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Potential use of marinas as nursery grounds by rocky fishes: Insights from four Diplodus species in the Mediterranean
Abstract
The construction of marinas along the shoreline has caused substantial habitat destruction within the sheltered coastal areas previously used as nursery grounds by many fish species. However, although the negative ecological impacts of these constructions have been reported extensively, their potential roles in the functioning of the coastal zone remain largely unknown. Here, we surveyed the juveniles of 4 Diplodus species in 5 marinas located along the French Mediterranean coast to assess whether rocky fishes can successfully settle inside these artificialized coastal areas. Inter-specific differences in the spatiotemporal use of the various artificial habitats provided by marinas were investigated between April and August over 2 consecutive years. We also tested the potential benefit of pegging additional artificial habitats (Biohuts) on docks and pontoons to increase their value as fish nursery grounds. Our results suggest that although variations in marina and artificial habitat preferences exist between species, Diplodus juveniles repeatedly colonize marinas. Their average abundances on added Biohut habitats were twice as high as on nearby bare surfaces. This suggests that increasing the complexity of the vertical structures of marinas can considerably enhance their suitability for juvenile rocky fishes, especially at the youngest stages, when mortality is highest. Therefore, as long as marina water quality is well controlled, ecological engineering within these man-made habitats might reduce the ecological consequences of urban development by providing suitable alternative artificial nursery grounds for rocky fishes.
... To this end, the structural complexity of man-made infrastructures is increasingly taken into account to mimic nature, either during their construction, with specific designs, or post-construction, with the addition of micro-structures (Airoldi et al., 2021). Among these projects, small artificial fish nurseries (1 m 2 to 50 m 2 ) are increasingly employed in ports in the Mediterranean with the goal to rehabilitate the fish nursery function (Bouchoucha et al., 2016;Joubert et al., 2023;Patranella et al., 2017). Currently, over thirty ports in the French Mediterranean region are equipped with these structures. ...
... Although monitoring these structures has revealed their effectiveness in increasing local juvenile fish abundance (Bouchoucha et al., 2016;Joubert et al., 2023;Patranella et al., 2017), existing studies are confined to small-scale projects, and surveys exclusively concentrate on the evaluation of fish abundance within ports. The connectivity between artificial fish nurseries and adult populations remains unexplored and the real capacity of these initiatives to support the renewal of adult fish populations with quantitative data has never been assessed (Macura et al., 2019). ...
... Based on these characteristics, we estimate the linear length of natural nurseries at 55 820m, at a scale of 1:500 (see Section SI.1 in Supporting Information for further details). During benthic settlement, a proportion of juvenile fish enter port areas (Bouchoucha et al., 2016;Joubert et al., 2023) and can be hosted in infrastructures at less than 2m depth (docks). Thus, we estimate the area of port nurseries to cover 24 771m (Fig. 2). ...
Conservation measures are implemented to support biodiversity in areas that are degraded or under anthropogenic pressure. Over the past decade, numerous projects aimed at rehabilitating a fish nursery function in ports, through the installation of artificial structures, have emerged. While studies conducted on these solutions seem promising on a very local scale (e.g., higher densities of juvenile fish on artificial fish nurseries compared to bare port infrastructures), no evaluation has been undertaken yet to establish their contribution to the renewal of coastal fish populations or their performance compared to other conservation measures such as fishing regulation. Here, we used a coupled model of fish population dynamics and fisheries management, ISIS-fish, to describe the coastal commercial fish population, the white seabream (Diplodus sargus) in the highly artificialized Bay of Toulon. Using ISIS-Fish, we simulated rehabilitation and fisheries management scenarios. We provided the first quantitative assessment of the implementation of artificial structures in ports covering 10% and 100% of the available port area and compared, at population level and fishing fleets level, the quantitative consequences of these rehabilitation measures with fishing control measures leading to strict compliance with minimum catch sizes. The rehabilitation of the nursery function in ports demonstrated a potential to enhance the renewal of fish populations and catches. When the size of projects is small the outcomes they provide remain relatively modest in contrast to the impact of regulatory fishing measures. However, we have demonstrated that combining fishing reduction measures and rehabilitation projects has a synergistic effect on fish populations, resulting in increased populations and catches. This study is the first quantitative assessment of fish nursery rehabilitation projects in port areas, by evaluating their effectiveness in renewing coastal fish populations and fisheries and comparing their outcomes with fishing control measures. Small-scale port-area nursery rehabilitation projects can support fish populations, but are less effective than controlling fisheries.
... The removal of natural fish nurseries may lead to the decline of adult populations that sustain local fisheries (Yan et al., 2021). Surprisingly, high juveniles abundances can be observed in shallow artificial habitats created by seaports (Ido & Shimrit, 2015), which could support a nursery function (Bouchoucha et al., 2016;Macura et al., 2019). Recent studies show that seaports host fish assemblages different from those present in natural habitats (Todd et al., 2019). ...
... Recent studies show that seaports host fish assemblages different from those present in natural habitats (Todd et al., 2019). Yet, fish biodiversity in seaports is still poorly known (Bouchoucha et al., 2016;Madon et al., 2023) with no consensus about the comparative level of biodiversity between natural and artificial habitats (Macura et al., 2019). This lack of knowledge and consensus partly comes from inappropriate or limited sampling designs and methods. ...
... partly due to invasion by nonindigenous species in seaports, but in our case, other reasons can be highlighted. The role of nursery played by artificial structures such as ports and marinas offer sheltered productive areas for many species (Bouchoucha et al., 2016;Mercader et al., 2019). We cannot rule out that contamination by dead fished species or urban water releases artificially increase the number of detected species in eDNA traces, although we tried to be very cautious in our sampling. ...
Coastal areas offer a diversity of habitats providing refugia and nursery for fish, promoting their biodiversity and associated contributions to people. Yet, natural coastlines are replaced by artificial infrastructures such as seaports and the influence of this artificialization on fish biodiversity remains poorly known. Here, we assessed fish biodiversity indicators using environmental DNA metabarcoding inside seaports and adjacent natural habitats including no‐take marine reserves. We found that species assemblages within seaports were primarily influenced by their area and habitat. We detected a similar species richness in seaports and reserves during lockdown, but seaports host more threatened species than natural habitats. Yet, species turnover between seaports was lower than between natural areas, reflecting biotic homogenization. Seaport managers should consider that complexifying artificial infrastructures could increase habitat diversity and coastal fish biodiversity. Our study illustrates that eDNA‐based indicators can be integrated in management and policy applications toward greener marine artificial infrastructures.
... The surface area of nurseries is therefore essential for the maintenance of these populations (Le Pape and Bonhommeau, 2015). However, the loss of nursery habitats due to urbanization has led to the over-mortality of juveniles, allowing only very limited success for recruitment to adult populations (Bouchoucha et al., 2016;Cheminée et al., 2017;Harmelin-Vivien et al., 1995). This impairs the renewal of adult nursery-dependent fish populations (Limiting Recruitment Hypothesis; Doherty, 1991). ...
... Flat, steep and smooth urban structures are considered inadequate for providing habitats for marine biodiversity, so artificial modules are added to them to increase their structural complexity (Bishop et al., 2022;Bradford et al., 2020). This approach is used to ensure marine benthic diversity (Bishop et al., 2022;Strain et al., 2020) as well as to restore the fish nursery function of urban habitats (Astruch et al., 2017;Bouchoucha et al., 2016;Lapinski et al., 2017;Patranella et al., 2017;Ushiama et al., 2019). ...
... Previous studies have shown the ability of artificial fish nurseries (AFN) installed on port structures, docks or pontoons, to host important densities of juvenile fish (Bouchoucha et al., 2016;Mercader et al., 2017). However, studies focusing on multiple species and with robust designs remain rare (Firth et al., 2020). ...
Port areas are subjected to multiple anthropic pressures that directly impact residing marine communities and deprive them of most of their essential ecological functions. Several global projects aim to rehabilitate certain ecosystem functions in port areas, such as a fish nursery function, by installing artificial fish nurseries (AFN). In theory, AFNs increase fish biodiversity and juvenile fish abundance in port areas, but studies on this subject remain scarce. Thus, the present study aimed to examine whether the use of such AFNs could restore part of the nursery function of natural habitats by increasing fish and juvenile abundance, and by decreasing predation intensity compared to bare docks. Two years of monitoring on AFNs showed they hosted 2.1 times more fish than on control docks and up to 2.4 more fish juveniles. Fish community structures were influenced by both treatment (AFN and Control) and year of monitoring. In general, AFNs hosted a greater taxonomic diversity of fish than controls. The predation intensity around these structures was significantly lower in the AFNs than in controls. Part of the definition of a fish nursery was thus verified, indicating that AFNs might be an effective restoration tool. However, we also noted that total fish abundance and Young of the Year (YOY) abundance decreased in controls, possibly due to a concentration effect. Further detailed monitoring is necessary to distinguish between these effects.
... The installation of artificial habitats with ecologically-engineered elements has been widely advocated and implemented for replacement of lost or degraded natural habitat, ecological conservation, biodiversity enhancement, and improvement of ecosystem services [11][12][13][14]. Specific goals of artificial habitats may include supporting local biodiversity and communities of fish or invertebrates of commercial or ecological interest [12,[15][16][17][18][19], building ecosystem resilience, and enhancing ecological connectivity [4,[20][21][22]. ...
... Evidence shows the efficacy of these artificial habitats in attracting marine organisms at different development stages, from larvae to adults, although the patterns of colonisation are context-dependent [17,20,[22][23][24]. These patterns can depend on processes of community assembly and succession that are determined, among others, by the timing of species colonisation and interactions among species [25][26][27]. ...
... The artificial habitats (Dock Biohut ® ; Ecocean SAS, Montpellier, Paris) were designed to provide ecological nursery habitat within commercial harbours and marinas [17,22]. We used a subset of existing monitoring data from these artificial habitats in three spatially distinct commercial harbours along the French Mediterranean coast where post-installation sampling replication allowed for comparison of colonisation across years. ...
In highly modified coastal environments, such as commercial harbours, the installation of artificial habitats has garnered support as a means of enhancing local biological recruitment and connectivity. The success of these measures depends largely on the patterns of species colonisation. Using post-installation monitoring data, we compared the composition of assemblages of invertebrates colonising artificial habitats that were immersed for different periods (~6 vs. ~18 months) in three commercial harbours along the French Mediterranean coast. The artificial habitats were colonised by taxonomically diverse invertebrate assemblages of ecological and economic importance, including molluscs, crustaceans, and echinoids. Composition differed significantly with the immersion time of the artificial habitats, with total abundance, species richness, and evenness being significantly higher after ~18 than after ~6 months of immersion, indicating that long periods are necessary to enrich these new habitats with economically and ecologically important species. These results can inform restoration protocols and emphasise the value of post-installation monitoring programs.
... One way to do so is to reduce the impacts of already deployed infrastructure by 'greening' existing man-made structures (Airoldi et al., 2021;Dafforn et al., 2015;Evans et al., 2019;Hall et al., 2018;O'Shaughnessy et al., 2020). The global principle behind the proposed technical solutions consists in modifying the three-dimensional structure of the marine urban structures, either by intervening directly on their topography when a new structure is built (Ido and Shimrit, 2015;Natanzi and Mcnally, 2018), or by adding complex artificial micro-structures a posteriori (Bouchoucha et al., 2016;Firth et al., 2016a;Mercader et al., 2017). The objective of the structural modification differs according to the context: in some cases, it consists in promoting recolonization by local and structuring species (Strain et al., 2020;Vozzo et al., 2021) or recreating small rockpools sheltering fauna and flora that cannot withstand emersion at low tide (Firth et al., 2013(Firth et al., , 2016aHall et al., 2019). ...
... The objective of the structural modification differs according to the context: in some cases, it consists in promoting recolonization by local and structuring species (Strain et al., 2020;Vozzo et al., 2021) or recreating small rockpools sheltering fauna and flora that cannot withstand emersion at low tide (Firth et al., 2013(Firth et al., , 2016aHall et al., 2019). In other cases, refuges are created against predators for fish juveniles (Astruch et al., 2017;Bouchoucha et al., 2016;Patranella et al., 2017;Selfati et al., 2018). All these pilot operations support the idea that harbor structures can be structurally modified to increase their attractiveness and quality for marine organisms, which allows them to contribute to the maintenance of coastal biodiversity while ensuring their primary function of coastal protection . ...
... Even if some ecological functions within man-made habitats are definitively lost, ecological engineering has been shown to be a tool for improving the fish nursery potential of harbor areas (Astruch et al., 2017;Bouchoucha et al., 2016;Patranella et al., 2017;Selfati et al., 2018). A nursery habitat provides two important functions for fish: nutrition and protection (Beck et al., 2001;Cheminée et al., 2011;Muller, 2017;Verdiell Cubedo et al., 2007;Whitfield and Pattrick, 2015). ...
Increasingly, ecological rehabilitation is envisioned to mitigate and revert impacts of ocean sprawl on coastal marine biodiversity. While in the past studies have demonstrated the positive effects of artificial fish habitats in port areas on fish abundance and diversity, benthic colonization of these structures has not yet been taken into consideration. This could be problematic as they may provide suitable habitat for Non-Indigenous Species (NIS) and hence facilitate their spreading. The present study aimed to examine communities developing on artificial fish habitats and to observe if the number of NIS was higher than in surrounding equivalent habitats. The structures were colonized by communities that were significantly different compared to those surrounding the control habitat, and they were home to a greater number of NIS. As NIS can cause severe ecological and economical damages, our results imply that in conjunction with the ecosystem services provided by artificial fish habitats, an ecosystem disservice in the form of facilitated NIS colonization may be present. These effects have not been shown before and need to be considered to effectively decide in which situations artificial structures may be used for fish rehabilitation.
... The existing quantitative data on fish populations does not paint a similar picture for fish biodiversity (Edgar and Shaw, 1995;Clynick, 2006;Hutchings et al., 2013). However, recent studies have highlighted that some harbours with artificial habitats (mainly in temperate regions) could be nursery areas for fish (Bouchoucha et al., 2016;Dufour et al., 2009;Mercader et al., 2017b;Patranella et al., 2017;Mercader, 2018). Breakwaters host high densities of juvenile fish (Ruitton et al., 2000;Pizzolon et al., 2008;Dufour et al., 2009) and in some areas (e.g., in Sydney harbour; Clynick 2008) adult fish species richness and abundance inside marinas are close to those found on natural rocky habitats. ...
... RPD: rostral pars distalis, PPD: proximal pars distalis, PI: pars intermedia of the adenohypophysis. fish, at least by comparison with highly urbanized neighbouring sections of the coastline (Dufour et al., 2009;Bouchoucha et al., 2016;Mercader et al., 2017b;Patranella et al., 2017;Mercader, 2018). Therefore, marinas, harbours, and ports may play a surprisingly vital role in the life cycle of some fish species. ...
... Indeed, changes in survival rates during this transition and post-settlement can have drastic effects on population replenishment. This is of particular concern as nurseries are mainly located in shallow coastal waters and some harbours are even qualified as nurseries (Bouchoucha et al., 2016;Mercader et al., 2017b;Patranella et al., 2017;Mercader, 2018) despite containing multiple stressors that can affect fish metamorphosis and subsequent juvenile quality. As such, harbours are ideal sites to study the impact of multiple stressors on fish endocrine pathways "in situ", in an ecologically relevant context. ...
Fish development and acclimation to environmental conditions are strongly mediated by the hormonal endocrine system. In environments contaminated by anthropogenic stressors, hormonal pathway alterations can be detrimental for growth, survival, fitness, and at a larger scale for population maintenance. In the context of increasingly contaminated marine environments worldwide, numerous laboratory studies have confirmed the effect of one or a combination of pollutants on fish hormonal systems. However, this has not been confirmed in situ. In this review, we explore the body of knowledge related to the influence of anthropogenic stressors disrupting fish endocrine systems, recent advances (focusing on thyroid hormones and stress hormones such as cortisol), and potential research perspectives. Through this review, we highlight how harbours can be used as "in situ laboratories" given the variety of anthropogenic stressors (such as plastic, chemical, sound, light pollution, and invasive species) that can be simultaneously investigated in harbours over long periods of time.
... A large number of studies have focused on the role of artificial structures such as fish attracting devices (Carr andHixon 1997, Rilov andBenayahu 2000) and their contribution to increasing fish biomass (Bohnsack 1989). Though marinas are among the most widespread artificial structures along the shoreline of the world, studies focusing on fish assemblages associated with marinas are still scarce (Clynick 2006, 2008, Bouchoucha et al. 2016. Breakwaters at the outer sides of marinas are frequently colonized by a range of fishes, at both juvenile and adult stages (Pizzolon et al. 2008, Cenci et al. 2011, Pastor et al. 2013. ...
... Breakwaters at the outer sides of marinas are frequently colonized by a range of fishes, at both juvenile and adult stages (Pizzolon et al. 2008, Cenci et al. 2011, Pastor et al. 2013. The inner sides of marinas, on the other hand, offer shallow and protected habitats, which can be suitable as nursery grounds for some fish species (Bouchoucha et al. 2016). In addition to direct impacts on natural shallow habitats, marinas can indirectly change local current patterns and increase sediment loads, which in turn have drastic consequences on the composition of benthic communities (Connell and Glasby 1999), altering the distribution, abundance and diversity of associated fauna (Clynick et al. 2007). ...
... Interestingly, all the individuals of D. vulgaris and D. sargus found on the inner sides of marinas were below their length at first maturity (Supplementary material Table S1). Bouchoucha et al. (2016) demonstrated that marinas can provide a suitable nursery habitat for juveniles of these species in the Mediterranean. This might be favoured by the high plasticity in habitat requirements of juveniles of the genus Diplodus, which may allow their successful recruitment and further growth on the inner sides of marinas. ...
Understanding the ecological role that artificial structures might play on nearshore fish assemblages requires the collection of accurate and reliable data through efficient sampling techniques. In this work, differences in the composition and structure of fish assemblages between the inner and outer sides of three marinas located in the temperate northern-eastern Atlantic Ocean were tested using three complementary sampling techniques: underwater visual censuses (UVC), baited cameras (BCs) and fish traps (FTs). UVCs and BCs recorded a comparable number and relative abundance of species, which in turn were much greater than those recorded by FTs. This finding supports the use of UVCs and BCs over FTs for broad ecologically studies, especially when dealing with structurally complex habitats such as artificial structures. We found differences in fish assemblage structure between the inner and outer sides of marinas, independently of the sampling method. Four small-sized species (Similiparma lurida, Thalassoma pavo, Sarpa salpa and Symphodus roissali) associated with structurally complex vegetated habitats dominated, in terms of abundance, the outer sides of marinas; Diplodus vulgaris, Diplodus sargus and Gobius niger, species with high ecological plasticity in habitat requirements, dominated the inner sides of marinas. The information provided in this study is of great interest for developing sound monitoring programmes to ascertain the effects of artificial structures on fish communities.
... Several recent studies have suggested that coastal man-made infrastructures, particularly those found inside ports, might provide suitable alternative nursery habitats for certain fish species (e.g. Pizzolon et al., 2008;Bouchoucha et al., 2016;Mercader et al., 2017). However, these conclusions were solely based on fish abundance (Bouchoucha et al., 2016;Mercader et al., 2017) or post-settlement growth and condition in ports when, in theory, fish nursery grounds are defined according to three conditions: they support high abundances of juveniles, they sustain faster somatic growth rates and they also enhance fish survival so their populations contribute more to the final adult stock (Beck et al., 2001). ...
... Pizzolon et al., 2008;Bouchoucha et al., 2016;Mercader et al., 2017). However, these conclusions were solely based on fish abundance (Bouchoucha et al., 2016;Mercader et al., 2017) or post-settlement growth and condition in ports when, in theory, fish nursery grounds are defined according to three conditions: they support high abundances of juveniles, they sustain faster somatic growth rates and they also enhance fish survival so their populations contribute more to the final adult stock (Beck et al., 2001). Therefore, the correct estimation of the nursery role played by ports implies estimating the relative contribution of port juvenile habitats to adult stocks. ...
... Two Diplodus species, D. sargus sargus (Linnaeus, 1758), hereafter D. sargus, and D. vulgaris (Geoffroy Saint-Hilaire, 1817) were chosen for this study. Both are very common in the Mediterranean (Coll et al., 2004;Morales-Nin et al., 2005;Lloret et al., 2008) and their juveniles are found in high abundances inside ports (Clynick, 2006;Bouchoucha et al., 2016). However there is temporal segregation between settlement periods of the two species (García-Rubies and Macpherson, 1995;Harmelin-Vivien et al., 1995;Vigliola et al., 1998;Cheminee et al., 2011;Ventura et al., 2014;Bouchoucha et al., 2016): D. sargus generally settles in one pulse, in May-June, and usually leaves its nursery grounds in September while D. vulgaris generally settles in two pulses, in November-December and in January-February, the first pulse being predominant, and leaves its nursery grounds in June-July. ...
... Marinas are among the most common human-made marine infrastructures, and can cause substantial habitat destruction within sheltered coastal areas previously used as nursery grounds by many fish species (Bouchoucha et al. 2016). Therefore, the need to reduce the impact of these infrastructures and even to enhance their ecological value is becoming urgent as their number is predicted to increase worldwide. ...
... Therefore, the need to reduce the impact of these infrastructures and even to enhance their ecological value is becoming urgent as their number is predicted to increase worldwide. Recently, the deployment of artificial microhabitats (Biohuts) (Fig. 1a) in marinas and ports (Bouchoucha et al. 2016;Mercader et al. 2017) as an ecological restoration action aiming at restoring the nursery function through habitat complexification, revealed that such artificial habitats enhance the diversity and density of juvenile fish by providing shelter from predators, thereby boosting the marina's and/or port's nursery value. ...
... Until now, Biohuts were deployed only in open-sea ports and marinas (Bouchoucha et al. 2016;Mercader et al. 2016Mercader et al. , 2017 as an ecological restoration action aiming at restoring the nursery function and thereby boosting the marina and port's nursery value. 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 (Seaman 2007). ...
Rapid urbanization has become an area of crucial concern in conservation, owing to urban infrastructure impacts on natural ecosystems. Urban infrastructures are often poor surrogates for natural habitats, and a diversity of eco-engineering approaches has been trialed to enhance their ecological value.
Marinas are among the most common human-made infrastructures found on the shoreline, and cause substantial habitat destruction within the sheltered coastal areas previously used as nursery grounds by many fish species. The present study aimed at testing the suitability of installing artificial habitats (Biohut®) in marinas to reinforce the nursery function of the Marchica coastal lagoon, which historically hosts many species of juvenile groupers, including the endangered dusky grouper Epinephelus marginatus.
Our hypothesis – that artificial habitats, by increasing habitat complexity, enhance the ecological value of a marina – was strongly supported by our results. The Biohuts hosted a high relative density of juvenile dusky and comb groupers in comparison with natural habitats. They can, therefore, be considered as a reservoir for juvenile groupers, including the endangered dusky grouper, and are suitable to reinforce the nursery function of this coastal lagoon.
Subsequently, Biohuts can act as a ready-made nursery area to support the creation of small marine reserves that can reinforce the grouper population re-colonization along the coast of North Africa, which is considered to be the region from which the individuals populating the north western Mediterranean originated, and thus provide for long-term recovery of the endangered dusky grouper.
... On the other hand, harbors are usually very enclosed, which might limit larval flow inside those infrastructures. The presence of juvenile fish within harbors has already been documented (Bouchoucha et al., 2016;Clynick, 2006Clynick, , 2008Dufour et al., 2009;Mercader et al., 2017) but comparison of the observed densities with nearby natural sites is very often lacking, preventing the assessment of their potential nursery role. Here, we compared the densities in harbors with those of natural sites and CDS and found that if juvenile fish do settle in harbors; the densities observed are lower than those of the other sites (CDS and natural). ...
... Since this species settles during winter, individuals are already at an intermediate developmental stage or even at a predispersal stage during the sampling period. During these stages, juveniles use all suitable habitats available or are even ready to leave their nursery to join adult habitat (Bouchoucha et al., 2016;Ventura et al., 2014;Vigliola and Harmelin-Vivien, 2001). This less restrictive habitat requirement would explain the broader distribution of this species inside the harbors. ...
... Given the amount of featureless docks inside harbors and the fact that juveniles only poorly use them due to their lack of complexity, it could be interesting to consider ecological engineering approaches on those structures. Recent studies showed that the use of small artificial habitats could enhance juvenile densities on docks and under pontoons (Bouchoucha et al., 2016;Mercader et al., 2017) and that even the protected dusky grouper (Epinephelus marginatus) could settle inside harbors (Mercader et al., 2016). Also, since harbors are usually seen as having a negative environmental impact, eco-engineering and restoration ecology approaches coupled with pollution reduction measures could represent another and complementary way, along with natural habitat preservation, to favor the nursery function of the Mediterranean coast even in highly urbanized areas. ...
Along the littoral, a growing number of anthropogenic structures have caused substantial habitat destruction. Despite their detrimental impact, these constructions could play a role in the functioning of coastal ecosystems. The objective of this work was to assess the distribution of juvenile coastal fish along a seascape composed of various natural and artificial habitats in order to determine the potential role of coastal infrastructures as juvenile habitat. We surveyed juvenile populations on various infrastructures and natural sites along a 100 km shoreline of the French Mediterranean coast. Juvenile densities varied according to the level of artificialization of the sites. Densities were the highest on coastal defense structures, intermediate in natural sites and lowest in harbors. Focusing inside harbors revealed highly variable densities depending on the type of habitat, with densities on ripraps or jetties that were equivalent to those of natural sites. Our results underline the importance of anthropogenic structures as potential juvenile habitats, which is too often not considered in management plans.
... However, results of ecological monitoring are generally associated with poorer and different mobile and sessile communities in comparison to natural reference ecosystems (AIROLDI et al., 2005;CLYNICK et al., 2007;BURT et al., 2013;BOSCH et al., 2017). If ecological processes which occurred in marine urban zones are still poorly understood, different projects have emerged all around the world in order to improve ecological functions of maritime technical infrastructures (CHAPMAN & UNDERWOOD, 2011;FIRTH et al., 2016;BOUCHOUCHA et al., 2016). Solutions mostly focused on the improvement of construction materials properties (porosity, rugosity, pH), water retention in intertidal areas and habitat complexity (different scale for different stages of life). ...
... As in other studies (e.g. BOUCHOUCHA et al., 2016), initial monitoring conducted on the inner sides of this port have highlighted that juvenile stages of fish can be observed along pile wharfs and riprap dikes. However, diving observations also concluded that many ecological factors described in suitable Mediterranean nurseries Mediterranean rocky coasts: Features, processes, evolution and problems for coastal fish were absent (mainly gentle slope and micro-habitats as mentioned by HARMELIN-VIVIEN et al., 1995;VIGLIOLA & HARMELIN-VIVIEN, 2001). ...
... The first solution has been designed to improve micro-habitats complexity of vertical timber pile wharfs. It is bio-inspired by the Posidonia oceanica seagrass meadows, one of the most important nursery grounds in the Mediterranean Sea (BOUDOURESQUE et al., 2006). Thus, artificial seagrass is shaped and dimensioned according to the biological characteristics of the plant at low depth (up to 40 cm length for the artificial leafs). ...
... Therefore defining fish nursery habitats not only requires the identification of habitats with high juvenile densities but also those which enhance survival, growth rates and contribution to adult stocks. During the last few years, several studies suggested that coastal man-made infrastructures, particularly those found inside ports, might provide alternative nursery habitats for several rocky fish species (Bouchoucha et al., 2016;Clynick, 2006;Dufour et al., 2009;Pastor et al., 2013). However, this conclusion was solely based on the high abundances of juvenile fish observed in ports. ...
... These two sparids are common in the Mediterranean and have high ecological and commercial value (Coll et al., 2004;Lloret et al., 2008;Morales-Nin et al., 2005). They are highly abundant in both natural and artificial rocky coastal areas (Tortonese, 1965) and their juvenile habitat use is fairly well known (Bouchoucha et al., 2016;Cheminee et al., 2011;García-Rubies and Macpherson, 1995;Harmelin-Vivien et al., 1995;Ventura et al., 2014;Vigliola et al., 1998): D. sargus settles in one pulse only, in June-July, and usually leaves its nursery grounds in September; conversely D. vulgaris settles in two pulses, one in November-December and one in January-February, and leaves its nursery grounds in June-July. Moreover, as migration is very limited in Diplodus juveniles (Macpherson et al., 1997) and given the distance between our sampling sites (between 1.5 and 8 km), the post-settlement growth, body condition and contamination levels of the juveniles of the two species should correctly reflect the quality of the sites in which they were collected. ...
... The link between environmental pollution and juvenile fish contamination and health is not a straightforward one. During the last few years, certain studies have shown that the abundances of juveniles of the most common rocky species inside ports also seem to be similar to those found in natural habitats (Bouchoucha et al., 2016;Clynick, 2008;Dufour et al., 2009). These observations strongly suggest that ports could serve as nursery habitats at least for some rocky fishes, providing them with shelter and enhanced feeding conditions. ...
High abundances of juvenile fish in certain ports suggest they might provide alternative nursery habitats for several species. To further investigate this possibility, post-settlement growth, metal uptake and body condition were estimated in 127 juveniles of two seabream species, collected in 2014-15, inside and outside the highly polluted ports of the Bay of Toulon. This showed that differences in local pollution levels (here in Hg, Cu, Pb and Zn) are not consistently mirrored within fish flesh. Muscle metal concentrations, below sanitary thresholds for both species, were higher in ports for Cu, Pb and V only. Otherwise, fish muscle composition principally differed by species or by year. Juvenile growth and condition were equivalent at all sites. Higher prey abundance in certain ports might therefore compensate the deleterious effects of pollution, resulting in similar sizes and body conditions for departing juvenile fish than in nearby natural habitats.
... Therefore defining fish nursery habitats not only requires the identification of habitats with high juvenile densities but also those which enhance survival, growth rates and contribution to adult stocks. During the last few years, several studies suggested that coastal man-made infrastructures, particularly those found inside ports, might provide alternative nursery habitats for several rocky fish species (Bouchoucha et al., 2016;Clynick, 2006;Dufour et al., 2009;Pastor et al., 2013). However, this conclusion was solely based on the high abundances of juvenile fish observed in ports. ...
... These two sparids are common in the Mediterranean and have high ecological and commercial value (Coll et al., 2004;Lloret et al., 2008;Morales-Nin et al., 2005). They are highly abundant in both natural and artificial rocky coastal areas (Tortonese, 1965) and their juvenile habitat use is fairly well known (Bouchoucha et al., 2016;Cheminee et al., 2011;García-Rubies and Macpherson, 1995;Harmelin-Vivien et al., 1995;Ventura et al., 2014;Vigliola et al., 1998): D. sargus settles in one pulse only, in June-July, and usually leaves its nursery grounds in September; conversely D. vulgaris settles in two pulses, one in November-December and one in January-February, and leaves its nursery grounds in June-July. Moreover, as migration is very limited in Diplodus juveniles (Macpherson et al., 1997) and given the distance between our sampling sites (between 1.5 and 8 km), the post-settlement growth, body condition and contamination levels of the juveniles of the two species should correctly reflect the quality of the sites in which they were collected. ...
... The link between environmental pollution and juvenile fish contamination and health is not a straightforward one. During the last few years, certain studies have shown that the abundances of juveniles of the most common rocky species inside ports also seem to be similar to those found in natural habitats (Bouchoucha et al., 2016;Clynick, 2008;Dufour et al., 2009). These observations strongly suggest that ports could serve as nursery habitats at least for some rocky fishes, providing them with shelter and enhanced feeding conditions. ...
High abundances of juvenile fish in certain ports suggest they might provide alternative nursery habitats for several species. To further investigate this possibility, post-settlement growth, metal uptake and body condition were estimated in 127 juveniles of two seabream species, collected in 2014–15, inside and outside the highly polluted ports of the Bay of Toulon. This showed that differences in local pollution levels (here in Hg, Cu, Pb and Zn) are not consistently mirrored within fish flesh. Muscle metal concentrations, below sanitary thresholds for both species, were higher in ports for Cu, Pb and V only. Otherwise, fish muscle composition principally differed by species or by year. Juvenile growth and condition were equivalent at all sites. Higher prey abundance in certain ports might therefore compensate the deleterious effects of pollution, resulting in similar sizes and body conditions for departing juvenile fish than in nearby natural habitats.
... Although ecological engineering has become a common practice in terrestrial and freshwater environments, it has just started to emerge over the last few years in marine environments (Browne and Chapman, 2011;Chapman and Blockley, 2009;Perkol-Finkel et al., 2006, 2008Sella and Perkol-Finkel, 2015). Still, this kind of approach is rarely applied in the development of ports (Bouchoucha et al., 2016;Hellyer et al., 2011;Paalvast et al., 2012). ...
... In a recent study, Bouchoucha et al. (2016) explored the potential role of marinas as habitat for juvenile seabreams (Diplodus spp.) and the used off small artificial units to increase habitat complexity. The habitats in large commercial ports are even more heavily transformed than in marinas, with much deeper waters, wide openings onto the sea and higher levels of human activities. ...
... Our study included two treatments in each area: normal docks (as controls) and equipped docks with increased complexity. In order to increase habitat complexity, we used Artificial Experimental Units (AEU) provided by the Ecocean ® company (dock Biohut ® ) composed of a pair of stainless steel alloy cages (50 cm × 80 cm × 25 cm) (as used in Bouchoucha et al., 2016). The inner cage has a 2.5 cm mesh and is filled with a biogenic component (oyster shells) to promote colonization by benthic fauna and flora, as well as to increase the structure complexity. ...
The concentration of human activities along the shoreline induces high levels of pressure, notably seascape urbanization caused by the proliferation of coastal and marine infrastructures such as ports, harbors, marinas and coastal defense structures. Because they are localized in sheltered and shallow coastal areas, these infrastructures inevitably lead to the loss of natural essential habitats once used as nursery ground by juvenile fish. Some studies have reported the presence of high juvenile densities on breakwaters and jetties suggesting those infrastructures could support the nursery function. However, ports seem unlikely to be used by juveniles due to their vertical and featureless docks. Here we explored the feasibility of using small artificial habitats to enhance the ecological value of ports. We set up a total of 108 artificial habitats in three different locations of the large commercial port of Marseille in the northwestern Mediterranean. We then surveyed juvenile fish on the artificial habitats and control docks on 7 different occasions between June and September 2014. Average species richness and densities were higher on the artificial habitats but displayed high spatial and taxa-specific variations. Hence, small artificial habitats are promising ecological engineering tools to enhance the nursery function inside ports and thus reduce the ecological footprint of those infrastructures.
... A large number of studies have focused on the role of artificial structures such as fish attracting devices (Carr andHixon 1997, Rilov andBenayahu 2000) and their contribution to increasing fish biomass (Bohnsack 1989). Though marinas are among the most widespread artificial structures along the shoreline of the world, studies focusing on fish assemblages associated with marinas are still scarce (Clynick 2006, 2008, Bouchoucha et al. 2016). Breakwaters at the outer sides of marinas are frequently colonized by a range of fishes, at both juvenile and adult stages (Pizzolon et al. 2008, Cenci et al. 2011, Pastor et al. 2013). ...
... Breakwaters at the outer sides of marinas are frequently colonized by a range of fishes, at both juvenile and adult stages (Pizzolon et al. 2008, Cenci et al. 2011, Pastor et al. 2013). The inner sides of marinas, on the other hand, offer shallow and protected habitats, which can be suitable as nursery grounds for some fish species (Bouchoucha et al. 2016). In addition to direct impacts on natural shallow habitats, marinas can indirectly change local current patterns and increase sediment loads, which in turn have drastic consequences on the composition of benthic communities (Connell and Glasby 1999), altering the distribution, abundance and diversity of associated fauna (Clynick et al. 2007). ...
... sandy and muddy bottoms, with a high concentration of organic material (da Cunha and Antunes 2008), i.e. conditions typically found on the inner sides of marinas. Interestingly, all the individuals of D. vulgaris and D. sargus found on the inner sides of marinas were below their length at first maturity (Supplementary materialTable S1).Bouchoucha et al. (2016)demonstrated that marinas can provide a suitable nursery habitat for juveniles of these species in the Mediterranean. This might be favoured by the high plasticity in habitat requirements of juveniles of the genus Diplodus, which may allow their successful recruitment and further growth on the inner sides of marinas. ...
Understanding the ecological role that artificial structures might play on nearshore fish assemblages requires the collection of accurate and reliable data through efficient sampling techniques. In this work, differences in the composition and structure of fish assemblages between the inner and outer sides of three marinas located in the temperate northern-eastern Atlantic Ocean were tested using three complementary sampling techniques: underwater visual censuses (UVC), baited cameras (BCs) and fish traps (FTs). UVCs and BCs recorded a comparable number and relative abundance of species, which in turn were much greater than those recorded by FTs. This finding supports the use of UVCs and BCs over FTs for broad ecologically studies, especially when dealing with structurally complex habitats such as artificial structures. We found differences in fish assemblage structure between the inner and outer sides of marinas, independently of the sampling method. Four small-sized species (Similiparma lurida, Thalassoma pavo, Sarpa salpa and Symphodus roissali) associated with structurally complex vegetated habitats dominated, in terms of abundance, the outer sides of marinas; Diplodus vulgaris, Diplodus sargus and Gobius niger, species with high ecological plasticity in habitat requirements, dominated the inner sides of marinas. The information provided in this study is of great interest for developing sound monitoring programmes to ascertain the effects of artificial structures on fish communities.
... species attached or associated with the ships' hull) [13], the incidence of NIS is increasing with the development of new infrastructure and shipping traffic and sailing [1,14,15]. It is also noteworthy that, in parallel with the negative ecological footprint mentioned above, marinas are also increasingly considered as potential habitats to contribute to the restoration of fish populations, particularly through the use of marinas as nurseries for local native fishes [16,17]. Marinas may thus be perceived both as degraded environments or refugees for some (overexploited) species. ...
... For the residents, we were careful to balance the gender of the respondents and the age groups. Age and gender are critical issues in the provision of public goods and environmental preservation in particular, where women and young people have been shown to contribute more [16,42]. This distinction could not be realized for boaters, whose reference population is mostly composed of men, often over 60 years old. ...
Marinas have a major ecological footprint, not only because of the pollution they generate but also because of the introduction and spread of non-indigenous species (NIS). This invites us to reconsider both the practices and in-frastructures of marinas but also their uses and users, as marinas are increasingly recognized as places of well-being. The twofold objective of this article is to analyze the public's perception of environmental and ecological degradation in marinas and to assess the willingness to pay to improve their environmental quality. We conducted a field survey among residents and boaters of four marinas in France and showed that both have a relatively low knowledge of NIS, as well as of the responsibility of the boating activity for their spread. Other environmental degradations, such as the pollution generated by boats, are better identified and many agree on the positive economic impact of marinas. We showed a high willingness to pay to improve the environmental quality of marinas and on this basis make recommendations on how to encourage support for reducing environmental degradation. In particular, we discuss the appropriation of marinas by a wider population, including residents, young people and women. The challenge is for marinas to become multifunctional spaces, with the extension of their uses to a wider range of users going hand in hand with an improvement in their environmental quality.
... Seaports may represent a shelter against exploitation as fishing is usually forbidden within their boundaries, and their enclosed architecture can provide protection from coastal streams. Seaports have been shown to play the key role of nursery grounds for some fish species when adding habitat complexity (Bouchoucha et al., 2016;Joubert et al., 2023;Selfati et al., 2018). ...
Coastal areas host a major part of marine biodiversity but are seriously threatened by ever-increasing human pressures. Transforming natural coastlines into urban seascapes through habitat artificialization may result in loss of biodiversity and key ecosystem functions. Yet, the extent to which seaports differ from nearby natural habitats and marine reserves across the whole Tree of Life is still unknown. This study aimed to assess the level of α and β-diversity between seaports and reserves, and whether these biodiversity patterns are conserved across taxa and evolutionary lin-eages. For that, we used environmental DNA (eDNA) metabarcoding to survey six seaports on the French Mediterranean coast and four strictly no-take marine reserves nearby. By targeting four different groups-prokaryotes, eukaryotes, metazoans and fish-with appropriate markers, we provide a holistic view of biodiversity on contrasted habitats. In the absence of comprehensive reference databases, we used bio-informatic pipelines to gather similar sequences into molecular operational taxonomic units (MOTUs). In contrast to our expectations, we obtained no difference in MOTU richness (α-diversity) between habitats except for prokaryotes and threatened fishes with higher diversity in reserves than in seaports. However, we observed a marked dissimilarity (β-diversity) between seaports and reserves for all taxa. Surprisingly, this biodiversity signature of seaports was preserved across the Tree of Life, up to the order. This result reveals that seaports and nearby marine reserves share few taxa and evolutionary lineages along urbanized coasts and suggests major differences in terms of ecosystem functioning between both habitats.
... The Toulon Bay is a highly urbanized area (Meaille and Wald 1990), with six marinas, several commercial harbors, a large military harbor and ferry activities over an area of approximatively 10 km². It is highly impacted by anthropogenic pressures such as habitat modification and loss (Bouchoucha et al. 2016(Bouchoucha et al. , 2018a, chemical contamination (Wafo et al. 2016;Araújo et al. 2019;Mazoyer et al. 2020), and the presence of introduced species (Zibrowius 1991;Ruitton et al. 2005;Gauff et al. 2023a)). The Old Harbor of Marseilles is a recreational marina with approximately 3200 boat moorings, a large hull cleaning area, and commercial activities such artisanal fisheries and short distance ferry transports. ...
Introduced species constitute a critical bio-security issue worldwide and the precise monitoring of their spread is crucial for their management. For species forming cryptic complexes this may remain difficult. Using integrative taxonomy, we formally report for the first time, well-established populations of the cosmopolitan introduced bryozoan Watersipora subatra in the French Mediterranean Sea and compile worldwide existing genetic data for Watersipora species alongside newly acquired data to establish the most complete phylogeny of the genus to date. This revealed pervasive erroneous identifications in Genbank, which in turn perpetrate further errors in recent studies, primarily misidentifying W. subatra as W. subtorquata . High abundance and geographic spread of W. subatra in our Mediterranean sampling sites suggest that this species has been present for some time but has been misidentified until now. We provide an updated species identification for all current reference sequences in the Watersipora genus, which may help future monitoring of W. subatra and other Watersipora species.
... Indeed, even though the hard substrate and the vertical inclination added can lead to more larvae selecting these locations to settle for food and shelter and increased fish abundance (Bulleri and Chapman 2010), the featureless surface of artificial substrates may fail to provide these functions (Mercader et al. 2018;2019). Consequently, habitat complexity, combined with other elements like connectivity to other habitats, may be the main reason for increased fish productivity and abundance (Bouchoucha et al. 2016;Perry et al. 2018). ...
Coastal ecosystems act as spawning grounds, settlement areas or nurseries for a diversity of fish species. Today, these ecosystems are under various anthropogenic stressors. One of these disturbances is the structural modification of the shallow littoral by coastal infrastructure such as ports, piers, marinas and roads. Here, we investigate whether there are differences between modified (artificial) and non-modified (natural) habitats in central Greece in terms of the fish assemblage structure, species diversity and richness, fish abundance and the proportion of juveniles. We carried out underwater visual census from September 2020 to August 2021 across two habitats (natural and artificial) in three locations of central Greece. The fish community and Shannon diversity index did not vary across habitat type; however, both species richness and total abundance were significantly higher in artificial habitats. The abundance of five (out of ten examined in total) taxa was significantly affected by habitat type. Higher abundance in the artificial habitat in the warmer or more productive months was found, possibly relevant to food availability. The significance of habitat interactions with location and the temporal component in community composition and species abundance models indicated intense heterogeneity in species-specific occupancy and may be linked to the type and characteristics of artificial habitats. Modeling of the percentage of small-sized individuals indicated patterns of juvenile occupancy requiring further investigation about the potential role of artificial habitats for some species. Future research should examine the impact of specific artificial habitat types on population dynamics and investigate the implications of artificial habitat construction for conserving fish diversity and maintaining coastal ecosystem functioning.
... Duggan et al. 2011;Bishop et al. 2017), the spread of non-native species (Bulleri and Chapman 2010;Foster et al. 2016), and water quality (Rivero et al. 2013;Valdor et al. 2019), have caused widespread conservation concern, research on the endangered estuarine seahorse, Hippocampus capensis, has shown that this species has benefitted from the suitable new subtidal habitat provided by marina canals (Claassens 2016;Claassens and Hodgson 2018). A positive effect of marinas on the survival of juvenile native seabreams, Diplodus spp, along the French Mediterranean coast has also been suggested (Bouchoucha et al. 2016), although this may be an artifact of acting as attractors of juvenile fish (Bosch et al. 2017). The impact of coastal marinas has generated a large volume of research but relatively little of this has concerned their effect on soft-sediment benthic invertebrates and effectively none on seagrass macrobenthos or on the new aquatic habitats constructed on brownfield sites (i.e. on previously developed land no longer in use); although unsurprisingly it is known that hard surfaces are a 'poor substitute' for natural soft-sediment habitats including seagrass beds (Momota and Hosokawa 2021). ...
Where ecologically 'tis better to go brown than green: enhanced seagrass macrobenthic biodiversity within the canals of a brownfield coastal marina Abstract At the start of the 21st century, a coastal residential-estate marina was developed on a previously degraded and polluted brownfield island site within Knysna estuarine bay, Garden Route National Park, South Africa, including the creation of 25 ha of new flow-through tidal canals. Canals near the larger entrance to this system now support permanently submerged beds of seagrass, which in turn support abundant macrobenthic invertebrates. In comparison with equivalent seagrass-associated assemblages present in natural channels around the island, those in the artificial marina canals were similarly structured and dominated by the same species, but the marina assemblages were significantly more species-rich (1.4 x on average) and were more abundant. Indeed, this area of marina supports the richest seagrass-associated macrofaunal biodiversity yet recorded from South Africa. The canals created de novo therefore now form a valuable addition to the bay's marine habitat, in marked contrast to the generality that marinas developed on greenfield sites represent a net reduction in intertidal and shallow marine area and associated seagrass-associated benthos. If located and constructed appropriately, brownfield marina development and conservation of coastal marine biodiversity clearly need not be antithetical, and brown-field sites may provide opportunity for the location and management of 'artificial marine micro-reserves' or for the action of 'other effective area-based conservation measures' for soft-sediment faunas.
... Firstly, a major drawback is the absence of a metric focusing on the nursery function of AS. Indeed, the nursery function of AS has been extensively studied, in particular in the field of eco-engineering (Bouchoucha et al., 2016;Mercader et al., 2017Mercader et al., , 2019. The ability of AS to facilitate reproduction and spawning of the megafauna plays an important role in the "attraction vs. production" debate and should consequently be taken into account when assessing the ecological effects and performance of these structures. ...
The current development of human activities at sea (e.g. land reclamation, maritime activity and marine renewable energy) is leading to a significant increase in the number of infrastructures installed in marine settings. These artificial structures provide new hard-bottom habitats for many marine organisms and can thus modify the structure and functioning of coastal ecosystems. In order to better evaluate the nature of these modifications as well as the potential benefits and/or impacts generated, it becomes essential to develop assessment methods that can be applied to a wide variety of study sites from harbours to coastal offshore environments. In this context, our study aims to review the different methods and indicators available which are used to measure the modifications of biodiversity and ecological functioning generated by such structures. Among the methods reviewed, we highlight some that were developed specifically for artificial structures, and others intended for various primary uses but which have been successfully transposed to artificial structures. Nevertheless, we also point out the lack of reliable methods concerning some biological ecosystem components impacted by artificial structures. In this context, we require the adaptation or creation of brand-new indicators to achieve a better characterisation of the ecological impacts generated by these structures. Overall, this study highlights a very high number of existing methods, which provide stakeholders with useful tools to study the impacts of artificial structures, and identifies the need to develop integrative indicators to enhance the deployment of new artificial structures.
... Bosch et al. (2017), comparing the fish fauna inside and outside three marinas in the temperate eastern Atlantic, found significant differences between the two zones. It can be hypothesised that the Forum bathing area provides protection and a relatively fishing-free location for adults and juveniles to establish and mature, as in the case of the Diplodus species (Bouchoucha et al., 2016). ...
The Mediterranean Sea is a hotspot for biodiversity and endemic species (between 4 % and 18 % of known species are endemic, depending on the group), but this environment, favourable for native species, also favours exotic species. To ascertain how biodiversity has been impacted by intense human activity, we surveyed the marine life in the Barcelona Forum bathing area, an artificial beach receiving large amounts of waste from neighbouring areas and effluent from the nearby sewage treatment plant. Despite such eutrophic influences and the replacement of natural substrates with artificial ones, a surprisingly rich marine biota of 514 species was found. The groups with most species identified were molluscs (176), fish (88), crustaceans (65) and algae (50). These results include 15 exotic species that have settled in this ecosystem, such as the sea hare Bursatella leachii and the polychaete Branchiomma luctuosum, and some iconic natives such as the Fan mussel (Pinna nobilis) and the Dusky grouper (Epinephelus marginatus). Urban litter was sampled and no significant deleterious effects on the biota were detected. The site acts as a refuge for fish and is conducive to the settlement of encrusting species that colonize new substrates.
... Le programme GIREL a quant à lui été mené dans l'enceinte du port maritime de Marseille. Ces études ont mis en évidence que lorsqu'on augmente la complexité de la structuration des zones verticales des infrastructures portuaires (quais, pontons) en installant des micro-récifs artificiels (Biohuts®), cela favorise l'attraction et la survie des plus jeunes stades de vie des poissons (Bouchoucha et al., 2016 ;Mercadet et al., 2017). ...
Etude de la dynamique et du fonctionnement écologique de la lagune du Brusc (Var). Actions de restauration écologique (transplantation de cymodocée) et de réhabilitation et réaffectation dans les aires adjacentes (ports du Brusc et des Embiez et anciens marais salants des Embiez).
... D. vulgaris and D. puntazzo) [60]. As juveniles they all settle within rocky reefs, where they are well protected from physical stresses and mainly threatened by density dependent competition with each other [61][62][63]. The decline of D. sargus and D. puntazzo due to overfishing may have released D. vulgaris from its competitive restrictions and it may in turn contribute to the further decline of the other congeners through direct competition within the adults and juvenile cohorts or by increased intraguild predation on juveniles of D. sargus and D. puntazzo [53]. ...
We performed over 19,000 lure-assisted, underwater visual fish census transects at over 140 shallow coastal sampling locations in the mid- eastern Adriatic sea of the Croatian mainland and islands, recording all fish taxa observed, their predatory behavior in response to the lure, and the cover of benthic habitats with which they were associated. We hypothesized that prey habitat preference was a learned or selected response to aggressive behavior by piscivorous mesopredators, and predicted that mobile prey would be spatially segregated from aggressive predators into different benthic habitats within local sampling sites. We found that aggressive piscivores were primarily wait-chase or cruise-chase mesopredators that preferentially foraged along heterogeneous habitat edges within juxtapositions of rock, unconsolidated sediment, macroalgae (Cystoseira spp.) and seagrass (usually Posidonia oceanica). Prey species and less aggressive piscivores avoided these heterogeneous habitats and preferred more homogeneous habitats that the aggressive predators in turn avoided. We found strong and consistent spatial segregation between aggressive predators on the one hand, and less aggressive predators and prey on the other hand. These results are consistent with the hypothesis that aggressive behavior by piscivorous species is the primary organizing force shaping assembly of fish communities at our study sites, driving preference and occupancy of heterogeneous and homogeneous benthic habitats. Management of shallow benthic resources should recognize the value of complementarity in habitats allowing coexistence of predators and prey through contrasting habitat preferences.
... unknown, yet harbours not only generate pollution cues but are often rich in inorganic nutrient inputs that stimulate primary production in the oligotrophic waters of the Mediterranean Sea, representing a significant and previously overlooked nutrient source for nearshore marine environments (Vaulot et al., 1996). The latter might imply 93 that if pollution levels are tolerable, these areas might be seen as refuges for growth: recent works have shown that harbours in the Mediterranean Sea may be suitable nursery areas for certain sparids (Bouchoucha et al., 2016) and dusky groupers (Mercader et al., 2016). Moreover, when compared with control water, the harbour collected water had a similar effect as the seagrass water (increase in the sprints). ...
... barnacles, ascidians) (Rivero et al. 2013). Ichthyofaunal diversity also tends to be lower within marinas compared to areas outside (Clynick 2008); however, marinas that are well designed with adequate structural complexity and good water quality can function as nurseries for juvenile fish (Dicken 2010;Bouchoucha et al. 2016). ...
The establishment of marinas alters physico-chemical conditions and affects distribution of resident epibiotic and pelagic communities along coastal areas. However, information on the soft bottom macrobenthos within and around these boating facilities in the tropics is limited. Here, we investigated if macrobenthic communities differed among three representative tropical marinas, and whether the communities inhabiting the marinas differed from those outside the marinas. Ekman grab sampling of the soft bottom sediment at three Singapore marinas – Raffles Marina (RM), ONEo15 Marina (OMC), Marina at Keppel Bay (MKB) – yielded a total of 73 taxa from eight phyla. Accounting for temporal variations, taxonomic richness did not differ among marinas, while Shannon index (MKB > RM = OMC) and abundance (RM > OMC > MKB) did. Macrobenthic community composition differed among the marinas, with RM dominated by a high proportion of opportunistic species and OMC supporting species that were sensitive to pollution. The surveys also revealed that communities within and outside marinas differed. Unlike RM which is more enclosed, diversity was higher within MKB than outside it, likely because the latter marina had a layout that encouraged flushing which maintained good water quality. The study showed that while Singapore’s tropical marinas can support diverse groups of macrobenthic taxa, the presence of high proportions of opportunistic species suggested that pollution within the marinas was still significant. Macrofaunal diversity in tropical marinas, such as those in Singapore, may be promoted by designs that improve water exchange.
... habitat destruction, changes in environmental quality, loss of native biodiversity and ecosystem functionality and spread of non-indigenous species). Microhabitats can be designed or retrofitted to favour the recruitment of different species or to offer refuge from herbivores and/ or predators (Hauser et al., 2006;Chapman and Blockley, 2009;Martins et al., 2010;Lapinski et al., 2014;Bouchoucha et al., 2016). Active 'seeding' and transplantation methods, by installing juveniles or adult individuals on artificial structures, are also being tested to favour space pre-emption by focal native habitat-forming species, thereby limiting the space for invasive species and enhancing desired ecosystem functions (Dean and Jung, 2001;Terawaki et al., 2003). ...
Coastal areas have been transformed worldwide by urbanization, so that artificial structures are now widespread. Current coastal development locally depletes many native marine species, while offering limited possibilities for their expansion. Eco-engineering interventions intend to identify ways to facilitate the presence of focal species and their associated functions on artificial habitats. An important but overlooked factor controlling restoration operations is overgrazing by herbivores. The aim of this study was to quantify the effects of different potential feeders on Cystoseira amentacea, a native canopy-forming alga of the Mediterranean infralittoral fringe, and test whether manipulation of grazing pressure can facilitate the human-guided installation of this focal species on coastal structures. Results of laboratory tests and field experiments revealed that Sarpa salpa, the only strictly native herbivorous fish in the Western Mediterranean Sea, can be a very effective grazer of C. amentacea in artificial habitats, up to as far as the infralittoral fringe, which is generally considered less accessible to fishes. S. salpa can limit the success of forestation operations in artificial novel habitats, causing up to 90% of Cystoseira loss after a few days. Other grazers, such as limpets and crabs, had only a moderate impact. Future engineering operations,intended to perform forestation of canopy-forming algae on artificial structures, should consider relevant biotic factors, such as fish overgrazing, identifying cost-effective techniques to limit their impact, as is the usual practice in restoration programmes on land.
... Throughout the colonisation process, the arrival, establishment and replacement of species has the potential to interact with natural and other artificial habitats at local and regional scales. Structures may attract spawning adults, become nursery areas for juveniles [4,5] and the output of propagules could theoretically have an impact on dispersal between natural and artificial habitats [6]. A higher regional diversity of species and assemblages resulting from a wide variation of natural and artificial habitat may be considered beneficial by conferring a degree of resilience to a wide range of disturbances [7]. ...
With increasing coastal infrastructure and use of novel materials there is a need to investigate the colonisation of assemblages associated with new structures, how these differ to natural and other artificial habitats and their potential impact on regional biodiversity. The colonisation of Europe’s first artificial surf reef (ASR) was investigated at Boscombe on the south coast of England (2009–2014) and compared with assemblages on existing natural and artificial habitats. The ASR consists of geotextile bags filled with sand located 220m offshore on a sandy sea bed at a depth of 0-5m. Successional changes in epibiota were recorded annually on differently orientated surfaces and depths using SCUBA diving and photography. Mobile faunal assemblages were sampled using Baited Remote Underwater Video (BRUV). Distinct stages in colonisation were observed, commencing with bryozoans and green algae which were replaced by red algae, hydroids and ascidians, however there were significant differences in assemblage structure with depth and orientation. The reef is being utilised by migratory, spawning and juvenile life-history stages of fish and invertebrates. The number of non-native species was larger than on natural reefs and other artificial habitats and some occupied a significant proportion of the structure. The accumulation of 180 benthic and mobile taxa, recorded to date, appears to have arisen from a locally rich and mixed pool of native and non-native species. Provided no negative invasive impacts are detected on nearby protected reefs the creation of novel yet diverse habitats may be considered a beneficial outcome.
... They suggested that these areas be recognized as valuable and that they be protected and serve as small (< 0.2 km 2 ) marine reserves called artificial marine micro reserve (AMMR). Bouchoucha et al. (2016) found that marinas provide a refuge for native juvenile Diplodus fish species and may provide artificial nursery for rocky species. Burt et al. (2013) highlight the importance of breakwaters for supporting coral reef fish communities in the rapidly developed marine environment of the Persian Gulf. ...
Intense human activity in the marine environment poses a threat to marine ecosystem. The ecosystem-based planning and management approach has developed over the past decades with the goal of reducing this threat by defining planning and management of uses in a way that mitigates negative effects on ecosystem structure and function. For oceans and coasts, marine spatial planning (MSP) can further aid the implementation of ecosystem-based management, a widely accepted tenet of planning for the marine environment. It can do so by allocating different uses of space in a way that reduces conflicts for the benefit of the environment. Here, we propose an approach to MSP that incorporates principles of reconciliation ecology for the planning of marine (nearshore) enclosures. The approach supports conservation within and around anthropogenic elements outside of marine protected areas. Since human activity typically involves some damage to natural ecosystem, this research contributes by proposing a way to incorporate ecosystem modeling for MSP that includes human activity. Examining areas of human activity under different management scenarios allows identification of possible trends in human-natural ecosystem interactions. Using such an approach increases marine conservation opportunities, and directs educated and cautious MSP in ways that allow implementation of an ecosystem-based approach.
... European seabass (Dicentrarchus labrax) ( Dufour et al., 2009), different sparids 434 ( Bouchoucha et al., 2016b) and dusky groupers ( Mercader et al., 2016). Moreover, Blüthgen et al., 2012;Gago-Ferrero et al., 2013), or concentrations in different 449 parts of the ecosystem ( Balmer et al., 2005). ...
Human pressure on coastal areas is affecting essential ecosystems including fish nursery habitats. Among these anthropogenic uses, the seasonal increment in the pressure due to leisure activities such as coastal tourism and yachting is an important environmental stressor in many coastal zones. These pressures may elicit understudied impacts due to, for example, sunscreens or other seasonal pollutants. The island of Majorca, northwest Mediterranean Sea, experiences one of the highest number of tourist visits per capita in the world, thus the surrounding coastal habitat is subject to high anthropogenic seasonal stress. Studies on early stages of fishes have observed responses to coastal chemical cues for the selection or avoidance of habitats. However, the potential interferences of human impacts on these signals are largely unknown. A choice chamber was used to determine water type preference and behaviour in naïve settled juvenile gilt-head sea bream (Sparus aurata), a temperate species of commercial interest. Fish were tested individually for behavioural changes with respect to water types from potential beneficial habitats, such as seawater with extract of the endemic seagrass Posidonia oceanica, anthropogenically influenced habitats such as water extracted from a commercial and recreational harbour and seawater mixed with sunscreen at concentrations observed in coastal waters. Using a Bayesian approach, we investigated a) water type preference; b) mean speed; and c) variance in the movement (as an indicator of burst swimming activity, or “sprint” behaviour) as behavioural descriptors with respect to water type. Fish spent similar percentage of time in treatment and control water types. However, movement descriptors showed that fish in sunscreen water moved slower (98.43% probability of being slower) and performed fewer sprints (90.1% probability of having less burst in speed) compared to control water. Less evident increases in sprints were observed in harbour water (73.56% more sprints), and seagrass (79.03% more) in comparison to control water. When seagrass water was tested against harbour water, the latter elicited a higher number of sprints (91.66% increase). We show that juvenile gilt-head seabream are able to react to a selection of naturally occurring chemically different odourscapes, including the increasingly important presence of sunscreen products, and provide a plausible interpretation of the observed behavioural patterns.
Coastal zones provide about 70% of the world’s ecosystem services. However, more than 25% of these habitats have been modified by human activity at both land and sea. At the intertidal eco-tonal zone, habitat modification is equally severe, as almost 20% of the world’s shoreline is now artificial. Coastal defense structures are more abundant in areas where the ecosystem richness, diversity and productivity are higher, such as coastal lagoons, estuaries and bays. As these degrad-ed areas are under high human pressure, their protection should be prioritized. Coastal infrastruc-ture, particularly those enclosing highly modified water bodies, such as ports and marinas, are hubs for pollution and human activities, such as trade and leisure. These have become a serious threat to marine coastal communities, due to habitat degradation and disease spread, and ecolog-ical-engineering interventions are now an imperative to integrate urban with nature and improve life and ecosystem quality for coastal settlements.
The design of anthropogenic marine structures can have unintended consequences for ecological communities. We describe differences in biofouling assemblages between two primary anthropogenic habitats—pontoons and pilings—in a marina in British Columbia, Canada, using multiple measures of diversity (i.e., richness, evenness, and Shannon indices) and multiple metrics of variability in taxonomic composition (i.e., Jaccard and modified Gower methods) using two complementary surveys. First, a video-transect survey revealed abundances of crawling benthic predators to be 19 times greater on pilings than on pontoons. Second, a photo-quadrat survey of sessile invertebrates revealed moderate differences in diversity but differences of 86% in taxonomic composition and 88% in non-indigenous species (NIS), owing largely to the dominance of mussels (Mytilus species complex) on pontoons and their absence on pilings. We discuss several environmental factors associated with the design of anthropogenic infrastructure and propose that contact with the seafloor is the key driver of observed differences between the biofouling assemblages at this site. Contact with the seafloor permits access to crawling predators and thereby drives the abundances of ecosystem-engineering taxa. Patterns of taxonomic composition and assemblage dispersion indicate that biofouling organisms are affected by these phenomena according to their roles either as prey or as competitors with mussels and not whether they are native or NIS. Finally, we consider how the growing body of ecological studies on biofouling communities such as ours can inform the implementation of infrastructure for the purposes of enhancing biotic diversity and resilience.
The rate of introduction of man-made habitats in coastal environments is growing at an unprecedented pace, as a consequence of the expansion of urban areas. Floating installations, due to their unique hydrodynamic features, are able to provide great opportunities for enhancing water detoxification through the use of sessile, filtering organisms. We assessed whether the application of sponges to floating pontoons could function as a tool for biomonitoring organic and inorganic pollutants and for improving water quality inside a moderately contaminated marina in the NW Mediterranean. Fragments of two common Mediterranean sponges (Petrosia (Petrosia) ficiformis and Ircinia oros) were fixed to either suspended natural fibre nets beneath a floating pontoon or to metal frames deployed on the sea bottom. We assessed the accumulation of organic and inorganic contaminants in sponge J o u r n a l P r e-p r o o f Journal Pre-proof fragments and, in order to provide an insight into their health status, we examined changes in their metabolic and oxidative stress responses and associated microbiomes. Fragments of both sponge species filtered out pollutants from seawater on both support types, but generally showed a better physiological and metabolic status when fixed to nets underneath the pontoon than to bottom frames. P. (P) ficiformis maintained a more efficient metabolism and exhibited a lower physiological stress levels and higher stability of the associated microbiome in comparison with I. oros. Our study suggests that the application of sponges to floating pontoon represents a promising nature-based solution to improve the ecological value of urban environments.
Since the commercial exploitation of marine oil and gas reserves began in the middle of the twentieth century, extensive networks of offshore infrastructure have been installed globally. Many of the structures are now nearing the end of their operational lives and will soon require decommissioning, generating renewed interest in their environmental impacts and in the ecological consequences of their removal. However, such work requires selection of a subsample of assets for surveying; censuses of the entire ‘population’ in any given jurisdiction are practically impossible due to their sheer number. It is important, therefore, that the selected sample is sufficiently representative of the population to draw generalized conclusions. Here, a formal clustering methodology, partitioning around medoids, was used to produce a typology of surface-piercing oil and gas platforms in the North Sea. The variables used for clustering were hydrocarbon product, operational state, platform design and material, and substructure weight. Assessing intra-cluster variability identified 13 clusters as the optimum number. The most important distinguishing variable was platform type, isolating floating platforms first, then concrete gravity-based and then fixed steel. Following clustering, a geographic trend was evident, with oil production more prevalent in the north and gas in the south. The typology allows a representative subset of North Sea oil and gas platforms to be selected when designing a survey, or an assessment of the representativeness of a previously selected subset of platforms. This will facilitate the efficient use of the limited funding available for such studies.
The importance of marinas as infrastructures for recreational boating is increasing substantially. However, information on their soft-bottom benthic communities, a key tool for managing programmes, is still scarce. We combined environment features with macro- and meiofaunal soft-bottom community information for assessing the ecological status of marinas with an integrative approach. To address this issue, we focused on eight marinas of the Southern Iberian Peninsula. Macro- and meiofauna data revealed high benthic heterogeneity at a spatial scale. The environmental variables which correlated best with macrofauna were mainly phosphorus, granulometry, and total organic carbon, and secondarily important variables were faecal coliforms, the biocide Irgarol, and heavy metals; total hydrocarbon concentration was also significant for meiofauna. Annelida was the dominant phylum in terms of number of species (37%) and abundance (66%) and were better descriptors of the environmental conditions than Arthropoda and Mollusca. Although identification to the species level is desirable and mandatory for assessing biological pollution, significant differences among marinas and correlations between fauna and abiotic variables were already detected at the level of family and order. This implies that biota assessment at higher levels may still be useful in monitoring programmes limited by time and budget constraints. The major novelty of this study lies in the development of an integrative assessment method based on the following selected ecological indicators: Marinas Environmental Pollution Index (MEPI), Biocontamination Index (BCI), macrofaunal biotic indices (AMBI, M-AMBI, BENTIX, MEDOCC and BENFES), macrofaunal taxa richness and Shannon-Wiener’s diversity, and nematode:copepod index. This approach was able to discriminate marinas of the Southern Iberian Peninsula based on their ecological status, which ranged from poor to good. The method can be useful to design standards for assigning “sustainable quality seals” to those marinas with better values of ecological indicators.
All aquatic ecosystems, and even some land‐based habitats, have been used by fish populations, with few ecological niches deprived of their presence, as evidenced by the examples of fish colonizing many different types of habitats. Reef corals create complex mineralized structures with an extreme diversity of habitats used by small fish whose size and morphology are perfectly adapted to the geometric structures created. The occupation of space by a species varies over time in accordance not only with the local hydrological fluctuations in its habitat during floods, low water levels, etc., but also the presence or absence of predators. Strong competition for food often occurs in natural environments between individuals of the same population, to the benefit of the largest, strongest and most dominant. The best, most nutritious and easily accessible prey is often its own congeners, especially if they are defenseless as they are early, in the egg, larvae and juvenile stages.
Les projets impliquant l'ingénierie écologique sont, la plupart du temps, mono-objectifs, alors que répondre à plusieurs finalités est souvent la vocation et la plus-value de l'ingénierie écologique. Cet ouvrage à destination des décideurs de la gestion de l'eau et des milieux aquatiques, met en évidence, pour les projets d'ingénierie écologique appliqués aux milieux aquatiques, les bénéfices ainsi que les bénéficiaires associés, en mettant l'accent sur le caractère multi-bénéfices de ces projets. En effet, les actions d'ingénierie écologique peuvent engendrer divers bénéfices, c'est-à-dire des gains, des profits ou des avantages d'ordres écologique, social ou économique. Elles sont multifonctionnelles et génèrent ainsi plusieurs bénéfices d'ampleurs différentes pour plusieurs bénéficiaires. Lors de la conception d'un projet d'ingénierie écologique, l'identification des bénéfices (et des inconvénients) qui pourront être développés par la solution préconisée, qu'ils soient écologiques, sociaux ou économiques, est importante. Ces bénéfices peuvent être qualitatifs ou quantitatifs. Ils peuvent également être évalués monétairement ou non. L'identification des bénéficiaires potentiels d'un projet passe par une identification des changements de fonctionnement du milieu, à l'origine des préjudices subis par des personnes. L'identification, la caractérisation et la priorisation des bénéficiaires peut permettre de définir le ou les plus importants pour les décideurs. La présentation de 17 retours d'expériences vient illustrer quatre sous-chapitres de cet ouvrage dont l'objet est de mettre en avant le caractère multi-bénéfices des projets d'ingénierie écologique à travers quatre grands types d'actions, correspondant chacun à un domaine d'application de l'ingénierie écologique : la restauration du lit d'un cours d'eau et la lutte contre les inondations, la gestion des eaux pluviales en milieu urbain et péri-urbain, l'amélioration de la qualité de l'eau des milieux aquatiques à l'interface péri-urbain/agricole, la création d'habitats en zone portuaire le long des petits fonds côtiers.
To support wind farm permit holders to design their wind farms in a nature inclusive way, a catalogue of nature inclusive design options has been developed by Witteveen+Bos and Wageningen Marine Research. This catalogue shows relevant nature inclusive design options for target species, the expected construction costs, and possible suppliers and manufacturers.
The Dutch Government stimulates nature enhancement within offshore wind farms. Currently, permit holders must take measures to increase the suitable habitat for species naturally occurring in the North Sea. The focus of the study was therefore on native species that are under pressure, such as cod (Gadus morhua) and European oyster (Ostrea edulis). At the same time many other species can also benefit from the measures. In addition, the catalogue focusses on a number of commercial species such as Edible crab (Cancer pagurus) and European lobster (Homarus gammarus) since there is also a lot of focus on co-using offshore wind farms for small scale fisheries. The catalogue was commissioned by the Dutch Ministry of Agriculture, Nature and Food Quality.
SUMMARY:
Sweden has a long and beautiful coastline with extensive archipelagos that offer exceptional conditions for recreational boating. There are more than 700 000 recreational boats in Sweden, which is one of the highest numbers in the world in relation to the population size. Small tidal differences and many sheltered bays also provide good conditions for storing boats at docks and piers and jetties. As a result, large areas of the Swedish coast are today covered with docks and marinas for recreational boats. The large number of boats and docks could have substantial negative effects on the environment. However, the understanding of the cumulative impact of recreational boating on Swedish coastal ecosystem has so far been incomplete. The goal with this report from the Swedish Institute for the Marine Environment has been to compile and summarize the present state of knowledge regarding how recreational boating affect shallow coastal ecosystems in Sweden, to determine the extent of the impact and if the development is sustainable. The aim has been to present scientific knowledge on these topics in an accessible way in order to facilitate the development of a more sustainable management of recreational boating in Sweden. The scientific literature strongly support that recreational boating generates many negative effects on the marine environment. Recreational boating requires a number of physical structures and generate a number activities that each results in several different pressures on the environment. An increased number of marinas, docks and dredged canals results in losses of important habitats, as well as long-term deterioration of the environmental conditions locally. Dredging and dumping of dredge material results in increased turbidity and dispersal of sediment, nutrients and pollutants over large areas with negative effects on many aquatic organisms, e.g. vegetation, fishes and mussels. Traffic from recreational boats and anchoring result in increased turbidity and sediment erosion as well as damage to habitats. Motor boats also create underwater noise that can disturb e.g. fishes, seals and porpoises. In addition, recreational boating result in substantial emissions of toxic substances and pollution from e.g. antifouling paint and combustion engines. More than 60% of all docks and marinas are found in wave sheltered, shallow (<3 m) areas with soft bottoms, despite that this environment only constitute 25% of shallow coastal areas in Sweden. These sheltered areas are well suited for storing boats, but also constitute one of the most productive and valuable environments along the coast. They are important environments for vegetation such as seagrass, pondweed and stoneworts, which in turn constitute important spawning and nursery areas for a large number of fish and invertebrates. The report shows that these shallow soft bottom environments are very sensitive to a majority of the stressors that recreational boating generate. Boating therefore create a disproportionally large impact on environments with high values. Although the impact from a single recreational boat or dock is limited, the cumulative effect is substantial because of the sheer number. According to recent inventories, there are today almost 110 000 docks along the Swedish coast covering almost 2 000 km of bottom. In comparison with the 1960s, the amount of docks has increased with almost 160%, which today constitutes an increase of 1 700 new docks per year. Recent studies show that vegetation is degraded as the number of docks and boats increase within shallow, wave sheltered areas. It is estimated that almost 20% of this important environment is negatively affected by recreational boating today; in the County of Stockholm and Västra Götaland around 30% of shallow, wave sheltered areas are estimated to be impacted. Despite several management measures in the last decades to decrease coastal exploitation, there are no signs that the rate of exploitation is decreasing. The large number of recreational boats with combustion engines, the trend of increasing engine size, and the fact that engines lack all forms of emission control result in substantial emissions of pollutants and greenhouse gases. Recent estimates suggest that the emissions from recreational boats are very high and comparable with other types of transport in Sweden. Emission of toxic copper from antifouling paint on recreational boats is also substantial and contributes to the high levels of copper in coastal waters, which is above the limit for good ecological status in 85% of the assessed coastal water bodies. Although most boat owners likely spend time at sea because they enjoy and care about the environment, the results presented in this report show that recreational boating have a substantial negative impact on the coastal environment, particularly in shallow, wave protected areas. In these areas, today’s use and development of recreational boating cannot be considered sustainable. However, the report also shows that there are ways to decrease the environmental impact from recreational boating. By changing the way we use and store recreational boats, and by improving management we can still allow coming generations to enjoy unexploited coastal environments with clear water and a rich plant and animal life. The report ends by discussing new, possible measures and solutions for a more sustainable use of recreational boats in Sweden, which could be a starting point for continuing such work. These include e.g. to identify vulnerable coastal environments in order to steer away exploitation and recreational boat traffic from these areas. By storing boats on land, the need for docks, dredging and toxic antifouling paint could decrease. Reduced speed limits and access limitations for recreational motorboats in certain areas could decrease negative impact on the most vulnerable habitats. Finally, new, environmentally friendly technology, and new financial instruments could be used to decrease negative impacts and create a more sustainable development of recreational boating.
(In Swedish with English Summary)
Eco-engineering and the installation of green infrastructure such as artificial floating islands (AFIs), are novel techniques used to support biodiversity. The European Convention on Biological Diversity highlighted the development of green infrastructure as a key method of enhancement in degraded habitats. Research specifically on AFIs in marine environments has largely focused on their ecological functioning role and engineering outcomes, with little consideration for the social benefits or concerns. The aim of this study was to gain an understanding of public perception of coastal habitat loss in the UK and AFIs as a method of habitat creation in coastal environments. This was achieved via a survey, consisting of six closed and two open questions. Of the 200 respondents, 94.5% were concerned about the loss of coastal habitats in the UK, but less than a third were aware of habitat restoration or creation projects in their area of residence. There was a positive correlation between proximity of residency to the coast and knowledge of habitat restoration or creation projects. The majority of the respondents understood the ecological functioning role of AFIs and 62% would preferably want successful plant growth and avian species utilising the AFI. Nearly a third of the respondents had concerns about AFI installations, such as the degradation of the plastic matrix, long term maintenance and disturbance of native species. Despite 90.9% of the respondents supporting the installation of AFIs, the concerns of the public must be addressed during the planning stages of any habitat creation project.
Man‐made infrastructures have become ubiquitous components of coastal landscapes, leading to habitat modification that affects the abundance and diversity of marine organisms. Marine coastal fish have a complex life cycle requiring different essential habitats. One of these habitats is known as a nursery, a place where juveniles can settle in large numbers, survive and grow to contribute to the adult population. Nurseries are mainly found in shallow, sheltered zones and are thus particularly impacted by urbanization, notably by harbors. The vertical featureless structure of docks is very unlikely to be used by juveniles, which need complex habitats to find food and shelter from predators. Recent attempts to rehabilitate the nursery function in such environments by using artificial habitats have proven efficient in increasing juvenile densities. However, nothing is known about the survival of juveniles in these habitats, preventing any conclusions on the effectiveness of this means of restoration from being drawn. Here, we set up tank experiments to test the relationship between habitat preferences and the survival rate of two species of seabream when facing stalk‐attacking combers. Habitat choice was consistent with survival results, indicating that artificial habitats might not represent unintended ecological traps for juveniles. However, the artificial habitats’ effect on survival was variable between species. Therefore, our results suggest that habitat diversity might be of prime importance to sustain juveniles of different species and stress the need for the development of diverse artificial habitats to counteract the effects of seascape homogenization.
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La perte d'habitat engendrée par l'artificialisation des côtes a de graves conséquences sur la biodiversité marine. Aussi, dans une optique de maintien de la biodiversité et des stocks de poissons, il peut s’avérer intéressant de restaurer certaines fonctions écologiques dans les zones anthropisées. Cette thèse avait pour objectif d’estimer le rôle potentiel des ports en tant qu’habitat pour les juvéniles de poissons côtiers et d’évaluer dans quelle mesure ce rôle peut être amélioré par le biais d’actions de restauration. Des expérimentations en aquarium ont permis d’estimer que le taux de survie des juvéniles sur des habitats artificiels utilisés à des fins de restauration était comparable à celui observé sur des roches. Une étude de la distribution spatiale des juvéniles à l’échelle d’un paysage sous-marin a ensuite montré que les ports pouvaient abriter des densités en juvéniles représentant de 50 à 90 % de celles retrouvées en milieu naturel. Les densités à l'intérieur des ports étaient cependant tributaires du type d’habitat considéré; les quais sans complexité structurale abritant les densités les plus faibles. Enfin, l'étude de cas concrets, a montré que la réhabilitation des ports pouvait significativement augmenter les densités de juvéniles à l’échelle de l’habitat, celles-ci pouvant atteindre des niveaux comparables au milieu naturel. Toutefois, ces bénéfices restaient faibles à l’échelle d’un port dans sa globalité. Ces travaux suggèrent un réel potentiel des infrastructures portuaires en tant qu’habitat juvénile alternatif, en particulier si des actions de restauration y sont entreprises. Cependant, pour plus d’efficacité, les projets de restauration devraient être menés à large échelle et utiliser une diversité d’habitats artificiels. La restauration écologique des ports peut ainsi être employée comme un outil complémentaire aux mesures de protection dans le cadre d’une gestion intégrée des zones côtières à l’échelle du paysage.
Ce mémoire de recherche présente mon étude portée sur l'utilisation du corail en tant que matériau de construction, dans l'objectif de créer une autosuffisance sédimentaire dans des zones définies. En effet, le travail s'applique aux plages Héraultaises, dont les besoins sont précisés dans l'étude. Pour ce faire une recherche en amont sur la source et les origines de sable fut réalisée. Il s'agit alors de comprendre sa provenance pour pouvoir s'atteler à sa production. Le présent travail démontre qu'il n'est plus nécessaire d'exploiter le sable quand nous pouvons le produire nous-même. L'idée est de s'appuyer sur le biomimétisme. Le corail mort est depuis des siècles, utilisé dans diverses régions du monde comme pierre de construction pour différents types d'édifices. Des exemples historiques sont ainsi détaillés dans l'étude. A travers mes recherches, je me suis procuré des informations sur un spécimen de poisson capable de produire du sable à partir du corail mort, grâce à son processus de digestion particulier.
Ce rapport tente alors de démontrer qu'en utilisant du corail comme matériau pour nos constructions futures, nous pouvons envisager de l'utiliser par la suite pour subvenir à nos besoins en sable, et ce grâce au poisson perroquet. Pour contenir et contrôler la production, la technique de l'aquaculture est alors suggérée. Il convient d'évaluer la faisabilité de cette méthode face aux besoins des plages Héraultaises.
Au cours de leur cycle de vie, la plupart des espèces de poissons marins côtiers passent par des nourriceries littorales dont la qualité influence largement le succès du recrutement et donc le maintien de l’abondance de leurs populations. Or, la construction de ports entrain irrémédiablement une perte de fonction pour les habitats côtiers impactés. Dans ce contexte,l’objectif général de cette thèse était de voir si les zones portuaires peuvent malgré tout servir de nourriceries alternatives pour les poissons marins côtiers. Pour cela, les abondances des juvéniles de quatre espèces de sars, du genre Diplodus, ont d’abord été suivies dans cinq ports méditerranéens. Ceci a permis de montrer que ces espèces côtières peuvent s’installer et grandir avec succès dans les ports. La complexification de la structure 3D de l’habitat augmente sensiblement les abondances de juvéniles. Dans un second temps, la croissance, la condition et les niveaux de contamination desjuvéniles de deux espèces de sars (D. sargus et D. vulgaris) ont été comparés entre différents ports et habitats naturels de la rade de Toulon. Ceci a montré que la croissance et la condition des juvéniles peut être équivalente dans certains ports et dans les zones naturelles adjacentes, avec des niveaux de contamination faibles, même dans les zones les plus polluées. Enfin, la composition multi- élémentaire des otolithes des juvéniles de D. sargus et D. vulgaris a été comparée entre trois ports et deux zones naturelles de la rade de Toulon. Aucun élément chimique lié aux activités portuaires n’aété retrouvé en plus forte concentration dans les otolithes des juvéniles issus des ports. Il n’existe donc pas une signature unique caractéristique de l’ensemble des ports. La composition chimique des otolithes peut néanmoins être utilisée pour étudier la contribution relative des ports aux stocks d’adultes à condition de caractériser la signature de l’ensemble des habitats juvéniles potentiels. L’ensemble des résultats acquis indiquent que les ports peuvent être utilisés comme nourriceries alternatives par plusieurs espèces de poissons marins côtiers. Les projets d’ingénierie écologiquevisant à augmenter la complexité structurale des habitats portuaires sont des pistes intéressantes pour maintenir la biodiversité côtières et les stocks de poissons.
The most important organizations for developing and advertising the yacht tourism in a country are the marinas. Yachting tourism, being a part of maritime sector tends to play a part in the tourist activities and provides important resources for the general economy. In this study, the developments in yachting tourism are explained by considering the current status of the marinas in the Mediterranean countries. Basic characteristics of different marinas of the Mediterranean countries will be discussed and also statistical figures will be given. The yachting routes and the potential of Turkey will be analyzed by emphasizing operational, infrastructural and service characteristics. The factors that should be taken into consideration and the methods used for marina marketing will be explained. By considering strengths, weaknesses, opportunities and threats, a SWOT analysis will be made for Turkey marinas. Suggestions will be given fur further development of marina management in Turkey.
This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the 'sampled patch size,' i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and Satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.
Over 80% of the money allocated to protect coastlines from climatic change is spent
building new seawalls or increasing the stability, height and length of existing seawalls. Although
this protects important infrastructure, it has serious consequences for intertidal biodiversity,
because walls are built and maintained according to engineering and financial criteria, despite
the fact that they are known to adversely affect intertidal biodiversity. We tested the predictability
and reliability of adding pots, designed to simulate rockpools, to seawalls as an artificial habitat to
mitigate against loss of intertidal species. Two sizes of concrete pots were attached at mid- and
highshore tidal levels to sandstone seawalls at 2 locations in Sydney Harbour, Australia. After
7 mo, pots increased intertidal biodiversity on the seawalls by adding additional species. They also
supported greater covers and densities of algae and many invertebrates compared with established
assemblages on the seawalls. The size of the pot, its height on the wall and its location
affected the assemblages that developed, with greater abundances and diversity of organisms in
shallower pots and those at midshore levels. Although there were slight differences between locations
for some taxa, these results show an easy cost-effective method that authorities can use to try
to mitigate the adverse effects on intertidal assemblages of armouring shorelines with featureless,
vertical walls.
Many exploited fish and macroinvertebrates that utilize the coastal zone have declined, and the causes of these declines, apart from overfishing, remain largely unresolved. Degradation of essential habitats has resulted in habitats that are no longer adequate to fulfil nursery, feeding, or reproductive functions, yet the degree to which coastal habitats are important for exploited species has not been quantified. Thus, we reviewed and synthesized literature on the ecological value of coastal habitats (i.e. seagrass beds, shallow subtidal and intertidal
habitats, kelp beds, shallow open water habitats, saltmarshes, mussel beds, macroalgal beds, rocky bottom, and mariculture beds) as feeding grounds, nursery areas, spawning areas, and migration routes of 59 taxa, for which the International Council for the Exploration of the Sea (ICES) gives management advice, and another 12 commercially or ecologically important species. In addition, we provide detailed information
on coastal habitat use for plaice (Pleuronectes platessa), cod (Gadus morhua), brown shrimp (Crangon crangon), and European lobster (Homarus gammarus). Collectively, 44% of all ICES species utilized coastal habitats, and these stocks contributed 77% of the commercial landings of ICES-advice species, indicating that coastal habitats are critical to population persistence and fishery yield of ICES species. These findings will aid in defining key habitats for protection and restoration and provide baseline information needed to define knowledge gaps for quantifying the habitat value for exploited fish and invertebrates.
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.
Genetic and physiological responses of flounder Platichthys flesus populations to chemical stress were investigated in 3 highly contaminated French estuaries (the Vilaine, Loire and Gironde) and compared to those observed in the Ster estuary, considered as a reference site because of its reletively low level of contamination. In the Vilaine, Loire and Gironde populations, multi-loci heterozygosity (allozymes: PGM, GPI-2, MPI, IDHP, AAT-1, AAT-2) was lower than in the reference site. The mean growth rate was measured by back-calculation from otoliths, and the mean condition factor corresponded to the somatic weight:fish length(3) ratio. The fish from contaminated estuaries displayed lower values for both parameters than those from the Ster. Among the alleles, PGM 85, AAT-1 95, and to a lesser extent MPI 90, MPI 95 and IDHP 90, could be considered as 'resistant' to contamination. In contaminated estuaries, these alleles were carried by individuals that displayed good fitness, measured as high DNA integrity (low coefficient of variation of DNA content in blood cells) by flow cytometry. The frequencies of these alleles were also more elevated compared to fish from the reference site. Moreover, the comparative analysis of the relationships between genotypic and phenotypic responses of flounder populations to pollution in the 4 studied estuaries highlighted some specificity in relation to contamination typology.
Nursery areas of European sea bass (Dicentrarchus labrax, L.) were investigated from spring 2005 to summer 2006 in areas along the French Mediterranean coast of the Gulf of Lion. Nurseries were identified by the presence of settling individuals of sea bass and young juveniles. These nurseries represent different types of sheltered shallow habitats, both natural such as coastal lagoons, estuaries, and artificial such as marinas. Settlement occurred from April to June during both years. The number of settling individuals varied between sites from just a few individuals to several thousand. In one given site, settlement also varied between 2005 and 2006. The size distribution of sampled individuals revealed that several pulses arrived in each nursery. At this stage, sea bass already exhibited a strong orientation capacity but a limited swimming ability. The magnitude of sea bass settlement in marinas requires better environmental management of such artificial areas.
Juvenile settlement of 3 sparid fish species, Diplodus puntazzo, Diplodus sargus and Diplodus vulgaris, was studied over 3 yr at 20 stations located at 5 sites in the NW Mediterranean Sea: 1 site in Spain (Girona), 2 in France (Banyuls and Marseille) and 2 in Italy (Portofino and Elba). When all sites and years were combined, 71% of the settlers recorded belonged to D. vulgaris, 25 % to D. sargus and 4% to D. puntazzo. Settlement was seasonal, with D. sargus settling in May-June, D. puntazzo in October-November, and D, vulgaris in 2 pulses, the first in November-December and the second in January-February. Settlement intensity varied spatially, temporally, and among species. At a small spatial scale (within site), settlement intensity varied between stations and particularly between years. At a large spatial scale (among sites), settlement intensity varied among sites, with Marseille and Girona generally experiencing higher settlement than other sites. No difference in settlement intensity was observed between protected and unprotected areas. The settlement of D. sargus was higher in 1994 than in 1993 and 1995 at all sites, suggesting the influence of meso-scale hydroclimatic conditions on the settlement success of this species. The settlement of D. vulgaris was higher in 1993 in the western part of the NW Mediterranean, and in 1994 in the eastern part. No consistent spatial trend over time was seen for D, puntazzo. Thus, settlement intensity of Diplodus species to nearshore habitats in the NW Mediterranean exhibited high year-to-year variations at both local and regional scales.
The influence of habitat quality on a species' demographics is critical for understanding its ecology and effective conservation. However, quantifying habitat quality is problematic because it may comprise of abiotic components at different spatial scales and also be influenced by biotic processes. This study investigated the relationship between reef-associated Caribbean fishes and habitat quality at 2 spatial scales: (1) multiple characteristics of Montastraea annularis coral colonies (<1 m(2)) and (2) coral density in a 5 x 5 m plot around each microhabitat. Furthermore, the influence on habitat quality of 2 biotic factors (predation pressure and interactions between competitively superior territorial damselfishes and other species) was considered. A total of 102 M. annularis colonies within thirty 25 m(2) plots were surveyed on a Belizean forereef. Generalised linear mixed-effect models demonstrated that both damselfishes and other reef associated species were correlated with colony-scale habitat quality (more abundant on taller, refuge-rich colonies). Adult reef-associated species were also correlated with larger-scale habitat quality, being more abundant on colonies with high densities of other Montastraea colonies within 25 m(2) (probably higher quality home ranges). However, the presence of damselfishes was associated with reduced abundances of other reef-associated species on M. annularis colonies, reflecting the importance of both biotic and abiotic controls of habitat quality. On reefs, coral mortality will reduce the density of optimal colonies and potentially increase the proportion occupied by damselfishes. This may lead to smaller populations of inferior competitors as they are increasingly displaced onto sub-optimal microhabitats.
The shallow inshore areas of coastal lagoons function as nursery grounds for the early life stages of marine fish.
Multi-species approaches and the assessment of several population variables are of great value in studies focused upon the
ecological importance of estuarine systems as fish nursery areas. Therefore, the objective of this study was to analyse the
spatial differences in the abundance, biomass, growth and condition indexes of juveniles from three marine species: Sparus
aurata, Liza aurata and Liza ramada, in order to assess the nursery role of the Mar Menor coastal lagoon for these species.
Results showed high spatial variability of the studied variables, with higher abundance and biomass values at those sites
closest to the inlet connecting the lagoon with the Mediterranean Sea. Moreover, there were significant relationships
between the growth and condition of the fish with hydrographical circulation patterns within the lagoon, indicating the
suitability of the Mar Menor as a nursery area for the three studied fish species.
Habitat protection is a strategy often proposed in fisheries management to help maintain viable populations of exploited species. Yet, quantifying the importance of habitat availability for population sizes is difficult, as the precise distribution of essential habitats is poorly known. To quantify the contribution from coastal nursery habitats to exploited fish population sizes, we related adult density to the amount of nursery habitat available for 12 populations of the two dominant predatory fish species in a 40 000-km(2) archipelago area of the Baltic Sea. Habitat distribution was mapped using three conceptually different techniques, Maxent, generalized additive models, and random forest, using spawning and 0-group point samples. Adult densities were estimated from gillnet surveys. Regressions demonstrated no evident effect from fishing, whereas habitat availability had a positive effect, explaining almost half of the variation in population sizes of both species. This result shows that a substantial proportion of the potential production of adult fish can be estimated by mapping essential nursery habitats distribution. Responses were non-linear, indicating that habitat protection has largest effects where there is little available habitat. By demonstrating the importance of habitat limitation of two exploited fish species, we provide quantitative support to the benefits of habitat protection for fisheries.
Ontogenetic changes in morphology and habitat use were studied for three species of the genus Diplodus (Pisces: Sparidae) from the Mediterranean Sea. From the settlement of larvae into the benthic environment to the recruitment of juveniles into adult habitats, two ecomorphological stages were determined. The first stage (transition juvenile) corresponds to fish from about 6.6 mm (settlement) to 22.5 mm SL (21.0-23.5 mm depending on species). During this period, fish acquire early morphological adaptations to the benthic habitat, become pigmented, and are restricted to specific settlement habitats in the nursery zone. The second stage (post-transition juvenile) corresponds to fish from about 22.5 mm to an average 43.7 mm SL (39.5-48.5 mm depending on species). During this period, fish complete their morphological adaptation to benthic life and colonize the whole nursery zone. Fish longer than about 43.7 mm become immature adults as they possess all the characteristics of adults except sexual maturity, and start leaving the nursery zone to colonize adult habitats. This phase corresponds to the recruitment of juvenile fishes. Finally, we developed a complete life-history model for Diplodus, analysed the extent to which our model can be extended to other demersal species and recommend the limits in size of each life stage be precisely defined for every study of post-settlement processes.
An inexpensive automated light-trap has shown great potential as a tool for quantifying spatial and temporal patchiness in assemblages of larval fishes. Automation means that simultaneous samples can be collected within narrow time-windows from multiple locations. With the right sampling design, synoptic maps of larval abundance can be produced with a resolution equivalent to the density of traps. Because the traps do not kill like other techniques, it is far easier to resolve the distributions of individual species and the live larvae can be used for further experimentation. Some data from Lizard Island, northern Great Barrier Reef, are reported to demonstrate the utility and the limitations of this technique.
Michael W. Beck, Kenneth L. Heck, Jr., Kenneth W. Able, Daniel L. Childers, David B. Eggleston, Bronwyn M. Gillanders, Benjamin Halpern, Cynthia G. Hays, Kaho Hoshino, Thomas J. Minello, Robert J. Orth, Peter F. Sheridan and Michael P. Weinstein
Fish assemblages associated with wave exposed and sheltered sides of breakwaters, and with adjacent sandy habitats were studied in western Calabria (Mediterranean Sea, south-western Italy). Overall, 26 fish taxa were recorded (21 associated with exposed breakwater sides, 21 with sheltered sides, and four with sand). Fish assemblages significantly differed between breakwaters (both sides) and sand, and, to a lesser extent, between exposed and sheltered sides of breakwaters in terms of whole assemblage structure, densities of species, and juvenile stages.
Populations of three species of juvenile Sparidae ( Diplodus puntazzo , Diplodus sargus and Diplodus vulgaris ) were sampled at different spatial scales in the north-western Mediterranean Sea over two years to follow growth after settlement. Length–frequency distributions were collected each week for periods of six months following the arrival of off-shore larvae in inshore habitats. Data were collected by underwater visual census along permanent transects.
Growth rate measured as the slope of the linear relationship between mean size and time varied between species. Diplodus puntazzo (0.160 mm d ⁻¹ ) and D. vulgaris (0.202 mm d ⁻¹ ), which are settling in winter experienced slower growth than D. sargus (0.567 mm d ⁻¹ ) which settles in summer. It is concluded that the difference was in part due to water temperature. Analysis of growth rate within each species also revealed significant differences among sites probably related to the currents and the water mass temperatures.
In situ surveys were used to examine the contribution of benthic herbivorous invertebrates and fishes to the organization of Mediterranean rocky sublittoral communities. Shallow (1–3 m) and deep (6–8 m) sampling sites, in natural areas and on man-made structures, were characterized by a structural complexity index (cavity index and mean size of cavity aperture), algal cover (encrusting, turfy, shrubby and arborescent algae) and the density of benthic herbivorous invertebrates and fish. A relationship between structural complexity and biota was only evident for some fish species (Diplodus spp. and Sarpa salpa) at deep sites, where they not only feed but also shelter. Three benthic herbivorous invertebrates, the sea urchins Paracentrotus lividus and Arbacia lixula, and the limpetPatella caerulea , are associated with communities dominated by encrusting algae. Variations in their abundance and role in structuring algal communities follow a depth gradient: P. caerulea and A. lixula are mainly present at shallow sites and P. lividus at deep sites. These benthic herbivorous invertebrates may account for the structure of shallow algal communities. In contrast, at deep sites, fishes (the omnivorous Diplodus spp. and the herbivorous S. salpa) have a potential importance in controlling sublittoral algae, in addition to invertebrates. It is suggested that the ecological impact of herbivorous and omnivorous fishes in temperate seas could be greater than is generally thought. Experiments should be designed to validate this postulate.
This work aimed at performing a large scale assessment of Diplodus spp. (Sparidae) nurseries along the rocky shore of Marseilles (France, NW Mediterranean) by locating and quantifying nursery microhabitats and estimating the settlement pattern along this shore in 2004. Nursery grounds of Diplodus spp. represented only 9% of the 52 km-long rocky shore of Marseilles. Their location, shallow rocky habitats sheltered within coves, made them vulnerable to human-induced habitat transformations. D. vulgaris settled along this coast at the end of February 2004 and D. puntazzo settled a couple of months earlier. Maximum densities observed reached 215 and 67 ind./100 m for D. vulgaris and D. puntazzo respectively. The settlement rates were spatially variable. At a regional scale, lower settlement rates were observed within the south and centre zones, compared to those observed in the west, east, and the Marseilles Bay zones. Suitable nurseries along this shore seem insufficient for the replenishment of adult assemblages, which suggests that they depend on the migration of adults from other areas. Along the Marseilles rocky shore, coastal development projects leading to the destruction of habitats would represent a major threat to the Diplodus life cycle, which could be even greater than usual given the vulnerability and small size of the nurseries. These results show that it is necessary to protect these scarce local nursery habitats and manage other nearby nurseries to ensure the survival of fish at a critical life stage and the replenishment of adult assemblages.
Mortality patterns from peak of settlement to dispersal from the nursery area, concurrently with integration of juveniles into adult populations, of 3 littoral fishes of the genus Diplodus (D. puntazzo, D. sargus, and D. vugaris) (Family Sparidae) were studied between May 1993 and June 1996. Twenty-one stations were censused weekly, weather conditions permitting, along the Mediterranean coasts of Spain, France, and Italy. Eight stations were located in protected areas and 13 in unprotected zones. Declines in abundance in all 3 species were particularly marked in the first month after settlement. Patterns of survivorship indicated that the 3 species were subject to density-dependent mortality from settlement to recruitment to the adult population. The effect of this mortality pattern was to reduce the variability in year-class strength, though without changing the rank order of abundance between years. The mortality rates for D. sargus were higher than for D. puntazzo and D. vulgaris. The results of this study indicated that mortality rates in protected areas did not differ significantly from those in unprotected zones, suggesting that marine reserves are not necessarily a sink for post-settlement fishes.
Over the centuries, land reclamation, coastal development, overfishing and pollution have nearly eliminated European wetlands, seagrass meadows, shellfish beds, biogenic reefs and other productive and diverse coastal habitats. It is estimated that every day between 1960 and 1995, a kilometre of European coastline was developed. Most countries have estimated losses of coastal wetlands and seagrasses exceeding 50% of the original area with peaks above 80% for many regions. Conspicuous declines, sometimes to virtual local disappearance of kelps and other complex macro-algae, have been observed in several countries. A few dominant threats have led to these losses over time. The greatest impacts to wetlands have consistently been land claim and coastal devel-opment. The greatest impacts to seagrasses and macroalgae are presently associated with degraded water quality while in the past there have been more effects from destructive fishing and diseases. Coastal development remains an important threat to seagrasses. For biogenic habitats, such as oyster reefs and maerls, some of the greatest impacts have been from destructive fishing and overexploi-tation with additional impacts of disease, particularly to native oysters. Coastal development and defence have had the greatest known impacts on soft-sediment habitats with a high likelihood that trawling has affected vast areas. The concept of 'shifting baselines', which has been applied mostly to the inadequate historical perspective of fishery losses, is extremely relevant for habitat loss more generally. Most habitat loss estimates refer to a relatively short time span primarily within the last century. However, in some regions, most estuarine and near-shore coastal habitats were already severely degraded or driven to virtual extinction well before 1900. Native oyster reefs were ecologically extinct by the 1950s along most European coastlines and in many bays well before that. These shellfish reefs are among the most endangered coastal habitats, but they receive some of the least protection. Nowadays less than 15% of the European coastline is considered in 'good' condition. Those fragments of native habitats that remain are under continued threat, and their management is not generally informed by adequate knowledge of their distribution and status. There are many policies and directives aimed at reducing and reversing these losses but their overall positive benefits have been low. Further neglecting this long history of habitat loss and transfor-mation may ultimately compromise the successful management and future sustainability of those few fragments of native and semi-native coastal habitats that remain in Europe.
Fishing changes the structure of fish communities and the relative impacts of fishing are assessed usefully against a baseline. A comparable baseline in all regions is fish community structure in the absence of fishing.
The structure of unexploited communities cannot always be predicted from historical data because fisheries exploitation usually precedes scientific investigation and non‐fisheries impacts, such as climate change, modify ecosystems over time.
We propose a method, based on macroecological theory, to predict the abundance and size‐structure of an unexploited fish community from a theoretical abundance–body mass relationship (size spectrum).
We apply the method in the intensively fished North Sea and compare the predicted structure of the unexploited fish community with contemporary community data.
We suggest that the current biomass of large fishes weighing 4–16 kg and 16–66 kg, respectively, is 97·4% and 99·2% lower than in the absence of fisheries exploitation. The results suggest that depletion of large fishes due to fisheries exploitation exceeds that described in many short‐term studies.
Biomass of the contemporary North Sea fish community (defined as all fishes with body mass 64 g−66 kg) is 38% lower than predicted in the absence of exploitation, while the mean turnover time is almost twice as fast (falls from 3·5 to 1·9 years) and 70% less primary production is required to sustain it.
The increased turnover time of the fish community will lead to greater interannual instability in biomass and production, complicating management action and increasing the sensitivity of populations to environmental change.
This size‐based method based on macroecological theory may provide a powerful new tool for setting ecosystem indicator reference levels, comparing fishing impacts in different ecosystems and for assessing the relative impacts of fishing and climate change.
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.
Microhabitat attributes were characterized for recently settled juvenile fishes in six species of Sparidae (Diplodus annularis, D. puntazzo, D. sargus, D. vulgaris, Oblada melanura, and Sarpa salpa) on the rocky shore near Marseille, French Mediterranean coast. Depth, slope, type of substratum, biotic cover and hydrodynamic conditions were recorded wherever sparid recruits occurred. Juvenile Diplodus annularis settled in Posidonia oceanica seagrass beds at 5-8 m deep. The five other sparid species recruited in very shallow water (<2 m). D. puntazzo, D. sargus and D. vulgaris were observed in sites presenting a gentle slope with coarse sand, gravel, pebbles or boulders. Sarpa salpa was less dependent on slope for recruitment, but was always associated with microalgae. Oblada melanura settlement occurred on rocky areas with various slopes, and was favoured by the presence of overhangs. When growing, juvenile sparids extended their home range vertically into deeper zones, and laterally in more exposed areas. Time partitioning in the use of suitable microhabitats for recruitment was observed for some species. Juveniles of Diplodus puntazzo and D. vulgaris shared the same sites from March to May, both exhibiting relatively low abundances. D. sargus recruited in far higher abundance in the same sites from May to September. Specific improvements in coastal man-made structures (harbours, artificial beaches) are suggested in order to increase the recruitment of some littoral fish species.
While variability in recruitment of young reef fish is now recognised, the question remains how the variation in recruitment will contribute to determining assemblage structure. This has been the basis for an active debate about whether patterns in abundance are determined by the supply of planktonic larvae or whether they result from competition (for space, food, etc.) between potential recruits leading to density-dependent recruitment. We tested population regulation of newly recruited juveniles of Sparidae in the north-western Mediterranean Sea. Recruitment of three species of Sparidae was followed over a three-month period in each of two years to estimate the peak density of new recruits settling from the ocean, the rate of mortality occurring during the first three months after settlement, and the final density after three months. Sites and species were carefully chosen in order to avoid migration during the survey. Initial density of recruited larvae of Diplodus spp. varied among species and sites from 0.045 to 3.8 individuals per metre of coastline. Mortality estimates also varied enormously. Between 24.3% and 99.4% of the initial population disappeared within three months. Our survey demonstrated that both post-settlement mortality (r = 0.847; p < 0.0001; n = 18) and final density (r = 0.818; p < 0.0001; n = 18) were correlated with density of recruitment and consequently that both pre-recruitment (larval phase) and post-recruitment processes regulated sparid populations of the Mediterranean Sea.