Placopecten Magellanicus Research Articles

De Novo Assembly and Characterization of Two Transcriptomes Reveal Multiple Light-Mediated Functions in the Scallop Eye (Bivalvia: Pectinidae)

BackgroundThe eye has evolved across 13 separate lineages of molluscs. Yet, there have been very few studies examining the molecular machinary underlying eye function of this group, which is due, in part, to a lack of genomic resources. The scallop (Bivalvia: Pectinidae) represents a compeling molluscan model to study photoreception due to its morphologically novel and separately evolved mirror-type eye. We sequenced the adult eye transcriptome of two scallop species to: 1) identify the phototransduction pathway components; 2) identify any additional light detection functions; and 3) test the hypothesis that molluscs possess genes not found in other animal lineages.ResultsA total of 3,039 contigs from the bay scallop, Argopecten irradians and 26,395 contigs from the sea scallop, Placopecten magellanicus were produced by 454 sequencing. Targeted BLAST searches and functional annotation using Gene Ontology (GO) terms and KEGG pathways identified transcripts from three light detection systems: two phototransduction pathways and the circadian clock, a previously unrecognized function of the scallop eye. By comparing the scallop transcriptomes to molluscan and non-molluscan genomes, we discovered that a large proportion of the transcripts (7,776 sequences) may be specific to the scallop lineage. Nearly one-third of these contain transmembrane protein domains, suggesting these unannotated transcripts may be sensory receptors.ConclusionsOur data provide the most comprehensive transcriptomic resource currently available from a single molluscan eye type. Candidate genes potentially involved in sensory reception were identified, and are worthy of further investigation. This resource, combined with recent phylogenetic and genomic data, provides a strong foundation for future investigations of the function and evolution of molluscan photosensory systems in this morphologically and taxonomically diverse phylum.

Small-scale spatial and temporal genetic structure of the Atlantic sea scallop (Placopecten magellanicus) in the inshore Gulf of Maine revealed using AFLPs

Despite long planktonic durations, many species of broadcast spawning invertebrates exhibit genetic structure at small spatial and temporal scales. Amplified fragment length polymorphisms were used to assess genetic variation in the sea scallop, Placopecten magellanicus, among four inshore and one offshore location in the Gulf of Maine and temporal genetic variation among age classes of sea scallops at one site. Our results indicated that genetic structure for P. magellanicus exists on smaller spatial scales (tens to hundreds of kilometers) than expected given the 40-day planktonic larval period. In addition, genetic differences among age classes may be influenced by inter-annual differences in larval supply or reproductive success. Future genetic studies should sample multiple age classes prior to comparison among locations.

Paralytic shellfish toxins in the sea scallop Placopecten magellanicus on Georges Bank: Implications for an offshore roe-on and whole scallop fishery

To protect public health from the potential risk of paralytic shellfish poisoning (PSP) in sea scallops, Placopecten magellanicus, from the Atlantic offshore U.S. waters of Georges Bank, harvesting of roe-on or whole scallops is banned. Only adductor muscles may be sold if harvested from Georges Bank, Gulf of Maine, or the PSP closure areas as far west as 71° West Longitude. Given the limited toxicity data available for sea scallops from this region both prior to and subsequent to implementation of this management strategy, this study sought a more extensive spatial and temporal evaluation of sea scallop gonad and viscera toxicities that would inform management decisions related to the roe-on and whole scallop fishery. Both overall toxicity and toxin composition were measured for sea scallop gonads and viscera collected from 232 stations in 2007 and 23 in 2010. Overall toxicity was assessed using two screening methods: field-deployable Jellett Rapid Tests (JRT) and quantitative, laboratory-based receptor binding assays (in 2007). Additionally, a quantitative liquid chromatography with fluorescence detection (LC-FD) method was used to determine toxin composition and overall toxicity (in 2010). The at-sea qualitative JRT screening tool results, whereby a positive indicated the sample contained at least 40μg saxitoxin (STX) equivalents 100g−1, were often inconsistent with results obtained using the quantitative methods. Sea scallop viscera toxicity represented the majority of toxin load in the organism and was often in excess of the regulatory guidance level. Sea scallop gonads accounted for a small percentage of total toxicity, but at times reached unsafe levels. Toxin composition in both the gonads and viscera was dominated by STX and gonyautoxin 2/3, as has been reported in previous studies. No predictive indices of gonad toxicity were found. Results at this time do not support a roe-on or whole scallop fishery on Georges Bank. While access restrictions to whole scallops on Georges Bank are unlikely to change based on these results, it seems plausible that a management strategy requiring at-sea testing of scallop gonads for PSP may be necessary in order for a safe roe-on scallop fishery from this region to be feasible.

Filtration of sea louse, Lepeophtheirus salmonis, copepodids by the blue mussel, Mytilus edulis, and the Atlantic sea scallop, Placopecten magellanicus, under different flow, light and copepodid‐density regimes

Population management of Lepeophtheirus salmonis in Canada currently relies on chemotherapeutants to remove attached stages of the ectoparasite. However, some populations of L.salmonis are developing resistance to chemotherapeutants making alternate management measures necessary. This article explores the ability of filter-feeding shellfish [i.e. blue mussels (Mytilus edulis) and Atlantic sea scallops (Placopecten magellanicus)] to consume the copepodid stages of L.salmonis in the laboratory under static and flowing water conditions, with variable copepodid densities, and with the aid of a light attractant. Mytilus edulis consumed copepodids under both static and flowing water conditions, and the proportion of individuals ingested was similar at low and high copepodid densities, suggesting that M.edulis was not saturated at the concentrations tested. Also, M.edulis consumed more copepodids when a light attractant was present, suggesting that lights may be useful to concentrate widely dispersed copepodids around cultured shellfish in the field. Finally, P.magellanicus consumed the same number of copepodids as an equivalent total wet weight of M.edulis. During each of the four separate experiments, shellfish consumed between 18 and 38% of the copepodids presented per hour, suggesting that both species are well suited for low level removal of copepodids over time.

Death of the genome paper

Death of the genome paper

The battle for user-friendly bioinformatics

The battle for user-friendly bioinformatics

To split or not to split: Assessment of Georges Bank sea scallops in the presence of marine protected areas

Marine protected areas (MPAs) may create challenges for stock assessments because most models are based on the assumption that fishing mortality is uniform in space. Using both actual data and simulations, we explored two approaches to the stock assessment of Georges Bank Atlantic sea scallops (Placopecten magellanicus), where fishery closures were implemented in December 1994. One approach modeled the stock in “aggregate”, using domed commercial selectivity functions for the time periods when the MPAs were closed to scallop fishing. In the second “split” approach, separate models were used for the scallops inside (closed areas) and outside (open areas) the MPAs. The aggregate model converged only in 17% of the simulated runs, compared with 93% convergence for the open and closed runs using the split approach. With actual data, and in those simulations where both methods converged, the two approaches gave similar results, although biomass estimates in the most recent years from the aggregate model tended to be biased low. The closed area model, and to a lesser extent the aggregate model, estimated natural mortality M fairly precisely, but open area model estimates of M were poorly defined. Retrospective patterns were reduced using the split approach and when natural mortality was estimated. We conclude that the split assessment approach is better for sea scallops, but it may be best to use both approaches for comparative purposes.

Shell Height-To-Weight Relationships for Atlantic Sea Scallops (Placopecten magellanicus) in Offshore U.S. Waters

Generalized linear mixed models were developed for allometric relationships in Atlantic sea scallops (Placopecten magellanicus). These models used environmental covariates such as depth, latitude, geographic area, fishing pressure, population density, and season. This study makes several technical improvements to existing allometric models. We found depth, latitude, and geographic area to be important covariates in models for scallops on Georges Bank, whereas depth and fishing pressure were important for mid-Atlantic scallops. Our allometric relationships have important implications for stock assessment and fisheries management.

Heterosis and Combining Abilities in Growth and Survival in Sea Scallops Along the Atlantic Coast of Canada

Selective breeding and crossbreeding are seen widely in genetic improvement of crops as well as molluscs. In this study, we constructed complete 4×4 diallel crosses using broodstock from 4 geographical subpopulations of sea scallops along the Atlantic coast of Canada, and heterosis and combining abilities in growth and survival rates at larval and adult grow-out stages were analyzed. The results indicated that variable heterosis in growth and survival exist in larval and adult stages. In many cases, the fitness traits increased with general combining abilities, especially at the larval stage, but in some cases, groups with high growth or survival rate but low general combining abilities were also observed. Reciprocal effects and maternal reciprocal effects were observed in growth and survival at the larval stage and also in adult growth. Two hybrid strains with superior growth and survival traits over purebred and other hybrid groups were selected that can be used in future culture practice.

Post-settlement predation by sea stars and crabs on the sea scallop in the Mid-Atlantic Bight

Year-class strength of benthic invertebrates is generally determined during early life-history stages. However, the contribution of different biotic and abiotic factors to the resulting abundance and spatial distribution of recruits is poorly understood. We infer the effect of postsettlement mortality by benthic invertebrate predators on recruitment of sea scallops Placopecten magellanicus based on an 11 yr time series of survey data from the east coast of the United States. We reconstructed predator densities at different life-history stages for scallops and identified the stages when scallop recruitment dynamics are best explained by predator densities. Based on spatial associations and temporal dynamics, we found evidence that sea stars Astro pecten americanus and crabs Cancer spp. are causing localized depletion of sea scallop recruits. Both predator groups appear to be affecting scallop recruitment primarily in the first year post-settlement. The spatial and temporal coherence in predator−prey fluctuations partially ex plains the most dramatic recruitment events in the past 3 decades and suggests that predation on recruits may also limit the geographic distribution of sea scallops in this region.

Timing of Shell Ring Formation and Patterns of Shell Growth in the Sea ScallopPlacopecten MagellanicusBased on Stable Oxygen Isotopes

ABSTRACT The ratio of 18O to 16O in the shell material of bivalves depends on the ambient water temperature at the time the shell material was deposited. By analyzing samples of shell material taken sequentially from the umbo to the shell margin, we obtained the oxygen isotopic records from the shells of 14 sea scallops (Placopecten magellanicus) and compared the isotope data with the visible rings on the upper valve. Using generalized additive models, we show that ring formation is related significantly to water temperature, and that rings were typically laid down near the annual temperature maximum. Shell ring formation was generally annual, although 2 of the mid-Atlantic scallops appeared to have laid down 2 rings in 1 y. Some of the scallops appear to form new shell material and increase in shell height over the entire year for the first few years of life, and in later years reduce or halt accretion at the shell margin during the coldest temperatures. The isotopic records obtained from near the umbo o...

Stock Definition and Recruitment: Implications for the U.S. Sea Scallop (Placopecten magellanicus) Fishery from 2003 to 2011

The United States sea scallop management plan applies fishing mortality in a uniform manner, assigning a single value of instantaneous fishing mortality (F) to the entire resource. Applying a single value of fishing mortality assumes the scallop resource is a single population. Dividing the resource into Georges Bank and Mid-Atlantic Bight reveals that each has been either excessively fished or underutilized based on the present definition of optimum yield. The sea scallop resource was highest in 2003 and has declined by about 50,000 metric tons, entirely from the Mid-Atlantic Bight. Abundance and the corresponding harvest levels will likely continue if the resource is a single population and scallops in the closed areas of Georges Bank populate the entire resource. Abundance and the corresponding harvest levels will likely decline if Georges Bank and the Mid-Atlantic Bight are separate populations in that scallops within these areas have a closed lifecycle. The depletion of the large number of small scallops in the Mid-Atlantic observed in 2003, and poor recruitment from 2009 to 2011, could lead to a rapid reduction in abundance, seriously impacting the fishery that was valued at US$455 million in 2010.

Multiple methods, maps, and management applications: Purpose made seafloor maps in support of ocean management

The establishment of multibeam echosounders (MBES) as a mainstream tool in ocean mapping has facilitated integrative approaches toward nautical charting, benthic habitat mapping, and seafloor geotechnical surveys. The inherent bathymetric and backscatter information generated by MBES enables marine scientists to present highly accurate bathymetric data with a spatial resolution closely matching that of terrestrial mapping. Furthermore, developments in data collection and processing of MBES backscatter, combined with the quality of the co-registered depth information, have resulted in the increasing preferential use of multibeam technology over conventional sidescan sonar for the production of benthic habitat maps. A range of post-processing approaches can generate customized map products to meet multiple ocean management needs, thus extracting maximum value from a single survey data set. Based on recent studies over German Bank off SW Nova Scotia, Canada, we show how primary MBES bathymetric and backscatter data, along with supplementary data (i.e. in situ video and stills), were processed using a variety of methods to generate a series of maps. Methods conventionally used for classification of multi-spectral data were tested for classification of the MBES data set to produce a map summarizing broad bio-physical characteristics of the seafloor (i.e. a benthoscape map), which is of value for use in many aspects of marine spatial planning. A species-specific habitat map for the sea scallop Placopecten magellanicus was also generated from the MBES data by applying a Species Distribution Modeling (SDM) method to spatially predict habitat suitability, which offers tremendous promise for use in fisheries management. In addition, we explore the challenges of incorporating benthic community data into maps based on species information derived from a large number of seafloor photographs. Through the process of applying multiple methods to generate multiple maps for management applications, we demonstrate the efficient use of survey data sets to maximize the benefit to a wide number of potential end users, and to facilitate the move toward an ecosystem-based approach to management.

Determination of Paralytic Shellfish Toxins in Shellfish by Receptor Binding Assay: Collaborative Study

A collaborative study was conducted on a microplate format receptor binding assay (RBA) for paralytic e shellfish toxins (PST). The assay quantifies the composite PST toxicity in shellfish samples based on the ability of sample extracts to compete with (3)H saxitoxin (STX) diHCl for binding to voltage-gated sodium channels in a rat brain membrane preparation. Quantification of binding can be carried out using either a microplate or traditional scintillation counter; both end points were included in this study. Nine laboratories from six countries completed the study. One laboratory analyzed the samples using the precolumn oxidation HPLC method (AOAC Method 2005.06) to determine the STX congener composition. Three laboratories performed the mouse bioassay (AOAC Method 959.08). The study focused on the ability of the assay to measure the PST toxicity of samples below, near, or slightly above the regulatory limit of 800 (microg STX diHCl equiv./kg). A total of 21 shellfish homogenates were extracted in 0.1 M HCl, and the extracts were analyzed by RBA in three assays on separate days. Samples included naturally contaminated shellfish samples of different species collected from several geographic regions, which contained varying STX congener profiles due to their exposure to different PST-producing dinoflagellate species or differences in toxin metabolism: blue mussel (Mytilus edulis) from the U.S. east and west coasts, California mussel (Mytilus californianus) from the U.S. west coast, chorito mussel (Mytilus chiliensis) from Chile, green mussel (Perna canaliculus) from New Zealand, Atlantic surf clam (Spisula solidissima) from the U.S. east coast, butter clam (Saxidomus gigantea) from the west coast of the United States, almeja clam (Venus antiqua) from Chile, and Atlantic sea scallop (Plactopecten magellanicus) from the U.S. east coast. All samples were provided as whole animal homogenates, except Atlantic sea scallop and green mussel, from which only the hepatopancreas was homogenized. Among the naturally contaminated samples, five were blind duplicates used for calculation of RSDr. The interlaboratory RSDR of the assay for 21 samples tested in nine laboratories was 33.1%, yielding a HorRat value of 2.0. Removal of results for one laboratory that reported systematically low values resulted in an average RSDR of 28.7% and average HorRat value of 1.8. Intralaboratory RSDr based on five blind duplicate samples tested in separate assays, was 25.1%. RSDr obtained by individual laboratories ranged from 11.8 to 34.9%. Laboratories that are routine users of the assay performed better than nonroutine users, with an average RSDr of 17.1%. Recovery of STX from spiked shellfish homogenates was 88.1-93.3%. Correlation with the mouse bioassay yielded a slope of 1.64 and correlation coefficient (r(2)) of 0.84, while correlation with the precolumn oxidation HPLC method yielded a slope of 1.20 and an r(2) of 0.92. When samples were sorted according to increasing toxin concentration (microg STX diHCl equiv./kg) as assessed by the mouse bioassay, the RBA returned no false negatives relative to the 800 microg STX diHCl equiv./kg regulatory limit for shellfish. Currently, no validated methods other than the mouse bioassay directly measure a composite toxic potency for PST in shellfish. The results of this interlaboratory study demonstrate that the RBA is suitable for the routine determination of PST in shellfish in appropriately equipped laboratories.

Changes in enzymatic activity during early ­development of bay scallops Argopecten irradians and sea scallops Placopecten magellanicus

Poor growth and survival of scallops is often reported during early developmental stages. Stage- and species-specific dietary requirements have been identified, but the mechanisms responsible for these differences remain largely unknown. Dietary success depends on food bio- chemical properties, digestive and/or assimilative capacity, as well as the animal's specific nutri- tional demands, which can vary over development and between species. The present study exam- ines developmental changes in the activities of key digestive enzymes in larval and postlarval bay scallops Argopecten irradians and sea scallops Placopecten magellanicus raised on a mixed algal diet until ~4 to 5 mm in shell height (SH) and sampled at intervals encompassing major transitions in feeding organ development. Colorimetric assays measured general protease, lipase (esterase) and carbohydrase (α-amylase, cellulase and laminarinase) activities. The most pronounced changes in enzymatic activity occurred prior to scallops attaining ~1.2 mm SH in both scallop species. The esterase:protease ratio exhibited similar ontogenetic patterns in both scallop species, decreasing sharply between larval and immediate postlarval stages before increasing to an intermediate level and stabilizing around 1.2 mm SH. In contrast, mean carbohydrase activities measured over the experimental duration differed between species, with bay scallops exhibiting higher specific activi- ties of α-amylase and cellulase but much lower activities of laminarinase than sea scallops. These findings have implications for understanding scallop utilization of the food supply in nature, as well as developing targeted diets that could enhance their growth and survival in culture.

Design, Evolution, and Assessment of a Sea Turtle Deflector Dredge for the U.S. Northwest Atlantic Sea Scallop Fishery: Impacts on Fish Bycatch

AbstractBetween May 2006 and November 2009 we tested five sequential dredge modifications during 37 trips on 13 different sea scallop fishing vessels. The testing evaluated the impacts of these modifications on the catch of sea scallops Placopecten magellanicus, the bycatch of fish and sea turtles in the families Cheloniidae and Dermochelyidae, and frame durability. We tested the modified dredges and an original New Bedford dredge (control) by conducting paired, side‐by‐side tows using identical tow parameters. A total of 4,059 paired tows were conducted in which tow data, scallop catch, and bycatch were recorded; data from 44% of the tows were sufficiently sampled for comparisons of bycatch. The dredge catches showed a significant 3% increase in sea scallop catch and significant decreases in the bycatch of many species, including yellowtail flounder Limanda ferruginea (46%), winter flounder Pseudopleuronectes americanus (69%), barndoor skate Dipturus laevis (18%), and winter skate Leucoraja ocellata (20%). The final design, the CFarm turtle deflector dredge, proved effective at guiding turtle carcasses over the top of the dredge by eliminating most of the bale bars and forming a ramp with a forward‐positioned cutting bar and closely spaced struts leading back at a 45° angle. The final design also proved effective in reducing bycatch for a number of nontarget fish species. Flow characterizations in a flume tank provided insight into the cutting bar and frame hydrodynamics that may explain the field trial results.Received February 2, 2011; accepted November 2, 2011

Swimming away or clamming up: the use of phasic and tonic adductor muscles during escape responses varies with shell morphology in scallops

The simple locomotor system of scallops facilitates the study of muscle use during locomotion. We compared five species of scallops with different shell morphologies to see whether shell morphology and muscle use change in parallel or whether muscle use can compensate for morphological constraints. Force recordings during escape responses revealed that the use of tonic and phasic contractions varied markedly among species. The active species, Amusium balloti, Placopecten magellanicus and Pecten fumatus, made more phasic contractions than the more sedentary species, Mimachlamys asperrima and Crassadoma gigantea. Tonic contractions varied considerably among these species, with the two more sedentary species often starting their response to the predator with a tonic contraction and the more active species using shorter tonic contractions between series of phasic contractions. Placopecten magellanicus made extensive use of short tonic contractions. Pecten fumatus mounted an intense series of phasic contractions at the start of its response, perhaps to overcome the constraints of its unfavourable shell morphology. Valve closure by the more sedentary species suggests that their shell morphology protects them against predation, whereas swimming by the more active species relies upon intense phasic contractions together with favourable shell characteristics.

Sterol composition of shellfish species commonly consumed in the United States

Background: Shellfish can be a component of a healthy diet due to a low fat and high protein content, but the cholesterol content of some species is often cited as a reason to limit their consumption. Data on levels of non-cholesterol sterols in commonly consumed species are lacking.Objective: Shellfish were sampled and analyzed to update sterol data in the United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference.Design: Using a nationwide sampling plan, raw shrimp and sea scallops, canned clams, and steamed oysters, blue crab, and lobster were sampled from 12 statistically selected supermarkets across the United States in 2007?08. For each species, four composites were analyzed, each comprised of samples from three locations; shrimp and scallops from six single locations were also analyzed separately. Using validated analytical methodology, 14 sterols were determined in total lipid extracts after saponification and derivatization to trimethylsilyethers, using gas chromatography for quantitation and mass spectrometry for confirmation of components.Results: Crab, lobster, and shrimp contained significant cholesterol (96.2–27 mg/100 g); scallops and clams had the lowest concentrations (23.4–30.1 mg/100 g). Variability in cholesterol among single-location samples of shrimp was low. The major sterols in the mollusks were brassicasterol (12.6–45.6 mg/100 g) and 24-methylenecholesterol (16.7–41.9 mg/100 g), with the highest concentrations in oysters. Total non-cholesterol sterols were 46.5–75.6 mg/100 g in five single-location scallops samples, but 107 mg/100 g in the sixth, with cholesterol also higher in that sample. Other prominent non-cholesterol sterols in mollusks were 22-dehydrocholesterol, isofucosterol, clionasterol, campesterol, and 24-norcholesta-5,22-diene-3β-ol (4–21 mg/100 g).Conclusions: The presence of a wide range of sterols, including isomeric forms, in shellfish makes the analysis and quantitation of sterols in marine species more complex than in animal and plant tissues. The detailed sterol composition reported herein provides data that may be useful in research on the impact of shellfish consumption on dietary risk factors.

Isolation, identification and pathogenicity of Vibrio chagasii fromPatinopecten yessoensis

In recent years cultured sea scallop (Patinopecten yessoensis) dead on a large-scale in seas near Changhai County, Dalian, China, in summer. The main symptom is the abscess on adductor muscle. The transmission experience was improved to indicate that a bacterium isolated from natural infected focus, named XJ02 displayed intense pathological activity to scallops, and the symptom is the same to natural intention. The bacterium XJ02 identification test through morphological specificity, physical and chemical properties and 16S rRNA gene sequence analysis showed the bacterium is Vibrio chagasii. There has been no any research on the pathogenicity of V. chagasii. This article for the first time to find a more compre-hensive's vibrio physicochemical properties of research. The dose-and temperature-dependent test indi-cated that the bacterium had the most pathogenicity at 19 ℃ while the concentration was 1.09×105 CFU/mL. The medicine sensitivity analysis that?s to check Ampicillin, Benzylpenicillin, Ciproflxacin etc is sensitive during 20 drugs sensitive test, to Tetracycline, Doxycycline is not sensitive element.

Mortality of sea scallops Placopecten magellanicus in the Mid-Atlantic Bight: Comment on Stokesbury et al. (2011)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 443:293-297 (2011) - DOI: https://doi.org/10.3354/meps09517 COMMENT Mortality of sea scallops Placopecten magellanicus in the Mid-Atlantic Bight: Comment on Stokesbury et al. (2011) Deborah R. Hart*, Burton V. Shank Northeast Fisheries Science Center, 166 Water St., Woods Hole, Massachussetts 02543, USA *Email: deborah.hart@noaa.gov ABSTRACT: Stokesbury et al. (2011; Mar Ecol Prog Ser 425:167−173) concluded that 10 billion sea scallops Placopecten magellanicus probably died from discarding during fishing operations between surveys in 2003 and 2004, based on the observed reduction in scallops between these 2 surveys. The reported mortality primarily occurred in a very large 2001 year class that was below commercial size in 2003−2004, whereas mortality rates were lower for larger commercial-sized scallops. This pattern is not consistent with mortality from discarding, because commercial scallop dredge gear is designed to retain commercial-sized scallops, allowing a substantial proportion of undersized scallops to escape through the dredge rings. Data from at-sea observers in the Mid-Atlantic indicate that only 319 million scallops were discarded during this period. Non-capture (incidental) fishing mortality was also too low to account for the observed mortality. However, juvenile scallop mortality due to predation increases with their density, primarily induced by crabs Cancer spp. The observed high mortality of juvenile scallops was therefore probably a result of increased predation, rather than discarding. KEY WORDS: Scallop · Cancer spp. · Predation · Fishery discards · Density dependence · Placopecten magellanicus Full text in pdf format PreviousNextCite this article as: Hart DR, Shank BV (2011) Mortality of sea scallops Placopecten magellanicus in the Mid-Atlantic Bight: Comment on Stokesbury et al. (2011). Mar Ecol Prog Ser 443:293-297. https://doi.org/10.3354/meps09517 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 443. Online publication date: December 20, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.