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Conservation efforts have raised awareness about the impact of small-scale fisheries on the distribution of seagrass plants. The patterns of recovery of the seagrass Zostera noltei and of the commercial bivalves Cerastoderma edule, Ruditapes decussatus and Ruditapes philippinarum after shellfish harvesting were studied in a field experiment in a shellfish bed in NW Spain. Sample plots were subjected to a single disturbance in two types of shellfish harvesting treatments in three zones characterized by different harvesting frequency and seagrass density. The photosynthetic efficiency (Fv/Fm), shoot density, leaf length and carbohydrate content of Z. noltei were monitored every three months during one year, and the C and N content of leaves and biomass of plants were measured one year after the disturbance. The abundance of adults, juveniles and recruits and the condition index of adult bivalves were quantified after the experimental harvesting. Shoot density and biomass of Z. noltei remained low during the ten months after the disturbance but recovered to control values after one year. Carbohydrate contents of apical rhizomes were lower in disturbed (treated) plots, whereas no effect was observed on Fv/Fm. Denser and more complex seagrass patches recovered faster. The abundance of adult bivalves below commercial size was lower in the disturbed plots, while the abundance of adults of commercial size, juveniles and recruits did not vary, indicating that abundance and condition were not hampered by harvesting pressure. The findings also suggest that Z. noltei meadows can recover within one year of the impact of shellfish harvesting if the harvesting areas are rotated and dense patches are preserved. [ABSTRACT FROM AUTHOR]

Introduction: Globally, the need for measuring exposure to algal toxins has become urgent due to ever-increasing reports of contamination in sea and freshwater, in shellfish and fish stocks and in aerosols. Methods: To address this issue, we evaluated the potential of determining autoantibodies to a panel of biomarkers known to be elevated following exposure to the hepatotoxin microcystin leucine-arginine. The presence of autoantibodies, specific to four selected stress-response, metabolomic and chaperone biomarkers, namely, Heat shock protein 1, Triosephosphate isomerase, Peroxiredoxin 1 and Peroxiredoxin 2 was employed in screening 371 serum samples from microcystin-exposed individuals in Tanzania. In addition, the capacity of the LightDeck fluorescence-based detector, a point-of-use device, to monitor these autoantibody responses in comparison to enzyme-linked immunosorbent assay was evaluated. Results: By using the determination of autoantibodies to this novel panel of biomarkers an altered response was observed following microcystin exposure, with levels generally upregulated. The presence of elevated levels of microcystin leucine-arginine in water, as well as in food sources in Tanzania, may potentially have significant health effects on the population. Discussion: This novel biomarker panel may have potential for the detection of microcystin leucine-arginine exposure as well as various microcystin exposure-associated cancers (e.g., hepatocellular cancer and colorectal cancer). In addition, the utilisation of the LightDeck point-of-use device proved successful for the rapid analysis of this biomarker panel. [ABSTRACT FROM AUTHOR]

Large‐scale assessments of fish and shellfish populations may be valuable for identifying the impacts of fishing pressure on stocks, but they are rarely possible due to a lack of long‐term datasets. In this study, a two‐part mixed‐effect model for lognormal data was used to obtain historical abundance indices for 16 priority fish and shellfish stocks in the Azores region derived from catch per unit effort (kg per day at sea per vessel) and landing per unit effort (kg per landing per vessel). This data was obtained over the past 30 years under the EC Data Collection Framework and, in addition to information on effort and catch, included details about the fishing operation such as quarter, vessel length and fishing gear. This information was analysed to investigate how abundance indices changed over the years, verify if trends from different data sources were different and, if possible, relate these results to the population and fishery dynamics. The abundance indices derived from both datasets were generally in agreement with each other. Declining trends have been observed for some commercially important species, such as forkbeard Phycis phycis, European conger Conger conger, parrotfish Sparisoma cretense, red scorpionfish Scorpaena scrofa, offshore rockfish Pontinus kuhlii, common spiny lobster Palinurus elephas, splendid alfonsino Beryx splendens and alfonsino B. decadactylus, which is concerning because they are particularly slow‐growing, long‐lived and have low natural mortality, making them susceptible to overfishing. The results of this study are very important and should help future stock assessment and management initiatives. [ABSTRACT FROM AUTHOR]

This article discusses the potential benefits of extracting valuable materials from wastewater. Researchers and commercial ventures are exploring the wealth of minerals, metals, and nutrients present in wastewater, which could be used to produce food, energy, and other goods. For example, wastewater contains significant amounts of phosphorus, potassium, and nitrogen, which are important components of fertilizers. Extracting these minerals from wastewater could meet 13% of global agriculture's fertilizer needs. Additionally, wastewater contains enough energy-producing potential to supply electricity to 158 million households. The article also highlights various methods and technologies being developed to extract and utilize these valuable materials from wastewater. [Extracted from the article]

Space is a critical component of fisheries management. Despite this, very few of the world's fish and shellfish stocks are currently assessed using methods that are spatially structured. In the Northeast Atlantic, northern shrimp in the North Sea and Skagerrak, is currently assessed using a spatially structured assessment model. This metapopulation model includes two spatial units (the Norwegian Deep and the Skagerrak), however, in the recent past, the fishery on northern shrimp in the North Sea also occurred in a third neighbouring fishing area, the Fladen Ground. Here, we have reconstructed the dynamics of northern shrimp in the Fladen Ground using historic landings, a standardized commercial index of abundance and fragmented survey data and integrated this third spatial unit into the assessment model of the stock. In doing so, we find evidence of sequential spatial depletion, whereby high rates of fishing mortality have successively eroded stock components in a west to east pattern of overexploitation and produced cryptic collapses. This finding is the first documented case of sequential spatial depletion in the Northeast Atlantic, a phenomenon that could be common and largely overlooked by stock assessment methods that are inherently non-spatial. [ABSTRACT FROM AUTHOR]

This article takes animal materials as contested elements of ecological knowledge production. The focus is on Ago Bay, a Japanese inlet at the mid-twentieth-century global epicenter of demand for "cultured" pearls that formed inside surgically manipulated shellfish, In 1950s Ago, long-established pearl cultivators complained that their pearls had thinner outer coatings than they expected. Tracing shifting ideas about shellfish stocking densities; smallholder aquaculture, rates of pearl formation, and the accumulation of organic wastes in water over time, this article reconsiders the puzzle of the thinly coated pearl. In its guise as host to thousands of working pearl farms and a network of researchers studying the effects of intensive pearl cultivation, Ago Bay is a rich site from which to think about aquaculture's ecological and infrastructural limits. The bay was not simply a natural receptacle that housed pearl cultivation. The shore, water, seafloor, and floating pearl oyster rat-and-cage systems could be-and were-defined as infrastructure that could undergo regulation and rearrangement Pearl cultivation did not just happen in the bay; it was part of the bayand it reshaped ideas about the bay. This paper is part of a special issue entitled "Making Animal Materials in Time," edited by Laurence Douny and Lisa Onaga. [ABSTRACT FROM AUTHOR]

Clams, razor clams and cockle are intertidal bivalve species collected on foot in the shellfish grounds of the Rías Altas (NW Spain). Spatio-temporal distribution of these bivalves are typically at the expenses of the environmental conditions of the region; however, the responses to the abiotic conditions are poorly understood. Using data from 6 species (Ruditapes decussatus , Venerupis corrugata , Ruditapes philippinarum , Cerastoderam edule , Donax trunculus and Solen marginatus) sampled in 51 intertidal shellfish grounds during 2007 and 2008, we characterized the influence of the environment (temperature, salinity, nutrient salts, suspended organic matter, or sediment granulometry and composition) on the distribution and size of these species through a comparative statistical analysis. Shellfish grounds were grouped according to their sediment and water characteristics revealing a land-ocean gradient and the influence of the geological imprint that separates bivalve grounds from West to East. Statistical models showed that R. decussatus, V. corrugata and R. philippinarum together with C. edule were more abundant in sites combining a strong marine influence with organic-rich finer sediments. However, each of those species also had different environmental niches mostly related to their particular sediment affinities, the proximity to the river mouth, and their physiological tolerances to temperature and salinity. D. trunculus was only found in outer exposed shellfish grounds, while S. marginatus abundance increased in muddy sediments. River distance was a sound descriptor of individual shell length and length variability with contrasting effects on the different species. Furthermore, slopes of length-weight relationships were steeper in autumn than in spring, and this allometry tended to be more positive in sites located closer to the rivers' mouth, which had a higher organic matter C/N ratio. Overall, harvested intertidal bivalves had identifiable environmental preferences that influence their spatial distribution in abundance, body size, and allometric growth. [Display omitted] • Land-ocean gradient and geological imprint define intertidal shellfish grounds. • Shellfish ground characteristics modulate bivalve presence and abundance. • Bivalve size and size variability are linked to shellfish grounds heterogeneity. • Life-history traits mediate species-specific responses to the environment. • Environmental variability across shellfish grounds affect bivalve allometric growth. [ABSTRACT FROM AUTHOR]

Ocean acidification has become one of the most intensively studied climate change topics and it is expected to have both direct and indirect impacts on species, ecosystems, and economies. Experiments have been performed on different taxa, life stages, and at different pH levels. Despite this wealth of information, several key challenges remain, including (1) uncertainty about how to incorporate current pH ranges and variability experienced by organisms into experiments, and (2) how to bring this information together to support analysis and assessments at the broader ecosystem level. Sophisticated modelling tools are needed to 'scale-up' from experimental results to regional-scale insights. This paper highlights the challenges of combining information to determine how commercially exploited species may be affected under future pH levels, and how modelling and experimental results might be better aligned, using northwest Europe and the waters around the British Isles as an example. We argue that in most cases the current evidence does not offer sufficient information into impacts at projected pH levels, and that future experiments should be designed to consider the pH levels actually experienced by organisms, as well as variability in pH. These types of study are key in safeguarding commercially exploited shellfish stocks. [ABSTRACT FROM AUTHOR]

Marine bivalves are valuable resources, however, some shellfish populations are endangered due to factors such as anthropogenic pressure, pathologies or lack of reproduction synchrony. Portuguese oyster (Crassostrea angulata) and striped venus clam (Chamelea gallina) have high socio-economic value and their endangered natural populations require rehabilitation. Cryopreservation is a valuable method for the preservation and management of genetic resources for aquaculture and restocking. Larvae cryopreservation is particularly valuable since diploid organisms are obtained upon thawing. The objective of this work was the establishment of C. angulata and C. gallina D-larvae cryopreservation through the selection of permeant cryoprotectant in the freezing solution, namely ethylene glycol (EG) and dimethyl sulfoxide (Me 2 SO). Cryoprotectants exposure showed that, in C. angulata, Me 2 SO promoted significantly higher incidence of abnormalities and enhanced glutathione reductase activity when compared to control (larvae without cryoprotectant exposure) or even to EG treatment. However, for both species, EG significantly reduced D-larvae average path velocity (VAP). In C. angulata post-thaw D-larvae, EG treatment promoted significantly lower motility and velocity when compared to control and Me 2 SO treatment. Superoxide dismutase (SOD) activity showed a reduction in C. angulata post-thaw D-larvae when compared to control, which was compensated by the enhancement of glutathione peroxidase (GPX) activity. In C. gallina post-thaw D-larvae, only motility, velocity and SOD activity were significantly lower than control. Therefore, the best treatment to cryopreserve C. angulata D-larvae was EG while for C. gallina Me 2 SO produced better results. This work established for the first time D-larvae cryopreservation protocols for C. angulata and C. gallina. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the potential effects from exposure to multiple metals, including cadmium (Cd), chromium (Cr), arsenic (As), mercury (Hg), nickel (Ni) and lead (Pb) that exist in shellfish in Chinese populations, and evaluate the impacts of cumulative exposures among individuals. A total 15,469 individual shellfish samples were analyzed following a protocol for elemental analysis. A total of 25,669 respondents were selected through stratified multi-stage cluster sampling from 31 survey sites in China. Individual shellfish consumption data and body weight were collected and analyzed with a 24-hour dietary recall method on three non-consecutive days. The consumers were divided into two groups: aged 2–12 years group and aged ≥13 years. Exposure levels were estimated based using a semi-probabilistic risk assessment method and cumulative exposures among individual persons using the maximum cumulative ratio (MCR) method. The mean, median and 95th percentile of all metals exposure for age 2–12 years group were higher than age ≥13 years group, but none exceeded the respective reference doses of the metals. The mean hazard indices (HI) of each metal in shellfish for both age groups were less than 1. The MCR values calculated among 1283 consumers ranged from 1.28 to 3.25 with the average MCR value was 2.22. There were 51 (3.98%) consumers in group I, 1186 (92.44%) consumers in group II, 26(2.03%) consumers in group III A, and 20 (1.56%) consumers in group III B. And cadmium (Cd) and lead (Pb) produced the HQMax that trigged cumulative exposures. It was concluded that heavy metals did not present a potential health risk to people solely through shellfish. The cumulative risks indicated that 7.56% of the surveyed consumers were of concern because of high HI of metals exposure, and Cd, Pb, and Ni made significant contributions to the potential risk. [ABSTRACT FROM AUTHOR]

The European lobster (Homarus gammarus) has been the subject of aquaculture and related research efforts for the last 150 years, due to both the wild fishery and cultural value of the species. Since the middle of the 20th century, increasing anthropogenic pressure has led to a severe decline in wild fish and shellfish stocks, including H. gammarus, with some fisheries yet to recover. H. gammarus is amongst the most exclusive and valuable European shellfish products, and whilst management measures have been implemented to safeguard stocks, H. gammarus aquaculture is an increasingly credible approach to help to secure a sustainable lobster supply. Historically, this has been achieved by relatively small‐scale release of hatchery‐reared juveniles during stock enhancement programmes. Until recently, commercial attempts at farming have not been viable, mainly due to cost‐prohibitive technical challenges. At present, there are several promising approaches to overcome bottlenecks hampering commercialisation of lobster aquaculture. This review summarises new technical and husbandry innovations in H. gammarus culture since the start of the 21st century, including technological innovations, husbandry and expansion of the stock enhancement (release) and farming (production) sectors. Additionally, likely directions for both sectors in the coming decades are summarised, knowledge gaps identified and the societal support required to achieve further potential are discussed. [ABSTRACT FROM AUTHOR]

Baynes Sound (BS), located in the waters of Georgia Strait, British Columbia (B.C.), is considered one of the most prolific production sites for bivalve culture in B.C. Bivalve production is influenced by a balance of water quality, hydrodynamics (bay flushing), and food supply (plankton). An ecological carrying capacity assessment is required to assess this balance, where mathematical models can integrate these complex interactions using a highresolution spatially-explicit model. The Finite Volume Community Ocean Model (FVCOM) was coupled with a Bivalve Culture Ecosystem Model (BiCEM) resorting to the Dynamic Energy Budget (DEB) to simulate bivalve physiology and their interactions with the ecosystem. These models were previously developed to address aquaculture issues in the Broughton Archipelago and Discovery Islands regions of B.C. The physical oceanographic conditions are simulated using FVCOM, analogous to previous aquaculture-motivated applications in the Broughton Archipelago and Discovery Islands. Both oceanographic observations and FVCOM outputs show a characteristic two-layered estuarine circulation over BS. This estuarine circulation appears to be strengthened or weakened by river run-off and atmospheric forcing on a seasonal scale and constitutes an overall key feature for the Sound's water inner circulation and exchange with the Strait of Georgia (SoG). The biogeochemical processes are simulated using BiCEM, which predicted that wind forcing, tidal mixing, and estuarine residual circulation contribute to the regular nutrient replenishment from the deep waters of the SoG, leading to high levels of pelagic primary productivity (phytoplankton). In turn, this phytoplankton productivity supports the potential for secondary production of zooplankton and bivalve culture. In general, the response of zooplankton and wild bivalve populations to the existing shellfish aquaculture activity indicates a system within the bounds of its ecological carrying capacity. Although the planned expansion of additional farm coverage and stock, currently under review, would impose an increased demand on the Sound's pelagic resources, the results do not indicate that the additional bivalve production could not be sustained. However, a precautionary approach should be considered with high-stocking scenarios and concentrated areas, such as, Fanny, Mud, and Deep Bays. Gradual aquaculture development in concert with proper monitoring of environmental and cultured shellfish conditions (Research Paper #2) in sensitive areas may provide sustainability of BS. [ABSTRACT FROM AUTHOR]

In the European Union (EU), the ecosystem approach to fisheries is implemented through several directives and polices, which are overarched by the Marine Strategy Framework Directive (MSFD). The MSFD requires the assessment of the environmental status of exploited fish and shellfish stocks, among others, to advise the EU Common Fisheries Policy (CFP) on sustainable catch options. The stock assessments for the CFP and the MSFD are supposed to be congruent, yet they differ in several substantial subjects. While the annual CFP assessment is based on two indicators, fishing mortality (F) and spawning stock biomass (SSB), in its Descriptor 3 (D3) the MSFD requires the assessment of three criteria (F , SSB, and age or size structure) within a six year period. Assessing exploited fish and shellfish stocks under the MSFD by using existing CFP assessments has therefore been a half-completed task, which had to be fulfilled by the member states of the EU. This paper suggests six easy steps, referred to as "quick wins" (QW), which are based on existing information from CFP stock assessments. The implementation of these six QW would allow for assessments of exploited fish and shellfish stocks that are compliant to D3. These QW are to (i) assess length/age structure within a stock, (ii) analyse and assess selectivity by fisheries, (iii) use all available information to assess a stock, (iv) use response indicators to assess environmental targets, (v) provide integrated stock-specific advice, and (vi) provide assessments with a mid-term perspective over a-period of six years. International Council for the Exploration of the Sea (ICES) combines the infrastructure and expertise to produce stock-specific assessment products tailored to the requirements of MSFD D3. Thereby, ICES could provide a valuable service to EU member states in the north-east Atlantic region by providing scientifically validated, quality-assured, and MSFD-compliant single-stock assessment products. This would be a big advancement towards implementing the ecosystem approach to fisheries management within Europe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Establishing a health baseline to assist with investigations into mass bivalve die-offs. • Higher bacterial loads isolated from mortality samples. • Lower gene copy number of Endozoicomonas spp. detected in mortality samples. • Changes in infection prevalence and intensity can be more easily measured. Disease is a major threat to the economic, ecological and cultural services provided by wild bivalve populations. Over the past decade anecdotal reports on declining health of native bivalve populations around Aotearoa New Zealand have been supported by increasing observations of mass die-offs. Causes of declining health and mass die-offs of wild bivalves are not clear and could be due to a number of interactive and cumulative factors, including declining water quality, climate change, or disease. Pipi/kōkota (Paphies australis) within the Whangārei area (northern New Zealand) have suffered repeated die-offs and declining health since at least 2009. Baseline health data for wild native bivalve populations are scarce making it difficult to identify changes in pathogen infection prevalence and intensity and infer their importance to host health. This research aimed to examine and document the health of pipi in Whangārei with the objective of identifying factors that may contribute to their ill health and lack of population recovery. We sampled pipi from four sites within Whangārei, eight times across two years (total n = 640) to establish a health baseline using histopathology, general bacteriology, and qPCR for the intracellular bacteria Endozoicomonas spp. Three pipi mass die-offs occurred during the sampling window that were opportunistically sampled to compare against the health baseline established using healthy pipi. An increase in bacterial growth and a decrease in the abundance of Endozoicomonas spp. in mortality pipi was observed compared with the health baseline. Establishing a health baseline for pipi from Whangārei provided a benchmark to assess changes in a pipi population experiencing high mortality. Such data can help identify factors contributing to die-offs and to help inform what mitigation, if any, is possible in wild shellfish populations. [ABSTRACT FROM AUTHOR]

The productivity of a suspended mussel farm depends on the abundance of naturally available food. This study constructs a tracer decay model that incorporates mussel filtration and integrates it with a well-established 3D ocean circulation model to examine the spatiotemporal variation of seston depletion at a large-scale suspended mussel farm on Gouqi Island, located offshore in the East China Sea. A novel Wirewalker ocean-wave-powered vertical profiling system was deployed to monitor chlorophyll-a concentration at the edge of the mussel farm. The observed profiles of chlorophyll-a concentration revealed that the current exiting the farm during ebb tide is associated with a lower concentration compared to the current entering the farm during flood tide. This suggests that the filter feeding activity of mussels within the farm is primary contributor to this reduced chlorophyll-a concentration. This finding is consistent with the tracer model results, which indicates a higher tracer concentration entering the farm and a lower tracer concentration exiting it. The model results suggest that the blocking effect of the farm can significantly exacerbate seston depletion, particularly during neap tide as opposed to spring tide. The interplay of tidal characteristics and topography has resulted in two areas that are particularly vulnerable to seston depletion: one centrally situated within the mussel farm, and another near the islands. However, it is possible to alleviate seston depletion by aligning the waterway within the farm with the major axis of the tidal ellipse. Consequently, it is crucial to consider tidal conditions surrounding the farm for optimal farm layout design, increased production, and enhanced stock quality in shellfish farms facing seston depletion. [Display omitted] • A tracer decay model can be employed to represent the seston consumption within large-scale mussel farms. • The water body exiting the mussel farm exhibited a lower concentration compared to that entering it. • The blockage of farm facilities can significantly aggravate seston depletion, more so during neap tide than spring tide. • The alignment of waterways within the farm with the major axis of tidal ellipses can mitigate the seston depletion. [ABSTRACT FROM AUTHOR]

Enhancement of shellfish populations has long been discussed as a potential nutrient reduction tool, and eastern oyster aquaculture was recently approved as a nutrient reduction best management practice (BMP) in Chesapeake Bay, USA. This study addressed BMP-identified data gaps involving variation in nutrient concentration related to ploidy, effects of reproductive development, and a paucity of phosphorus concentration data. Diploid and triploid oysters were collected from farms in Maryland and Virginia across the typical local reproductive cycle. The nutrient concentration of tissue and shell was consistent with the currently implemented BMP. Minor variation observed in nitrogen and phosphorus concentration was within the previously reported range, for farm location, ploidy, and reproductive cycle timing. Ploidy-based differences in tissue dry weight were not observed at either farm, which contrasts with current nutrient reduction estimates. These results suggest separate crediting values for diploids and triploids may need further investigation and potential re-evaluation. • Nitrogen (N) & phosphorus (P) in tissue and shell was consistent with prior studies. • Only minor variation in tissue N & P was observed in association with reproduction. • Ploidy-based differences in tissue dry weight were inconsistent with prior studies. • N & P reductions can be predicted with high confidence for nutrient management. [ABSTRACT FROM AUTHOR]

Losses due to predation are recognized as an important factor affecting shellfish stocks, restoration efforts and aquaculture production. Managing and mitigating the impact of predators require information on the population dynamics and functional responses to prey availability under varying environmental conditions. Asterias spp. are well-known keystone predators with the capacity to exert a top down control on shellfish populations. Asterias spp. populations are extremely plastic, booming fast when prey is abundant and exhibiting a remarkable individual resilience to starvation and adverse environmental conditions. These aspects have led Asterias spp. to be considered pests by shellfish producers and fishers and to be catalogued among the most devastating invasive species. Assessment and mitigation of the impact of Asterias rubens in northern Europe have been the objective of several projects. However, there is still a limited understanding of the processes behind A. rubens population plasticity and how environmental conditions affect individual growth and predation. Under these circumstances a comprehensive eco-physiological model becomes necessary. These models can integrate available information on biology and eco-physiology to gain understanding of the effect of the environmental conditions on the impact of A. rubens. In this work, we performed a number of eco-physiological experiments and combined them with field data from a Danish estuary to estimate and validate the parameters of a dynamic energy budget (DEB) model for the whole life cycle of A. rubens. DEB models can be used to assess the effects of environmental variability on the life cycle and key population traits allowing the prediction of the performance, abundance, resource requirements and potential distribution of individuals and populations under dynamic environments. As such the DEB model presented in this study aims to become a tool to be used to assess and manage the impact of A. rubens in cultured and natural shellfish populations. The successfully parameterised DEB model describes A. rubens as a plastic species, an efficient predator with low maintenance costs and, at least while feeding on mussels, a high energy yield from its prey. The model validation against independent data resulted in the model being capable to assess growth, food demand, reproductive output and reserves dynamics of A. rubens under experimental and natural conditions. Moreover, application of the model to the Limfjorden seastar fishery is used to further discuss the use of the model to understand biology and ecology of this pest species in the context with the management of shellfish stocks and impact mitigation. [ABSTRACT FROM AUTHOR]

Shellfish have been introduced to countries beyond their native distributions in order to develop new fisheries, but the success of such translocations has been variable. In 2003 and 2006, adult trochus (Rochia nilotica), a herbivorous coral reef gastropod, were translocated from Fiji and Vanuatu to Samoa. This translocation extended their natural range and created a new fishery in Samoa. In 2018, we had the opportunity to assess the population structure of trochus stocks at 28 sites around Samoa's two main islands using underwater visual censuses along transects. This assessment revealed that the distribution of populations showed no correspondence with initial translocation sites. Densities of trochus were spatially variable, and very high (>500 individuals/ha) at some sites. Size‐frequency distributions also varied among sites, yet all populations contained some large individuals. There was no evidence of competitive dominance of trochus over native gastropods or negative impacts to coral communities. This study shows that stocked shellfish such as trochus can develop to exploitable population levels within 15 years. Translocations of marine organisms must be considered with great caution. Our study indicates that livelihood benefits of introducing alien shellfish species are likely to be spatially variable. Translocations of the right species could support food webs and provide further food security and livelihood options to coastal fishing communities. [ABSTRACT FROM AUTHOR]

The softshell clam (Mya arenaria) is found all along Québec's coastlines, where it is harvested recreationally and commercially. Since 2008, harvesting has been performed exclusively with hand tools. For management purposes, Québec's coastal areas are divided into shellfish harvest areas in three main regions: the North Shore, Gaspé-Lower St. Lawrence, and the Îlesde-la-Madeleine. Recreational harvesting is carried out in all three regions, while commercial harvesting is limited to the Upper North Shore and the Îles-de-la-Madeleine. Commercial landings on the Îles-de-la-Madeleine have been small (< 3 t) for a number of years, and the current commercial fishery is limited almost exclusively to the Upper North Shore. Commercial landings on the Upper North Shore reached a peak in 2000, at 1,173 t, and then declined rapidly, with average landings of 26 t recorded in 2017-2019. Total allowable catches (TACs) are not fully utilized owing to the low fishing effort. Commercial landings come mainly from 10 shellfish harvest areas. Since 2017, the average size of landed clams has ranged between 65 mm and 74 mm in the six areas sampled, with sub-legal size clams (< 51 m) making up only a very small proportion of landings. In all, 23 shellfish harvest areas on the Upper North Shore were surveyed from 2016 to 2019; eight of these had been previously covered in surveys from 2002 to 2014. Commercial density (i.e., the density of legal-size clams) increased substantially in five of these eight areas. However, the current area of some of these beds is much smaller than that measured in surveys from 1967 to 1977. Indicators used for assessing softshell clam stocks in the shellfish areas surveyed in 2016-2019 include harvestable area, density of 20-50 mm clams, density of legal-size clams (= 51 mm) and commercial biomass. In order to protect the reproductive potential of each shellfish harvest area, it is recommended that the exploitation rate be limited to a maximum of 5% of the commercial biomass. However, at a 5% exploitation rate, certain shellfish areas could be more vulnerable to a loss of reproductive potential. Therefore, it is suggested that this rate be adjusted downward for shellfish areas with a harvestable area of less than 0.05 km2 and an average density of sublegal size clams (20-50 mm) of less than 15 clams/m2. The suggested exploitation rates apply to all removals (from both commercial and recreational harvests). [ABSTRACT FROM AUTHOR]

Since 2017, the Shellfish Aquaculture Demonstrative Center (S-ADC), established under the coordination of the General Fisheries Commission for the Mediterranean (GFCM) within NIMRD "Grigore Antipa", has been acting as a regional hub able to respond to Black Sea countries' needs and expectations for aquaculture development, raising awareness at every level on the shellfish aquaculture potential. So far, three training courses have been performed in the frame of the S-ADC, in 2018, 2019 and 2020. During 13-16 April 2020, due to the COVID-19 confinement, the Shellfish Aquaculture Demonstrative Center team in Constanta launched the "ADC-Online: Free online courses on techniques and technologies in aquaculture". More than 1,500 persons participated in the first training by ADC Online, according to GFCM statistics. Another major outcome of the S-ADC was the settlement of legislative drawbacks that prevented both the cultivation and the harvesting of bivalves from the natural environment in Romania, namely the microbiological classification of the Black Sea waters, as required by Regulation (EC) no. 627/2019. NIMRD elaborated, thus, within SADC, "The documentary, shoreline and hydrodynamics survey in order to establish and microbiologically classify the areas of production and relaying of live bivalve mollusks in the Romanian Black Sea sector as per Regulation (EC) no. 627/2019", which was made available to the National Sanitary-Veterinary and Food Safety Authority, to effectively start the sampling procedures and carry out the microbiological classification. NIMRD, through the SADC, performs sustained efforts to solve another issue hindering the development of aquaculture in Romania, namely the lack of an adequate legislative framework, which will allow the concession of the water (Black Sea surface), in order to locate the aquaculture facilities. [ABSTRACT FROM AUTHOR]

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. • Heatwaves strongly affect the transcriptome of R. philippinarum. • The seagrass Zostera noltei mitigates the transcriptomic response of R. philippinarum to heat stress. • Transcriptomic variations between Ruditapes species are due to distinct heat-induced behaviours. • Undisturbed Z. noltei patches act as thermal refuges for bivalves. [ABSTRACT FROM AUTHOR]

Sediment transport and resuspension are essential processes in soft-sediment environments that mediate shellfish population dynamics, water column turbidity, and estuary geomorphology at multiple scales. Adult cockles, Austrovenus stutchburyi (in New Zealand), are key organisms on intertidal sand flats that influence sediment properties, and their removal could impact the stability of the seabed and affect crucial feedback processes in this system. We conducted a field experiment to explore our hypothesis that the loss of adult cockles will increase sediment transport and resuspension non-linearly. Changes in sediment transport regimes will then influence the properties of sediment such as grain size, organic content, and chlorophyll a content. We also expected that the direction and magnitude of this effect would depend on the varying environmental characteristics across the sites, such as hydrodynamic activity and sediment grain size. We excluded adult cockles from 3 × 3 m intertidal plots at 15 sites across a natural adult cockle density gradient (300–3500 ind/m2). After seven months, sediment traps were deployed in exclusion and control plots to measure the sediment transported over two tidal cycles associated with the bedload and water column with differing densities of adult cockles. Adult cockle density was a significant predictor in all models to explain sediment transport and accounted for the largest proportion of variability explained. Relationships between cockle density and sediment transport changed between sites and over time. In these situations, simple linear relationships were not always apparent due to the interacting effects of cockle density, hydrodynamic process, and sediment characteristics. The influence of adult cockles on sediment transport was also affected by the standing stock of microphytobenthos and interacted with the mud content in their surrounding environment. Our study demonstrates the existence of an important feedback between adult cockle density, sediment stability and sediment transport that is mediated by hydrodynamic processes and sediment characteristics. • We used traps to measure sediment transport across a cockle density gradient. • Changes in adult cockle densities alters sediment stability non-linearly. • Adult cockles interact with their environment to drive sediment transport processes. • Sediment transport is highly context-dependent, influenced by physical processes. [ABSTRACT FROM AUTHOR]

The development of aquaculture activities has posed an alternative solution for the preservation of some overexploited shellfish fisheries worldwide. In the same way, endemic Mediterranean bivalves such as Pinna nobilis , highly threatened by habitat loss and coastal pollution, could found in aquaculture a solution for preserving the continuity of the species. Given the endangered status of the species, the biological and ecological processes regulating natural populations have been well studied, but there are still important knowledge gaps preventing the development of viable artificial cultures. This study describes for the first time the larval development of P. nobilis (from fertilization until pediveliger larval stages) in captivity conditions. Moreover, different rearing tanks of 5, 16 and 80 L, larvae density from 1 to 600 larvae mL − 1 , light conditions, food doses, were tested in order to establish the bases for the optimal rearing of the species and provide a source of individuals for restoring field populations. Results showed that 16 L tanks with a concentration of 2 larvae mL − 1 , constant temperature of 21 °C, 12/12 h photoperiod and fed with an “ optimal ” mixture of 25 cells per μL of Chaetoceros calcitrans + 33.3 cells per μL of Pavlova lutheri + 100 cells per μL of Isochrysis galbana ” appear to be the best conditions to rear larvae of P. nobilis . Different captivity conditions such as lower or higher tank volume, larvae density, or food doses; light privation did not report better results for larval development. [ABSTRACT FROM AUTHOR]

The present study aimed to analyze the concentrations of polycyclic aromatic hydrocarbons (PAHs) in populations of the shellfish Anomalocardia brasiliana and oysters Crassostrea rhizophorae three years after the 2019 oil spill, as well as evaluate histopathological changes on the gill tissues of the bivalves. Individuals of both species were sampled at points along the northern and southern coast of Pernambuco, Brazil. The permanence of oil residues was confirmed, evidenced by the total concentration of PAHs in the shellfish from the northern coast, which was roughly four times higher than the southern one. Among the PAHs analyzed, the low molecular weight compounds naphthalene and anthracene were the main contributors to the total concentration. Histological changes in the gills of the bivalves, were more severe in the specimens sampled on the north coast indicating alterations in the bivalve's health, mainly on the state's northern coast. • Polycyclic aromatic hydrocarbon concentrations decreased after three years on the Pernambuco coast; • Low molecular weight PAHs naphthalene and anthracene persisted on the wet tissues of the bivalves; • Histological changes in the gills of the bivalves were more severe in the northern Pernambuco coast. [ABSTRACT FROM AUTHOR]

This work focuses on the selection of new areas for shellfish farming along the coast of the Northern Adriatic Sea (Italy). Shellfish site suitability was assessed by means of a methodology based on Spatial Multi-Criteria Evaluation (SMCE), which provided the framework to combine mathematical models and operational oceanography products. Intermediate level criteria considered in the analysis included optimal growth conditions, environmental interactions, and socio-economic evaluation (e.g. organic carbon deposition; distance to harbour). Results showed that the whole coastal area comprised within 0 and 3 nm is highly suitable for farming of mussel, while the area comprised between 3 and 12 nm is divided between a highly suitable northern part, and a less suitable southern one. Seven different scenarios of development of shellfish aquaculture industry were explored. The introduction of a new species, and the assessment of the exposure to storm events are specific aspects taken into account in development scenarios. Results show that the degree of suitability for shellfish aquaculture in this area would not change dramatically with the introduction of oyster farming. Furthermore, results highlight that: (i) the growth potential in this area is high; (ii) the space with suitability index >0.5 increases when prioritizing the optimal growth condition criteria, and (iii) the socio-economic is the most restrictive Intermediate Level Criteria. Results were discussed by deriving general lessons concerning the use of SMCE in aquaculture space allocation, from the specific application in the Northern Adriatic Sea. Challenges and opportunities related to the proposed methodological framework, with particular reference to the use of resources provided by remote sensing and operational oceanography by means of mathematical models, were also discussed. Results can support a science-based identification of allocated zones for aquaculture in order to avoid conflicts, and promote sustainable aquaculture in the Mediterranean Sea, where the space for these activities is becoming increasingly limited. [ABSTRACT FROM AUTHOR]

The fine periodic growth patterns on shell surfaces have been widely used for studies in the ecology and evolution of scallops. Modern X-ray CT scanners and digital cameras can provide high-resolution image data that contain abundant information such as the shell formation rate, ontogenetic age, and life span of shellfish organisms. We introduced a novel multiscale image processing method based on matched filters with Gaussian kernels and partial differential equation ( PDE) multiscale hierarchical decomposition to segment the small tubular and periodic structures in scallop shell images. The periodic patterns of structures (consisting of bifurcation points, crossover points of the rings and ribs, and the connected lines) could be found by our Space-based Depth-First Search ( SDFS) algorithm. We created a MATLAB package to implement our method of periodic pattern extraction and pattern matching on the CT and digital scallop images available in this study. The results confirmed the hypothesis that the shell cyclic structure patterns encompass genetically specific information that can be used as an effective invariable biomarker for biological individual recognition. The package is available with a quick-start guide and includes three examples: . [ABSTRACT FROM AUTHOR]

The earth is in the midst of a biodiversity crisis, and projections indicate continuing and accelerating rates of global changes. Future alterations in communities and ecosystems may be precipitated by changes in the abundance of strongly interacting species, whose disappearance can lead to profound changes in abundance of other species, including an increase in extinction rate for some. Nearshore coastal communities are often dependent on the habitat and food resources provided by foundational plant (e.g., kelp) and animal (e.g., shellfish) species. We quantified changes in the abundance of the blue mussel ( Mytilus edulis), a foundation species known to influence diversity and productivity of intertidal habitats, over the past 40 years in the Gulf of Maine, USA, one of the fastest warming regions in the global ocean. Using consistent survey methods, we compared contemporary population sizes to historical data from sites spanning >400 km. The results of these comparisons showed that blue mussels have declined in the Gulf of Maine by >60% (range: 29-100%) at the site level since the earliest benchmarks in the 1970s. At the same time as mussels declined, community composition shifted: at the four sites with historical community data, the sessile community became increasingly algal dominated. Contemporary (2013-2014) surveys across 20 sites showed that sessile species richness was positively correlated to mussel abundance in mid to high intertidal zones. These results suggest that declines in a critical foundation species may have already impacted the intertidal community. To inform future conservation efforts, we provide a database of historical and contemporary baselines of mussel population abundance and dynamics in the Gulf of Maine. Our results underscore the importance of anticipating not only changes in diversity but also changes in the abundance and identity of component species, as strong interactors like foundation species have the potential to drive cascading community shifts. [ABSTRACT FROM AUTHOR]

The Puget Sound estuary provides one of the most valuable shellfish habitats in the Pacific Northwest, USA. Shellfish are important economically, ecologically, and socially to the Puget Sound basin. The State of Washington manages the safety of shellfish harvest areas by assessing water quality on an ongoing basis and instituting advisories and closures based on water quality thresholds. Managers currently have little information to understand the effect of these closures on harvesting effort or economic values. In order to address this important need, we recently conducted a contingent behavior survey of recreational shellfish harvesters that use Puget Sound beaches. The survey elicited the number of annual trips respondents would expect to take under alternative closure scenarios, including a baseline of no closure. We estimate the demand for recreational trips using a count model system, quantifying the economic value lost to harvesters when beaches are closed due to pollution or biotoxins. [ABSTRACT FROM AUTHOR]

The Thau lagoon is a Mediterranean coastal lagoon used for shellfish farming. It is periodically affected by anoxia events that trigger oyster mortality. To investigate the effects of an anoxia event focussed on nutrient dynamics and the responses of the microbial planktonic communities a 13-day in situ experiment was performed in September 2020. Transparent mesocosms (270 L) were placed at a depth of 4 m, inserted in the sediment, and kept closed throughout the experiment. The experiment comprised three treatments: i) Natural environment (N), i.e. in the natural water outside the mesocosms containing a rope of 30 oysters (Crassostrea gigas), ii) Control mesocosm (C) filled with natural water with no oysters, and iii) Oyster mesocosm (O) filled with natural water containing a rope of 30 oysters. Oyster respiration in the oyster mesocosm depleted oxygen after 54 h. All the oysters from O mesocosm were dead after nine days and decomposition of their flesh combined with releases from the water-sediment interface increased dissolved inorganic nitrogen (dominated by ammonium), phosphates, and ∑H 2 S up to 390, 17 and 295 μmol·L−1, respectively. Phytoplankton biomass consequently increased by 20 (11.8 μg chl al −1) and abundance by 4.5 (186 × 106 cells·L1) dominated largely by green algae <5 μm. During the oyster mortality period (day 6 to day 9) high abundances of heterotrophic flagellates and large ciliate specimens were observed. This shift in the community towards small phytoplankton favours the microbial loop and is detrimental to shellfish farming. In a context of global warming in which the risk of anoxia is higher, the results of the present investigation demonstrate that anoxia triggers shellfish mortality and that the change in the plankton community disrupts the normal functioning of the ecosystem, causing serious financial losses. In this context, it is crucial to predict possible hypoxia and anoxia events using high frequency measurements of dissolved oxygen, by avoiding using shallow zones for oyster production and by reducing shellfish stocks, or by mechanically lifting the oysters out of the water during the night to reduce oxygen respiration in the ecosystem. • In presence of oysters, anoxia was reached after 54 h in the mesocosm. • A picophytoplankton bloom was observed during anoxia and oyster decomposition. • Anoxia and oyster mortalities induced a community shift towards small plankton. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) directly impacts marine calcifying organisms including ecologically and commercially important shellfish species such as Arctica islandica (A. islandica). To test whether documented growth resilience of A. islandica to OA is a general response across ages and populations or a function of adaptation to local habitat, we cultured juvenile and adult clams collected from an environment with little pH variation under four pH levels (7.5, 7.7, 7.9, and 8.1) for three months and integrated our understanding with relevant literature. The average shell growth over the experiment among all (69) individuals was 57 ± 55 μ m, and there were no statistically significant differences in growth among pH treatments, including the control treatment, despite the general growth rate differences between juveniles and adults. Our results show that A. islandica can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions (0.65 and 0.83 for pH 7.5 and 7.7 treatments, respectively), supporting the hypothesis that resistance to OA conditions is likely a generalized response across populations. Although the present results show A. islandica can maintain their shell growth under short-term OA, long-term impacts of OA on A. islandica shell growth and other physical parameters including shell density and microstructure are still needed to better assess the sustainability of A. islandica in a more acidified future and to provide guidance on managing this important shellfish stock. • We cultured both juvenile and adult A. islandica collected from northern Norway under a range of pH • Arctica islandica from Norway can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions. • Our results show that shell growthresilience in acidified seawater is likely a multi-population adaptation in A. islandica. [ABSTRACT FROM AUTHOR]

In 2015 the EU Commission decided to review the structure of the criteria and indicators of the Marine Strategy Framework Directive (MSFD). This paper reviews some shortcomings of the current structure of Descriptor 3 (D3) addressing the status of exploited fish and shellfish stocks and suggests a more operational structure for D3. By reframing D3, the assessments of stock size and size distribution within the stock could be addressed within two distinct criteria. When relating status parameters, such as stock size and size structure to human pressures, the first criterion would assess fishing intensity while the second criterion would assess the selectivity pattern acting upon a fish stock. Within each criterion, the indicators would be embedded within an indicator framework and thereby assigned to predefined indicator types. Three different indicator frameworks were compared and analysed with regards to its operationality within D3, namely pressure-state ( p -S), pressure-state-response (PSR) and driver-pressure-state-impact-response (DPSIR) frameworks. P-S or DPSIR were found to be either incomplete in fulfilling the MSFD reporting requirements ( p -S) or too complicated to be implemented in the mid-term (DPSIR). PSR thus appears to provide the best compromise between operationality and MSFD requirements and could be applied to criteria within other descriptors to obtain a consistent indicator structure within the MSFD. [ABSTRACT FROM AUTHOR]

The growth and spread of non-indigenous green crabs (Carcinus maenas) in Atlantic Canada is of concern to the sustainability of shellfish resources, particularly in areas recently invaded. Commercial green crab fishing has been initiated on Prince Edward Island to help control this species and provide a new resource for inshore fishermen. Developing a soft-shell crab product modelled after the Venetian ‘Moleche’ would provide an economic incentive beyond the existing hard-shell crab bait market. However, answers to questions such as the timing and characteristics of green crab moulting are required. A pilot study conducted in 2014–2015 collected seven groups of crabs and held them in individual compartments for 2–4 weeks to record moulting rates and physical characteristics. We found that a synchronized ‘moulting window’ occurs during July for male crabs. Field experiments in 2015 had an average moulting rate of 34%, with group-specific rates as high as 60%. The same cohort of crabs held in the laboratory had an average moulting rate of 48%, with group-specific rates as high as 75%. We observed a gradual increase in moulting rates from early to mid-July, after which all crabs caught had recently moulted, with evidence of new carapaces on all crabs. In 2015, the moulting window followed a 5°C increase in water temperature. Regarding morphology, the presence of a ‘halo’ on the episternites of the carapace was an indicator that a crab would soon moult. These promising results represent the first step in assessing the feasibility of a soft-shell, green crab industry. [ABSTRACT FROM PUBLISHER]

Recent reports demonstrate that Arabian Gulf Shellfish and Finfish fisheries are in serious decline, in particular those of Kuwait. This decline is attributed to over fishing, pollution, loss of nursery ground, reduction in riverine input via the Shatt Al-Arab, and climate change. When completed in 2018, Sabah Al-Ahmad Sea City, Kuwait, will contain circa 200 km of waterways providing over 50% of extra coast line for Kuwait. Seine netting and gargoor traps have been deployed annually, since the first phase (A1) of this coastal township was opened to the sea in 2004, to monitor Shell and Fin fish populations within the waterways. Present work describes the diversity and abundance of commercial (edible and potential ornamental value) species now inhabiting the waterways, which comprise over 60% of the species marketed in Kuwait. Analysis of catch data reveals that the waterways act as spawning, nursery and feeding habitats for important species such asEpinephelus coioides(Orange-Spotted Grouper),Penaeus semisulcatus(Banana Shrimp) andPortunus segnis(Blue Swimming Crab). As no commercial fishing is allowed, the Sea City waterways act as a significant conservation area for Kuwait's fish stocks. [ABSTRACT FROM AUTHOR]

Litopenaeus vannamei has a high commercial value and is the primary cultured shellfish species globally. In this study, we have compared the hemolymph physiological responses between two L . vannamei strains under acute hypoxia. The results showed that hemocyanin concentration (HC) of strain A6410 was significantly higher than strain Zhengda; Total hemocyte counts (THC) decreased significantly in both strains under hypoxic stress ( p < 0.05). We also investigated the temporal and spatial variations of hypoxia inducible factors 1 (HIF-1) by qRT-PCR. The results showed that hypoxia for 12 h increased the expression levels of HIF-1α in tissues of muscle and gill from the two strains ( p < 0.05). In the hepatopancreas, the expression levels of HIF-1 increased significantly in strain Zhengda and decreased significantly in strain A6410 ( p < 0.05). No significant changes of HIF-1 expression were detected in the same tissues between the two strains under hypoxia for 6 h ( p > 0.05), but in the gills and hepatopancreas under hypoxia for 12 h ( p < 0.05). Additionally, the expression level of HIF-1 was higher in the strain Zhengda than A6410 in the same tissue under hypoxia for 12 h. It was indicated that the hypoxic tolerance of Litopenaeus vannamei was closely correlated with the expression level of HIF-1, and the higher expression level of HIF-1 to hypoxia, the lower tolerance to hypoxia in the early stage of hypoxia. These results can help to better understand the molecular mechanisms of hypoxic tolerance and speed up the selective breeding process of hypoxia tolerance in L . vannamei . [ABSTRACT FROM AUTHOR]