Native Clam Research Articles

Synthesis and application of natural clam shell derived adsorbents for removal of azo dyes from wastewater

The research aims to evaluate their effectiveness as adsorbents for azo dyes. The nanomaterials were synthesized via hydrothermal methods, and their adsorption capacities were scrutinized against a spectrum of dyes, including methylene blue (MB), crystal violet (CV), rhodamine B (RB), malachite green (MG), safranin (SR), as well as commercial red and blue dyes. Remarkably, the clam shell nanoparticles (CSNPs) exhibited notable dye removal efficiencies, achieving removal rates of approximately 87%, 89%, 97.75%, 97.60%, and 97.11% for MB, RB, CV, MG, and SR, respectively. These removal rates were accomplished within varied interaction times ranging from 45 to 10 minutes, utilizing a dose of 100 mg/L of nanoadsorbent. Furthermore, the nanomaterials displayed removal efficiencies exceeding 80% against commercial blue and red dyes. Considering their exceptional adsorption capacities, clam shell nanomaterials stand out as cost-effective, efficient, and environmentally friendly biosorbents for effectively removing dyes from aqueous solutions. This study highlights the promising potential of clam shell-based nanomaterials in addressing the challenges presented by water pollution.

Genetic diversity of the Ruditapes decussatus and evidence of its hybridization with the alien R. philippinarum in the Western Mediterranean Sea

The introduction of alien species in marine ecosystems is often driven by the increasing demand of fishery resources. This is the case of the Manila clam (R. philippinarum), imported in Europe from Japan since the 1970s, to meet the growing demand for clams that the native species, the grooved carpet shell clam (Ruditapes decussatus), could not satisfy. Alien species introduction could threaten the genetic diversity and integrity of the native clam, also causing hybridization (i.e., gene flow from one species into the gene pool of another). Since R. philippinarum recently spread in a few important Mediterranean coastal areas, a combined approach based on morphological characteristics, length differences of two nuclear species-specific markers (ITS2, 5SrDNA) and the sequence of the mitochondrial gene cytochrome c oxidase subunit I (COI), was used to investigate the presence of hybrids in six Mediterranean wetlands (Sardinia, Italy). Eight individuals morphologically identified as R. decussatus were hybrids, having sequences specific to both R. decussatus and R. philippinarum in their nuclear DNA (ITS2 and 5SrDNA). Most of these individuals were found to be post-first generation (F1) hybrids indicating that F1-hybrids may be fertile. Secondly, to study the genetic diversity of R. decussatus in the Sardinian wetlands as well as in its whole distribution area, >380 new COI sequences from the eastern Atlantic Ocean and Mediterranean Sea were analysed along with those available from public databases. Mitochondrial COI data revealed variable haplotype and nucleotide diversities in different areas, which were not dependent on sample sizes. The aquaculture breeding activities and clam transplantation between different countries, along with the long pelagic larval dispersal and the commercial import of other bivalve species might have promoted gene exchange between different sites and thus higher diversity levels in a few wild populations. Our research, evaluating the genetic makeup of wild and hatchery stocks and clarifying the degree of hybridization, can contribute to develop further recommendations for conserving the genetic integrity of R. decussatus.

Resource partitioning of a Mexican clam in species-poor Baltic Sea sediments indicates the existence of a vacant trophic niche

Invasive species are often generalists that can take advantage of formerly unexploited resources. The existence of such vacant niches is more likely in species-poor systems like the Baltic Sea. The suspension feeding wedge clam, Rangia cuneata, native to estuarine environments in the Gulf of Mexico, was sighted for the first time in the southeastern Baltic in 2010 and a few years later in the northern Baltic along the Swedish coast. To explore possible competition for food resources between R. cuneata and the three native clams inhabiting Baltic shallow soft bottoms, stable isotope and fatty acid analyses were conducted. There was no overlap between R. cuneata and any of the native species in either stable isotope or fatty acid niches. This suggests efficient partitioning of resources; multivariate analyses indicate that separation was driven mainly by δ13C and by fatty acids reflecting diatoms and cyanobacteria, respectively (e.g. 16:1ω7 and 18:3ω3). R. cuneata reflected seasonal variation in phytoplankton more than other clams reflecting higher trophic plasticity. In conclusion, the addition of R. cuneata to the Baltic shallow soft bottoms suggests the existence of a vacant trophic niche in these sediment habitats, however the long-term effects on other species and nutrient cycling requires further studies focusing on the population dynamics of R. cuneata and its impact on the Baltic Sea ecosystem.

Induced spawning, larval rearing, and innate diet analysis of Indian black clam, Villorita cyprinoides: An alternative to resource restoration through aquaculture

Villorita cyprinoides (Gray, 1825) also called the Indian black clam is a native species from the Indian peninsula directly related to the livelihood of many beneficiaries. The wild population of this Cyrenid clam is confronted with substantial challenges, including various climatic stressors and anthropogenic pressures such as overfishing and habitat destruction. A balance between capture fisheries and aquaculture through the development of hatchery technology is inevitable for ensuring the sustainable use of resources. The declining population of V. cyprinoides underscores the urgency of standardizing breeding protocols and implementing proper farming practices to foster a sustainable black clam fishery, given that Villorita is a potential candidate species for aquaculture. This paper describes the first successful induced spawning of the clam with successful rearing of larvae up to the umboned veliger stage and evaluates the efficacy of induced spawning through combined physical and chemical stimuli. Furthermore, our study employs eDNA metabarcoding to analyze plankton dynamics in waters from native clam beds. This sheds light on the potential microalgal dietary preferences of the species, which can be valuable in preparing diets for larval development and aquaculture in the future.

Hiding from heat: The transcriptomic response of two clam species is modulated by behaviour and habitat

Rising occurrence of extreme warming events are profoundly impacting ecosystems, altering their functioning and services with significant socio-economic consequences. Particularly susceptible to heatwaves are intertidal shellfish beds, located in estuarine areas already stressed by factors such as rainfall events, red tides, eutrophication, and pollution. In Galicia, Northwestern Spain, these beds support vital shellfisheries, featuring the native clam Ruditapes decussatus and the non-indigenous R. philippinarum. Over recent decades, these populations have experienced notable abundance shifts due to various anthropogenic impacts, including climate change. In this habitat, patches of the seagrass Zostera noltei that coexist with bare sand can act as thermal refuges for benthic organisms such as clams. To assess the impact of heatwaves on these ecosystems, a mesocosm experiment was conducted. Juveniles of both clam species in two habitat types—bare sand and sand with Z. noltei—were exposed to simulated atmospheric heatwaves during diurnal low tide for four consecutive days. Subsequent transcriptomic analysis revealed that high temperatures had a more pronounced impact on the transcriptome of R. philippinarum compared to R. decussatus. The habitat type played a crucial role in mitigating heat stress in R. philippinarum, with the presence of Z. noltei notably ameliorating the transcriptomic response. These findings have direct applications in shellfishery management, emphasizing the importance of preserving undisturbed patches of Z. noltei as thermal refuges, contributing to the mitigation of heatwave effects on shellfish populations.

The stress response of the seagrassZostera nolteiand three commercial clam species to low salinity associated with heavy rainfall

AbstractThe maintenance of stocks of estuarine species strongly depends on the ability of the species to cope with environmental stress. In NW Spain, commercial clam beds, which are usually co-occupied by the seagrass Zostera noltei, are often exposed to reduced salinity caused by intense rainfalls. Our goals were to evaluate the effects of low salinity events on both juvenile clams and Z. noltei, including their interactions. A mesocosm experiment was performed to simulate three salinity decreases (35–35, 25–10, and 20–5), and several indicators of clam and seagrass performance were measured after 3 and 6 days of exposure and again after a recovery period of 4 days. No differences were observed in the non-native clam Ruditapes philippinarum, while oxygen consumption, clearance rate and growth decreased significantly in the native clams R. decussatus and Venerupis corrugata in response to low salinity stress. Zostera noltei indicators did not vary in response to low salinity exposure, except the sucrose content, which decreased. Moreover, the seagrass buffered juvenile clams from salinity fluctuations in the short term, although the interactions were weak. The species-specific sensitivity to low salinity should be a major concern in future management plans for the shellfish beds in the context of climate change.

Assessment of Risks Associated with Extreme Climate Events in Small-Scale Bivalve Fisheries: Conceptual Maps for Decision-Making Based on a Review of Recent Studies

Extreme climate events, such as heatwaves and torrential rain, affect the physiology and functioning of marine species, especially in estuarine habitats, producing severe ecological and socioeconomic impacts when the affected species support important fisheries, such as artisanal shellfisheries. Studies of the impact of sudden decreases in salinity and increases in temperature were reviewed with the aim of producing comprehensive conceptual maps to aid the management of fisheries of the native clams Ruditapes decussatus and Venerupis corrugata, the introduced Ruditapes philippinarum, and the cockle Cerastoderma edule in Galicia (NW Spain). The maps show the effects on mortality, scope for growth, ability to burrow, changes in gonad development or predation risk. While V. corrugata will generally be more affected by low salinity (5 to 15) or high temperature (30 °C) during only two tidal cycles, C. edule populations may recover. Both species are also expected to become more vulnerable to predators. The clams R. philippinarum and R. decussatus will be more resistant, unless extreme events occur after massive spawning episodes; however, the presence of the intertidal seagrass Zostera noltei may buffer the negative effects of high sediment temperature on the growth of some species, such as R. decussatus. Finally, recommendations for assessing climate risk and designing management actions for shellfisheries are given.

Effects of warming on biological interactions between clams and the seagrass Zostera noltei: A case study using open top chambers

Bivalves and seagrasses can interact through diverse environmentally-modulated mechanisms. To assess the effects of climate warming on bivalve-seagrass interactions, we carried out a pioneering field experiment in which open top chambers (OTCs) were used to increase air and sediment temperature in a shellfish bed in NW Spain during two consecutive spring tides (16 days of exposure to OTCs). The temperature increase produced by OTCs was significant, as observed in the daily maximum and mean temperature and in degree hours, although the difference was greater in air and at the sediment surface (up to 8 °C and 3 °C, respectively) than at 5 cm depth (up to 1 °C). Warming was less acute in boxes with the seagrass Zostera noltei, which acted as a thermal buffer, reducing the mean temperature by 1 °C at the sediment surface in OTC boxes and control boxes (without OTCs). Although the short-term increase in temperature did not greatly affect physiological responses of Z. noltei, the carbohydrate reserves and nutrient content increased in the presence of clams. Growth of the native clam Ruditapes decussatus was significantly slower in OTC boxes with bare sediment, and the seagrass thus buffered the negative effect of warming on growth. The presence of Z. noltei may save clams from having to spend energy to burrow deeper to encounter cooler conditions, leaving more energy available for growth. Conversely, growth of the introduced clam R. philippinarum did not differ between habitats or treatments. Our findings confirm a two-way facilitative interaction that may be particularly important in relation to the resilience of both species in the current context of global warming.

A sustainable natural clam shell derived photocatalyst for the effective adsorption and photodegradation of organic dyes

In response to an increasing desire for modern industries to be both green and sustainable, there has been increasing research focus on the reutilization of natural waste materials to effectively remove and degrade toxic wastewater effluents. One interesting food industry waste product is clam shell. Here a new photocatalytic nanomaterial derived from marine clam shells was successfully prepared and characterized. Thereafter the material was applied for the removal of two target dyes from aqueous solution, where the effect of both catalyst dose and initial dye concentration on adsorption and photocatalysis was investigated. The maximum adsorption capacities of methylene blue (100 mg/L) and Congo red (500 mg/L) were 123.45 mg/g and 679.91 mg/g, respectively, where adsorption followed pseudo second order kinetics predominantly via a chemical adsorption process. The photodegradation removal efficiencies of the two dye solutions under visible light irradiation were 99.6% and 83.3% for MB and CR, respectively. The excellent degradation performance in a mixed dye solution, with strong degradation capability and low cost, demonstrated that the clam shell catalyst material was a good candidate for practical field remediation of dye contaminated wastewater.

A Biological Analysis on the Invasiveness of the Corbicula Fluminea

Corbicula fluminea is an invasive species that has been observed to outcompete the native clams at the American River located near Sacramento in the Central Valley in California. We hypothesized that C. Fluminea has advantages exhibited physically including utilization of filter-feeding methods and relative spacing of its cirri as compared to the native American River clams. To investigate what makes the species so successful, we tested C. Fluminea versus the native clams in algal and E.coli environments to predict the relative advantage of a filter feeder. In addition, we used computer programs to digitally analyze the spacing between the actual cirri, which help bivalves capture food particles, of the two species. The findings pointed towards C. Fluminea’s inherent advantage in both physical and genetic traits over the native clams species which allowed it to flourish and successfully invade the American River ecosystem. However, the species’ genetic findings are found through DNA analysis.

An Investigative Study into the C. flumenia and its Interactions with its Surrounding Ecosystem

his research focused on the physical characteristics of Corbicula flumenia, an invasive species of clam found in the American River, and how these characteristics give it a possible survival advantage over native clam species of the river. Clams were collected from the American River and dissected, while river water and soil samples were also collected. The water and soil were analyzed for levels of coliforms such as E. coli, since this could be a food source that gives the Asian Clam an advantage over native species. The Asian clams were analyzed for their feeding efficiency of E. coli compared to algae and also compared for anatomical differences to the native species by measuring cirri size, which could increase feeding rates within these clams, giving them a competitive edge over their native competitors. It was found that there was much E. coli in the water and soil, but no significant correlation was found between clam cirri size and feeding rate. The Asian clam’s DNA and protein expression was analyzed for genetic mutations that contribute to the species’ invasive advantage.

Detection of SARS-CoV-2 RNA in bivalve mollusks and marine sediments

The presence of SARS-CoV-2 in wastewater pose the question of whether this new pandemic virus could be released into watercourses and potentially continue to finally reach coastal waters. In this study, we employed two bivalve molluscan species from the genus Ruditapes as sentinel organisms to investigate the presence of SARS-CoV-2 signals in the marine coastal environment. Estuarine sediments from the natural clam banks were also analyzed. Viral RNA was detected by RT-qPCR, targeting IP4, E and N1 genomic regions. Positive samples were also subjected to a PMAxx-triton viability RT-qPCR assay in order to discriminate between intact and altered capsids, obtaining indirect information about the viability of the virus. SARS-CoV-2 RNA traces were detected in 9/12 clam samples by RT-qPCR, from which 4 were positive for two different target regions. Viral quantification ranged from <LoQ to 4.48 Log genomic copies/g of digestive tissue. Regarding the sediment samples, 3/12 were positive by RT-qPCR, but only IP4 region was successfully amplificated. Quantification values for sediment samples ranged from <LoQ to 3.60 Log genomic copies/g of sediment. RNA signals disappeared in the PMAxx-triton viability RT-qPCR assay, indicating non-infectious potential. In addition, the recently discovered human-specific gut associated bacteriophage crAssphage was also quantified as a biomarker for the presence of human-derived wastewater contamination on the study area. CrAssphage was detected in 100% of both types of samples with quantification values ranging from <LoQ to 5.94 Log gc/g digestive tissue and from <LoQ to 4.71 Log gc/g sediment. Statistical analysis also showed that quantification levels for the crAssphage in clams are significantly higher than in sediments. These findings represent the first detection of SARS-CoV-2 RNA in the marine environment, demonstrating that it can reach these habitats and make contact with the marine life.

Genetic characterization of wild, broodstock and seed samples of Polititapes rhomboides (Bivalvia: Veneridae): Implications for hatchery seed production

The banded carpet shell Polititapes rhomboides is a fishery resource and a suitable candidate for the development of native clam aquaculture in Europe. Here, we analyzed nine microsatellite loci in wild samples to provide estimates of genetic diversity and population differentiation for NW Spain, the main production area of this clam. We also analyzed wild-caught broodstock and hatchery-reared seed to investigate the genetic consequences of seed production for stock enhancement purposes by mass spawning. We examined the seed sample as a whole (total seed), but also subdivided it into three size classes to assess the genetic consequences of size grading. While wild samples, broodstock included, displayed minimal or no genetic differences, the total seed showed a reduction in allelic richness (12–24 %) and a significant level of differentiation (FST = 0.026−0.043) with respect to wild samples. After performing parentage assignment, we detected a drastic reduction in the effective number of breeders (Ne) compared to the census number (85 %), and an inbreeding rate of 0.036 per generation. The low Ne and high inbreeding rate were mainly due to high variance in reproductive success. The seed size classes also showed a decrease in allelic richness and significant genetic differentiation, but we did not find significant differences in parental contribution to each size class. Our results may help the genetic-assisted management of wild populations, give insight into the genetic composition of the seed produced by mass spawning and provide a basis for the development of more effective hatchery practices and sustainable stock enhancement programs in P. rhomboides.

Invasive clams (Ruditapes philippinarum) are better equipped to deal with harmful algal blooms toxins than native species (R. decussatus): evidence of species-specific toxicokinetics and DNA vulnerability

This study aims to assess and compare the kinetics (accumulation/elimination) of the marine biotoxins okadaic acid (OA) and dinophysistoxin-1 (DTX1), between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) clam species, and their genotoxic effects and DNA recover capacity after, exposure to toxic dinoflagellates Prorocentrum lima. Clams were fed with P. lima for 5 days and then to non-toxic algae (post-exposure) during other 5 days. Toxin concentrations determined in clams by LC-MS/MS were related with DNA damage and repair assessment through the comet and base excision repair (BER) assays, respectively. Differential accumulation patterns were observed between the invasive and native species. The invasive species consistently and progressively accumulated the toxins during the first 24 h of exposure, while the native clams showed drastic variations in the toxin accumulation. Nevertheless, at the end of a 5 days of exposure period, the native clams presented higher toxin concentrations, nearly reaching the legal regulatory limit for human consumption. In addition, native clams were vastly affected by OA and DTX1, presenting an increment in the DNA damage since the first day, with a correspondent increase in the repair activity. On the other hand, invasive clams were not affected by the dinoflagellate toxins, exhibiting only some signs of the challenge, namely an increase in the DNA repair mechanisms in the post-exposure period. Invasive clams R. philippinarum are better adapted to cope with harmful algal blooms and OA-group toxins than native species. These results may increase farming interest and may lead to new introductions of the invasive clams. In sympatry sites, exposure to OA-group toxins may unbalance clams species biomass and distribution as exposure to toxic dinoflagellates affects the native clams from cellular to a population level, representing a significant threat to development and maintenance of R. decussatus populations.

Calcium chloride pollution mitigates the negative effects of an invasive clam

Invasive bivalves can drastically alter freshwater ecosystems and affect ecosystem services, but they can be influenced by external factors including calcium concentrations. When a common road salt, calcium chloride (CaCl2), enters freshwater ecosystems, it may be toxic to organisms or facilitate bivalves by serving as a calcium source. Therefore, CaCl2 could benefit invasive mollusks tolerant to chloride that require calcium to grow. We used mesocosms to investigate the impacts of CaCl2 (35–187 mg Ca2+ L−1) and invasive bivalves (Asian clams, Corbicula fluminea; zebra mussels, Dreissena polymorpha) on a native lake food web. We hypothesized that invasive bivalves facilitate benthic algae because they reduce phytoplankton and excrete waste. These changes in primary producers would subsequently impact consumers. We also hypothesized that low to moderate CaCl2 concentrations promote the survival, growth, and reproduction of native and invasive mollusks, while causing few toxic effects. If so, we hypothesized that invaded communities exposed to CaCl2 experience stronger impacts from the invasive bivalves. We found that invasive bivalves decreased phytoplankton, which led to decreases in periphyton, zooplankton, and native clams. They caused increases in filamentous algae and isopods. While zebra mussels survived poorly in all treatments, moderate concentrations of CaCl2 substantially reduced Asian clams, which reduced their community effects. Our highest CaCl2 treatments also reduced zooplankton densities. Thus, while freshwater salinization from road salts poses a concern, we observed no indication that CaCl2 road salt will benefit Asian clams and zebra mussels. However, the community-wide consequences from Asian clams at low CaCl2 emphasize the extensive effects that invasive bivalves can have on freshwater communities and the immense concern surrounding their invasions.

Биоэлектронная автоматическая станция для контроля состояния водной среды в аквакультуре

Based on the experience of the development and maintenance of oceanographic measuring equipment the proposal to create a complex of automatic coastal station having high autonomy and reliability with long-term use in marine and freshwater areas for expeditious of environmental monitoring of coastal zones and on aquaculture farms is formulated. The bioelectronic complex on basis of native clams and the distributed temperature sensing device measuring vertical profile of temperature and dynamics of its variability is the proposed equipment of the station. The feature of such configuration of the system is high reliability on functioning of submersible clusters and metrological stability of measuring channels during long-term operation in natural conditions without maintenance for a period of more than a year that allows to avoid of constant maintenance costs. Thus, a long-term operating automatic control of significant hydrological parameters of the environment and the generalized indication of ecological conditions of water area can be provided on the basis of the analysis of reactions of clams as biosensors.

Microplastic pollution in clam (Meretrix Lyrata Sowerby, 1851) at Mekong Delta river, Vietnam

The problem of microplastic pollution (&lt;5 mm) is becoming one of the biggest challenges facing countries. One of the problems is the export value of seafood products. Therefore, to assess the microplastic accumulation in clam (Meretrix lyrata), this study investigated the concentration of microplastics (MPs) in clam and their habitat in four clam culture beds (Tan Thanh, Ba Tri, Ganh Hao, and Ba Dong) in three consecutive months (from January to March 2020). The samples were analyzed by the method of oxidation of organic compounds and MPs flotation solution. The result showed that the concentrations of MPs in all three types of samples (seawater, surface sediment, and clam tissues respectively 36,66 ± 11.94 items 1 L- of seawater; 169.34 ± 42.01 items 1 kg- of soil; 13.79 ± 1.06 items individual- 10 g-, w.w) were markedly different between the four clam culture beds in three months (p-value &lt;α = 0.05). Among which, the natural clam culture at Ganh Hao beach had the lowest concentration of MPs compared to Tan Thanh, Ba Dong, and Ba Tri cultured beds by households. Furthermore, the concentration of MPs in March was also the lowest compared to January and February. Hard plastic fibers were found the most (&gt; 50%) compared to other types of plastic. The conclusion that microplastics have appeared everywhere in the environment and were found in the organism of clam, affecting the life of aquatic organisms.

Assessment of oxidative stress, genotoxicity and histopathological responses in the digestive gland of Ruditapes decussatus collected from northern Tunisian lagoons

The aim of the present study was to investigate the combined effects of seasonality and anthropogenic pressure on a battery of oxidative stress, lipid peroxidation, protein oxidation, DNA damage and histological alterations in the native clam Ruditapes decussatus collected from a less contaminated area (LCA), Ghar El Melh, a moderately contaminated area (MCA), the North Lake, and a highly contaminated area (HCA), the South Lake, all located in the southern Mediterranean Sea. The accumulation of cadmium, lead, copper, iron and zinc was higher in the digestive glandsof clams collected from the MCA and the HCAthan in those from the LCA, particularly during the warm season. Our results reveal that metallothionein, lipid peroxidation, protein oxidation levels and antioxidant defence systems were higher, while acetylcholinesterase activity was lower, in clams from the MCAand HCAthan in those from the LCA. The results also indicate that clams from the MCA and the HCAare characterized by histological alterations and DNA damage. In conclusion, the evident changes of antioxidant defence systems and macromolecules between the studied lagoons reveal the perturbation of the physiological states of clams from polluted sites thatcope with seasonal changes and trace element accumulations.

Genetic variability in Ruditapes decussatus clam combined with Perkinsus infection level to support founder population selection for a breeding program.

Clam farmers worldwide face several challenges, including irregular seed supply and high mortalities due to pathogenic organisms such as Perkinsus olseni. In Europe, there is a high unmet consumer demand for native clam species such as Ruditapes decussatus. The high market value of R. decussatus makes the culture of this species potentially more attractive than that culture of the alien species Ruditapes philippinarum. Thus, there is a market opportunity in breeding and producing R. decussatus at an industrial scale. A selective breeding program to improve R. decussatus performance will be carried out in Portugal; and the first critical step to develop such a breeding program is the establishment of a founder population. In this study, intra- and interpopulation genetic diversity was assessed using 13 microsatellite markers in eight natural beds located in Portugal, Spain and Italy. Also, allele and genotypic frequencies of each microsatellite locus were assessed discriminating between clams infected and non-infected by P. olseni. All locations showed similar values for several genetic diversity parameters. Analyses of population differentiation (FST, Bayesian clustering and AMOVAs) revealed five genetically differentiated regions: Rías Altas and Rías Baixas (NW Spain), North/Central Coast of Portugal, Gulf of Cadiz and Adriatic Sea. Significant differences in the allelic and genotypic frequency distribution between infected clams and non-infected ones at four microsatellite loci are reported suggesting that resistance to the disease could have a genetic basis. Moreover, a positive or negative relationship between the frequency of certain alleles and the parasite infection was inferred. Further studies should confirm the potential use of those alleles as genetic markers for P. olseni infection. Integrating results of genetic diversity within and between populations and Perkinsus infection levels, a founder population for a R. decussatus breeding program is proposed, composed by individuals from Barallobre (Rías Altas), Pontevedra or Cangas (Rías Baixas), Óbidos (North/Central Coast of Portugal), Algarve (Gulf of Cadiz) and Venice (Adriatic Sea).

A scientific framework for conservation aquaculture: A case study of oyster restoration in central California

The emerging field of conservation aquaculture focuses on the potential for incorporating aquaculture techniques into restoration. Extensive loss of oyster reefs worldwide has led to restoration initiatives that sometimes incorporate aquaculture, but few scientific studies of this approach have been published. We developed a scientific framework to determine whether aquaculture is an appropriate conservation tool, and applied it to Olympia oysters (Ostrea lurida) in Elkhorn Slough, an estuary in central California, USA. Over 12 years of monitoring, we documented precipitous declines in density, highlighting the need for restoration. We tracked settled oysters and found that growth and survivorship is high, showing that hatchery-raised juveniles have the potential to survive to reproductive age. No natural recruitment has occurred in the estuary in seven years, suggesting that this population is recruitment limited. Thus, we determined a need for conservation aquaculture. We produced juvenile oysters from local broodstock in a hatchery and settled them on native clam shells, which we attached to stakes to form small clusters that mimic natural biogenic habitat created by this species. We deployed these near the upper limit of the intertidal range of oysters, where oyster cover dominates over non-native fouling species. The outplanted oysters grew to adult, reproductive size within months of outplanting, and survivorship was generally high, providing the first new generation of oysters in this estuary in seven years. The science-based approach we implemented and our incorporation of traditional restoration principles of natural habitat structure and dominance by native species can serve as a model for conservation aquaculture for oysters and other species.