EFFECT OF HEMISPHERICAL STEEL NET COVERING ARTIFICIAL REEF ON FISH AGGREGATION

RECENT ADVANCES IN MARINE SCIENCE AND TECHNOLOGY 2006: 11-22 (2007)

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EFFECT OF HEMISPHERICAL STEEL NET COVERING ARTIFICIAL REEF ON FISH AGGREGATION

Hiroaki Terashima1, Ken Sakurai2, Masahiro Taniguchi2, Seiichi Sasaki2,

Hidehisa Noguchi2, Kohta Asamidori2, Takashi Hoshino3

1IC Net Limited Saitama, Japan

[email protected]

2Nippon Steel Metal Products Co., Ltd. Tokyo, Japan

3Umikohboh Limited

Kawasaki, Japan

ABSTRACT An artificial reef with a steel guard net was developed for protecting the main body from gill net fisheries. The reef was a twenty-meter high structure made of concrete walls and steel frames and covered by a hemispherical steel net. The artificial reef was established on sandy bottom at a depth of 70m off the Genkai district, in Kyushu, Japan in 1998. A Remotely Operated Vehicle (ROV) observation was undertaken on November 2005 to evaluate the effects of the guard net structure around the artificial reef on fish aggregation. Fourteen (14) fish species were observed around the artificial reef. Apogon semilineatus, Lutjanus ophuysenii, Parapristipoma trilineatum, and Thamnaconus modestus were dominant species from the perspective of appearance ratio and estimated number of individuals. Among these species, Apogon semilineatus was the most dominated species that clustered around the artificial reef’s guard net. The aggregation composed of juvenile or young individuals showed repetitive ambulation both inside and outside of the guard net. This behavior seems to conform to movement of carnivorous fish such as the yellowtail amberjack, Seriola quinqueradiata. It was suggested that the small fish in a school utilized the guard net as a shelter from its predators.

INTRODUCTION

Within the 12-meter-high artificial reef (AR) which was developed for gill net fisheries, demersal fish such as snapper, grouper and horse mackerel were observed. Through the years, this reef has grown in utilization and popularity among local fishers for its high efficacy since its establishment. It would be assumed the advantageous effect is dependent on the steel guard net as a distinct characteristic on this model in comparison with other artificial reefs though few researches have been undertaken to verify it. In recent years, many artificial reef projects implemented in deeper waters were aimed at the development of new fishing grounds and enhancing fish stocks in Japan (Ito and Terashima, 2004). In order to contribute to these projects, several hi-rise or tower-type artificial reefs have been developed in Japan (e.g. Takagi et al.,


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2000; Fukuda, 2001; Kimura, 2001; Ohno, 2001; Takagi et al., 2002; Moriwaki et al., 2005). These types have expected multiple effects for providing habitat for demersal to pelagic fishery resources (Takagi, 2000). Many researches in conjunction with fish assemblage associated with artificial reefs (e.g. Bayle-Sempere et al., 1994; Relini et al., 1994; Charbonnel et al., 2000; Abelson and Shlesinger 2002, Charbonnel et al., 2002; Santos et al., 2002; Relini et al., 2002), have been done, however the spatial utilization pattern by fish species aggregating around these artificial reefs is not clear. One of the difficulties of visual surveys of fish aggregating around artificial reefs has been recognized as a limited activity, especially in deep waters (Okamoto, 1998). Additionally, the high swimming activity of migratory fish such as Trachurus japonicus and Seriola quinqueradiata make it increasingly difficult to implement scientific research. Arimoto (1998) suggested that an underwater camera or ROV carried by research divers or a fixed underwater camera would be a main factor of visual survey targeting mobile organisms for enabling objective quantitative data collection. In addition, the ROV might make it possible to quietly stay in one position for long periods to record fish behavior in less disturbed conditions. In this context, we implemented ROV observation for fish behavior around artificial reefs in order to collect information of spatial utilization patterns in artificial reefs, especially on how fish utilized the guard net.

MATERIALS AND METHODS Study site and Artificial reef structure The artificial reef was deployed on a sandy bottom at a depth of 67m off the Genkai district, Kyushu, Japan (34° 04.113’ N, 130° 23.879’ E) in 1998 (Fig. 1). The bottom topography of the site was flat and consisted mainly of sand. The artificial reef devoted for this research was made of concrete walls and steel frames and was covered by a hemispherical steel net (Fig. 2). The outside dimension was 8.45m x 8.45m x 12.00m and the total weight of 26.9 tons consisted of 15.5 tons of steel frames and 11.4 tons of concrete parts. The mesh size of the hemispherical steel net was approximately 1× 2m.

Fukuoka

MunakataKita-kyushu

Fukutsu

10km

-67m34° 04.113’ N,

130° 23.879’ E

Fukuoka

MunakataKita-kyushu

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130° 23.879’ E

Fukuoka

MunakataKita-kyushu

Fukutsu

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-67m34° 04.113’ N,

130° 23.879’ E

Figure 1. Survey site

The mesh size is approximately 1m × 2m

12m

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The mesh size is approximately 1m × 2m

12m

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8.45mFigure 2. Diagram of target

artificial reef


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Survey method for fish aggregation We implemented a visual survey on the artificial reef from 21-23 November 2005. The data was collected twice (morning and afternoon) a day. The general visual survey by ROV was undertaken from bottom to top to monitor a distribution pattern of fish aggregating around the artificial reef (Fig 3). The artificial reef was virtually partitioned by depth and frame into twelve sections for descriptive purpose. The devoted ROV then observed and recorded each species of fish aggregating in these sections (Fig. 4). After a general observation, we implemented a continuous visual survey for approximately four hours (235, 234 and 214 minutes by date) on the top layer of the artificial reef to analyze movements of fish aggregation composed of multiple individuals (Apogon semilineatus). In this observation, we especially emphasized the location of fish aggregation around the guard net. The devoted ROV was quietly laid on the top of the guard net and its driving motor and lighting system halted in order to avoid undue disturbance. We classified the movement of fish aggregation into four categories based on relative location to the guard net, viz. spread upward, moving inside, staying inside, and moving outside in order to measure the time fish expended in each category. As a supplementary observation, research divers checked species, size and quantity of fish around the AR, especially upstream side where the survey by ROV is usually difficult as the capstan and connecting cord of the ROV often gets stuck in bulges of artificial reef. Fish survey by research divers was done by visual census using the point stationary method (Bohnsack and Bannerot, 1986) within each 3m layer from bottom to top of the artificial reef, in addition to the general survey by ROV mentioned above. If large schools of fish were found we used a modified point stationary method with video analysis (Terashima et al., in printing), which consisted of taking photographs by underwater camera with known angle of view underwater in several places and counted the number of fish in each photograph after field survey. We then estimated the volume of space transcribed in the photograph and deduced the density of fish within the sampling area. (Fig. 5). Prior to the survey, we measured vertical water temperature and salinity by using STD (Salinity Temperature Depth) profiler.

Figure 3. schematic diagram of field survey Figure 4. Schematic diagram showing

observation partition based on the depth and frame of the artificial reef


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β1

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Figure 5. Calculation for volume estimation

Statistical analysis To examine distributional patterns in fish location, mean time of each location category was compared using a Kruskal-Wallis non-parametric test. We did not analyse the data with parametric tests because of the data showing non-normal distribution and heterogeneity of variances. When significant differences were detected between means after the Kruskal-Wallis test, nonparametric Dunn's multiple comparison test was used to determine which of the mean groupings was significantly different (Zar, 1999). All values have been expressed as the means ± one standard error. Result Fishes observed by ROV and research divers in this survey are shown in Table 1. The number of species and its composition around the artificial reef was substantially stable though the number of species observed varied slightly on each survey date (21-23 November) as 13, 11 and 12 respectively; it was 12 on the research diver's observation on 23 November. The species composition also showed little difference. The following ten species viz. Pterois lunulata, Apogon semilineatus, Lutjanus ophuysenii, Parapristipoma trilineatum, Chaetodontoplus septentrionalis, Oplegnathus fasciatus, Choerodon azurio, Platax orbicularis, Stephanolepis cirrhifer, and Thamnaconus modestus were found in every survey. Epinephelus septemfasciatus was not observed on the 21st but was on the 22nd and 23rd, Epinephelus akaara and Platax orbicularis were not observed on the 22nd but were on the 21st and 23rd. We also observed three individuals of Seriola quinqueradiata on 21 November though we could not get a sight of this species in following two days. In the 21st, the S. quinqueradiata repeatedly approached the top side of the artificial reef though it never entered the inside of the guard net. It seemed that Apogon semilineatus was heavy on moving inside and outside of the guard net in conjunction with the behavior of S. quinqueradiata; namely, A. semilineatus rushed to inside of the guard net and stayed there when S. quinqueradiata moved closer to artificial reef while A. semilineatus spread out over the artificial reef when S. quinqueradiata disappeared. Within species we observed, the following four species viz. Apogon semilineatus, Lutjanus ophuysenii, Parapristipoma trilineatum, and Thamnaconus modestus were referable to the dominant species from the perspective of appearance ratio and the estimated number of individuals (Figs. 6-9).


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A. semilineatus which made a huge aggregation was composed of juvenile or young individuals and was always observed in the upper current side in the top and second layers of the artificial reef while it was not apparent in other areas at all (Fig. 6). L. ophuysenii was only observed at the bottom layers of the inside of the artificial reef (Fig. 7). P. trilineatum was observed at mainly the upper current side at the top and second layers of the artificial reef in common with A. semilineatus. Where its appearance range was wider than A. semilineatus and rather outside of the artificial reef these two species' aggregation have not commingled (Fig. 8). T. modestus was observed in various areas inside the artificial reef, especially around middle layers (Fig. 9). Consequently, it seems these species roughly separated their habitats in the artificial reef and A. semilineatus and P. trilineatum which shared the top side of the artificial reef as their habitat showed repetitive movement which was probably linked to accession of S. quinqueradiata (Fig. 10).

Figure 6. Location and frequency of occurrence of Apogon semilineatus around the artificial reef

Figure 7. Location and frequency of occurrence of Lutjanus ophuysenii around the artificial reef

Figure 8. Location and frequency of occurrence of Parapristipoma trilineatum around the artificial reef

Figure 9. Location and frequency of occurrence of Thamnaconus modestus around the artificial reef


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Figure 10. Schematic diagram showing habitat demarcation of dominant species around the artificial reef The aggregation of A. semilineatus repeatedly moved inside and outside of the guard net within a short time cycle. Its expended seconds of repetitive ambulation in four categories are shown in Figure 11. The expended seconds for "staying outside" of the guard net on the 21st to 23rd were 29.24 ± 8.00, 47.43 ± 15.15 and 59.68 ± 19.41 respectively. Therefore, the magnitude relation of staying outside of the guard net was 21st < 22nd < 23rd and the expended seconds was significantly different among these three days (H=10.14, p<0.05). Dunn's multiple comparison test detected significant differences between 23rd and 22nd (Q=2.61, p<0.05) and 23rd and 21st (Q=3.70, p<0.05) whereas it didn't perceive significant difference between 22nd and 21st (Q=1.22, p>0.05). The expended seconds for "moving inside" of the guard net on the 21st to 23rd were 7.89 ± 0.66, 6.63 ± 0.32 and 7.08 ± 0.39 respectively. These values hardly perceived significant difference (H=1.54, p=0.46). Dunn's multiple comparison test also didn't perceive any significant differences between the 23rd and the 22nd (Q=1.22, p>0.05), the 23rd and the 21st (Q=0.81, p>0.05) and the 21st and the 22nd (Q=0.37, p>0.05). The expended seconds for "staying inside" of the guard net on the 21st to the 23rd were 9.74 ± 1.23, 3.09 ± 0.46 and 1.71 ± 0.44 respectively. The magnitude relation of the staying inside of the guard net was the 21st > the 22nd > the 23rd, and the expended seconds was significantly different among these three days (H=76.54, p<0.05). Dunn's multiple comparison test detected significant differences between the 21st and the 22nd (Q=6.33, p<0.05) and the 21st and the 23rd (Q=8.46, p<0.05), whereas it didn't perceive significant difference between the 22nd and the 23rd (Q=2.38, p>0.05). The expended seconds for "moving outside" of the guard net on the 21st to the 23rd were 23.92 ± 4.88, 12.44 ± 0.89 and 11.11 ± 0.57 respectively. The magnitude relation of moving outside of the guard net was 21st > 22nd > 23rd. The expended seconds was significantly different among these three days (H=8.27, p<0.05). Dunn's multiple comparison test detected significant differences between the 21st and the 22nd (Q=2.48, p<0.05) and the 21st and the 23rd (Q=2.53, p<0.05) whereas it didn't perceive significant differences between the 22nd and the 23rd (Q=0.18, p>0.05). The expended seconds for "total interval" on the 21st to the 23rd were 70.78 ± 13.67, 69.60 ± 15.56 and 79.35 ± 19.97 respectively. The magnitude relation of the total interval was therefore 23rd > 21st > 22nd while significant difference among these three days was imperceptible (H=4.34, p=0.11). Dunn's multiple comparison test also didn't perceive significant


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differences between the 23rd and the 21st (Q=1.95, p>0.05), the 23rd and the 22nd (Q=1.64, p<0.05) and the 21st and the 22nd (Q=0.28, p>0.05).

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Figure 11. Expended seconds of repetitive ambulation in four categories of Apogon semilineatus A vertical profile data of water temperature and salinity around the artificial reef is shown in Figure 12. There is no discontinuity layer for water temperature and salinity and these vertical profiles of each criterion shows almost the same values and inclination from the surface to bottom.

Figure 12. vertical profile of water temperature and salinity around artificial reef

DISCUSSION Within our survey period, 10 species among 14 were observed every on occasion we implemented around the target artificial reef and these species seemed to dwell in the artificial reef due to its appearance in almost the same sections of the reef. The ratio of these species in total observed species was approximately 70 percent. Bohnsack et al. (1991) reviewed previous research and concluded that the residency composition was usually similar even in different regions, based on data from the U.S. and Australia. According to their description, the appearance ratio of "residents" abiding long term after settlement to artificial reef occupied 62-72% of total observed species. Our result from Japan conformed to their view.

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Four dominant species showed habitat separation in the artificial reef. Although it was unclear whether this phenomenon occurred regularly or it was just an adventitious pseudo-segregation due to our short observations, these separations seemed stable within our research period. Several researchers described residency patterns of fish aggregating around artificial reefs (Talbot et al. 1978; Bohnsack and Talbot, 1980; Nakamura, 1984; Ogawa, 1984; Ookubo and Kakimoto 1991; National Coastal Fisheries Development Association 2000). To illustrate, the National Coastal Fisheries Development Association (2000) classified fishes into the following four categories. According to its description, type-I fishes usually attach their body to surface of artificial reef, type-II fishes stay in close proximity to the artificial reef, type-III fishes stand apart from the artificial reef, which are usually epi- to meso-pelagic species and type-IV fishes inhabit the sandy or muddy bottom around the artificial reef. However these categories might be insufficient for habitat analyses of high-rise or tower type artificial reefs providing vertical structure. Recently, several researches had been undertaken for analyzing a performance of oil rigs and gas platforms for reef dwelling fish in offshore areas (Hastings et al., 1976; Love et al., 1994; Bull and Kendall, 1994; Stanley and Wilson, 1998; Fabi et al.. 2002). Fabi et al. (2002) concluded that these structures have consecutively attracted reef dwelling, demersal and mesopelagic fishes and have raised species richness. The high-rise or tower type artificial reef deployed in offshore areas ranged between 50-100m might fulfill a same roll due to their resemblant vertical structures which is rare in natural environment, hence it should make a major impact to natural surroundings. It may need to rearrange the classification of fish types based on vertical affinity as well as preferable distance to artificial reef so as to understand aerial residency composition and apply for new reef design in future. Huge aggregation composed of juvenile and young individuals of A. semilineatus moved between inside and outside of guard net in short cycle. The behaviural pattern of A. semilineatus on 21st was significantly different to the behavioural pattern of other the two days. On the 21st, the aggregation stayed inside of the guard net significantly longer and stayed on the outside significant shorter than the other two days. The movement to the outside on the 21st was significantly more sluggish than on the other two days. The thermo- and salino-condition of the water made little difference among those days and it is unclear the reason of these behavioral differences. We, however, presume it was led by the appearance of S. quinqueradiata even though the mesh size of the guard net was feasible for S. quinqueradiata to enter inside of the guard net. Hixon and Beets (1989) described a number of large shelters showed inverse correlation with the number of small fish while the number of appropriate size of shelters was strongly associated with the abundance of reef fish in a coral reef area. Furthermore, several researchers reported that the preferable habitat for common reef fish is strongly correlated to its complexity (Abelson and Shlesinger, 2002; Charbonnel et al.. 2002; Sherman et al., 2002; Kawasaki et al., 2003). However, these researches mainly targeted solitary or loose aggregatory species and might have excluded species behaving in larger masses. Steele (1996) reported that any difference could not detect between the effects on prey by shelters that screened out predators and others that allowed predators to attack prey. He also suggested that the structure, which was accessible by predators, still positively effected survivorship of prey. It might be related to high speed predators' behavioural requirement for minimal diameter in making a turn, the relative brightness of the inner part of the reef, and the acoustic circumstances.


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Correspondingly, the result of this study suggests that A. semilineatus positively utilizes the guard net as its refuge even if the mesh size of guard net is accessibly large to its predator such as S. quinqueradiata. It seems that fish species making huge aggregation as A. semilineatus need suitable shelter for its aggregation size instead of the individual size though there is not sufficient evidence to positively pin down this hypothesis. Further study, especially long-term observation by ROV or fixed camera, seems to be required to clarify these issues.

ACKNOWLEDGEMENTS This study was undertaken as a monitoring survey to clarify the effect of tower type artificial reef under the sponsorship of Nippon Steel Metal Products Co., Ltd. We would like to thank Mr. Haruhito Ando of Oita Fisheries Cooperation Association, Mr. Kazuhiro Nishimura and Mr. Yasuhiro Sanada of Oita Prefectural Agriculture, Forestry and Fisheries Research Center for their logistic support. We are grateful to Mr. Yasushi Ito of the Japanese Institute of Technology on Fishing Ports, Grounds and Communities, Mr. Hideo Nakamura of Umikohboh Ltd., Mr. Yoshito Yokoyama and Mr. Noriaki Nakahata of Coastal Consultant Ltd. for their invaluable assistance. Special thanks to Dr. Daniel J. Sheehy of Aquabio Inc., Dr. Hitoshi Ida of Kitasato University, Dr. Hiroyuki Kawasaki of ICNet Ltd. and Mr. Sreenivasan Soondron of Albion Fisheries Research Centre for their valuable comments and advice on this manuscript.

REFERENCES Abelson, A. and Y Shlesinger. 2002. Comparison of the development of coral and fish communities on rock-aggregated artificial reefs in Eilat, Red Sea. ICES J. Mar. Sci. 59(supplement): S122-S126. Arimoto, T. 1998. Diving techniques for underwater observation of capture process. Abstracts for the symposium "Observation of Marine organisms by scientific diving and its analysis of behavioral records": 11. Ocean Research Institute, The University of Tokyo. Bayle-Sempere, J.T., A.A. Ramos-Esplá and J.A. Garcia-Charton. 1994. Intra-annual variability of an artificial reef fish assemblage in the marine reserve of Tabarca (Alicante, Spain, SW Mediterranean). Bulletin of Marine Science. 55: 824-835. Bohnsack, J.A. and F.H. Talbot. 1980. Species- packing by reef fishes on Australian and Caribbean reefs: An experimental approach. Bulletin of Marine Science, 30: 710-723. Bohnsack, J. A. and S. P. Bannerot. 1986. A stationary visual census technique for quantitatively assessing community structure of coral reef fishes. U.S. Dept. of Commerce, NOAA Technical Report NMFS 41. iii+15pp. Bohnsack, J.A., D.L. Johnson and R.F. Ambrose. 1991. Ecology of artificial reef habitats and fishes. In W. Seaman and L.M. Sprague ed. Artificial habitats for marine and freshwater fisheries. Academic Press. USA. 61-107.


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Charbonnel, E., P. Francour, J.G. Harmelin, D. Ody and F. Bachet. 2000. Effects of artificial reef design on associated fish assemblages in the Côte Bleue Marine Park (Mediterranean Sea, France). 365-377. In C. Jensen, K.J. Collins and A.P.M. Lockwood. Artificial reefs in European Seas. Kluwer Academic, Netherlands. Charbonnel, E., C. Serre, S. Ruitton, J.G. Harmelin and A. Jensen. 2002. Effects of increased habitat complexity on fish assemblages associated with large artificial reef units (French Mediterranean coast). ICES Journal of Marine Science, 59: S208-S213. Fabi, G., F. Grati, A. Lucchetti and L. Trovarelli. 2002. Evolution of the fish assemblage around a gas platform in the northern Adriatic Sea. ICES Journal of Marine Science. 59: S309-315. Fukuda, K. A experimental hybrid reef HR-2016. Technical Report of Artificial reef. 4: 13-17. (in Japanese). Hastings, R.W., L.H. Ogren and M.T. Mabry. 1976. Observations on the fish fauna associated with offshore platforms in the northeastern Gulf of Mexico. Fishery Bulletin, 74: 387-340. Hixon, M.A. and J.P. Beets. 1989. Shelter characteristics and Caribbean fish assemblages: experiments with artificial reefs. Bull. Mar. Sci. 44: 666-680. Ito, Y. and H. Terashima. 2004. Potential of artificial reefs for enhancement of fisheries resources: Case study from Japan. CD-ROM for Abstracts and documents for regional workshop on artificial reefs in southeast Asia. SEAFDEC/TD, Thailand. Kawasaki, H., M. Sano and T. Shibuno. 2003. The relationship between habitat physical complexity and recruitment of the coral reef damselfish, Pomacentrus amboinensis: and experimental study using small-scale artificial reefs. Ichthyological Research, 50: 73-77. Kimura, K. 2001. A experimental hybrid reef P-1100A. Technical Report of Artificial reef. 4: 1-6. (in Japanese). Love, M., J. Hyland, A. Ebeling, T. Herrlinger, A. Brooks and E. Imamura. 1994. A pilot study of the distribution and abundances of rock fishes in relation to natural environmental factors at an offshore oil and gas production platform off the coast of southern California. Bulletin of Marine Science, 55: 1062-1085. Moriwaki, S., T. Tameishi, H. Wakabayashi, H. Matumoto, N. Tamaka and H. Saito. 2005. Changes in catch composition of the gathered fish to High-rise artificial reef off Hamada. Tech. Rep. Shimane Prefectural Fisheries Experimental Station. 12: 1-6. Nakamura, M. 1984. Selecting reef sites. 46.52. In O. Sato ed. Artificial reefs. Koseisya-Koseikaku. Tokyo, Japan. National Coastal Fisheries Development Association of Japan. 2000. Artificial reef fishing grounds construction planning guide - H.12 edition., 226pp. (in Japanese).


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Ogawa, Y. 1984. Fish fauna attracted to artificial reef. 32-45. In O. Sato ed. Artificial reefs. Koseisya-Koseikaku. Tokyo, Japan. Ohno, T. 2001. A experimental hybrid reef SK-1300. Technical Report of Artificial reef. 4: 7-12. (in Japanese). Okamoto, M. 1998. Human diving technology: From ocean exploitation to marine science. In eds. J.T. Tanacredi and J. Loret. OCEAN PULSE. Plenum Press, New York. 101-115. Ookubo, H. and H. Kakimoto. 1991. Changes in community composition around artificial reefs. Proceeding of the Japan-U.S. symposium on artificial habitats for fisheries. 82-86. Japan International Marine Science and Technology Federation. Tokyo, Japan. Relini, M., G. Relini and G. Torchia. 1994. Seasonal variation of fish assemblages in the Loano artificial reef (Ligurian Sea, NW Mediterranean). Bulletin of Marine Science. 55: 401-417. Relini, G., M. Relini, G. Torchia and G. Palandri. 2002. Ten years of censuses of fish fauna on the Loano artificial reef. ICES Journal of Marine Science, 59: S132-S137. Santos, M.N., C.C. Monteiro and M.B. Gaspar. 2002. Diurnal variations in the fish assemblage at an artificial reef. ICES Journal of Marine Science, 59: S32-S35. Scarborough Bull, A. and J.J. Kendall Jr. 1994. An indication of the process: offshore platforms as artificial reefs in the Gulf of Mexico. Bulletin of Marine Science, 55: 1086-1098. Sherman, R.L., D.S. Gilliam and R.E. Spielerb. 2002. Artificial reef design: void space, complexity, and attractants. ICES Journal of Marine Science, 59(supplement): 196-200. Stanley, D.R. and C.A. Wilson. 1998. Spatial variation in fish density at three petroleum platforms as measured with dual-beam hydroacoustics. Gulf of Mexico Science, 16: 73-82. Steele, M.A. 1996. Effects of predations on reef fishes: separating cage artifacts from effects of predation. J. Exp. Mar. Biol. and Eco. 198: 249-267. Takagi, N. 2000. Development of high-rise artificial reef. Technical Report of Artificial reef. 2: 1-11. (in Japanese). Takagi, N., A. Moriguchi, K. Kimoto, K. Arai, T. Hasuo, H. Nakamura and K. Kimura. 2000. Development of large-scale high-rise artificial reef and its effect. Tech. Rep. Nat. Res. Inst. Fish. Eng. 22: 1-14. Takagi, N., A. Moriguchi, Y. Ito, N. Ishioka and K. Arai. 2002. The research on a large-scale high-rise artificial steel reef at Yamaguchi prefecture in the Sea of Japan. Tech. Rep. Nat. Res. Inst. Fish. Eng. 24: 31-42.


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Talbot, F.H., B.C. Russell and G.R.V. Anderson. 1978. Coral reef fish communities: Unstable high-diversity system? Ecological Monographs, 48: 425-440. Terashima, H., M. Sato, H. Kawasaki and D. Thiam. 2007. Quantitative biological assessment of a newly installed artificial reef in Yenne, Senegal. Zoological Study, 46: in printing. Zar, J.H. 1999. Biostatistical analysis, 5th edition. Prentice Hall International, Inc., New Jersey. 663pp+212 app.

Table 1 Fishes observed by ROV and research divers

M* A* M* A* M* A*

1 Pterois lunulata 30 ○ ○ ○ ○ ○ ○ ○ 3solitarily moved inside of bottom layer and surrundings of AR

2 Epinephelus septemfasciatus 35 - ○ ○ ○ ○ - ○ 2solitarily moved inside of AR from bottom to top

3 Epinephelus akaara 40 ○ - - ○ ○ ○ ○ 1solitarily moved inside of AR from bottom to top

4 Apogon semilineatus 3 ○ ○ ○ ○ ○ ○ ○ 78500 made huge aggregation around top layer of gurdnet of AR

5 Seriola quinqueradiata 80 ○ ○ - - - - - - 2-3 individuals moved around top layer of gurdnet of AR

6 Lutjanus ophuysenii 20 ○ ○ ○ ○ ○ ○ ○ 58 40-50 individuals moved inside of bottom layer of the AR

7 Parapristipoma trilineatum 10 ○ ○ ○ ○ ○ ○ ○ 350 around 100 individuals moved around top layer of AR

8 Diagramma pictum 30 ○ ○ ○ ○ ○ ○ - -solitarily moved inside of bottom layer and surrundings of AR

9 Chaetodontoplus septentrionali 15 ○ ○ ○ ○ ○ ○ ○ 6solitarily moved inside of bottom layer and surrundings of AR

10 Oplegnathus fasciatus 25 ○ ○ ○ ○ ○ ○ ○ 18 solitarily moved inside and surrundings of AR

11 Choerodon azurio 25 ○ ○ ○ ○ ○ ○ ○ 2solitarily moved inside of bottom layer and surrundings of AR

12 Platax orbicularis 25 ○ ○ - - ○ - ○ 6 2-3 individuals moved around middle layer of AR

13 Stephanolepis cirrhifer 25 ○ ○ ○ ○ ○ ○ ○ 8 moved inside of middle layer of the AR

14 Thamnaconus modestus 30 ○ ○ ○ ○ ○ ○ ○ 83 moved inside of middle layer of the AR

13 13 11 12 13 11 12

Approx. No. of Indi.

Location observed around artificial reef (AR)

*: M: morning , A: afternoonTotal number of species

Observed by research Observed by ROVFishes approx.

TL(cm)No. 21st Nov. 2005 22nd Nov. 2005 23rd Nov. 2005 23rd Nov. 2005

EFFECT OF HEMISPHERICAL STEEL NET COVERING ARTIFICIAL REEF ON FISH AGGREGATION

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