Effects of habitat modification on coastal fish assemblages

The purpose of this study was to assess the influence of anthropogenic modification of coastal habitats on fish assemblages in Taiwan, comparing the abundance, species richness and taxonomic composition of fishes on natural v. artificial habitats. While there was no significant variation in the abundance or richness of fishes between natural and artificial habitats, the species composition of fishes in artificial habitats was significantly different from that of natural habitats. Natural reefs were characterized by greater abundance of Stethojulis spp. (Labridae), Abudefduf spp. (Pomacentridae) and Thalassoma spp. (Labridae), whereas anthropogenic habitats were dominated by Parupeneus indicus (Mullidae), Pempheris oualensis (Pempheridae) and Parapriacanthus ransonneti (Pempheridae). In general, it appears that specialist reef-associated species are being replaced with fishes that are much more generalist in their habitat-use. The loss of natural coastal habitats may threaten some species that cannot live in anthropogenically altered habitats, though the overall abundance and diversity of coastal fishes was not significantly different between natural and artificial habitats in Taiwan.     

Contrasting Fish Behavior in Artificial Seascapes with Implications for Resources Conservation

Artificial reefs are used by many fisheries managers as a tool to mitigate the impact of fisheries on coastal fish communities by providing new habitat for many exploited fish species. However, the comparison between the behavior of wild fish inhabiting either natural or artificial habitats has received less attention. Thus the spatio-temporal patterns of fish that establish their home range in one habitat or the other and their consequences of intra-population differentiation on life-history remain largely unexplored. We hypothesize that individuals with a preferred habitat (i.e. natural vs. artificial) can behave differently in terms of habitat use, with important consequences on population dynamics (e.g. life-history, mortality, and reproductive success). Therefore, using biotelemetry, 98 white seabream (Diplodus sargus) inhabiting either artificial or natural habitats were tagged and their behavior was monitored for up to eight months. Most white seabreams were highly resident either on natural or artificial reefs, with a preference for the shallow artificial reef subsets. Connectivity between artificial and natural reefs was limited for resident individuals due to great inter-habitat distances. The temporal behavioral patterns of white seabreams differed between artificial and natural reefs. Artificial-reef resident fish had a predominantly nocturnal diel pattern, whereas natural-reef resident fish showed a diurnal diel pattern. Differences in diel behavioral patterns of white seabream inhabiting artificial and natural reefs could be the expression of realized individual specialization resulting from differences in habitat configuration and resource availability between these two habitats. Artificial reefs have the potential to modify not only seascape connectivity but also the individual behavioral patterns of fishes. Future management plans of coastal areas and fisheries resources, including artificial reef implementation, should therefore consider the potential effect of habitat modification on fish behavior, which could have key implications on fish dynamics.     

海洋生物礁类型、生态功能及其生态修复

海洋生物礁是由具有造礁能力的海洋生物聚集而成的一种三维礁体结构,其形成改变了海底地貌、增加了不同尺度上的地形复杂性,为其他海洋生物提供了栖息地并维持了生物多样性。近年来,由于自然因素和人为因素影响,海洋生物礁受到了严重威胁,已成为海洋生态保护和修复领域的重要研究对象。综述了海洋生物礁的类型、生态功能及其生态修复的研究进展。根据形成海洋生物礁的优势造礁生物种类,将海洋生物礁分为海藻礁、海绵礁、刺胞动物礁、贝类礁和多毛类礁,其优势造礁生物分别是珊瑚藻和仙掌藻、钙质海绵和硅质海绵、造礁珊瑚、牡蛎、龙介虫。目前国内对海洋生物礁的全面了解相对较少,主要集中在珊瑚礁和牡蛎礁。海洋生物礁的生态功能主要有海岸防护、提供栖息地、净化水体、固碳作用和能量耦合等。全球变暖和海洋酸化等全球气候变化以及海洋污染、破坏性渔业捕捞、海岸工程、水产养殖和敌害生物等自然和人为因素对海洋生物礁构成了严重威胁。海洋生物礁的生态修复方法分为两类：在退化生物礁区投放造礁生物逐渐成礁,投放人工礁体补充造礁生物逐渐成礁。针对海洋生物礁保护和修复的需要,提出下一步应加强海洋造礁生物生态特征、海洋造礁生物种群丧失因素和海洋生物礁保护与...     

Temporal and spatial comparison of food web structure in marine pastures in the Pearl River Estuary: Implications for sustainable fisheries management

The biological and ecological integrity of marine ecosystems in the Pearl River Estuary (PRE) has been compromised due to overfishing and water pollution. Fishing moratorium and artificial reef construction have been implemented in Wanshan and Miaowan for resource protection and restoration. Therefore, food web structure and trophic pathways of Wanshan, Miaowan, and Wailingding in different temporal and spatial situation will be determined using the Ecopath model, as well as the keystone species affecting these ecosystems, which can provide a basis for fishery management. The results showed that the energy transfer efficiency of IV and V trophic levels (TL) was higher than that of II and III‐TL before and after fishing moratorium, and the energy transfer efficiency of artificial reefs II and III‐TL was only slightly higher than that of nonartificial reefs in Wanshan. In addition, the mean values of ecosystem property indicators (consumption, respiration flow, total system throughput, and total biomass) after the fishing moratorium were significantly higher than those before the fishing moratorium. The average value of the ecosystem attribute indicators (consumption, respiration flow, total system throughput, and total biomass) of artificial reefs is lower than those of nonartificial reef areas, which may be related to the differences in community composition between artificial reefs and non‐artificial reefs. Finally, Nemipterus japonicus and Gastrophysus spadiceus are keystone species that distinguish the Wanshan and Miaowan artificial reefs from other areas. Overall, the fishing moratorium has a positive effect on the short‐term restoration of fishery resources, mainly restoring short‐life cycle organisms. However, the construction of artificial reefs will be more conducive to the persistence of ecosystem restoration. In addition, reasonable proliferation, release and fishing of N. japonicus and G. spadiceus will be beneficial to the sustainable utilization of fishery resources.     

Experiments testing the use of waste material in estuaries as habitat for subtidal organisms

In addition to producing extensive coastal infrastructure, urbanized estuaries are also often littered with large amounts of waste material. This can be used as habitat by fish and benthic plants and animals. Apart from studies of colonization of artificial reefs, which are usually deployed specifically to enhance populations of fish or to replace degraded habitat, there have been few studies that have specifically examined the use of waste material as habitat. Neither have previous studies compared different types of waste material that one characteristically finds in urbanized estuaries, nor the use of small patches of habitat typically created by waste. Spatial comparisons of species found on previously dumped artificial material may be confounded by the fact that different types of waste may be dumped in different places, or may be of different age. This study built small patch reefs of three different types of widespread waste material (tyres, wood or metal) and compared colonization of these over 19 months to colonization of patch reefs of similar age and size made from natural sandstone. Algal assemblages were similar among the different types of reefs, with all showing more cover and diversity on horizontal surfaces. Invertebrates similarly showed few differences among reefs, although there was greater diversity, primarily due to bryozoans, on the vertical surfaces of wooden reefs. Fish rapidly colonized and used all reefs, with cryptic species showing no differences among types of reefs. Schooling species were, however, more common on all of the waste reefs than on the natural sandstone reefs. Small patches of waste material dumped in estuaries can therefore provide useable habitat for a wide range of estuarine organisms and may form a valuable resource if natural habitats continue to be degraded or lost. Although we are not advocating that rubbish simply be discarded into estuaries with the excuse that it provides habitat, removal of existing rubbish should be considered in terms of multiple changes and disturbances to the environment.     

象山港日本对虾增殖放流的效果评价

日本对虾是中国近海重要的增殖品种,2010年象山港分两批次放流日本对虾苗种约1.67亿尾。通过对放流苗种存活状况、洄游分布、生长特性及回捕情况的跟踪调查,对象山港日本对虾的增殖效果做出初步评价。结果表明:(1)日本对虾放流苗种在8月中旬成为补充群体,集中于港区底部进行索饵育肥;9月中旬,第1、2批放流苗种的平均体长分别达到95.4 mm和71.4 mm,成活率分别约为0.79%和1.06%;10月上旬,随着港区水温降低,增殖苗种资源量锐减。(2)协方差分析表明:日本对虾增殖群体和自然群体的体长-体重关系存在显著性差异,增殖群体的体征状况明显优于自然群体。(3)日本对虾放流苗种在港区主要为桁杆拖虾和地笼网渔业所利用,在港区滞留期间,回捕率约为0.25%。总结发现:栖息地破坏及放流苗种的过早利用是制约象山港日本对虾增殖效果的重要因素,优化增殖策略、保护港区生态环境应是今后港区增殖工作的重点。     

From grey to green: Efficacy of eco‐engineering solutions for nature‐based coastal defence

Climate change is increasing the threat of erosion and flooding along coastlines globally. Engineering solutions (e.g. seawalls and breakwaters) in response to protecting coastal communities and associated infrastructure are increasingly becoming economically and ecologically unsustainable. This has led to recommendations to create or restore natural habitats, such as sand dunes, saltmarsh, mangroves, seagrass and kelp beds, and coral and shellfish reefs, to provide coastal protection in place of (or to complement) artificial structures. Coastal managers are frequently faced with the problem of an eroding coastline, which requires a decision on what mitigation options are most appropriate to implement. A barrier to uptake of nature‐based coastal defence is stringent evaluation of the effectiveness in comparison to artificial protection structures. Here, we assess the current evidence for the efficacy of nature‐based vs. artificial coastal protection and discuss future research needs. Future projects should evaluate habitats created or restored for coastal defence for cost‐effectiveness in comparison to an artificial structure under the same environmental conditions. Cost‐benefit analyses should take into consideration all ecosystem services provided by nature‐based or artificial structures in addition to coastal protection. Interdisciplinary research among scientists, coastal managers and engineers is required to facilitate the experimental trials needed to test the value of these shoreline protection schemes, in order to support their use as alternatives to artificial structures. This research needs to happen now as our rapidly changing climate requires new and innovative solutions to reduce the vulnerability of coastal communities to an increasingly uncertain future.     

Temporal constraints on the potential role of fry odors as cues of past reproductive success for spawning lake trout

Deciding where to reproduce is a major challenge for most animals. Many select habitats based upon cues of successful reproduction by conspecifics, such as the presence of offspring from past reproductive events. For example, some fishes select spawning habitat following odors released by juveniles whose rearing habitat overlaps with spawning habitat. However, juveniles may emigrate before adults begin to search for spawning habitat; hence, the efficacy of juvenile cues could be constrained by degradation or dissipation rates. In lake trout (Salvelinus namaycush), odors deposited by the previous year's offspring have been hypothesized to guide adults to spawning reefs. However, in most extant populations, lake trout fry emigrate from spawning reefs during the spring and adults spawn during the fall. Therefore, we postulated that the role of fry odors in guiding habitat selection might be constrained by the time between fry emigration and adult spawning. Time course chemical, physiological, and behavioral assays indicated that the odors deposited by fry likely degrade or dissipate before adults select spawning habitats. Furthermore, fry feces did not attract wild lake trout to constructed spawning reefs in Lake Huron. Taken together, our results indicate fry odors are unlikely to act as cues for lake trout searching for spawning reefs in populations whose juveniles emigrate before the spawning season, and underscore the importance of environmental constraints on social cues.     

Using bioacoustics and conventional netting methods to assess the initial effectiveness of a newly deployed artificial reef on fish assemblages in Xiangshan Bay near Ningbo,Zhejiang Province,China

Objectives of the study were ascertaining the temporal variation of fish density and biomass as well as the changes in fish species composition in a surveyed area before and after deployment of an artificial reef. The study was initiated within an area of 0.25 km² in response to a strong demand for fisheries enhancement and resource conservation in Xiangshan Bay, Zhejiang Province, China. This survey data was collected through a SIMRAD EY60 system and bottom trinal nets pre‐ and post‐construction of the artificial reefs, May 2011 to September 2012 in Xiangshan Bay. The raw data were analyzed using fisheries acoustic Echoview (Myriax) software combined with bottom trinal net data. The results showed that estimated fish density, represented by a nautical area scattering coefficient (NASC) at the artificial reef increased by 14.04, 31.10, 17.35% in May, July and September 2012 after construction of the artificial reef, and that the fish biomass increased by 8.92, 29.06, and 18.09% in these three months of 2012 in contrast to 2011. The numbers of fish species varied from 7 to 9 in May, from 10 to 14 in July and from 9 to 12 in September of 2012. These temporal changes in the fishery status were considered as being mainly due to deployment of the artificial reefs in early April 2012.     

Are artificial reefs surrogates of natural habitats for corals and fish in Dubai,United Arab Emirates?

Artificial reefs are often promoted as mitigating human impacts in coastal ecosystems and enhancing fisheries; however, evidence supporting their benefits is equivocal. Such structures must be compared with natural reefs in order to assess their performance, but past comparisons typically examined artificial structures that were too small, or were immature, relative to the natural reefs. We compared coral and fish communities on two large (>400,000 m³) and mature (>25 year) artificial reefs with six natural coral patches. Coral cover was higher on artificial reefs (50%) than in natural habitats (31%), but natural coral patches contained higher species richness (29 vs. 20) and coral diversity (H′ = 2.3 vs. 1.8). Multivariate analyses indicated strong differences between coral communities in natural and artificial habitats. Fish communities were sampled seasonally for 1 year. Multivariate fish communities differed significantly among habitat types in the summer and fall, but converged in the winter and spring. Univariate analysis indicated that species richness and abundance were stable throughout the year on natural coral patches but increased significantly in the summer on artificial reefs compared with the winter and spring, explaining the multivariate changes in community structure. The increased summer abundance on artificial reefs was mainly due to adult immigration. Piscivores were much more abundant in the fall than in the winter or spring on artificial reefs, but had low and stable abundance throughout the year in natural habitats. It is likely that the decreased winter and spring abundance of fish on the artificial reefs resulted from both predation and emigration. These results indicate that large artificial reefs can support diverse and abundant coral and fish communities. However, these communities differ structurally and functionally from those in natural habitats, and they should not be considered as replacements for natural coral and fish communities.     

The status of pike-perch culture in Finland

Pike-perch ( Stizostedion lucioperca (L.)) brood-fish are captured from natural populations just before and during spawning time. One to three spawning pairs are put together with an artificial nest in a net-cage. After spawning the eggs attached to the nest are transported to a hatchery 1 day before hatching begins. The production of newly hatched fry, 30 million in 1994, is used for fingerling production in ponds with natural food. The production of pike-perch fingerlings in Finland increased rapidly in the 1980s and reached 10 million fish in 1994. The fingerlings are stocked into lakes particularly in central Finland, where many lakes lost their native pike-perch populations in the 1960s. In some lakes pike-perch fingerling stockings have been profitable and new populations have been established. Experiments on intensive rearing of newly-hatched pike-perch fry have not been successful. However, one-summer-old pond-reared pike-perch fingerlings are being reared intensively to provide captive brood fish.     

Artificial habitats and the restoration of degraded marine ecosystems and fisheries

Artificial habitats in marine ecosystems are employed on a limited basis to restore degraded natural habitats and fisheries, and more extensively for a broader variety of purposes including biological conservation and enhancement as well as social and economic development. Included in the aims of human-made habitats classified as artificial reefs are: Aquaculture/marine ranching; promotion of biodiversity; mitigation of environmental damage; enhancement of recreational scuba diving; eco-tourism development; expansion of recreational fishing; artisanal and commercial fisheries production; protection of benthic habitats against illegal trawling; and research. Structures often are fabricated according to anticipated physical influences or life history requirements of individual species. For example, many of the world’s largest reefs have been deployed as part of a national fisheries program in Japan, where large steel and concrete frameworks have been carefully designed to withstand strong ocean currents. In addition, the differing ecological needs of porgy and sea bass for shelter guided the design of the Box Reef in Korea as a device to enhance productivity of marine ranching. The effect of these and other structures on fisheries catch is positive. But caution must be exercised to avoid using reefs simply as fishing devices to heavily exploit species attracted to them. No worldwide database for artificial habitats exists.The challenge to any ecological restoration effort is to define the condition or possibly even the historic baseline to which the system will be restored; in other words, to answer the question: “Restoration to what?” Examples of aquatic ecosystem restoration from Hong Kong (fisheries), the Pacific Ocean (kelp beds), Chesapeake Bay (oysters) and the Atlantic Ocean (coral reefs) are discussed. The degree to which these four situations consider or can approach a baseline is indicated and compared (e.g., four plants per 100 m² are proposed in one project). Measurement of performance is a key factor in restoration planning. These situations also are considered for the ecosystem and fishery contexts in which they are conducted. All use ecological data as a basis for physical design of restoration structures. The use of experimental, pilot and modeling practices is indicated.A context for the young field of marine restoration is provided by reviewing major factors in ecosystem degradation, such as high stress on 70% of commercially valuable fishes worldwide. Examples of habitat disruption include an extensive hypoxic/anoxic zone in the Gulf of Mexico and nutrient and contaminant burdens in the North Sea. Principles of ecological restoration are summarized, from planning through to evaluation. Alternate approaches to facilitate ecological recovery include land-use and ecosystem management and determining levels of human population, consumption and pollution.     

History,ecology and trends for artificial reefs of the Ligurian sea,Italy

From 1970 to the present 10 artificial reef sites have been developed in coastal waters of the Ligurian Sea, Italy. They range from Ventimiglia, in the west, to La Spezia, in the east, with the largest and best known reef complex being located in the Gulf of Genoa at Loano and consisting of 2,745 m³, about 5,200 t of material and covering a surface of 350 ha. Design and construction practices have advanced from an initial, unsuccessful effort that used automobile bodies (now banned) to current use of custom-designed concrete modules deployed systematically. Funding for reef construction has come since 1983. The earliest aim of reefs was as a physical barrier to protect habitats against illegal otter trawl fishing. Newer objectives include habitat restoration, enhancement of biodiversity and fishing catch, and research to test materials and designs for physical and ecological performance. Reefs also functions as environmental observation stations, with the invasive species Caulerpa taxifolia (Vahl) C. Agardh, being recorded on the reef at Alassio. For some Artificial Reefs (Ars), benthic organisms and fishes, settlement, biomass and development of community are recorded. In Loano AR, immersed in 1986, more than 150 algae species are recorded, more than 200 benthic animal species and 78 species (87 taxa) of fishes. Fifty-six species (61 taxa) of fishes are recorded by visual census, the others are caught only by trammel net and long line. Trammel catches at Loano are on average about 2.32 kg/100 m net. Comparisons among ARs reveal that age of the reef, location and presence of seagrass meadows are crucial for success. An indication of functional equivalence between ARs and natural rocky reefs is seen if both fish and sessile macrobenthos are compared. After 34 years of investigation a database comprising at least one hundred scientific articles based on research programs of up to 15 years, and other unpublished reports, provides information to guide future planning of reefs. On the basis of acquired experience, some management advice is suggested and the best design for the basic module in the Ligurian sea is described. The role of ARs, providing protection of coastal environment against the illegal otter trawling, nursery, microhabitat and food supply, while increasing biodiversity, biomass of benthos and fishes, and facilities for ecotourism, is outlined.

Current problems in marine biodiversity studies

This paper deals with a discussion of terminology and six proposed levels of biodiversity. Recent data and estimates were used to compare species and taxonomic diversity of terrestrial, freshwater, and marine organisms. About 1.5 million terrestrial species and 320000 aquatic species are hitherto known. In spite of a long history of research, only about 280000 marine species have been discovered, of which 180000 species are invertebrates. Of 33 metazoan phyla, 31 are found in the sea, 13 of these being exclusively marine. Seventeen metazoan phyla contain freshwater species, and only 11 phyla comprise terrestrial animals. Two phyla (freshwater Micrognathozoa and terrestrial Onychophora) possess no marine species. In this paper, we review the assessment reports on marine biological diversity in coral reefs, coastal ecosystems, macrobenthos, and meiofauna. Recent data on the number of known species are listed for each metazoan phylum; the number of anticipated new species to be discovered is estimated. Deep-sea macrobenthos are believed to comprise about 25 million species; meiofauna seems to be composed of 20 to 30 million species, ten million of whom are marine nematodes. Hypotheses are discussed that can account for the high species diversity of deep-sea macrobenthos and meiofauna.     

中国沿海日本囊对虾线粒体16S rRNA基因序列变异及遗传分化

对中国东南沿海4个日本囊对虾地理群体16S rRNA基因片段进行了序列测定和分析.在获得的467bp 序列中,共检测到45个变异位点,多态位点比例为9.64%.具有10种单倍型,三亚群体单倍型多样性最高(0.900±0.161).各群体的核苷酸多样性(π)为0.0007～0.0082,其中三亚群体核苷酸多样性最为丰富,远高于湛江、北海和海口群体.群体间遗传分化指数(F_(st))为0.000～0.945.结合已报道的16S rRNA基因序列,构建了NJ分子系统树,中国海域日本囊对虾可分为3支.香港至台湾沿岸所有单倍型聚集为一分支,湛江、海口和北海群体内的所有单倍型聚集成另一分支,两分支分别属于已报道的变种Ⅰ和变种Ⅱ,但三亚群体内的4个单倍型单独聚集成一分支,与前两分支的核苷酸序列差异大(7.95%～8.35%),遗传分化明显,可能为一亲缘关系很远的新种(或变种).研究结果可为日本囊对虾的资源管理和遗传选育提供参考.     

Dispersal of wild and domestic masu salmon fry (Oncorhynchus masou) in an artificial channel

The day and night pattern of upstream and downstream dispersal of masu salmon fry of wild and domestic origin was compared in artificial channels (45 m long), for two ages of planting: unfed alevins and eyed eggs. Early dispersal was important for the wild stock (48–50%) compared with the domestic one (16–36%). More wild fry moved downstream than upstream, and more domestic fry dispersed upstream. Upstream movement in wild and domestic fry was more active by day than by night, except for wild fry planted as eyed eggs, where upstream migration was higher at night. In contrast, downstream movement in wild and domestic fry was more common by night than by day, but daylight catches were not negligible for the wild stock.     

Abrolhos bank reef health evaluated by means of water quality, microbial diversity, benthic cover, and fish biomass data

The health of the coral reefs of the Abrolhos Bank (Southwestern Atlantic) was characterized with a holistic approach using measurements of four ecosystem components: (i) inorganic and organic nutrient concentrations, [1] fish biomass, [1] macroalgal and coral cover and (iv) microbial community composition and abundance. The possible benefits of protection from fishing were particularly evaluated by comparing sites with varying levels of protection. Two reefs within the well-enforced no-take area of the National Marine Park of Abrolhos (Parcel dos Abrolhos and California) were compared with two unprotected coastal reefs (Sebasti?o Gomes and Pedra de Leste) and one legally protected but poorly enforced coastal reef (the "paper park" of Timbebas Reef). The fish biomass was lower and the fleshy macroalgal cover was higher in the unprotected reefs compared with the protected areas. The unprotected and protected reefs had similar seawater chemistry. Lower vibrio CFU counts were observed in the fully protected area of California Reef. Metagenome analysis showed that the unprotected reefs had a higher abundance of archaeal and viral sequences and more bacterial pathogens, while the protected reefs had a higher abundance of genes related to photosynthesis. Similar to other reef systems in the world, there was evidence that reductions in the biomass of herbivorous fishes and the consequent increase in macroalgal cover in the Abrolhos Bank may be affecting microbial diversity and abundance. Through the integration of different types of ecological data, the present study showed that protection from fishing may lead to greater reef health. The data presented herein suggest that protected coral reefs have higher microbial diversity, with the most degraded reef (Sebasti?o Gomes) showing a marked reduction in microbial species richness. It is concluded that ecological conditions in unprotected reefs may promote the growth and rapid evolution of opportunistic microbial pathogens.     

Fish Assemblages on Estuarine Artificial Reefs: Natural Rocky-Reef Mimics or Discrete Assemblages?

If the primary goal of artificial reef construction is the creation of additional reef habitat that is comparable to adjacent natural rocky-reef, then performance should be evaluated using simultaneous comparisons with adjacent natural habitats. Using baited remote underwater video (BRUV) fish assemblages on purpose-built estuarine artificial reefs and adjacent natural rocky-reef and sand-flat were assessed 18 months post-deployment in three south-east Australian estuaries. Fish abundance, species richness and diversity were found to be greater on the artificial reefs than on either naturally occurring reef or sand-flat in all estuaries. Comparisons within each estuary identified significant differences in the species composition between the artificial and natural rocky-reefs. The artificial reef assemblage was dominated by sparid species including Acanthopagrus australis and Rhabdosargus sarba. The preference for a range of habitats by theses sparid species is evident by their detection on sand-flat, natural rocky reef and artificial reef habitats. The fish assemblage identified on the artificial reefs remained distinct from the adjacent rocky-reef, comprising a range of species drawn from naturally occurring rocky-reef and sand-flat. In addition, some mid-water schooling species including Trachurus novaezelandiae and Pseudocaranx georgianus were only identified on the artificial reef community; presumably as result of the reef''s isolated location in open-water. We concluded that estuarine artificial reef assemblages are likely to differ significantly from adjacent rocky-reef, potentially as a result of physical factors such as reef isolation, coupled with species specific behavioural traits such as the ability of some species to traverse large sand flats in order to locate reef structure, and feeding preferences. Artificial reefs should not be viewed as direct surrogates for natural reef. The assemblages are likely to remain distinct from naturally occurring habitat comprised of species that reside on a range of adjacent natural habitats.     

Responsible estuarine finfish stock enhancement: an Australian perspective

The responsible approach to marine stock enhancement is a set of principles aimed at maximising the success and benefits of artificially re‐stocking depleted fisheries. The benefits of such an approach are evident in the 400% increase in survival of stocked striped mullet in Hawaii through refinement of release techniques, however financially or temporally constrained stocking programs in Australia have not adhered to all principles. A pragmatic approach to address these principles is proposed, using international examples and Australian marine finfish pilot stockings of barramundi, mulloway, sand whiting, dusky flathead and black bream. Biological ranking of candidate species by estuarine residency, a low natural‐mortality to growth ratio, a large L _∞ and comparison by recreational value and available rearing technologies, show that mulloway, barramundi and sea mullet are ideal species for stocking in Australia. Australian intermittently closed opening landlocked lagoons and recreational fishing havens, especially near cities, provide experimental opportunities to apply this approach and stock suitable species through small‐scale pilot experiments. This would allow evaluation of production and carrying capacity, and density dependent processes with respect to optimal stocking strategies unconfounded by emigration and commercial fishing practices. Twenty per cent of Australians fish each year, and harvest approximately 27 000 t of finfish. Stocking recreationally important species in Australia should give a greater financial benefit, which is spread across a larger cross‐section of the community, compared to stocking to enhance commercial fisheries. The pragmatic application of the responsible approach, and stocking of fast growing estuarine residents into recreational fishing havens would enhance the benefit from marine stocking.     

The use of artificial reefs in enhancing fish communities in Singapore

Intense development of the coastal zone in Singapore has resulted in the degradation of much of the marine ecosystem. In order to restore and enhance fish communities of denuded areas, an artificial reef consisting of a tyre reef and a concrete reef, was established in the vicinity of the southern islands of Singapore. Results from fish visual censuses after the establishment of the artificial reef indicated an increase in numbers of juveniles and adults. A total of 37 and 32 fish species were recorded over a period of 1/2 years at the concrete and tyre reefs respectively. The dominant fish families were Pomacentridae, Labridae, Chaetodontidae, Apogonidae, Gobiidae and Nemipteridae. The artificial reefs also serve as a nursery ground for some species (e.g. Neopomacentrus sp.) which are important primary consumers of algae on natural reefs. Greater numbers of target (food-important) fishes were observed at the concrete reef while the tyre reef harboured more juveniles and smallersized adults. The results indicate that the concrete modules were more effective than the tyre reef in terms of fish abundance per unit volume. Such structures can enhance the biological resources of relatively unproductive areas.