McLachlan A.,University of Sydney |
Defeo O.,UNDECIMAR |
Jaramillo E.,Austral University of Chile |
Short A.D.,University of Sydney
Ocean and Coastal Management | Year: 2013
This paper addresses the need for a simple model for managers to employ when planning strategies for management of sandy beaches. It is based on the premise that in the overwhelming majority of cases beaches are suitable for recreation or for conservation or a combination of the two, whereas other uses are rare. The broad range of physical, ecological and socio-economic factors relevant to beaches, are reviewed briefly. Then three key factors are selected to develop each of two simple indices, an index of conservation value, CI, based on dune state of health, the presence of iconic species and macrobenthic species richness; and an index of recreation potential, RI, based on the extent of infrastructure, the level of safety/health of the beach and its physical carrying capacity. By combining these two indices, a beach can be simply classified as suitable for intensive recreation, or primarily for conservation, or for mixed use. Ten principles are outlined for consideration and potential application to beach management strategies. Finally, 23 beaches from three continents are classified, with detailed descriptions of a beach typical of each major use type. © 2012 Elsevier Ltd.
Defeo O.,UNDECIMAR |
McLachlan A.,Nelson Mandela Metropolitan University
Geomorphology | Year: 2013
Global patterns in species richness in sandy beach ecosystems have been poorly understood until comparatively recently, because of the difficulty of compiling high-resolution databases at continental scales. We analyze information from more than 200 sandy beaches around the world, which harbor hundreds of macrofauna species, and explore latitudinal trends in species richness, abundance and biomass. Species richness increases from temperate to tropical sites. Abundance follows contrasting trends depending on the slope of the beach: in gentle slope beaches, it is higher at temperate sites, whereas in steep-slope beaches it is higher at the tropics. Biomass follows identical negative trends for both climatic regions at the whole range of beach slopes, suggesting decreasing rates in carrying capacity of the environment towards reflective beaches. Various morphodynamic variables determine global trends in beach macrofauna. Species richness, abundance and biomass are higher at dissipative than at reflective beaches, whereas a body size follows the reverse pattern. A generalized linear model showed that large tidal range (which determines the vertical dimension of the intertidal habitat), small size of sand particles and flat beach slope (a product of the interaction among wave energy, tidal range and grain size) are correlated with high species richness, suggesting that these parameters represent the most parsimonious variables for modelling patterns in sandy beach macrofauna. Large-scale patterns indicate a scaling of abundance to a body size, suggesting that dissipative beaches harbor communities with highest abundance and species with the smallest body sizes. Additional information for tropical and northern hemisphere sandy beaches (underrepresented in our compilation) is required to decipher more conclusive trends, particularly in abundance, biomass and body size. Further research should integrate meaningful oceanographic variables, such as temperature and primary production, in deciphering latitudinal trends. © 2013 Elsevier B.V.
Gutierrez N.L.,University of Washington |
Hilborn R.,University of Washington |
Nature | Year: 2011
One billion people depend on seafood as their primary source of protein and 25% of the world's total animal protein comes from fisheries. Yet a third of fish stocks worldwide are overexploited or depleted. Using individual case studies, many have argued that community-based co-management should prevent the tragedy of the commons because cooperative management by fishers, managers and scientists often results in sustainable fisheries. However, general and multidisciplinary evaluations of co-management regimes and the conditions for social, economic and ecological success within such regimes are lacking. Here we examine 130 co-managed fisheries in a wide range of countries with different degrees of development, ecosystems, fishing sectors and type of resources. We identified strong leadership as the most important attribute contributing to success, followed by individual or community quotas, social cohesion and protected areas. Less important conditions included enforcement mechanisms, long-term management policies and life history of the resources. Fisheries were most successful when at least eight co-management attributes were present, showing a strong positive relationship between the number of these attributes and success, owing to redundancy in management regulations. Our results demonstrate the critical importance of prominent community leaders and robust social capital, combined with clear incentives through catch shares and conservation benefits derived from protected areas, for successfully managing aquatic resources and securing the livelihoods of communities depending on them. Our study offers hope that co-management, the only realistic solution for the majority of the world's fisheries, can solve many of the problems facing global fisheries. ©2011 Macmillan Publishers Limited. All rights reserved.
Carranza A.,UNDECIMAR |
Defeo O.,UNDECIMAR |
Arim M.,Seccion Zoologia Vertebrados
Diversity and Distributions | Year: 2011
Aim Phylogenetically related species share attributes that lead to common responses to environmental conditions, but which could also produce the exclusion of species by its relatives. These processes could generate the patterns of phylogenetic attraction or repulsion in local communities, where related species would tend to coexist more or less than expected by chance. This paper aims to (1) analyse the phylogenetic structure of a benthic gastropod assemblage in the south-western Atlantic Ocean (SAO); (2) explore the linkages between phylogenetic structure and spatial distribution patterns; (3) compare outcomes driven by the analysis of presence-only data and predictive species distribution models; and (4) explore which aspects of the gained knowledge can be useful to the design of sound conservation and/or management actions.Location Uruguayan shelf and slope in the SAO.Methods Spatial patterns in taxonomical relatedness were assessed using (1) raw presence/absence data (i.e. realized niche approach) and (2) reconstruction of the potential composition of the assemblage from niche modelling (i.e. fundamental niche approach). Null models were used to test hypotheses on assemblage structure.Results Significant departures from the null hypothesis that all species were drawn from the same assemblage were observed irrespectively of the approach, indicating the existence of non-random structures. However, a high proportion of local communities can be thought as random subsets of the regional species pool. This lack of a strong signal of a taxonomic effect could be related to the absence of a linkage between taxonomic distances and ecological similarities.Main conclusions Our results suggest a random assembly of local communities from the regional species pool and/or niche filtering independent of phylogeny as main determinants of local community composition. We also suggest that local assemblages displaying significantly higher (or lower) than expected taxonomic relatedness should be taken into consideration for designing spatially explicit conservation measures. © 2010 Blackwell Publishing Ltd.
Defeo O.,UNDECIMAR |
McLachlan A.,University of Sydney
Marine Ecology Progress Series | Year: 2011
Species richness and abundance of macrofauna on sandy shores increase from micro - tidal reflective to macrotidal dissipative beach conditions. However, no attempt has been made to deconstruct these patterns. Using information on the macrofauna from 63 microtidal sandy beach surveys in South America, we deconstructed the community to discriminate among taxonomic groups, supralittoral and intertidal forms, and groups with different feeding habits and development modes. We also separated the effects of development mode and beach zone (intertidal vs. supralittoral) at the species level and scaled body size to density estimates. Total species richness decreased towards reflective beaches, but this trend was less marked in crustaceans than in molluscs or polychaetes. Supralittoral air-breathing crustaceans increased in richness and abundance from dissipative to reflective conditions, a reverse trend to that seen in intertidal crustaceans. Development modes (species with direct development and with planktonic larvae) showed the same response to beach type as the community as a whole. Filter feeders, scavengers and deposit feeders showed the same trend, but the latter were scarce or absent on reflective beaches. Zone was more important than either development or feeding modes in determining individual species responses to beach type. Body size decreased and density increased from reflective to dissipative beaches, suggesting that smaller forms are more sensitive to harsh conditions where density is lower, and hence there is less scope for biological interactions in reflective beaches. The deconstruction approach provided insights into the relationships between life cycle characteristics and richness and abundance patterns and the relative importance of environmental variables in beach ecology. © Inter-Research 2011 www.int-res.com.
Defeo O.,UNDECIMAR |
Castilla J.C.,University of Santiago de Chile
Current Opinion in Environmental Sustainability | Year: 2012
We discuss coastal shellfisheries management and governance models in Latin America and the Caribbean (LAC) at different scales. Self-imposed governance with spatial property rights, internal rules and co-management resulted in successful local shellfisheries. At the national level, the long-term Chilean governability system, which included sea-zoning for artisanal and industrial fleets and exclusive allocation of rights to artisanal shellfish communities, successfully tamed wicked management problems. However, the combination of weak governance, globalization of markets, fishing pressure and climate change exacerbated depletion patterns in most LAC shellfisheries. Increasing market prices exceed the low costs of harvesting low abundance coastal shellfish, and together with illegal trade, have driven some species to levels close to extinction (anthropogenic Allee effect). Mass shellfish mortalities driven by climate variability are threatening stocks and may swamp management and governance schemes. Coastal shellfisheries urgently require the implementation of resilient management and effective long-term governance schemes under pressing conditions of change and uncertainty. © 2012 Elsevier B.V.
Horta S.,UNDECIMAR |
Fisheries Research | Year: 2012
The global fisheries crisis has critical socioeconomic impacts on small-scale fisheries. In addition, the crisis also exacerbates the conflicts and technological interdependencies between artisanal and industrial fisheries. In the coastal zone of Uruguay, both the artisanal and the industrial fleet target the whitemouth croaker Micropogonias furnieri (Desmarest, 1823). In this paper, we assess the spatial dynamics of the artisanal fleet and evaluate technological interdependencies with the industrial fleet. To this end, information gathered from logbooks, vessel monitoring systems and monthly landing reports for five consecutive years was analyzed using a Geographic Information System (GIS). An Index of Fisheries Interdependencies (IFI) was developed to identify and measure the intensity of spatial overlap between the fleets. A strong intra-annual displacement of the artisanal fleet was observed along the coast, as the fleet followed the migrations of the stock to the coastal spawning areas. The catches increased from April to July for both fleets, whereas an inverse trend was observed from October to January. This finding indicated the negative effects of the activities of the industrial fleet on the artisanal catches. Declining Catch per Unit Effort (CPUE) trends and high IFI scores were detected at nursery and spawning areas and suggest early warning signals of stock overexploitation. Artisanal exclusive-use zones and spatio-temporal management windows are recommended to decrease the potential interdependencies between fleets. © 2012 Elsevier B.V.
Bergamino L.,UNDECIMAR |
Lercari D.,UNDECIMAR |
Estuarine, Coastal and Shelf Science | Year: 2011
The food web structure of two sandy beach ecosystems with contrasting morphodynamics (dissipative vs. reflective) was examined using stable carbon (δ13C) and nitrogen (δ15N) isotope analysis. Organic matter sources (POM: particulate organic matter; SOM: sediment organic matter) and consumers (zooplankton, benthic invertebrates and fishes) were sampled seasonally in both sandy beaches. Food webs significantly differed between beaches: even though both webs were mainly supported by POM, depleted δ13C and δ15N values for food sources and consumers were found in the dissipative system (following the reverse pattern in δ13C values for consumers) for all the four seasons. Primary consumers (zooplankton and benthic invertebrates) use different organic matter sources on each beach and these differences are propagated up in the food web. The higher productivity found in the dissipative beach provided a significant amount of food for primary consumers, notably suspension feeders. Thus, the dissipative beach supported a more complex food web with more trophic links and a higher number of prey and top predators than the reflective beach. Morphodynamic factors could explain the contrasting differences in food web structure. The high degree of retention (nutrients and phytoplankton) recorded for the surf zone of the dissipative beach would result in the renewed accumulation of POM that sustains a more diverse and richer fauna than the reflective beach. Further studies directed to assess connections between the macroscopic food web, the surf-zone microbial loop and the interstitial compartment will provide a deeper understanding on the functioning of sandy beach ecosystems. © 2010 Elsevier Ltd.
Lercari D.,Undecimar |
Bergamino L.,Undecimar |
Ecological Modelling | Year: 2010
We model and compare for the first time the ecosystem structure and trophic networks of two sandy beaches with contrasting morphodynamics (i.e. dissipative and reflective). To this end, an Ecopath model was implemented to represent the macroscopic food web on each sandy beach ecosystem. The dissipative beach model comprised 20 compartments and the reflective nine, including detritus, phytoplankton, zooplankton, benthic invertebrates, fishes and seabirds. Input data mainly came from direct surveys, whereas additional information was gathered from published and unpublished sources. Results revealed a major number of top predators and higher trophic levels (TLs) in the dissipative beach (seabirds, fishes, gastropods and the polychaete Hemipodus olivieri) than in the reflective one (fishes and Hemipodus olivieri). Detritivorous and filter feeding benthic invertebrates constituted intermediate trophic levels on both beaches. Exportation of most primary production and detritus was a common feature, with a detritivory:herbivory ratio of 0.42 in the dissipative beach and 0.51 in the reflective, indicating a higher utilization of the primary production in the former. The aggregation analysis showed five TLs in the dissipative beach and four in the reflective. Lower transfer efficiencies in the reflective beach could be attributed to a lower diversity of predators when compared to the dissipative system. Comparison of global ecosystem properties showed that the dissipative system had higher values for total system throughput, total biomass, net production, Ascendency and total number of pathways. We concluded that the greater diversity and biomass in the dissipative beach are reflected in a higher dimension and ecosystem organization than in the reflective beach, thus providing new evidences at the ecosystem level about well-established differences in biological descriptors between beach types. Finally, we stressed the need for acquiring experimentally-based information on benthic invertebrate's consumption rates and the inclusion of the surf zone microbial loop and the interstitial compartment to test for differences in structure and functioning of these coastal ecosystems. © 2010 Elsevier B.V.
Gomez J.,UNDECIMAR |
Estuarine, Coastal and Shelf Science | Year: 2012
Exposed marine beaches are physically rigorous habitats in which macrofaunal patterns have been well correlated with physical factors. In this context, the habitat safety hypothesis (HSH) predicts an increase in abundance of supralittoral species from dissipative to reflective conditions in microtidal oceanic beaches. However, the HSH has not been adequately tested in estuarine sandy beaches. Here, we build a predictive model based on the supralittoral talitrid amphipod Atlantorchestoidea brasiliensis that allowed us to test the HSH along a macroscale estuarine gradient. Fifteen Uruguayan sandy beaches along a salinity gradient (from 0.1 to 34.3) generated by the Río de la Plata estuary (SW Atlantic Ocean) were sampled over a two-year period. A conditional two-step procedure using a General Additive Model (GAM) was performed in order to model A.brasiliensis occurrence (1st-step) and abundance (2nd-step), based on a comprehensive set of environmental variables [salinity, water temperature, beach face slope (BFS), mean grain size, wave height and sand compaction, moisture and organic matter]. Each GAM was parameterized using generalized linear models (GLMs). An external validation procedure was used. Data were divided randomly into training (75%) and test (25%) sets. The 1st-step GAM/GLM retained 5 physical descriptors in the model (decreasing order of importance): wave height, salinity, BFS, organic matter and sand compaction. The 2nd-step GAM/GLM retained 6 physical descriptors: sand compaction, water content, salinity, wave height, water temperature and organic matter. The predictive ability of these models and the resulted combined model, as well as their external validity, was highly significant and supported the predictions of the HSH. However, the highest and lowest abundances were observed, respectively, on reflective and dissipative beaches in the outer estuary; i.e., the predictions based on the HSH did not account for the high levels of abundance observed on these beaches compared with oceanic ones. Therefore, the HSH was expanded to include microtidal estuarine beaches. © 2011 Elsevier Ltd.