Scallop Populations Research Articles

Extreme population densities reduce reproductive effort of Atlantic sea scallops in high-density recruitment events

The Atlantic sea scallop Placopecten magellanicus supports one of the most valuable federal fisheries in the USA, with annual ex-vessel values of US$400-600 million since 2010. Among other strategies, the fishery utilizes rotational area management to protect juvenile sea scallops, increasing yield per recruit and spawning potential. While generally successful, area management was challenged by 2 extremely high-density recruitment events. Juveniles at both study sites, the Nantucket Lightship Closed Area and the Elephant Trunk portion of the Mid-Atlantic Access Area, persisted at high densities (up to 39 and 5 sea scallops m-2, respectively) and initially exhibited poor growth, yield, and gamete production. The effect of sea scallop population density on reproduction was investigated through quarterly sampling from May 2018 through January 2020 in low-, medium-, and high-density strata. Reproductive effort, i.e. the proportion of energy devoted to gamete production, was quantified to investigate differences in energy allocation across density, depth, shell height, reproductive stage, and sex. Reproductive activity was limited in the Nantucket Lightship high-density stratum, where the percentage of sea scallops staged as mature or spawning reached 50% during only 1 of 7 sampling trips, compared to 4-6 sampling trips in other strata. Population density was a significant predictor of reproductive effort, with a 28% reduction in reproductive effort from the highest densities to more typical densities. These results illustrate the complexities of managing fisheries for heterogeneous populations of sessile benthic invertebrates. Negative density-dependent effects should be monitored and accounted for in future extreme recruitment events.

Let 'Em Grow: Scalloping Best Practices

Recreational scalloping is a popular summertime activity that attracts participants from far and wide to Florida's Gulf Coast. Coastal counties that serve as vessel launch points rely on this fishery for economic viability, but the biology of the bay scallop and the environmental stressors this species endures have led to limited populations of bay scallops remaining along Florida's Gulf Coast . Therefore, it is essential to implement best practices for harvesting bay scallops so that future generations can enjoy this marine resource activity. This publication gives recreational scallopers tips on how to sort through scallops in the water so that scallops that are too small are returned immediately to the same spot where they were taken. Improving harvesting techniques can help sustain this valuable fishery.

Genome-wide analysis with additive and epistasis effects reveals growth-related loci and candidate genes in hybrid Argopecten scallops

The first filial (F1) generation from the successful hybridization of bay scallops (Argopecten irradians) and Peruvian scallops (A. purpuratus) exhibits significant heterosis, playing a crucial role in enhancing the germplasm and increasing yields of the scallops. However, there is significant variation in the growth traits of the F1 hybrid population, and there is little information concerning its hereditary basis. To unravel the heterosis mechanism and identify key loci and genes contributing to superhybrids, genome-wide association study (GWAS) with additive and epistasis models were conducted for six growth-related traits in the F1 hybrid scallop population in this study. In total, 18,789,547 single nucleotide polymorphisms (SNPs) were identified after filtering from 198 hybrid individuals, comprising 63.5% of maternal loci and 36.5% of paternal loci. The additive model revealed 2768 associated SNPs and 14 candidate genes, with most of the loci associated with the body mass traits. The additive-additive epistatic model identified 133,094 SNP interaction pairs and 20 candidate gene pairs with exon region SNPs, which were predominantly associated with shell morphology traits. Almost all the SNP pairs associated with body mass traits were maternal-maternal interactions, but the shell morphology traits had the most maternal-paternal and maternal-maternal interactions, suggesting that body mass traits might be affected mainly by maternal effects and that parental interaction effects mainly contributed to the shell size of the hybrid scallops. Both in the shell morphology and the body mass traits, multiple loci participate in epistasis, interacting with more than one locus and forming high-order epistatic interactions, which could be critical factors contributing to the heterosis observed in hybrid scallops. The identified associated loci and candidate genes not only constitute valuable resources for the molecular breeding of hybrid scallops, contributing to the improvement of growth-related traits, but also revealed mechanisms underlying heterosis in aquatic species, providing insights into the advantages of heterosis and paving the way for future research on hybridization in aquatic organisms.

A newly discovered trematode parasite infecting the bay scallop, Argopecten irradians

A novel parasite infecting the gill tissue of bay scallops (Argopecten irradians) was first observed in North Carolina in 2012 and has also been found infecting bay scallop populations along the Gulf Coast of Florida. Because the parasite infects a host of great fisheries interest and is extremely conspicuous to the naked eye, and yet was not observed before 2012, it is likely an introduced species. Preliminary morphological analyses indicate that this parasite is a trematode in the superfamily Hemiuroidea and that it uses the bay scallop as a first intermediate host. All other hosts are currently unknown. Phylogenetic analyses show that this novel parasite belongs to family Didymozoidae and forms a strongly supported clade with a recently described trematode from Australia, Saccularina magnacetabula. Histological analysis indicates that Saccularina sp. sporocysts inhabit and greatly expand the afferent vessels of the host's gills. Prevalence monitoring of Saccularina sp. in caged and wild bay scallop populations in North Carolina shows a strong pattern of seasonality that is consistent across sites, but no latitudinal gradient was found, suggesting that prevalence is likely driven by final host distribution in time and space. This research provides important baseline information on the basic biology of Saccularina sp. and impacts on its economically important host, the bay scallop.

Underwater hyperspectral imaging technology has potential to differentiate and monitor scallop populations

Accurate and low-impact monitoring of scallop abundance is critical for stock assessment, especially in sensitive habitats. The possibility of using low-impact hyperspectral imaging (HSI) for differentiating scallop species in the marine environment was investigated. Live saucer (Ylistrum balloti) and mud (Ylistrum pleuronectes) scallops (N = 31) were scanned inside a sea simulator using a visible to near infrared (400–1000 nm) line-scanner HSI camera. Partial least square discriminant analysis (PLS-DA) was trained to distinguish between the species using their spectral signatures. Important wavelengths were identified and new models were developed using these wavelengths to reduce the model complexity and potentially increase the imaging speed when applied under at-sea conditions. The PLS-DA model distinguished between saucer and mud scallops using any area of the left valve that was exposed above the sediments, with 90.73% accuracy when all 462 available wavelengths were used. Using the subset of important wavelengths (N = 13) reduced the classification accuracy to 84%. Overall, our results showed that HSI has potential for detecting, distinguishing and counting commercially important saucer scallops for low-impact monitoring and resource management, and to complement RGB imaging that relies solely on morphological properties.Graphical abstract

Symbiotic survey of the bay scallop (Argopecten irradians) from the Gulf coast of Florida, USA

The bay scallop Argopecten irradians supported a commercial fishery in Florida but their population declined and the fishery closed in 1994. A recreational fishery remains open along the west coast of Florida despite continued threats from overfishing and a changing environment. Disease is among those threats, as it is for bivalve fisheries globally. We examined the relationship between bay scallop population density, its symbiotic microbiome, and geographic location. We focused on three sites within the range of Florida’s recreational scallop fishery: St. Joseph Bay (northern extent), offshore of the Steinhatchee River (central), and offshore of Hernando County (southern extent). The study was conducted prior to the seasonal opening of the fishery to minimize the impact of fishing on our results. We also sampled caged scallops that are used for restocking in St. Joseph Bay to assess the effect of artificially high density and confinement on the scallop pathobiome. Using a combination of traditional histological methods, molecular diagnostics, and metagenomics, a suite of 15 symbionts were identified. Among them, RNA-seq data revealed four novel + ssRNA viral genomes: three picorna-like viruses and one hepe-like virus. The DNA-seq library revealed a novel Mycoplasma species. Histological evaluation revealed that protozoan, helminth and crustacean infections were common in A. irradians. These potential pathogens add to those already known for A. irradians and underscores the risk they pose to the fishery.

An apicomplexan parasite drives the collapse of the bay scallop population in New York

The bay scallop, Argopecten irradians, represents a commercially, culturally and ecologically important species found along the United States’ Atlantic and Gulf coasts. Since 2019, scallop populations in New York have been suffering large-scale summer mortalities resulting in 90–99% reduction in biomass of adult scallops. Preliminary investigations of these mortality events showed 100% prevalence of an apicomplexan parasite infecting kidney tissues. This study was designed to provide histological, ultrastructural and molecular characteristics of a non-described parasite, member of the newly established Marosporida clade (Apicomplexa) and provisionally named BSM (Bay Scallop Marosporida). Molecular diagnostics tools (quantitative PCR, in situ hybridization) were developed and used to monitor disease development. Results showed that BSM disrupts multiple scallop tissues including kidney, adductor muscle, gill, and gonad. Microscopy observations allowed the identification of both intracellular and extracellular stages of the parasite. Field surveys demonstrated a strong seasonal signature in disease prevalence and intensity, as severe cases and mortality increase as summer progresses. These results strongly suggest that BSM infection plays a major role in the collapse of bay scallop populations in New York. In this framework, BSM may synergistically interact with stressful environmental conditions to impair the host and lead to mortality.

Commercial Quality, Biological Indices and Biochemical Composition of Queen Scallop Aequipecten opercularis in Culture

Market demand for scallops has considerably increased in recent decades. Although natural populations of scallops are vulnerable, the queen scallop, Aequipecten opercularis, can represent a possible alternative to at-risk species. The aim of this study was to determine the effect of seawater parameters on the commercial quality, biological indices and nutritional quality of the scallop A. opercularis in 1900 L tanks in ex situ conditions. The condition index (CI) and meat yield (MY) peaked in autumn (89.92% and 40.29%, respectively). The muscle index (MI) showed the highest peak during the winter season (5.96%), while the gonadosomatic index (GSI) (34.06%) peaked in the spring months. Protein content (6.89–9.56 g/100 g), lipids (2.58–2.79 g/100 g) and carbohydrates (0.12–0.33 g/100 g) varied during the study period. Seasonal fluctuations in seawater temperature and pH negatively influenced the CI, MY and protein and lipid content, while positively affecting carbohydrate and moisture content. The most suitable period of the year for the consumption of the scallop A. opercularis was found to be the winter and spring periods, when the scallops achieved their highest nutritional value. It can be stated from this study that queen scallops in the Adriatic Sea have a high nutritional quality and that they can be proposed for higher human consumption.

Long-term Variations in the Black Sea Population of Smooth Scallop, Flexopecten glaber (Linnaeus, 1758) (Bivalvia: Pectinidae): A Review

Data on the presence and characteristics of smooth scallop Flexopecten glaber (Linnaeus, 1758) aggregations in various parts of the Black Sea shelf (BSS) have been subjected to a retrospective analysis. The waters of the northern (Crimean coast), eastern (Central and North Caucasian), and Anatolian sectors of BSS can be considered the most favorable habitats for smooth scallop, where massive beds of this species were found in the first half of the 20th century. However, no such data are available for the northwestern and western BSS, where freshwater discharges from the Danube, Dniester, and Dnieper form a permanent zone of lower water salinity. The period of decline in the Black Sea scallop population recorded in the 1970s–1990s generally coincided with the well known ecological crisis due to the anthropogenic eutrophication of the Black Sea in the second half of the 20th century. In the late 2000s and the 2010s, the scallop beds in the Crimean BSS showed a tendency to recover, which may be associated with the general improvement of the ecological condition of the Black Sea basin. A similar recovery of scallop beds is expected to occur in the eastern (North and Central Caucasian) and southern BSS, but has not yet been recorded. The results obtained suggest a possibility of downgrading the conservation status of this species in the Red Data Books of the City of Sevastopol and the Republic of Crimea from the `species declining in abundance` to the `species recovering in abundance and distribution`.

Resiliency of Marine Benthic Communities in Sea Scallop Rotational Management Areas on Georges Bank

Area closures allow fish and shellfish populations and associated habitats to recover from the effects of fishing. Determining the appropriate duration of rotational management closures for the Atlantic sea scallop (Placopecten magellanicus) fishery requires information on both the recovery of scallop populations for subsequent harvest and the resiliency of marine benthic ecosystems for conservation objectives. Here, the effects of scallop fishing on the benthic communities of the northern edge of Georges Bank were examined with a control-impact environmental study comparing an area that had been closed to fishing for over 20 y to an area continually fished. Substrate composition, faunal density, and taxonomic richness data were collected using drop camera surveys. These areas have similar substrate composition, mostly cobble and gravel. Sediment in the control area shifted to larger particle sizes over time, whereas the sediment in the impact area remained the same, suggesting fishing activity prevented this shift in the impact area. Comparing survey stations of like substrate showed that as fishing effort subsided from 2015 to 2017, there was a marked recovery of taxonomic richness and abundance in the impact area. The impact and control areas shifted in a similar manner but varied in the intensity of the shift. This suggests the benthic communities in this area of Georges Bank were relatively resilient to the effects of fishing effort with mean densities of all categories recovering within 2 years.

Scoping Bay Scallop Restoration in Rhode Island: A Synthesis of Knowledge and Recommendations for Future Efforts

The bay scallop is a culturally important species that once supported significant fisheries along the U.S. east coast. Mass population declines in the 1900s led to a nearly total loss of the fishery in most states, including Rhode Island. In certain areas, intensive, long-term restoration efforts have effectively restored scallop populations and fisheries on a small scale, but indicate that such plans must be scoped specific to systems. In an effort to support the development of an upcoming Rhode Island Shellfish Restoration Plan, relevant knowledge on bay scallops was collated and summarized, and this information was used to create a habitat suitability index that can act as a guide to identify suitable restoration sites for renewed bay scallop restoration efforts in one of the largest coastal salt ponds in Rhode Island, Point Judith Pond. Point Judith Pond was once the epicenter of the bay scallop fishery in the state of Rhode Island, and the ranked index suggests multiple sites throughout the pond are likely to once again provide adequate habitat for bay scallops. Restoration strategies such as caged spawner sanctuaries and the release of competent larvae in areas identified as suitable by the index are recommended for future restoration planning of this species.

Temperature-associated selection linked to putative chromosomal inversions in king scallop (Pecten maximus).

The genomic landscape of divergence—the distribution of differences among populations or species across the genome—is increasingly characterized to understand the role that microevolutionary forces such as natural selection and recombination play in causing and maintaining genetic divergence. This line of inquiry has also revealed chromosome structure variation to be an important factor shaping the landscape of adaptive genetic variation. Owing to a high prevalence of chromosome structure variation and the strong pressure for local adaptation necessitated by their sessile nature, bivalve molluscs are an ideal taxon for exploring the relationship between chromosome structure variation and local adaptation. Here, we report a population genomic survey of king scallop (Pecten maximus) across its natural range in the northeastern Atlantic Ocean, using a recent chromosome-level genome assembly. We report the presence of at least three large (12–22 Mb), putative chromosomal inversions associated with sea surface temperature and whose frequencies are in contrast to neutral population structure. These results highlight a potentially large role for recombination-suppressing chromosomal inversions in local adaptation and suggest a hypothesis to explain the maintenance of differences in reproductive timing found at relatively small spatial scales across king scallop populations.

Pile driving repeatedly impacts the giant scallop (Placopecten magellanicus)

Large-scale offshore wind farms are a critical component of the worldwide climate strategy. However, their developments have been opposed by the fishing industry because of concerns regarding the impacts of pile driving vibrations during constructions on commercially important marine invertebrates, including bivalves. Using field-based daily exposure, we showed that pile driving induced repeated valve closures in different scallop life stages, with particularly stronger effects for juveniles. Scallops showed no acclimatization to repetitive pile driving across and within days, yet quickly returned to their initial behavioral baselines after vibration-cessation. While vibration sensitivity was consistent, daily pile driving did not disrupt scallop circadian rhythm, but suggests serious impacts at night when valve openings are greater. Overall, our results show distance and temporal patterns can support future mitigation strategies but also highlight concerns regarding the larger impact ranges of impending widespread offshore wind farm constructions on scallop populations.

Detection and quantification of differences in catch rates among research vessel gears and commercial vessels

Commercial fishing vessels can be a cost-effective alternative to research vessels for performing towed gear fishery-independent surveys, if catch rates are comparable among commercial vessels and with research vessels. A parallel fishing experiment was conducted off the coast of Wales, United Kingdom, to compare the king scallop (Pecten maximus) catch rates of three commercial vessels using commercial dredges and a research vessel using two types of scientifically modified dredges. The scientific dredges are currently used in the fishery-independent survey of local scallop populations. Size-structured scallop catch-per-unit-effort (CPUE) was compared among vessel-gear combinations. Two similarly sized commercial vessels had generally similar CPUEs, however there were some significant differences with scallop size. A smaller commercial vessel had significantly lower CPUEs for a broad range of scallop sizes. The research vessel dredges had significantly higher CPUE for smaller scallops than the commercial vessels. Vessel size is likely to be driving the differences among commercial vessels and belly ring size is likely to be driving differences among research and commercial dredges. These findings highlight commercial vessel CPUE should not be assumed the same, whilst also showing that vessel size may be the best indicator of catch rate similarity. These results also highlight that changing the fishery-independent vessel and gear to the commercial options trialled here would result in a considerable loss of information about the smaller scallops in the population. These findings will be of interest to fishery scientists or managers using multiple vessels, or considering a change of vessels, for fishery-independent surveys.

Predation on planted and wild bay scallops (Argopecten irradians irradians) by busyconine whelks: studies of behavior incorporating acoustic telemetry

Quantifying predator–prey interactions and gaining insights into predator behavior are crucial for optimizing restoration strategies. However, such knowledge is often lacking for marine invertebrates. We examined potential impacts of predation by channeled Busycotypus canaliculatus and knobbed whelks Busycon carica on natural and planted populations of bay scallops in the Peconic Bays, New York, through laboratory and field investigations. In lab experiments, mean predation rates exhibited by small channeled whelks were low: 0.06 and 0.005 scallops d−1 for adult and juvenile scallops, respectively. Predation rates of small knobbed whelks on juvenile scallops were 22 × higher. Eighty-six percent (86%) of scallops consumed by channeled whelks had undamaged shells, while 73% eaten by knobbed whelks had notched ventral margins. In field plots where scallop densities were manipulated via removals/plantings, whelks consumed ~ 2% of ~ 19,100 planted juveniles, whereas crabs and presumably finfish consumed > 40% overall. Acoustic telemetry revealed that tagged channeled whelks moved shorter distances and spent more time in plots planted with scallops versus those without scallops. Whelks spent more time in low versus high-density plots, but consumed far more scallops in the latter. In trials without scallops, whelk movement rates were 5 × higher, presumably due to increased exploratory behavior. Overall, whelks were most active during crepuscular hours and during periods of increasing wind speeds. Our results, combined with population abundance data, suggest that whelks (especially B. carica) are drawn to planted bay scallop aggregations, but probably contribute to relatively low overall mortality in the context of restoration efforts.

Modeling Atlantic sea scallop (Placopecten magellanicus) scope for growth on the Northeast U.S. Shelf

AbstractAtlantic sea scallops support one of the most valuable fisheries in the eastern United States. The scallop population is susceptible to climate‐related environmental stress. Assessing and projecting climate impacts rely on the fundamental understanding of scallop ecophysiology, including the influences of temperature and food supply on its energy balance and growth potential. In this study, we developed a scope for growth (SFG) model driven by high‐resolution hydrodynamic and biological models to assess the spatial and seasonal variability of scallop energy dynamics. The overall SFG on the Northeast U.S. Shelf is higher in May–June and lower in January–February, with substantial spatial heterogeneity. In the Mid‐Atlantic Bight (MAB), negative SFG occurs from July to October due to strong thermal stress. Particulate organic matter in detrital form is an important food source for scallops, with higher/lower contribution in the cold/warm seasons, respectively. Warming and food deficiency induce a noticeable contraction of suitable scallop habitats in the MAB, while their impacts on Georges Bank are insignificant. Known seasonal spawning patterns and observed growth rates in these regions match the patterns of SFG generated by the model. The sensitivity of SFG to the variations in food and temperature increases with scallop size. Large scallops are more likely to experience low or negative SFGs than smaller ones, implying that the habitats shrink as scallops grow older/bigger. This study provides key information about scallop growth potential and biogeography from the perspective of energy balance, thus helping the development of adaptive fisheries management strategies.

Comparison of Visual Surveys Versus Dredging for Monitoring Bay Scallops (Argopecten irradians) in Seagrass Beds

Bay scallops (Argopecten irradians), once a profitable fishery species in North Carolina, have declined in population size following harmful algal blooms in the late 1980s. To prepare for future scallop restoration efforts, appropriate survey methods should be identified to evaluate the status of the population with respect to managing harvest. The North Carolina Division of Marine Fisheries monitors bay scallop populations in seagrass beds using a scallop dredge, though it is still unclear what the current natural densities of bay scallops are. In this study, visual surveys in three time treatments (5, 10, and 20 min) were compared with dredging in terms of quantifying scallop density and the catch per unit effort (CPUE) in seagrass beds in Core Sound, North Carolina. There was no significant difference in scallop density and the CPUE among visual survey time treatments. Scallop densities observed during visual surveys were three times higher than densities using a scallop dredge; however, the CPUE was five times higher using a scallop dredge compared with visual surveys. If visual surveys indicate the true natural density of bay scallops in this study system, then the dredge sampling efficiency for evaluating bay scallop density was 33%. Dredging for bay scallops can uproot seagrass and displace juvenile bay scallops. Visual surveys provide a low-impact method for identifying the distribution and abundance of bay scallops in seagrass bed habitats.

Estimating genetic parameters of muscle imaging trait with 2b-RAD SNP markers in Zhikong scallop (Chlamys farreri)

Genetic improvement is a crucial tool to deal with the increasing demand for high-quality, sustainably produced meat in the scallop industry. Breeding programs are based on genetic parameters, such as heritability, genetic correlations, and breeding values (BVs). By X-ray technology, we used adductor muscle area percentage (AMAP) obtained by dividing adductor muscle area (AMA) by shell area (SA) in an X-ray scallop image as a novel muscle imaging trait in a non-invasive manner. The goals of this study are 1) to estimate the genetic parameters of the muscle imaging trait AMAP and the adductor muscle weight percentage (AMWP), which is traditionally determined by weighing after dissection causing low efficiency in measurement and failure to collect data in vivo, and 2) to compare estimation accuracies of breeding values of AMAP and AMWP in a Zhikong scallop (Chlamys farreri) population. 2b-RAD SNPs were applied in 449 two-year-old healthy and active Zhikong scallops randomly sampled from an artificially bred population in the same culture sea area. The estimates of SNP-based heritability conducted using all SNPs (17,495 SNPs with MAF > 2%) were 0.551 (S.E. 0.07) for AMAP and 0.515 (S.E. 0.08) for AMWP, respectively. Chromosome-wise heritabilities for AMAP and AMWP were regressed against the chromosome lengths with significant linear trends (P = 0.02969 and P = 0.03043), implying that the genetic contribution to muscle trait is scattered across the genome and driven by many loci with small effect rather than a few causal loci with a large effect. The phenotypic and genetic correlations between AMAP and AMWP were 0.769 (S.E. 0.002) and 0.917 (S.E 0.043), suggesting that we can use the image-based trait AMAP in substitution for the muscle growth trait AMWP for genetic improvement of meat in live scallops. The impact of population genome structure (e.g., the effective population size Ne), number of independent chromosome segments (Me), SNP marker densities, and training population sizes on genomic prediction accuracy of AMAP and AMWP was investigated as well. These results will provide important reference information and methodology basis for breeding through image-based traits in scallops.

Environmental variability and larval supply to wild and cultured shellfish populations

Coastal upwelling ecosystems support some of the most productive fisheries of the planet together with a large shellfish aquaculture sector that depends on oceanographic processes to deliver planktonic larvae to replenish and feed the farmed stock. Coastal shellfish aquaculture operations in Chile and Perú have experienced large interannual fluctuations in larval supply over the past decade, yet the drivers of such variability remain unidentified. We focused on the effects of environmental variability on larval supply of the farmed Peruvian bay scallop Argopecten purpuratus in a bay in northern Chile (Tongoy Bay, 30∘S) that accounts for over 90% of countrywide landings. We examined the hypothesis that the environmental processes governing larval supply were shared with wild benthic invertebrates with planktonic larval development and compared time series of larval abundance for the scallop with larval supply rates to benthic populations of two well-studied wild intertidal species: the Chthamalid barnacle Jehlius cirratus and the purple mussel Perumytilus purpuratus. To this end, we examined the cross-correlation of larval supply to environmental variability using MODIS satellite fields of sea surface temperature (SST) chlorophyll-a concentration (chl-a) and fluorescence line height (nFLH), together with three climate indices relevant for the south east Pacific sector: the Southern Oscillation index (SOI), the Pacific Decadal Oscillation (PDO) and the Antarctic Oscillation Index (AAO). Our results showed that over the five-year study period (2009–2013), patterns of larval supply to the scallop population were related to inter-annual variability in the environmental processes as captured by their Empirical Orthogonal Functions (EOFs), likely to adult condition before spawning. Surprisingly, larval supply for none of the wild species showed a clear association to the EOFs. In contrast, scallops and wild species showed significant association to lower frequency climate variability as captured by the SOI and the PDO, but not the AAO. Results suggest that larval supply patterns to Tongoy Bay may be modulated by regional patterns of climatic variability, particularly of tropical origin. Thus, changes in coastal oceanography associated with ongoing changes in global climate could have strong and lasting effects on the supply of seedstock for wild and cultivated species across this eastern boundary coastal system and argue for the establishment of long-term ocean observing and early warning systems along the region.

A Genome-Wide Association Study Identifies Candidate Genes Associated With Shell Color in Bay Scallop Argopecten irradians irradians

Molluscan shell color has consistently drawn attention for its abundant diversity and commercial use in shellfish breeding projects. Recently, two new strains of bay scallop (Argopecten irradians irradians) with different shell colors as marked phenotypic traits have been artificially bred to improve their economic values; however, the inheritance mechanism of their shell pigmentation is still unclear. In this study, a genome-wide association study (GWAS) was conducted to determine the genetic basis of shell color in bay scallops utilizing 29,036 high-quality single-nucleotide polymorphisms (SNPs) derived from 80 purple-red (PP) and 80 black-brown (BP) shell color individuals. The result of the GWAS showed that 469 SNPs (p <1.72E−6) significantly associated with shell color were mainly distributed in chromosome 7. The top three SNPs (i.e., chr7-12764003, chr7-13213864, and chr7-11899306) are located in the genic region of G-protein-coupled receptor-like 101 (GRL101), polyketide synthase 1 (PKS1), and phosphoinositide phospholipase C (PLC1), which have been widely reported to be involved in pigmentation. Successfully, the top three SNPs were verified in another non-breeding bay scallop population. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses obtained 38 GO terms covering 297 genes and aggregating pathways involving 252 annotated genes. Specifically, the expression profiles of the top three identified candidate genes were detected in mantles of PP and BP individuals by real-time quantitative reverse transcription PCR. The significantly higher expression levels of GRL101 (6.43-fold) and PLC1 (6.48-fold) in PP, and PKS1 (12.02-fold) in BP implied that GRL101 and PLC1 potentially functioned in PP shell coloration, and black pigmentation in BP might be principally regulated by PKS1. Our data provide valuable information for deciphering the phenotype differences of shell color in the bay scallop.