment.

• To determine fish diversity and abundance of Sampela reef and subsequently any knock on effects since the installation of the artificial reefs last year.

• To determine how the artisanal Baju fisheries will benefit from the artificial reefs.

• To compare fish diversity and abundance of Sampela reef to a pristine reef (Kaledupa) and determine any differences from last year.

• To construct an artificial reef made of coral rubble and concrete on a dynamite blast site at Kaledupa.

• To monitor the recovery of a dynamite blast site at Kaledupa.

• To evaluate the effectiveness of cleaner wrasse stations as a valid fish census technique.

  Artificial reef monitoring

Three artificial tyre reefs and three concrete rubble reefs were installed last year adjacent to Sampela reef (See Lipi report 2000 for a description of reef construction).

Before reef installation (last year) a full survey was carried out on Sampela reef and Kaledupa reef. The surveys consisted of fish abundance and diversity and total coral, algae and invertebrate cover. Topography surveys were also carried out. The surveys were conducted along a series of 25 m transact lines at different depths on the reef slope:

1. On the sand flat adjacent to the reef (site of reef installation).
2. At the bottom of the reef slope (depth approximately 10-12 m).
3. Mid reef slope (depth approximately 7m).
4. Reef crest (depth approximately 5m).

Each week from reef deployment until the end of October each artificial reef was monitored for fish species, abundances, sizes (adults or juveniles). Colonization of benthic fauna and flora were also monitored and growth rates of some species were monitored.

This year the same surveys have been carried out each week. Fish surveys involved a total fish count of all fish occupying each artificial reef. Each fish was identified to species and sizes of each individual were recorded.

Benthic fauna and flora were recorded and identified when possible to species level. Corals were measured each week using calipers to monitor growth rates along with the underwater video photometry technique (Work carried out with Professor James Crabbe). (Paper to be published). Each benthic species was given an abundance score depicted in the table below:

Analysis of leachates from tyre reefs

An analysis of the benthic organisms growing on the tyres will be assessed to determine if there has been any bio-accumulation of heavy metals (cadmium, copper, lead, nickel and zinc). Different organisms were collected (algae, hydroids, tunicates and sponges). Each organism was sun dried and stored in vessels and sent to LIPI. The samples will then be sent to Southampton University where analysis will be carried out using flame atomic absorption spectrometry using Pye Unicam SP9AAS. of nitric acid digests. Samples (200 mg dry weight) will be digested in concentrated nitric acid (2 ml) at 80 ^oC for 12 hours. BDH Spectrosol standard solutions will be used to prepare calibration curves with each batch of analyses (Joint paper to be published, with Dr. Ken Collins, Southampton University).

Fish abundance and diversity surveys (Sampela and Kaledupa reefs)

Fish abundance and diversity were conducted along the 25 m transect lines depicted in section 1.21. At the beginning of the transect line fish from 0 - 5 m were counted 2.5 m either side of the transect line for 5 minutes (5 m² area). The total number of fish, species and sizes of individuals were recorded within this area. After 5 minutes the next 5 m² section of the transect line was monitored and the process was repeated until the whole 25 m transect line had been completed. Each transect line was monitored at least 10 times and will be continued to be monitored until the end of the season. Coral and fish diversity and species richness between Sampela reef and Kaledupa reef will be statistically analysed using Correlation, Regression, ANOVA and Shannon Weiner’s index of diversity (Paper to be published comparing last years data to this year).

Along each 25 m transect line and 2.5 m either side of the transect line coral abundance and diversity was determined. Each coral was identified to species level. Total percentage cover of hard coral, soft coral, dead coral, rubble, sand, sponges, algae and other impacts such as coral bleaching, mining, blast or anchor damage were also assessed in each 5 m² section.

Artisanal fisheries and artificial reefs

A comparison between fish catches (sizes, species and numbers) from the artisanal fisheries (Sampela) and the fish present on the artificial reefs were compared.

Artificial reef construction on a dynamite blast site (Kaledupa)

An artificial concrete and coral rubble reef will be constructed in the next few weeks on a dynamite blast site on the reef crest at Kaledupa reef. The depth of the reef will be 4-5 m, the total area of the blasted site was approximately 20 m², approximately 5-10 m² of this area will be occupied by concrete blocks (approximately 50 cm²) with holes of varying sizes. The holes will aid in the attraction of fish and the sides of the concrete blocks will allow for the settlement of corals and other benthic organisms. The success of the colonisation of this reef by fish and corals will be compared to another blast site on Kaledupa reef that will be left to recover naturally.

Monitoring the recovery of a dynamite blast site (Kaledupa reef)

n August 8^th 2001 (Kaledupa buoy 1), an area approximately 5 m² on the top of the reef crest was dynamite blasted by an unknown fisherman. This area had been monitored previously last year and again this year for fish and invertebrate diversity and abundance. On the day of the blast hundreds of fish mainly the Yellowpatch fusilier (Pterocaesio randalli) were found scattered all over the reef, up to 20 m away from the blast epi-centre. Many corals were destroyed during the blast. Many of the corals close to the blasted area started to show deterioration (bleaching) several days after the event. Eight transect lines (20 m) were laid from the blast epi-centre (North, North-east, East, South-east, South, South-west, West and North-west). Along each transect line a line-intercept survey was carried out. Line-intercept involved recording all of the benthic life forms encountered directly underneath the transect lines. At each point where the life form changed the transition point in centimetres and the code of the life form was recorded (Codes can be found in the Survey Manual for Tropical Marine Resources by English, Wilkinson and Baker). Hence, along the length of a transect (XY) a number of points (T) were recorded for each of the life forms. The intercept of each of the life forms encountered under the transect (I) is the difference between the transition points recorded for each life form. Each coral present under the transect line was identified and measured (surface area) and the state of the coral (healthy, bleached, partial bleaching) was recorded. If the coral was bleached, the size of the bleached area was also measured. A general assessment of all bleached corals in the area surrounding the blast was determined by measuring the sizes of the corals and once again the amount of area that was bleached, either partially or totally. The recovery of some of the large corals was undertaken by visual observations and video photometry (Paper to be published).

An evaluation of Cleaner wrasse stations as a standard visual fish census technique

Along the transect lines fish present in each 5 m² section was recorded as described in the method above. Along the same transect lines cleaner stations were observed for a period of up to 10 minutes and fish found visiting each cleaner station were identified and sizes estimated. A direct comparison between the fish present in each 5 m² area will be compared to the fish visiting the cleaner stations. If the surveys are comparable, then Cleaner wrasse stations may be a useful tool to aid in fish census surveys on coral reefs.

The success of artificial reefs in terms of fish and benthic colonisation

All artificial reefs have proven to be extremely successful in attracting fish and benthic flora and fauna into areas that were depleted of life. All artificial reefs were slightly different in terms of what species of fish they attracted mainly due to positioning of the artificial reef. Each reef will be described in turn below:

Artificial tyre reef 1

This reef was located to the left of Sampela village and 10 m away from the bottom of the reef slope at a depth of 12-14 m. (GPS: S05^o29.044’ E123^o 45.074’). At the end of last season (October 2000) there were 24 species of fish, i.e. 3.5 months after deployment. It appeared that after this time period the reef had reached its carrying capacity as there was no further increase in fish species when monitored this season (species fluctuated between 24-30 species, 616 individuals). This reef proved to be an important nursery and breeding ground for juvenile reef fish, as well as adults. The main adult reef fish were the Beaufort’s crocodile fish (Cymbacephalus beauforti), Fimbriated moray (Gymnothorax fimbriatus), Lionfish (Pterois volatans), Reticulated dascyllus (Dascyllus reticulateus), Ringed pipefish (Dorhyramphus dactyliophorus), Canarytop wrasse (Halichoeres leucoxanthus), Goldtail demoiselle (Chrysiptera parasema) (all present last year) as well as the Three spot dascyllus (Dascyllus trimaculatus). This reef was an important breeding ground for C. parasema, D. trimaculatus and the Scaly chromis (Chromis lepidolepis) as all spawned on the artificial reef to produce juveniles. Many other juveniles were also important on this reef for example the Golden-lined snapper (Lutjanus boutton), Finelined surgeonfish, (Acanthurus grammoptilus), Groupers and Bluestreak cleaner wrasse (Labroides dimidiatus).

Coral growth on this artificial reef was very successful as Favia sp., Favites sp, Porites sp. and some unidentifiable corals had developed on the inside ring of the tyres. Many of the colonies were 10-15 cm in diameter, which is remarkable in such a short space of time. The corals are mainly cryptic and found where they were protected from sedimentation. Many other benthic life forms had developed for example many species of tunicates, sponges, hydroids, algae, bryozoans, nudibranchs, sea cucumber, feather stars, cleaner shrimp and Hinge beak shrimp.

 

Artificial tyre reef 2

This reef was located to the left of Sampela village and 30 m away from the bottom of the reef slope at a depth of 14-16 m. (GPS: S05^o 29.013’ E123^o 44.968’). Once again this reef had reached its carrying capacity at the end of last season with a total of 26 species of fish (101 individuals). This year species diversity was between 26 and 30 species. However the total number of individuals had increased ten fold with almost 1000 individuals present. The dominant species present was the juvenile Golden-lined snapper L. boutton (750 individuals). This is an incredibly high number of fish for the total area of artificial reef (3 x 5 m²). Even on the natural reef at Sampela species numbers were never this high and occasionally at Kaledupa (pristine site) species diversity was not as high as the artificial reefs.

L. boutton was not found on Sampela natural reef and therefore the artificial reefs are providing a ‘new habitat’ for the success of this species in the Sampela reef area. Other important species present on this reef include many species of juvenile groupers, Klein’s butterflyfish (Chaetodon kleinii), Gold-spotted sweetlips (Plectrorhinchus celebicus), Lionfish (P. volatans), Finelined surgeonfish, (A. grammoptilus) and the Longfin bannerfish (Heniochus acuminatus).

Benthic fauna and flora were similar to those present on artificial tyre reef 1.

 

Artificial tyre reef 3

This artificial reef was placed 100 m from the bottom of the reef slope at 17 m depth (GPS S05^o 28.911’ E 123^o 44.675’). This reef was an important home to the Red mouth grouper (Aethaloperca rogaa) (also present last year several weeks after deployment). Other important species present were the Ringed pipefish (Dorhyramphus dactyliophorus), juvenile Bluefin trevally (Caranax melampygus), Golden-lined snapper (L. boutton), juvenile Bigeye emperor (Monotaxis grandoculis) and many species of juvenile and adult cardinal fish.

Once again benthic fauna was similar to the other two tyre reefs, however there were many more coral colonies and soft corals.

 

Concrete and coral rubble reefs

The concrete coral rubble reefs were less successful in terms of numbers of fish when compared to the tyre reefs. The tyre reefs were much larger than the concrete / rubble reefs and had greater spatial heterogeneity and hence would appear more attractive to fish. However there were still a high number of fish and a fairly high diversity on the concrete coral rubble reefs. Important species were the adult and juvenile Goldtail demoiselle (C. parasema), juvenile Crescent wrasse (Thalassoma hardwicke), juvenile Highhfin grouper (Epinephelus maculates) and juvenile Redtooth triggerfish (Odonus niger). The benthic cover was very good on these reefs, with similar species to the artificial tyre reefs.

Fish abundance and diversity surveys (Sampela and Kaledupa reefs)

Fish diversity and abundance was much greater on the pristine reef at Kaledupa than the degraded reef at Sampela. Results seem comparable to last year but further statistical analysis needs to be conducted once all data has been collected this season. Often the artificial reefs show a greater species diversity than the pristine reef and they certainly show a higher species diversity and abundance than Sampela natural reef.

Artisanal fisheries and artificial reefs

The artisanal fisheries at Sampela have shown that many of the species of fish that are caught in the Wakatobi marine park are residents of the artificial reefs. In particular the Golden-lined Snapper (L. boutton) is often caught. Therefore the artificial reefs are extremely useful to the artisanal fisheries both directly and indirectly as they provide breeding and nursery grounds for many reef fish and some pelagic species. The juveniles will also restock the natural reefs in the Wakatobi Marine Park. Further analysis will be carried out once all the data has been collected this season.

Monitoring the recovery of a dynamite blast site (Kaledupa reef)

The small dynamite blasted area on Kaledupa reef caused substantial damage. Hundreds of fish were destroyed as well as hundreds of years worth of coral growth. A total of 24 species of coral were destroyed which had a total percentage cover of 70 % (5 m²) area. The main species of corals that were adversely affected in the vicinity of the blast were the massive Porites species, mainly Porites lobata and P. speciosa. A huge 200-year-old P. lobata colony (3355 cm²) was adversely affected by the blast, as coral bleaching occurred four days after the blast (200 cm²) and 495 cm² was partially bleached. One week later the amount of bleaching had spread to 220 cm² and this was totally covered in green filamentous algae. The area partially bleached had recovered slightly (330 cm²). Two weeks after the blast the bleaching had spread further (300 cm²) and was totally covered in green filamentous algae. This part of the coral colony will never recover. Over half of the partially bleached area had recovered further (140 cm²). Many other corals had also been affected 25 m away from the blast epi-centre. All of this was documented on underwater video. The recovery of this site is still being monitored until the end of the season. This will be compared to the artificial reef that will be deployed in the next few weeks at another blast area on Kaledupa reef.

An evaluation of Cleaner wrasse stations as a standard visual fish census technique

Fish data from the 25 m transect lines will be directly compared to the cleaner stations present along the transect lines. Statistical analyses to be carried out will be Two-way ANOVA.

A paper entitled The success of artificial reefs for the artisanal fisheries in the Wakatobi Marine National Park will be prepared by Dr Debbie Lloyd, University of Essex by May 2002.

A paper entitled A heavy metal bioaccumulation analysis of benthic fauna and flora growing on artificial tyre reefs in the Wakatobi Marine National Park, SE Sulawesi will be produced by Dr Debbie Lloyd, University of Essex by May 2002.

A paper entitled A comparison of fish abundance and diversity on a degraded and pristine reef in the Wakatobi Marine National Park, SE Sulawesi will be produced by Dr Debbie Lloyd, University of Essex by May 2002.

A paper entitled The recovery of a dynamite blasted reef in the Wakatobi Marine National Park, SE Sulawesi will be produced by Dr Debbie Lloyd, University of Essex and Professor James Crabbe, University of Reading by May 2002.

A paper entitled A comparison of traditional visual fish census techniques and observations made at cleaner stations on an Indonesian reef will be produced by Dr Magnus Johnson, University of Hull and Dr Debbie Lloyd, University of Essex by May 2002.

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Carr, M. H. and Hixon, M. A. 1997. Artificial reefs: The importance of comparisons with natural reefs. Fisheries 22: 28-33.

Chou, L. M. and Lim, T. M. 1986. A preliminary study of the coral community on artificial and natural substrates. Malay. Nat. J. 39: 225-229.

Clark, S. and Edwards, A. J. 1994. Use of artificial reefs structures to rehabilitate reef flats degraded by coral mining in the Maldives. Bulletin of Marine Science 55: 724-744.

Hatcher, B. G., Johannes, R. E. and Robertson, A. I. 1989. Review of research relevant to the conservation of shallow tropical marine ecosystems. Oceanogr. Mar. Biol. Ann. Rev. 27: 337-414.

Pickering, H., Whitmarsh, D. and Jensen, A. (1998). Artificial reefs as a tool to aid rehabilitation of coastal ecosystems: Investigating the potential. Marine Pollution Bulletin. 37: 505-514.