Francisco Leitão

A comparison of direct macrofaunal mortality using three types of clam dredges

The white clam Spisula solida is harvested along the entire coast of Portugal using mechanical dredges. In this study, the total direct mortality of the macrobenthic community caused by three types of clam dredges (north dredge—ND, traditional dredge—TD, and the metallic grid dredge—GD) used in the S. solida fishery was determined and compared. The relationship between mortality and catching efficiency for each type of dredge was also assessed. Our results showed significant differences for total direct mortality between the ND and both the GD and TD dredges. This difference was largely attributed to the mortality of animals that died in the dredge track as a direct result of the physical damage inflicted by the dredge passing. It was also found that the damage to uncaught individuals is directly related to gear efficiency. The lower catching efficiency of the ND (64%) led to a higher proportion of damaged individuals being left in the dredge path, when compared with the more efficient GD (98%) and TD (90%) dredges. Short and long-term implications of the impact of dredging on the composition of benthic communities are discussed. From fisheries management and ecological points of view, there are obvious advantages to introduce into the bivalve dredge fisheries more efficient and selective dredges in order to reduce the number of damaged individuals and by-catch, and consequently decreasing the impact on the macrobenthic communities.

Trends in landings of fish species potentially affected by climate change in Portuguese fisheries

Fisheries are an important source of food, with a high economic value and social significance. The present worrying situation of the world fisheries is the result of the interaction between different factors (e.g. climatic variations, natural oscillations, technological innovation), but the greatest challenges are overfishing and climate change. The species richness of the Portuguese coast is generally higher than that found in northern Europe and similar to that of the Mediterranean, since many species have their southern or northern distribution limits along the Portuguese coast. The zoogeographic importance of this latitudinal area has long been recognized, representing the transition between north-eastern Atlantic warm-temperate and cold-temperate regions, which makes the Portuguese coast an area of great sensitivity to the detection of climate change. Official landing data for commercial species that have the Portuguese coast as their distribution limit were analysed together with sea surface temperature for the period of 1927–2011. In general, landings of species with affinity for temperate waters presented a decreasing trend, whereas species with affinity for subtropical/tropical waters showed an increasing trend. These variations were associated with variation in temperature: lower landings of temperate species occurred mainly in warm years, whereas landings of subtropical/tropical species presented an opposite trend, with higher landings in warm years. Preparing for the impacts of climate change is crucial for the sustainability of fisheries. Management should take into consideration information about environmental factors that affect species distribution and abundance.

Macrobenthic Colonisation of Artificial Reefs on the Southern Coast of Portugal (Ancão, Algarve)

Artificial reef systems play an important role in the increase of natural production of biological marine resources and they have been deployed worldwide. In Portugal, seven artificial systems have been deployed along the southern coast of the Algarve. Research to date has focussed mainly on fish populations, particularly those of economical importance. The present work aims to study the macrobenthic communities of the artificial reef structures, as these will enhance the food resources and shelter, making the reefs more attractive to fish. In particular, we experimentally analysed the sequence of colonisation of macrobenthic communities of the Ancao artificial reef system, which was deployed in the summer of 2002. The study of the colonisation of benthic communities was done using samples of concrete cubic units (15 × 15 cm) that were suspended at the reef modules at a depth of 20 m, at the time of the reef immersion. Four replicate samples were collected by SCUBA diving from two groups of the Ancao reef every three months from the starting date. Sampling was done using essentially non-destructive methods to assess the percentage cover of macrobenthic organisms in both vertical and horizontal surfaces. The percentage cover of the taxonomic groups was compared within the different surfaces of the samples and between the two reef groups. The bottom surface of cubic samples had a significantly higher colonisation related to the dominance of barnacle cover, probably due to lower sedimentation levels. Samples from both reef groups showed a similar pattern of colonisation. Barnacles, bryozoans and serpulids dominated the samples three months immediately after the beginning of the experiment. Other invertebrates groups, such as Porifera, Hydrozoa, Anthozoa, other sessile Polychaeta, Decapoda, Gastropoda and Bivalvia, were more abundant after six months of colonisation.

Effect of depth and reef structure on early macrobenthic communities of the Algarve artificial reefs (southern Portugal)

This study was carried out on the “Faro/Ancao” artificial reef (AR), located off Faro, deployed in May 2003. We aimed to characterise early macrobenthic community colonisation of two concrete AR groups located at different depths (16 m and 20 m depth) and to test the effect of reef structure on these communities. The non-colonial organisms were counted; barnacles and colonial species were quantified using biomass. Multivariate analyses indicated that early macrobenthic communities (6 months of immersion) were affected by depth, and that barnacles and colonial species were also affected by reef structure. Univariate analyses showed that the biomass of barnacles and colonial species was significantly different among reefs and layers of modules. Both AR groups were characterised by the species Balanus amphitrite, Gregariella subclavata, Musculus cf. subpictus, Paleanotus cf. bellis and Syllidia armata. Jassa marmorata and Bugula neritina were characteristic species at 16 m depth, particularly on the AR Upper layer of modules, whereas Anomia ephippium was particularly common at 20 m, especially on the Lower layer of modules.

Artificial reefs: from ecological processes to fishing enhancement tools

Polovina published the article “ Artificial reefs: nothing more than benthic fish attractors” in 1990 and in it debated the potential for artificial reefs to substantially increase standing stock of marine resources. Artificial Reef (AR) technology was strictly oriented towards improving commercial fishing (STONE et al., 1991) from the 1930s, when the Japanese government invested in large scale artificial reefs, until the 1990´s. The first three International Conferences on Artificial Reefs and Related Aquatic Habitats (CARAH) focused on the improvement of fisheries around the world (SEAMAN; SPRAGUE, 1991; GROVE; WILSON, 1994). However, over the last twenty years, the expansion and diversification of AR use has resulted in a shift in the focus of AR-based research towards a more ecosystematic approach (largely due to advances in SCUBA), focusing on a better understanding of the ARs ecological function and its effect on marine benthic and fish communities (JENSEN, 2002; BORTONE et al., 2011). Questions concerning the ARs function address the interactions between the artificial and natural environments, and understanding how benthic and fish species (mostly commercial species) benefit from the presence of artificial habitats. Production at higher trophic levels (usually of commercial species) normally depends on production at lower levels (bottom-up control). Production levels can be modulated by physical forcing and the structure of the marine food webs (top-down control), with environmental constraints determining the community structure of the fauna and flora (SNELGROVE; BUTMAN, 1994). Physical factors (e.g. currents) and chemical bottom sediment components (in particular phosphorous) are therefore vital for reef production. An alternative approach for assessing the ecological implications of reef structures is the use of a bottom-up approach, i.e. assessing the role of ARs in enhancing primary production and energy transfer to the lower trophic levels of the benthic food web. ARs are normally deployed in areas where sandy habitats predominate. The presence of these man-made reef structures will affect: i) nearby sandy areas and also ii) water column processes in the vicinity of ARs. Habitat linkages among distinct reef compartments are driven by hydrological processes (changes in water flow patterns), sediment type, geomorphological, chemical-physical and biological processes (FABI et al., 2002; KIRKE, 2003; DEDIEU et al., 2007; FALCAO et al., 2007, 2009) and also biotic processes (YANAGI; NAKAJIMA, 1991; LINDQUIST et al., 1994; PEPE et al., 1998; SHENG, 2000; DALE; PREGO, 2002; WILLIAMS; POLUNIN, 2001; FABI et al. 2006; EINBINDER et al., 2006). AR structures can affect biological processes differently within different reef compartments. The understanding of the different mechanisms behind these processes is essential for evaluating community responses to man-made perturbations, including fishing. ARs are known to affect nearby sandy benthic sediments and their communities (BULLERI, 2005). When an AR obstructs current flow, a lee wave or stationary wave is formed, which can trap drifting larvae and seaweeds (SHENG, 2000). Moreover, fish attracted to ARs can significantly increase nutrient production in the water column - by excreting ammonium, urea and faeces - which is then incorporated into the reef food web. This process contributes to the organic enrichment of sediments due to entrapped drift algae and other organic materials driven from reef biological activities and deaths of reef associated organisms. Deposition of biomass in the lee of the reefs favours benthic remineralization, promoting nutrient regeneration in pore water (FABI et al., 2002; DEDIEU et al., 2007). Sediment nutrient enhancement from deposited organic material can be incorporated into the reef food web, enhancing sandy benthic production which contributes to the rehabilitation of sandy coastal areas via sediment chemical trophic chain pull-out (FALCAO et al., 2007, 2009). The biochemical role of ARs in this respect is particularly important in shallow coastal

Is surface orientation a determinant for colonisation patterns of vagile and sessile macrobenthos on artificial reefs

In order to examine how substratum colonisation can affect community structure, a 1-year study was conducted at the Faro/Ancão artificial reef (Algarve, Portugal). In the study of hard substratum communities, motile species are usually neglected and only the conspicuous species are taken into account. Therefore, the development of vagile and sessile components of the epibiotic community were analysed separately. Differences between assemblages on horizontal surfaces, but not on vertical surfaces, were detected. Multivariate analysis detected differences in macrobenthic community structure either considering sessile or motile components. However, significant differences were only detected for vagile fauna. Moreover, this study suggests that for hard substratum communities, analysis of the vagile fauna is important and should be taken into account in the functioning of the artificial raft.

Influence of Environmental Variables and Fishing Pressure on Bivalve Fisheries in an Inshore Lagoon and Adjacent Nearshore Coastal Area

Climate changes affect marine ecosystems and the survival, growth, reproduction and distribution of species, including those targeted by commercial fisheries. The impact of climate change has been reported for many fish species, but studies focusing on the effects of climate on bivalve resources are lacking. In Portugal, the harvesting of bivalves is an old and artisanal activity, of special importance along the Algarve coast (South of Portugal). This study aims to evaluate the influence of climatic, environmental and fisheries factors on the landings of intertidal coastal lagoon and coastal bivalve species (subtidal nearshore species). The environmental and fisheries parameters considered to affect the landings of bivalves in the eastern Algarve were: fishing effort (number of fishing events), sea surface temperature, North Atlantic Oscillation (NAO) index, upwelling index, wind magnitude and direction and river discharges. Analysis of time series data using min/max autocorrelation factor analysis and dynamic factor analysis showed that, for most species, fishing effort was positively related with landings per unit effort trends in the following year. Lagoon bivalve species (Cerastoderma edule and Ruditapes decussatus) responded to different environmental variables than the coastal bivalve species (Chamelea gallina, Pharus legumen, Donax spp. and Spisula solida). Upwelling index had a significant effect on the lagoon bivalves while the NAO index, wind magnitude and direction, and river discharges only affected the coastal species. This study highlighted the need to adapt fishing effort regimes, while considering the background effects of environmental variability, in order to improve fisheries management.

The role of environmental and fisheries multi-controls in white seabream (Diplodus sargus) artisanal fisheries in Portuguese coast

Abstract Evaluating the effects of fishing and environmental factors on fish populations are fundamental tenets of fisheries science. In this study, we assess associations between environmental variables (sea surface temperature; North Atlantic Oscillation index; upwelling; wind magnitude; westerly winds; northerly winds; river discharge) and fishing variables (fishing effort) in Diplodus sagus catch rates accounting for regional analyses (northwest coast; southwest coast and Algarve—Algarve south coast). Different time series models for data fitting (multi-model approach) were used. The models were lagged, according to species fishing recruitment age based on the hypothesis that fisheries catches depend on larvae recruitment and survivorship. D. sargus catch rates across areas were unrelated to fishing effort but correlated to environmental variables, with seasonal events explaining much of the variability in trends. On the northwestern coast, the catch rates were mainly set by sea surface temperature (SST) and wind magnitude; however, southwestern coast catch rates were set by NAO winter. On the south coast, only one statistical model (SST, upwelling and westerly winds) associated spring conditions with D. sargus catch rates. The multi-model approach revealed autumn, winter and spring seasonal effects to be related with northwest, southwest and Algarve coastal catch rates, respectively, indicating a possible coastal longitudinal gradient related with given periods of spawning and larval availability. The metadata analysis yielded different results from the regional analyses. In summary, marine resource management should take regional environment characteristics and variability into account when determining sustainable catch rates in given areas for species with high habitat site fidelity.

Are submarine groundwater discharges affecting the structure and physiological status of rocky intertidal communities

This study evaluated the impacts of submarine groundwater discharges (SGD) on a rocky intertidal community of South Portugal, during April-November 2011. Chlorophyll-a concentration was higher at the SGD site in respect to the Reference site. Epibenthic community structure differed between sites, with an increase in Chthamalus spp. and a decrease in macroalgae coverage at the SGD site. The abundance and body size of Mytilus galloprovincialis were consistently higher at the SGD site. During mid-spring, under potentially higher SGD and less favorable conditions for coastal phytoplankton, the ecophysiological condition of M. galloprovincialis and G. umbilicalis was also higher at the SGD site. These beneficial effects on filter-feeders and herbivores probably resulted from local increases in prey availability, supported by SGD-driven nutrient inputs. Conversely, P. depressa was not favoured by SGD, probably due to a lower dependency on algae as food. The analysis of epibenthic community structure and ecophysiological condition represents a promising approach to disentangle the ecological impacts of SGD on intertidal ecosystems.

On the Choice of Linear Regression Algorithms for Biological and Ecological Applications

MARETEC, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal. Departamento de Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20.559-900, Rio de Janeiro, Brazil. Department of Biology, Saint Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada. Universidade Autónoma de Lisboa, Rua de Santa Marta, no 56 1169-023, Lisboa, Portugal. CCMAR, Center of Marine Science, University of Algarve, Campus Gambelas, 8005-139 Faro, Portugal. Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. CNRS, Sorbonne Universités, UPMC University Paris VI, UMI 3614, Evolutionary Biology and Ecology of Algae, Station Biologique de Roscoff, CS 90074, Place G. Tessier, 296888 Roscoff, France.