Intraspecific hybridization has been a strategy used frequently in mollusc aquaculture to improve the performance of traits for productive interest. In this study, the effect of hybridization between a natural population (Arica = A) and a cultivated population (Coquimbo = C; without genetic management for more than 30 y) of the Peruvian scallop Argopecten purpuratus was evaluated to assess the effect of this strategy on the performance of the cultivated population in terms of growth, survival, and stress tolerance due to hypoxia and increased temperature. To this end, progenies from intrapopulation (C × C and A × A) and reciprocal hybrid (C × A and A × C) crosses were produced and were evaluated after 6 mo under sea cultivation and in a controlled environment. Stress responses were evaluated via metabolic rates and the transcriptional level of stress-associated genes [superoxide dismutase (SOD) and HSP70]. The results showed that CC and the reciprocal hybrids CA and AC had greater size and survival rates than AA; on the other hand, AA presented the highest metabolic rates when exposed to stress; and, in parallel, AA and both hybrids (CA and AC) presented greater antioxidant capacity (SOD) when exposed to hyperthermia. Therefore, growth and survival showed positive heterosis because the hybrids performed better in these traits than the parental mean. In addition, hybridization with the Arica population would allow the Coquimbo stock under cultivation to improve its resilience to temperature increases associated to oceanographic oscillations or to climate change.

Since 2000, information to support the sustainable management of the weathervane scallop Patinopecten caurinus in the Gulf of Alaska is largely derived from fishery-dependent observations from a small fleet (≤8 vessels total). As a supplement to this information, the Alaska Department of Fish and Game collected more than one million high-resolution underwater photographs of the sea floor in five previously unsurveyed scallop beds off Kodiak Island during the spring of 2014. Weathervane scallop distribution, abundance, and size composition in these beds were assessed by analyzing more than 150,000 images subsampled in 50-image strips (stations) using a 100-m grid. In addition, the influence of local abiotic habitat features, including depth, substrate, and shell remains, on weathervane scallop distributions was explored. An estimated 26.8 [95% confidence interval (CI) = 23.5–30.7] million scallops in the five beds, with densities ranging from 0.08 (95% CI = 0.067–0.084) to 0.26 (95% CI = 0.221–0.297) ind.•m^–2 among the beds. Shell size compositions differed significantly despite the relative proximity of the beds. Weathervane density was positively related (in order of influence) to gravel, shell debris, shell hash, mud, and cobble. Optical assessment of these five previously unsurveyed scallop beds in the Gulf of Alaska demonstrates the efficacy of this approach for weathervanes and suggests that the expansion of optical survey coverage to include other known beds as a viable path to overcoming the limitations of fishery-dependent information for scallop assessment and management in Alaskan waters.

Scanning electron micrograph sequences are presented of the disarticulated shell valves of laboratory-reared larval and post-larval stages of Donax fossor obtained from adult specimens collected in the oceanic surf zone of beaches along the east coast of Assateague Island, VA. These sequences accurately depict the gross morphologies/morphometries and hinge (provinculum) structures of consistently-oriented, disarticulated shell valves of the larvae and/or postlarvae of this species. It is emphasized, however, that a scanning electron microscope is not necessary to observe even fine hinge structures associated with the early ontogenetic stages of the individual specimens depicted in these sequences. Such structures are readily visible using a wide range of optical compound microscopes equipped with high-intensity reflected light sources. The depicted morphologic and morphometric characters provide researchers with invaluable aids for discriminating (using routine optical microscopic techniques) the early life history stages of D. fossor from those of other sympatric species of bivalves isolated from plankton and benthic samples.

In the sandy shores of the Spanish Mediterranean, Donax trunculus (Linnaeus, 1758) has a high commercial interest. In the Gulf of Valencia, poor management of fishing activity led to its closure in June 2015. The objective of this study was to analyze the evolution of the catches of D. trunculus before the closure of the fishery as well as the biomass and density of the population in the months following the closure, plus 2 y later. The area of study was located in the main fishing area of the Gulf of Valencia, which belongs to the fleet of the Gandia Fishermen's Guild. The fishing beds for this clam are found on sandy sediments in shallow waters (between 0 and 2 m). During the 10 y previous to the fishery closure, the annual catch per unit effort of D. trunculus suffered a sharp decrease, falling from values between 37 and 42 (kg small vessel^–1 d^–1) during the period 2004–2008 to 5.5 in 2014. After the closure, the biomass and density of the wedge clam showed a seasonal pattern, with maximum values in summer, as well as notable differences in densities along the shore in each sampled month. Furthermore, a different size–frequency distribution across depth, with smaller individuals in the shallower areas, was observed. Nevertheless, a general and considerable decline for biomass and density from 2015 (monthly mean of commercial biomass ranged from 24 to 48 kg ha^–1) to 2017 (from 4 to 13 kg ha^–1) was noted. This indicates that the closure did not improve the state of the population. There are several hypotheses that could explain this decline such as overfishing, changes in environmental conditions, higher predation (in benthic and planktonic phases), and the reduction of food availability. Therefore, there would be a need to study them in greater depth, as well as to increase the understanding of the spatial dynamics and connectivity of the Donax beds.

In this study, fishery-independent data were used to analyze changes in average density and biomass of Panopea globosa between 2007 and 2018. Different statistical estimators based on the probabilistic density function, such as Gaussian and generalized distributions, were used, all of them associated with the spatial patchy distribution of the geoduck clam. Both average density and biomass showed a dramatic decline throughout the study period, decreasing from 31 geoducks/50 m² (2007) to 10 geoducks/50 m² (2018) and from 126,000 to 35,000 t, respectively. In addition, a high harvest of individuals greater than 175 mm of shell length was observed, increasing the possibility of recruitment overfishing. Finally, a Kobe phase chart applied to P. globosa fishery in Bahía Magdalena showed that the stock status was identified as overfished.

The taxonomy of Saccostrea oysters is problematic because of their highly variable shells. Molecular studies have revealed diverse sequence lineages that do not correspond to valid species names including some Saccostrea mordax–like oysters. The S. mordax–like oysters (n = 202) were collected from southern China and classified into three lineages, A, B, and C, based on both shell morphology and mitochondrial 16S ribosomal RNA (16S) and cytochrome oxidase I (COI) sequences. Molecular and morphological analyses indicate lineages A and B are S. mordax, and lineage C is a new species Saccostrea mordoides sp. nov. The shell morphology of the new species is variable, as in other Saccostrea oysters, but distinctive in that shell height is similar to shell length with the right valve much smaller than the left valve and having undulate laminae. The average Kimura's two-parameter distance between S. mordoides sp. nov. and other Saccostrea oysters is 0.046–0.120 for 16S and 0.106–0.240 for COI, which are significantly higher than typical distances among closely related oyster species. This study shows that S. mordoides is a new species different from S. mordax, highlighting rich species diversity of Saccostrea oysters and the need for molecular taxonomy.

Aquaculture of the blue mussel Mytilus edulis in the Gulf of Maine is a growing industry at a time when wild mussel populations are threatened by a rapidly changing ocean. Intertidal mussel beds have largely disappeared in the region raising concerns over the long-term viability of mussel farming. Histology and lipid fatty acid analysis were used to assess gametogenesis, energy investment, and pathology of farmed mussels collected twice monthly for three years in Casco Bay, ME. Energy investment in reproduction and storage differed significantly between years, suggesting interannual variability. Wet weight of fatty acids such as DHA and EPA corresponded to pre-spawning periods, when gonad tissue was most abundant. Overall, pathology assessment showed low levels of common pathogens, parasites, and cellular abnormalities. The survey did, however, reveal high levels of oocyte atresia, a probable indicator of physiological or environmental stress from unfavorable spawning conditions. In addition, the presence of the potentially damaging digenetic trematode Proctoeces maculatus was documented using histology, marking the northernmost detection in the Northwest Atlantic and a likely climate-driven range expansion. These trends may signal a challenging future for blue mussels in the Gulf of Maine. Forward-looking farm mitigation practices informed by these results should be developed to ensure future sustainability of this industry.

Marine organisms are constantly exposed to stress, such as changes in seawater temperature, which may elicit biochemical, molecular, and physiological changes. In the present study, an integrative approach to evaluate stress in the green-lipped mussel Perna canaliculus exposed to control, moderate, and severe heat stress was used. Flow cytometry (FCM) was used to measure hemolymph parameters, including hemocyte concentration, viability, and reactive oxygen species (ROS) production. Spectrophotometry and a handheld electrochemical meter were used to determine the total antioxidant capacity (TAC) of hemolymph and gill tissue, and metabolomics was used to contrast specific metabolic responses among treatments. For hemolymph parameters measured using FCM, the number of nonviable hemocytes increased with the severity of heat shock. The proportion of superoxide-positive hemocytes mirrored the increase in nonviability; by contrast, the general ROS production initially increased following moderate heat shock, but then decreased after severe heat shock. Trolox-equivalent antioxidant capacity in the gill tissue and fast-acting antioxidant levels in the haemolymph showed small but significant decreases following heat shock, whereas the reciprocal pattern was seen for slow-acting and TAC in the hemolymph. Metabolomic profiles discriminated between treatments, with energy metabolism pathways appearing the most affected. The approach used in this study provides a deeper mechanistic understanding of the stress responses of organisms exposed to heat stress; however, these analytical techniques may be combined or used independently to measure stress in marine organisms in the laboratory or in the field, which can improve health assessments of wild and farmed aquatic organisms.

Characterizing relative temporal and spatial variations in both the living and detrital components of bivalve food is required to predict bivalve growth across environments with contrasting seston compositions. The present article describes how remote sensing can be applied for such characterization, both over large spatial scales and fine spatial resolutions (i.e., farm scale; 10's of meters), thereby providing key information for bivalve aquaculture operations and site selection, including the restoration of native species. Using natural seawater samples collected from contrasting culture sites in North America and Europe, a simple model was developed to predict the total particulate organic matter (POM) available as food to bivalves from high-resolution remote-sensing images of coastal embayments which estimate chlorophyll (CHL) and turbidity, in which CHL acts as a proxy for living organics and turbidity as a measure of total suspended particulate matter (SPM). The resulting POM derived from satellite images, along with temperature and CHL, are then used as inputs to the bivalve bioenergetic model, ShellSIM, to predict the growth of Mytilus edulis, Crassostrea virginica, and Ostrea edulis along the coast of Maine, one of the most convoluted coasts in the United States, for aquaculture site selection.

Abalones are poikilotherms, and their rate of development is intrinsically linked with temperature. Understanding the effect of temperature on development is key for the successful production planning in abalone hatcheries and the reseeding of cultured abalone larvae for stock enhancement. This study investigates the effect of temperature on the development of the abalone larvae Haliotis midae. Newly hatched trochophore larvae were raised at temperatures of 14°C, 16°C, 18°C, 20°C, and 22°C until settlement. The temperature had a significant effect on the larval development—most rapid at 22°C [3 days and 65 degree-days (DD), °C day] and slowest at 14°C (6.7 days and 95 DD). Larval settlement was highest at 22°C (43.44% ± 3.73%, larvae). Larvae should preferably be seeded at temperatures between 20°C and 22°C as this will potentially increase settlement, thereby reducing larval dispersion outside of the seeding area.

Temperature and hypoxia anomalies are observed in many coastal regions, and climate change is likely to cause a more frequent and intense occurrence of environmental extremes. Understanding their impacts on benthic populations is critical, especially on those with little or no mobility. In this contribution, the effects of hyperthermia (to 26°C) and hypoxia (to 1.0 mg O₂ L^–1) were analyzed and compared with their combined occurrence through the evaluation of the physiological condition of juveniles of the green abalone Haliotis fulgens. Sudden, single-time exposure of 8 h and the recurrent exposure to 8-h weekly episodes for 6 wk were tested to identify changes in the physiological condition by estimating the respiration rate (RR), the biochemical contents (soluble protein [SP] and glucose [Glc]), and physicochemical variables (osmolality [Osm] and pH) in hemolymph, and energy status (adenylate energy charge [AEC]) was measured in the muscle. The strongest responses under sudden hyperthermia were an increase in RR and Osm as well as a reduction in SP, pH, and AEC, and under hypoxia and combined effects, reductions in RR, Osm, and pH were observed. Abalone's responses to the combined stressors under the recurrent regime were different, showing increases in SP and Glc contents and reductions in pH and AEC. Results suggest that under recurrent stress of hyperthermia or hypoxia alone, the juveniles of H. fulgens can adapt, whereas under recurrent events of the combined stressors, the observed response is similar to that of sudden stimuli (without evidence of adaptation).

California abalone Haliotis spp., listed as species of concern, have been slow to recover, after 22 years of fishery closure, or are not recovering at all because of low-density populations and recruitment failure. It is not known if there is successful recruitment in populations in the wild in Southern California. This work examines, for the first time, whether newly settled abalones (<3 mm) are present in the wild at Santa Catalina Island to determine if recruitment is occurring. Natural cobbles with crustose coralline algae cover were sampled for recently settled abalones at two sites and at three depths over the reproductive season of green and pink abalone. A total of 128 abalone recruits (Haliotis spp.) were found over a cumulative rock surface area of 7.47 m², on 325 cobbles, for a total recruitment density of 17.14 recruits per m². Abalone recruits ranged in size from 220 to 2,120 µm, with an average recruit size of 490 ± 20 µm (mean ± SE, n = 124). Recruitment was similar across depths (2–4, 6–8, and 10–12 m) but differed between the two study sites, and was highest in June and September. Genetic work is needed to confirm species identification of the new recruits; however, they were most likely green abalone which would be consistent with the signs of green abalone recovery at the island. This work quantifies abalone settlement in Southern California, confirming successful recruitment. These methods can aid future restoration efforts empowering managers and restoration practitioners to monitor and quantify recruitment dynamics for abalones in California.

The white shrimp fisheries in South Carolina and Georgia, USA, have undergone substantial reductions in commercial landings over the past few decades. These declines are associated with reduced commercial effort, shifting climate patterns, and disease outbreaks. For example, recent increases in the occurrence of gill melanization, also known as black gill, have led to the suggestion that this epidemic is a major contributor to reduced shrimp abundance in the region. The goal of this study was to assess long-term patterns and drivers of black gill, and its effects on white shrimp abundance, particularly during the fall, when most of the commercial harvest of white shrimp in this region has historically occurred. Data were compiled for fishery-independent (2002–2017) metrics of white shrimp abundance and black gill prevalence from seven estuaries along the South Carolina and Georgia coasts. Phenology of black gill was variable among years, but mean black gill prevalence was significantly related to the Pacific Decadal Oscillation and El Niño–Southern Oscillation climate indices. These analyses show that the prevalence of black gill is sensitive to large-scale fluctuations in climate patterns.

Ensuring sustainability of the world fisheries is a key conservation and economic objective. Traceability of seafood from the final sale back to the point of harvest is an important aspect, supporting both fishery management and consumer protection. Stable isotope–based geolocation can be applied to trace the spatial origin of seafood, drawing on comparisons between the isotopic compositions of the product and those of a reference dataset from known spatial locations. This study tests the extent to which stable isotope–based geolocation can be applied to identify catch location of the Norwegian lobster Nephrops norvegicus. Carbon, nitrogen, and sulfur isoscapes across UK shelf seas are used as the reference dataset and test the accuracy of assignment estimates using a variety of bivariate and multivariate stable isotope geolocation approaches. Two alternative Bayesian inversions, one balanced and one weighted, are applied to the outcomes of the statistical models to determine the most accurate methods of assignment. Of all the methods trialed, the multivariate approach using carbon, nitrogen, and sulfur isoscape data produced the most accurate assignments, with c. 60% of samples from each site correctly assigned among six possible fishery origins. Weighted Bayesian approaches resulted in more correct assignments to highly fished sites, but at a cost of reduced correct assignments to sites of low fishing activity. Processed Nephrops samples obtained from supermarkets were assigned to potential fishery location, with results indicating the majority were captured in the west of Scotland. The isoscape methods explored can be calibrated to any marine feeding organism and provide a useful tool for more efficient management of marine stocks.

Oysters and seagrasses provide structurally complex estuarine habitat for fish and invertebrate species. On the U.S. West Coast, complex oyster habitat was historically provided by the native Olympia oyster Ostrea lurida but is now provided by the commercially cultured oyster Crassostrea gigas. Ostrea lurida is found in subtidal and low intertidal areas, whereas C. gigas is predominantly cultured at higher intertidal elevations, resulting in a potential shift in available habitat for other fish and invertebrates that use this intertidal habitat. This change in the available habitat and its use was examined for the juvenile Dungeness crab Metacarcinus magister, and results showed the following: (1) comparable crab densities in remnant and restored populations of O. lurida and cultured C. gigas in two estuaries, (2) generally higher crab densities in both of these shell habitats than those observed in eelgrass Zostera marina or open mud habitat, (3) contemporary juvenile crab density in intertidal areas of Willapa Bay was most influenced by distance from the estuary mouth (declining with increasing distance) but also declined with increasing tidal elevation, and (4) when extrapolated to the estuarine ecosystem scale using areal estimates of habitat coverage, historical habitat provided by O. lurida potentially produced three times more juvenile crabs than those currently produced in cultured C. gigas. Nonetheless, both intertidal oyster habitats contribute more to juvenile crab production than eelgrass or open unstructured mud, and the ecosystem services associated with the placement of native and commercial oyster beds should be considered when defining goals for and permitting both aquaculture and native oyster restoration in Willapa Bay and other U.S. West Coast estuaries. Managers should consider this shifting temporal baseline in intertidal habitat provision, but also conducting similar evaluations at this broader estuary scale when evaluating habitat value for other resources that use these habitats differently.

The effects of high hydrostatic pressure (HHP) processing at 200 MPa, 400 MPa, and 600 MPa on the proximate composition, inactivation of bacteria, and color of the red claw crayfish Cherax quadricarinatus were evaluated. High hydrostatic pressure processing resulted in complete shelling and a significant decrease in the moisture content (P < 0.05), whereas no significant differences were observed in the content of ash, crude protein, and crude lipid, except for the crude lipid content between 200 MPa and 600 MPa groups (P < 0.05). After pressurization, the Escherichia coli, Vibrio vulnificus, and Vibrio parahaemolyticus counts decreased significantly with the increase of pressure, even to an undetected level for V. vulnificus and V. parahaemolyticus at 400 and 600 MPa (P < 0.05), respectively. During 30-d storage at 4°C and –20°C, the counts of these three bacterial species increased significantly with increased storage time and temperature. After HHP processing, a* value changed substantially, whereas L* and b* values had little change for meat. The total color difference (ΔE*) suggested that the HHP-treated red claw crayfish exhibited very distinctive or substantial differences compared with fresh individuals.