Abundance of lamprey larvae and physical habitat

Synopsis Southern brook lamprey larvae,Ichthyomyzon gagei, were collected from four creeks in Alabama and Mississippi. Larvae abundance (number m^–2) and length (mm) were measured over a range of sites to quantify some of the physical parameters involved in larval habitat selection. Particle size distribution, hydraulic conductivity, porosity and organic content were the factors analyzed. Abundance of larvae was greatest when particles smaller than 0.15 mm and 1.–2.0 mm in diameter represented at least 40% and 8% dry weight of the substrate, respectively. Abundance of larvae was lowest when the small particles represented less than 10% dry weight of the substrate. A strong inverse relationship was observed between density and length of larvae. All other parameters did not significantly affect lamprey habitat selection. Results of this study may be applicable in directing attempts at aquatic habitat restoration for lamprey in endangered streams.     

Effects of ship‐induced waves on littoral benthic invertebrates

1. Ship‐induced waves can affect the physical characteristics of lake and river shorelines, and laboratory studies have shown effects on littoral invertebrates. Here, we explored whether these effects could be observed under field conditions along a natural lake shore affected by wave sequences (trains) produced by boats. 2. Individuals of five invertebrate species (Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeselii, Laccophilus hyalinus) were exposed to waves with increasing shear stress in five habitats differing in structural complexity. 3. Detachment of invertebrates increased with increasing shear stress and was best modelled using sigmoid response curves. Habitat structural complexity mitigated the effects of shear stress, and detachment rate was influenced more by habitat type than by species. A threshold (90% of the individual invertebrates unaffected) stress level of 0.64 N m^?2 was found for a structurally complex reed habitat, compared to 0.37 N m^?2 for a simple sand habitat. 4. Shear stress associated with wave trains created by recreational boating at a distance of 35 m from the shore and at a speed of 11 km h^?1 resulted in 45% detachment of littoral invertebrates. Decreasing the boat‐to‐shore distance to 20 m increased wave shear stress by 30% and invertebrate detachments up to 75%. 5. Disturbance of littoral habitats and invertebrate assemblages are widespread in inland waters used for recreational and/or commercial navigation. Our findings show that the integrity of littoral zones of navigable surface waters could be much improved by implementing management measures such as physically protecting complex habitats with dense reed belts and tree roots, and reducing boat speeds and increasing their minimum shoreline distance.     

Mangrove restoration without planting

Mangrove forests are disappearing at an alarming rate. Mangrove planting is the most common method of restoring these forests. However, this approach is not often successful, especially when the reasons for mangrove degradation were not removed prior to planting new seedlings or propagules. A successful mangrove restoration project may not necessarily include a planting phase. When the stressors are removed and suitable environmental conditions such as correct hydrology and calm area, particularly on exposed coasts, are provided, natural regeneration processes could recover mangroves from degradation. This paper describes an approach to mangrove restoration applied to an exposed shoreline on the west coast of Peninsular Malaysia. In this method a detached breakwater was erected seaward at the shoreline to shelter the restoration area from wave action, prevent the ongoing erosion and promote sediment deposition raising the elevation of the substrate to the target elevation. Survival of Avicennia marina seedlings transplanted in the sheltered area was significantly affected by sediment burial (P < 0.05). However, about eight months after construction of the breakwater, the sedimentation rate decreased and the substrate became stable. Subsequently, natural recruits appeared on the site. We postulate that waterborne seeds or propagules were available from adjacent stands in the study area but wave exposure reduced the possibility of natural recruitment. Thus the breakwater presence provided favourable conditions which could attract mangrove recruits, facilitating reestablishment and natural recovery of the mangrove ecosystem without planting.     

Mapping microhabitat thermal patterns in artificial breakwaters: Alteration of intertidal biodiversity by higher rock temperature

Urbanization is altering community structure and functioning in marine ecosystems, but knowledge about the mechanisms driving loss of species diversity is still limited. Here, we examine rock thermal patterns in artificial breakwaters and test whether they have higher and spatially less variable rock temperature than natural adjacent habitats, which corresponds with lower biodiversity patterns. We estimated rock temperatures at mid‐high intertidal using infrared thermography during mid‐day in summer, in both artificial (Rip‐raps) and natural (boulder fields) habitats. We also conducted diurnal thermal surveys (every 4 hr) in four seasons at one study site. Concurrent sampling of air and seawater temperature, wind velocity, and topographic structure of habitats were considered to explore their influence on rock temperature. Rock temperature was in average 3.7°C higher in the artificial breakwater in two of the three study sites, while air temperature was about 1.5–4°C higher at this habitat at summer. Thermal patterns were more homogeneous across the artificial habitat. Lower species abundance and richness in the artificial breakwaters were associated with higher rock temperature. Mechanism underlying enhanced substrate temperature in the artificial structures seems related to their lower small‐scale spatial heterogeneity. Our study thus highlighted that higher rock temperature in artificial breakwaters can contribute to loss of biodiversity and that integrated artificial structures may alter coastal urban microclimates, a matter that should be considered in the spatial planning of urban coastal ecosystems.     

Habitat preference by grayling (Thymallus thymallus) in an artificially modified, hydropeaking riverbed: a contribution to understand the effectiveness of habitat enhancement measures

This paper describes a case study to rehabilitate habitat for adult European grayling (Thymallus thymallus L.) in a large river reservoir in northern Finland. A channelled river reach was restored by building small islands and reefs as well as cobble and boulder structures for grayling. The total area of the restored stretch was 1.0 ha. The physical habitat was mapped using an echosounder, Doppler device, tachometer and scuba diving, and modelled with a 2D hydraulic model. The mean water velocity in the modelled stream section was 0.28 m s^?1 during 110 m³ s^?1 flow and 0.43 m s^?1 during 300 m³ s^?1 flow. Twelve adult grayling, tagged with transmitters, were released into the area and tracked for a maximum period of 30 days. The grayling largely stayed in the restored area and tended to avoid the unchanged channel of the river. The range of daily movement was from stationary to 2700 m per day. The adult grayling preferred water velocities between 0.20 and 0.45 m s^?1, water depths between 0.20 and 1.55 m and coarse substrate. The study provides a small part of the information needed in habitat restoration for grayling.     

A scientific basis for restoring fish spawning habitat in the St. Clair and Detroit Rivers of the Laurentian Great Lakes

Loss of functional habitat in riverine systems is a global fisheries issue. Few studies, however, describe the decision‐making approach taken to abate loss of fish spawning habitat. Numerous habitat restoration efforts are underway and documentation of successful restoration techniques for spawning habitat of desirable fish species in large rivers connecting the Laurentian Great Lakes are reported here. In 2003, to compensate for the loss of fish spawning habitat in the St. Clair and Detroit Rivers that connect the Great Lakes Huron and Erie, an international partnership of state, federal, and academic scientists began restoring fish spawning habitat in both of these rivers. Using an adaptive management approach, we created 1,100 m² of productive fish spawning habitat near Belle Isle in the Detroit River in 2004; 3,300 m² of fish spawning habitat near Fighting Island in the Detroit River in 2008; and 4,000 m² of fish spawning habitat in the Middle Channel of the St. Clair River in 2012. Here, we describe the adaptive‐feedback management approach that we used to guide our decision making during all phases of spawning habitat restoration, including problem identification, team building, hypothesis development, strategy development, prioritization of physical and biological imperatives, project implementation, habitat construction, monitoring of fish use of the constructed spawning habitats, and communication of research results. Numerous scientific and economic lessons learned from 10 years of planning, building, and assessing fish use of these three fish spawning habitat restoration projects are summarized in this article.     

The ecology of freshwater wrack along natural and engineered Hudson River shorelines

Organic matter that is washed onto shore, or “wrack,” is an important component of shoreline ecosystems, providing habitat for macroinvertebrates and organic matter and nutrients to both the upland terrestrial communities and aquatic ecosystems. While marine wrack has been studied extensively, wrack along freshwater shorelines has received less attention. In this article, we report on the standing stocks, mobility, decomposition rates, and macroinvertebrate communities of wrack on different types of Hudson River shorelines (natural: sand, rock, bedrock; and engineered: riprap, cribbing, and bulkhead). Standing stocks of wrack sometimes exceeded 1 kg dry mass/m², and were the highest on shorelines having flat slopes. Artificial wrack (hay) placed below the high tide mark was rarely retained for more than a few tidal cycles, particularly on highly exposed shores. Wrack on cribbing shorelines decayed significantly faster than on other shoreline types. Macroinvertebrate abundance and diversity were significantly different among shoreline types, with the lowest abundance found on cribbing, along with significantly lower diversity. Consequently, if managers use structures such as cribbing and bulkheads to rebuild or reinforce shorelines, then certain ecological functions may be lost.     

Oyster reef restoration: substrate suitability may depend on specific restoration goals

A limited supply of oyster shell for restoration practices has prompted investigations of alternative substrates used in construction of artificial oyster reefs. The success of oyster reef restoration projects is increasingly focused not only on oyster densities, but also on habitat provisioning for associated fauna. A subtidal oyster reef complex (0.24 km²) was restored in the Mission‐Aransas Estuary, Texas, U.S.A., in July 2013 using replicated mounds of concrete, limestone, river rock, and oyster shell substrates. Oyster and reef‐associated fauna characteristics were quantified quarterly for 15 months, using sampling trays that were deployed 3 months after construction. The highest densities of oyster spat occurred 9 months after tray deployment (July 2014, 1,264/m²), whereas juvenile oyster densities increased throughout the study period to 283/m². Concrete (1,022/m²) and limestone (939/m²) supported the highest number of oysters over all dates. Oyster shell (1,533/m²) and concrete (1,047/m²) substrates supported the highest densities of associated motile fauna. Faunal diversity (Hill's N1) did not vary by substrate material, but did show seasonal variation. A simple benefit–cost ratio was used to indicate the localized monetary value for each of the substrates. Oyster shell and concrete substrates returned the highest benefit–cost ratio for motile fauna, while concrete yielded the highest benefit–cost ratio for oyster abundance. Incorporating benefit–cost ratios in restoration planning will allow practitioners to better integrate substrate‐specific ecological values with economic considerations and project goals to maximize return on restoration investments.     

Evaluation of instream habitat enhancement options using fish habitat simulations: case-studies in the river Pas (Spain)

In the northern coast of Spain there are rivers with Atlantic salmon populations. In the upper reaches of one of these streams, river Pas, the effectiveness of habitat enhancement measures was evaluated, under different instream flow conditions. By means of the Instream Flow Incremental Methodology and using a two dimensional hydraulic model (River2D, Steffler P (2000) Software River2D. Two Dimensional Depth Averaged Finite Element Hydrodynamic Model. University of Alberta, Canada), the potential value of stream habitat for different salmon development stages requirements was measured by Weighted Useable Area (WUA). This habitat evaluation was carried out for the unmodified stream reach, which represent the control or natural conditions. Habitat improvement measures (alternate deflectors and low dams) were simulated in the original riverbed topography. Over this modified base, habitat was estimated running River2D again. By comparing the salmon habitat evaluations in the control conditions with those obtained under those improvement conditions we have been able to assess the effectiveness of each one, and the instream flow environment at which maximum improvement is reached. The maximum habitat improvement was obtained around 10 m³/s for the adult salmon, and for the fry and parr it was around 6 m³/s. However, the habitat simulation results show that with both improvement measures, under a natural flow regime the mean annual habitat increases around 1% of the WUA in relation to the control conditions, which is not a significant improvement. A similar small WUA increase was obtained when changing the bed topography, considering geomorphological adjustments due to the new erosion and sedimentation areas caused by the presence of these structures. Therefore, these types of habitat improvement measures are not recommended in these stream reaches.     

Multi-level assessment of ecological coastal restoration in South Texas

Adaptive management can be a very useful tool for assessing and improving coastal ecological engineering restoration projects. A shoreline restoration project using ecological engineering approaches to mitigate coastal erosion was developed and implemented in 2003 at Loyola Beach, Baffin Bay, TX. The project incorporated riprap, fiber matting, geotextile, and vegetation as an alternative to conventional hard structures for erosion control. As part of the restoration expansion, a detailed evaluation of the previous project was completed at several levels, including the landscape, geotechnical design, environmental and ecological considerations, and social and economic factors. The findings indicated that the vegetation and its underlying geotechnical integrity have played an important role in erosion mitigation. Overall the project was successful in the protection of the shoreline and was shown to be more ecologically beneficial than other hard structures. Based on the preliminary success of the initial project, the restoration techniques were adapted for another beach extension to the west. The assessment did reveal some weaknesses in the original project design including the need for more substantial toe protection and periodic maintenance requirements. Based on these assessments, some additional new methods for the restoration extension were proposed and implemented. The broader applicability of this restoration approach outside the local region has been presented through several outreach activities and delivered to coastal planners and land owners throughout the Texas Coastal Bend and Northern Mexico.     

18 Morphology, 16s rRNA gene sequences, and internally transcribed (ITS) regions: towards a meaningful systematic framework for the cyanobacteria

The establishment and growth of Nereocystis luetkeana communities are limited by many environmental and biotic factors. Temperature, light quantity and quality, turbidity, salinity, wave motion, and competition for space and light all determine where populations of this annual kelp will establish and persist from season to season. Like much of the nearshore marine vegetation in Puget Sound and the San Juan Archipelago, Nereocystis is negatively impacted by anthropogenic disturbances, such as shoreline development and sediment loading from terrestrial erosion. These events can alter or eliminate optimal habitat and conditions that support adult populations, as well as interfere with the development of the microscopic life stages. Various techniques to establish a Nereocystis bed in the northern waters of Washington, USA are examined and will serve as a model for future restoration efforts. Techniques being investigated are as follows: 1) out-planting Nereocystis during different seasons; 2) out-planting at different stages of maturity, i.e., zoospore and microscopic sporophyte (0.5–1.0 mm blade length) from cultures; 3) out-planting directly on natural substratum versus at elevated positions; 4) transplanting juveniles (10 cm stipe length); and, 5) seeding natural substratum with out-planted sori (sporophylls), bypassing the lab culturing phase. Results of this study will help define the optimal restoration procedure, including environmental parameters, for Nereocystis in order to aid coastal managers in the implementation of nearshore restoration projects. Preliminary results will be presented.     

The Colonisation of Human-made Structures by the Invasive Alga Codium fragile ssp. tomentosoides in the North Adriatic Sea (NE Mediterranean)

Human-made structures, such as groynes, breakwaters, seawalls, pier pilings and floating pontoons, are becoming common features of the landscape in urbanised coastal and estuarine areas. Despite this tendency few studies have focused on their ecology or on their potential impacts on natural assemblages of organisms. When artificial structures are introduced in areas with little or no hard substrata, they not only provide novel habitats, which enables the colonisation of sandy areas by hard-bottom dwelling species, but they can also provide suitable habitats for exotic species. Along the north-east coast of Italy, sandy shores are protected from erosion by a line of breakwaters, which runs almost uninterrupted for about 300 km. These structures provide habitat for a variety of macroalgae and invertebrates and also for the invasive green alga Codium fragile ssp. tomentosoides. The aim of this study was, therefore, to investigate patterns of distribution of this alga on breakwaters in Cesenatico. In particular, we compared the density of thalli, biomass, length and degree of branching of C. fragile ssp. tomentosoides between the landward and the seaward sides of breakwaters, to test the hypothesis that sheltered habitats (landward) represent more suitable habitats than exposed habitats (seaward). In general, the landward side of breakwaters supported greater numbers of thalli of C. fragile ssp. tomentosoides than seaward sides. Thalli grew longer and more branched in sheltered habitats, leading to an overall larger biomass of the alga on the landward side of breakwaters. The presence of sheltered human-made hard substrata in the vicinity of major trading ports and sources of eutrophication could enhance the dispersal of invasive species across regional and geographic scales. Thus, the effects of artificial structures and introduced species on coastal assemblages cannot be evaluated separately, but their synergistic nature should be considered in planning strategies for conservation of biodiversity in coastal habitats.     

Impacts of Channel Reconstruction on Invertebrate Assemblages in a Restored River

Ecosystem restoration often aims to recreate the physical habitat needed to support a particular life‐stage of a focal species. For example, river channel reconstruction, a common restoration practice along the Pacific coast, is typically used to enhance spawning habitat for adult Chinook salmon, a species experiencing large population declines. These restoration efforts rarely consider, however, that altering spawning habitat could have indirect effects on other life‐stages, such as juveniles, which might occur if, e.g. reconstruction alters the benthic food web. To determine how channel reconstruction impacts benthic macroinvertebrates, juvenile Chinook's primary prey, we conducted two studies at a restoration site in the Merced River, California. We asked (1) has gravel enhancement altered invertebrate assemblages in the restored reach compared with an unrestored reach? and, if so, (2) can shifts in the invertebrate community be explained by increased substrate mobility and by reduced heterogeneity that results from restoration? We show that invertebrate abundance and biomass were lower in the restored reach and that these changes were accompanied by a shift from dominance by filter‐feeding caddisflies (Hydropsyche) in the unrestored reach to grazing mayflies (Baetis) in the restored reach. Using an in situ manipulation, we demonstrated that this trend was driven by increased substrate mobility that reduces the abundance of Hydropsyche and by decreased substrate heterogeneity that reduces the abundance of Baetis. Our studies suggest that geomorphic changes typical of reconstructed rivers can alter food webs in ways that may have important implications for supporting the focal species of restoration efforts.     

17 Restoration Techniques For Nereocystis Luetkeana (Mertens) Postels Et Ruprecht (Bull Kelp)

The establishment and growth of Nereocystis luetkeana communities are limited by many environmental and biotic factors. Temperature, light quantity and quality, turbidity, salinity, wave motion, and competition for space and light all determine where populations of this annual kelp will establish and persist from season to season. Like much of the nearshore marine vegetation in Puget Sound and the San Juan Archipelago, Nereocystis is negatively impacted by anthropogenic disturbances, such as shoreline development and sediment loading from terrestrial erosion. These events can alter or eliminate optimal habitat and conditions that support adult populations, as well as interfere with the development of the microscopic life stages. Various techniques to establish a Nereocystis bed in the northern waters of Washington, USA are examined and will serve as a model for future restoration efforts. Techniques being investigated are as follows: 1) out‐planting Nereocystis during different seasons; 2) out‐planting at different stages of maturity, i.e., zoospore and microscopic sporophyte (0.5–1.0 mm blade length) from cultures; 3) out‐planting directly on natural substratum versus at elevated positions; 4) transplanting juveniles (10 cm stipe length); and, 5) seeding natural substratum with out‐planted sori (sporophylls), bypassing the lab culturing phase. Results of this study will help define the optimal restoration procedure, including environmental parameters, for Nereocystis in order to aid coastal managers in the implementation of nearshore restoration projects. Preliminary results will be presented.     

Shoreline distribution and parasite infection of black‐striped pipefish Syngnathus abaster Risso, 1827 in the lower River Danube

This study aimed to characterise the shoreline distribution and metazoan parasite community in black‐striped pipefish Syngnathus abaster along the freshwater section of the River Danube (Bulgaria). An extensive survey of the shoreline zone showed the regular presence of S. abaster along the entire stretch from Vetren to Vrav (395–836 river km). The preference of shoreline habitat was analysed using abundance data and the proportion of this species in the fish community within particular habitat types. Highest frequencies of occurrence and density were found in sites with a muddy substrate, as compared to gravel and sand. A subsample of S. abaster from the upper section of the Bulgarian stretch was examined for metazoan parasites. The parasite fauna comprised eight metazoan species, representing half the parasite species richness known from its original range. Only three parasite species previously reported from S. abaster were found in the Danubian range of expansion: the adult trematode Orientocreadium siluri, metacercariae of Diplostomum sp., and an accidental finding of the trematode Nicolla skrjabini. The other five species appear to have been acquired in the new area, although these were recorded at a very low prevalence and/or abundance. Syngnathus abaster, therefore, is not likely to represent an important component in native parasite life cycles. Fish condition was not affected by either total parasite abundance or abundance of core species. Regular occurrence and dominance of Syngnathus abaster indicates that this species now represents a significant component of the Danubian shoreline fish community.     

Oyster reefs as natural breakwaters mitigate shoreline loss and facilitate fisheries

Shorelines at the interface of marine, estuarine and terrestrial biomes are among the most degraded and threatened habitats in the coastal zone because of their sensitivity to sea level rise, storms and increased human utilization. Previous efforts to protect shorelines have largely involved constructing bulkheads and seawalls which can detrimentally affect nearshore habitats. Recently, efforts have shifted towards "living shoreline" approaches that include biogenic breakwater reefs. Our study experimentally tested the efficacy of breakwater reefs constructed of oyster shell for protecting eroding coastal shorelines and their effect on nearshore fish and shellfish communities. Along two different stretches of eroding shoreline, we created replicated pairs of subtidal breakwater reefs and established unaltered reference areas as controls. At both sites we measured shoreline and bathymetric change and quantified oyster recruitment, fish and mobile macro-invertebrate abundances. Breakwater reef treatments mitigated shoreline retreat by more than 40% at one site, but overall vegetation retreat and erosion rates were high across all treatments and at both sites. Oyster settlement and subsequent survival were observed at both sites, with mean adult densities reaching more than eighty oysters m(-2) at one site. We found the corridor between intertidal marsh and oyster reef breakwaters supported higher abundances and different communities of fishes than control plots without oyster reef habitat. Among the fishes and mobile invertebrates that appeared to be strongly enhanced were several economically-important species. Blue crabs (Callinectes sapidus) were the most clearly enhanced (+297%) by the presence of breakwater reefs, while red drum (Sciaenops ocellatus) (+108%), spotted seatrout (Cynoscion nebulosus) (+88%) and flounder (Paralichthys sp.) (+79%) also benefited. Although the vertical relief of the breakwater reefs was reduced over the course of our study and this compromised the shoreline protection capacity, the observed habitat value demonstrates ecological justification for future, more robust shoreline protection projects.     

Aquatic diversity in a former floodplain: Remediation in an urban context

The Lobau, a former floodplain area of the Danube River situated within the city limits of Vienna (Austria), was strongly affected by the river regulation in 1875. The reduced hydrological connectivity led to an increasing loss of aquatic habitats. A water enhancement scheme with a maximum water input of 0.5 m³ s^?1 was initiated in 2001. The present study assesses the effect of this scheme on biodiversity using three target species groups – aquatic molluscs, dragonflies and fish – following a common Before–After Control-Impact design (BACI). Dragonflies and molluscs were positively affected, reflecting the habitat alterations in the system. For fish, no significant impact was observed. The aim of the scheme has been achieved: increased habitat diversity and improved habitat conditions for the system's initial community and further rheophilic/rheotolerant species. Water enhancement schemes can be effective remediation measures and deserve further attention in the management of urban wetlands.     

Design of Polarization Independent SERS Substrate with Raman Gain Evaluated Using Purcell Factor

Surface-enhanced Raman scattering (SERS) is a very promising detection/diagnostic technique at trace levels as the molecules exhibit a significant increase in their Raman signals when they are attached or are in proximity to plasmonic structures. In this study, a numerical design of SERS substrate as a probe has been demonstrated for detection and diagnosis of blood, water and urea samples. The proposed nanospiral design is polarization independent, and it offers the enhancement of the electric field strength ~ 10⁹. The substrate design is based on 3D finite difference time domain simulations and is robust, versatile and sensitive even at low concentrations of the analyte. It works equally well when used in the reflection mode. In this study, the cavity quantum electrodynamics (CQED) Purcell factor has also been transposed to plasmonics. The Purcell factor in corroboration with CQED has been used to achieve efficient light–matter interaction at nanoscale by providing a more realistic result. It takes into account the randomness of incident wave polarizations and arbitrary orientations of interacting molecules. This gives a deeper insight into electromagnetic Raman gain in SERS and can be used to design novel SERS substrates.

     

The fish grazing of rocky shore algae in the Gulf of Guinea

There is a conspicuous absence of large algae on five breakwater systems surveyed along the northern shore of the Gulf of Guinea. Such algae are a distinctive feature of most natural, rocky areas in the region and their absence on these artificial structures may be accounted for by heavy sedimentation and pollution inside the harbours, and as a result of fish grazing on the outside. Herbivorous pomacentrids (Abudefduf, Pomacentrus), parrot fish (Pseudoscarus) and surgeon fish (Acanthurus) are common along parts of the breakwaters sheltered from direct wave action. Preliminary experiments and observations show the importance of fish grazing and indicate diurnal differences in its intensity. The ‘broken-up’ nature of the breakwaters with moderate wave action is the probable reason for the occurrence of large fish populations and hence the presence largely of grazing-tolerant algae.     

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.