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Populations of marine bivalves are subject to large interannual fluctuations as a result of their sensitivity to unfavourable environmental conditions. These populations have a strong dependence on recruitment, which constitutes a risk to stock conservation and the sustainability of the commercially exploited species. Bivalve sanctuaries comprising no‐take areas can promote the restocking of large coastal areas as a result of the high fecundity and the potentially long‐distance larval dispersal of bivalves. The present study explores a novel spatio‐temporal approach to investigate suitable locations for bivalve sanctuaries, aimed at protecting and enhancing stocks along the Algarve coast in southern Portugal. In the context of small‐scale fisheries, bivalve dredging constitutes an important socio‐economic activity. Three bivalve species are targeted: the striped venus (Chamelea gallina), the donax clam (Donax trunculus), and the surf clam (Spisula solida). Data gathered from 36 bivalve fishing surveys conducted over three decades (1986–2015) were analysed using geostatistical methods, accounting for temporal and spatial autocorrelation to produce continuous prediction maps of species distribution for each survey. The approach taken permitted the use of all scattered historical data collected by different methods. The predictions were then used to summarize and illustrate the spatial distribution of species across time, in terms of average biomass, variability, and maximum potential biomass, and to delimit the areas as a function of the species persistence (recurrent, occasional, or rare). The temporal patterns through space were further investigated using empirical orthogonal function (EOF) analysis. The areas accounting for 80% of the species biomass were also estimated. Results of this set of analyses led to the proposal of locations for establishing bivalve sanctuaries, aimed at enhancing the stocks of commercial bivalve species in the long term. Such an innovative spatio‐temporal approach and management strategy is replicable in other fishing resources and geographic areas.

Harvested populations of the sea urchin (Paracentrotus lividus) from the northwestern (Carreco) and southwestern (Aljezur) coasts of Portugal were surveyed to describe the species reproductive cycle and assess possible relationships with geographical location and seawater temperature. Individuals were sampled monthly to analyze gonad histology, mean gonadal index (GI), and gonadosomatic index (GSI) during 2 consecutive years (November 2010-November 2012). Both populations presented an annual reproductive cycle, with synchronous gonad maturation and gamete release between sexes. Gonad maturation occurred throughout autumn-winter, followed by a single but prolonged spawning season during spring-summer. The duration of the spawning season displayed a latitudinal gradient likely related to the north-south increasing trend in seawater temperature, with the northwestern population (Carreco) exhibiting a shorter spawning period compared to the southwestern population (Aljezur). The timing and duration of the spawning season was compared with several populations throughout the distributional range of P. lividus in the Atlantic Ocean and Mediterranean Sea. In the population from Carreco, the size at first sexual maturity (test diameter = 35.9 mm) was considerably smaller than the minimum conservation reference size (MCRS) of 50 mm test diameter legally established for P. lividus. This study confirms that sustainable exploitation depends on harvesters' awareness of and compliance with the MCRS and provides useful information for the eventual establishment of a closed season in the harvesting of P. lividus. Fisheries Operational Programme European Maritime and Fisheries Fund Fisheries Operational Programme European Maritime and Fisheries Fund

This study reports a detailed description of the bycatch, discards and survival rates in the cuttlefish (Sepia officinalis) trap fishery off the Algarve coast (southern Portugal). A total of 86 fishing surveys involving 6,311 cuttlefish traps were performed between May and September from 2009 to 2014. Bycatch species were caught in 1,037 traps (bycatch catchability rate of 16.4%), comprising 1576 individuals with an overall weight of 268.3 kg. During the study period, bycatch CPUEs were 12.5 ind./50 traps and 2.1 kg/50 traps, with bycatch rates of 21.1% by number and 15.9% by weight. Thirty-four species (89.5% of bycatch taxa) were discarded at sea, corresponding to discard rates of 19.5% by number and 11.1% by weight. The short-snouted seahorse, Hippocampus hippocampus (L.), was the third most abundant bycatch species (11.6% No.; 0.4% kg) and the second most discarded (12.6% No.; 0.6% kg), being invariably discarded live and undamaged owing its conservation status. This markedly seasonal small-scale trap fishery constitutes a locally important socio-economic activity during spring and summer, characterised by low bycatch and discard rates, complemented by high survival rates of discards. Agência financiadora Interreg IVB-Atlantic Arc Programme European Union (EU) Fisheries Operational Programme MAR 2020 European Maritime and Fisheries Fund EMFF 2014-2020 info:eu-repo/semantics/publishedVersion

This paper presents a management model developed to promote the sustainability of artisanal fisheries, considering socioeconomic and environmental dimensions. The management of artisanal fisheries faces many challenges, including the lack of appropriate tools to support policy makers and stakeholders in the decision-making process. The model presented in this study is based on system dynamics and allows the simulation of the behavior of the artisanal dredge fishery on the south coast of Portugal, including four main species and two fleets. Two scenarios were simulated to assess the impact of regulatory measures on the system sustainability: scenario 1 simulated a permanent reduction of fishing effort, returning an improvement of biologic and economic sustainability; scenario 2 simulated the closure of one species for a period of one year to allow its recovery. It was found that although the revenue of fisheries decreases in that year, the system is able to return to the average levels of revenue three years after the closure. The study aimed to guide decision makers in the selection of the most appropriate measures toward the preservation of marine ecosystems and socioeconomic stability of fishing communities. The developed system dynamics model, combining available data with knowledge of fisheries experts, proved to be a useful scientific tool to identify management policies and organizational structures leading to greater success. This technique can be applied to the study of other fishery systems worldwide.

The pullet carpet shell Venerupis corrugata is an economically valuable species in several European countries, however, nowadays stocks are under high fishing pressure. Hatchery production of juveniles for release is a major contributor to strengthen the stock and consequently improve the sustainability of the natural stocks. This study aimed to determine the feasibility of rearing V. corrugata larvae with different larval densities (10, 40 and 200 larvae per mL) in a recirculating aquaculture system (RAS), compared with the traditional larval rearing methodology (Batch). The mean survival, growth and metamorphic rate of V. corrugata larvae in RAS was higher (11.1%; 71.3m; 21.6% respectively) than in the Batch system, in all tested densities. The larval growth was not affected by the initial density until 40 larvae per mL, however, 200 larvae per mL decreased the larval growth in length nearly 54m. The larval rearing time was shortened in 2days in the RAS system. The physical, chemical and microbiologic parameters suggested that the tested densities were not excessive to disturb the biofilter stability of RAS. The V. corrugata larval rearing performed at high larval stocking densities in RAS system present a reduction in the operating costs to produce this species. Marinaqua (PROMAR) and Reproseed (FP7-KBBE-2009) project and acknowledge Ciência 2008 program (FCT).

1. Razor clams are found in different habitats ranging from sheltered systems (e.g. lagoons and estuaries) to open coasts. They are distributed worldwide and comprise a small number of species of high economic value. Depending on the specific habitat and species exploited, different mechanical and hand-harvesting techniques are employed. While the environmental effects resulting from mechanized methods have been described by several authors, the impacts caused by traditional hand-harvesting methods remain unknown. Therefore, a study was undertaken in Ria Formosa lagoon (South of Portugal) addressing the environmental effects resulting from harvesting Solen marginatus with salt. 2. No significant impact on the sediment was found; the main effect was an increase in salinity after covering the area with salt, which decreased rapidly with the flood tide and after a few hours had returned to pre-harvesting levels. 3. No effects on benthic communities were observed, with similar fluctuation patterns recorded in control and experimental areas, the observed differences being attributed to the natural variability of benthic populations. 4. Based on the results obtained in the present study, a razor clam fishery using salt in intertidal areas can be considered environmentally ‘friendly’. Copyright © 2008 John Wiley & Sons, Ltd.

Mitochondrial DNA is transmitted maternally in metazoan species. This rule does not hold in several species of bivalves that have two mtDNA types, one that is transmitted maternally and the other paternally. This system of mitochondrial DNA transmission is known as doubly uniparental inheritance (DUI). Here we present evidence of DUI in the clam Donax trunculus making Donacidae the sixth bivalve family in which the phenomenon has been found. In addition, we present the taxonomic affiliation of all species in which DUI is currently known to occur and construct a phylogeny of the maternal and paternal genomes of these species. We use this information to address the question of a single or multiple origins of DUI and to discuss whether failed attempts to demonstrate the presence of DUI in several bivalve species might be due to problems of detection or to genuine absence of the phenomenon.

1. The non-indigenous species Corbicula fluminea (Muller, 1774) is one of the most invasive bivalves in freshwater ecosystems. This Asian clam was first reported in the River Minho estuary in 1989. After a short period of time, it became the major component of the local benthic fauna in terms of abundance and biomass. 2. In the autumn of 2004 and 2005, spatial and temporal variations in abundance, biomass and population structure of C. fluminea were investigated at 16 sites in the freshwater subtidal area of the River Minho estuary. Mean abundance and biomass per site ranged from 80 to 4185ind.m−2 and 8.5 to 465.9g AFDWm−2, respectively. 3. The environmental characterization of the area was performed through multivariate analysis, which revealed three distinct areas subjected to different abiotic conditions. C. fluminea population structure is well correlated with these three distinct areas. 4. The combination of several abiotic variables determining C. fluminea biomass distribution was evaluated through a stepwise multiple regression. This model showed that redox potential, nutrient concentrations, hardness, organic matter and sediment characteristics explained almost 60% of the variation in C. fluminea biomass in the freshwater subtidal area of the River Minho estuary (R2=59.3%, F[9,86]=13.9, p

The commercially fished striped venus clams Chamelea gallina and C. striatula (Bivalvia: Veneridae) are difficult to distinguish by inexperienced observers and the taxonomy of these species is still an issue of discussion. The differences in shape between C. gallina and C. striatula from Portuguese coastal waters were studied through conventional linear and geometric morphometric analysis, using both contour (elliptic Fourier analysis) and landmark-based methods. The relationships shell length vs. height, width, and total weight were significantly different between species. However, because there was a considerable overlap in the data sets, the species could not be distinguished using any combination of those linear measurements. Geometric morphometric methods provided shape variables that led to 0–6% misclassification rates between species; linear morphometric measures led to 16.8% error. Contour analysis revealed differences primarily in the shell umbo and lunular area. The umbo was more “sharp” and the lunula less pronounced in C. striatula than in C. gallina. Generalized procrustes superimposition (landmark analysis) showed that the main differences between species reside in the length of the pallial sinus. Thus, an index was developed (PI: Pallial Index = pallial sinus length/shell length), which was successfully used to separate the species (with 100% correct classification), i.e., specimens with PI lower than 0.119 belonged to C. gallina, whereas greater PI values were attributed to C. striatula. The use of these geometric morphometric methods allowed the detection of differences in shape between these two species and to develop an easy-to-use identification index. We encourage the development of analogous indices that apply the methods of geometric morphometrics to distinguish between other species whose identification is complicated. J. Morphol., 2006. © 2006 Wiley-Liss, Inc.