Placopecten Magellanicus Research Articles

Influence of artefacts in marine digital terrain models on habitat maps and species distribution models: a multiscale assessment

AbstractRemote sensing techniques are currently the main methods providing elevation data used to produce Digital Terrain Models (DTM). Terrain attributes (e.g. slope, orientation, rugosity) derived from DTMs are commonly used as surrogates of species or habitat distribution in ecological studies. While DTMs’ errors are known to propagate to terrain attributes, their impact on ecological analyses is however rarely documented. This study assessed the impact of data acquisition artefacts on habitat maps and species distribution models. DTMs of German Bank (off Nova Scotia, Canada) at five different spatial scales were altered to artificially introduce different levels of common data acquisition artefacts. These data were used in 615 unsupervised classifications to map potential habitat types based on biophysical characteristics of the area, and in 615 supervised classifications (MaxEnt) to predict sea scallop distribution across the area. Differences between maps and models built from altered data and reference maps and models were assessed. Roll artefacts decreased map accuracy (up to 14% lower) and artificially increased models’ performances. Impacts from other types of artefacts were not consistent, either decreasing or increasing accuracy and performance measures. The spatial distribution of habitats and spatial predictions of sea scallop distributions were always affected by data quality (i.e. artefacts), spatial scale of the data, and the selection of variables used in the classifications. This research demonstrates the importance of these three factors in building a study design, and highlights the need for error quantification protocols that can assist when maps and models are used in decision‐making, for instance in conservation and management.

Prevalence and description of Ichthyophonus sp. in yellowtail flounder (Limanda ferruginea) from a seasonal survey on Georges Bank

Ichthyophonus sp. is a ubiquitous parasite infecting numerous fish species. Ichthyophonus sp. infection of yellowtail flounder (Limanda ferruginea) was first identified in Canadian waters in 1968. Between 2012 and 2014, fifteen seasonal survey cruises by Coonamessett Farm Foundation, randomly sampled a total of 1325 fish for at-sea examination at fixed stations on the U.S. Georges Bank sea scallop fishing grounds. A subsample of yellowtail flounders were examined internally on board the ship and animals with visible lesions were collected, processed, and examined histologically. Infected fish were concentrated in eastern Georges Bank with only two of the 32 infections collected from western Georges Bank. Both macroscopic and histological evaluation of tissues showed that 81.3% of the animals infected with Ichthyophonus sp. were severely infected.

Evaluating the interaction of the invasive tunicate Didemnum vexillum with the Atlantic sea scallop Placopecten magellanicus on open and closed fishing grounds of Georges Bank

Abstract An invasive colonial tunicate (Didemnum vexillum) was initially observed on Georges Bank in 1998, and it has since spread in benthic environments on fishing grounds and areas closed to bottom-fishing. It can form dense mats on gravel substrates that are also a preferred habitat for the Atlantic sea scallop (Placopecten magellanicus), which supports one of the most valuable commercial fisheries in the United States. We used HabCam, a vessel-towed underwater imaging system, to investigate the spatial distributions of P. magellanicus and D. vexillum in a region that includes fishing grounds and an area protected from bottom-fishing. We found a negative relationship between P. magellanicus and D. vexillum, even after controlling for substrate and management status, suggesting that D. vexillum competes for habitat with P. magellanicus. We also applied the geostatistical method of universal kriging to interpolate the distribution of D. vexllium based on the covariables gravel, depth and area. Our results indicate that D. vexillum is more common in areas open to fishing than in the areas closed to fishing, even taking bottom substrate effects into account. Didemnum vexillum appears to have spread over portions of the northern edge of Georges Bank. This research evaluates potential fish and invertebrate habitat degradation caused by an invasive species.

Identification of persistent benthic assemblages in areas with different temperature variability patterns through broad-scale mapping.

Ecosystem-based management is a place-based approach that considers the relationships between system parts. Due to the complexity of ecosystems in the marine environment it is often difficult to define these relationships in space and time. Maps illustrate spatial concepts. Here we promote ecosystem-based spatial thinking by layering datasets from a larger project that mapped benthic fauna, substrate characteristics, and oceanic conditions on monthly, annual and decadal time scales along the U.S. continental shelf. By combining maps of persistent benthic megafauna and bottom temperature variability over approximately 90,000 km2, we identified wide spread benthic animal assemblages and regional disparity in temperature variability. From a broad-scale perspective the locations of the assemblage appear to be related to sea scallop population dynamics and indicate potential regional differences in climate change resiliency. These findings offer information on a scale that correlates with marine spatial planning, and could be used as a starting point for further investigation. To spur additional analysis and facilitate their linkage to other datasets, these datasets are available through public, online data portals. Overall, this study demonstrates how the growth of maps from single to multiple elements can help promote and facilitate the multifactor, ecosystem-based thinking needed to support regional ocean planning.

Setting biological reference points for sea scallops (Placopecten magellanicus) allowing for the spatial distribution of productivity and fishing effort

Management for the major sea scallop (Placopecten magellanicus) fisheries in Canada is based on maximum sustainable yield (MSY) biomass and fishing mortality reference points applied to the whole stock, under the assumption that fishing mortality is uniformly distributed in space. However, scallop fishing vessels concentrate fishing in areas that consistently exhibit high densities resulting in a nonuniform spatial distribution of fishing effort. This study applies a spatial model for fishing effort derived from satellite vessel monitoring system data, scallop habitat suitability maps, and relative scallop density from a spatial stock assessment model to evaluate precautionary approach reference points in support of sustainable management. Target harvest rates were evaluated in terms of MSY for the higher habitat suitability areas. The results indicated that although MSY for the spatial model were similar to those when assuming a uniform distribution of effort, the biomass and catch rates over all areas were higher. The spatial model predicted that the MSY would be taken with less fishing effort, potentially lessening the benthic impacts from the scallop fishery.

Complete mitochondrial genome sequence of Cucullaea labiata (Arcoida: Cucullaeidae) and phylogenetic implications

The complete mitochondrial genome of Cucullaea labiata (Arcoida: Cucullaeidae) was firstly determined in this study in order to better understand the phylogenetic relationship between Cucullaeidae and Arcidae. The C. labiata mitochondrial genome was 25,845 bp in size and contained 12 protein-coding genes, 2 rRNA and 22 tRNA genes. The number and the location of the tRNA genes were different from three Arcidae species (Scapharca broughtonii, Scapharca kagoshimensis and Tegillarca granosa). Gene arrangement also differed dramatically. The length of the non-coding regions was 10,559 bp, in which the largest one (6057 bp) included eight point nine copies of a 659 bp repeat motif. The number of repeated sequences was different in different individuals, similar to the findings from the mitochondrial genome of S. broughtonii and Placopecten magellanicus. One intron was found in cox1 gene both in CL_98 and in CL_99 individuals of C. labiata. The reason why mitochondrial introns are retained so scarcely in bivalve taxa needs further research. Phylogenetic analyses based on 12 concatenated amino acid sequences of protein-coding genes supported Cucullaeidae was the sister group of Arcidae.

Possible Prediction of Scallop Swimming Styles from Shell and Adductor Muscle Morphology

Modifications in shell structure, mantle, and adductor muscle are considered derived adaptations that allowed scallops to swim. This suggests that morphological properties of the adductor muscle and shell should relate to swimming performance in scallops. Various morphological characteristics of the shell (mass, aspect ratio, and volume between the valves) and the adductor muscle (size, position, and attachment to the shell) were measured in six scallop species (Amusium balloti, Placopecten magellanicus, Equichlamys bifrons, Pecten fumatus, Mimachlamys asperrima, and Crassadoma gigantea) with distinct swimming strategies, as documented by measurements of muscle use during induced escape responses. Morphological characteristics of the shell and adductor muscle differed markedly between the species, but did not always follow their swimming strategies. Principal components analysis revealed that shell width, shell and muscle masses, and associated morphological attributes were closely linked with swimming endurance. The intensity of the escape response was best predicted by the aspect ratio and the obliqueness of the adductor muscle.

Geographic Concentration of the Atlantic Sea Scallop Fishery

The concentration patterns in the Northeast U.S. sea scallop industry are examined from 1996-2014 using generalized indices of concentration and exploratory spatial data analysis. Absolute and relative Theil indices of concentration are computed to describe the regional pattern of concentration within ports over time. Moran’s I provides a complementary measure of concentration of activity among neighboring ports. The Moran scatterplots and confidence plots provide insight into local patterns of concentration in this industry. The analysis reveals large changes from year to year in the geographic concentration of the scallop industry, which is likely to be related to natural variability of the environment and regulations enacted by fisheries managers in response to the variability of the environment.

Comparing Selections of Environmental Variables for Ecological Studies: A Focus on Terrain Attributes.

Selecting appropriate environmental variables is a key step in ecology. Terrain attributes (e.g. slope, rugosity) are routinely used as abiotic surrogates of species distribution and to produce habitat maps that can be used in decision-making for conservation or management. Selecting appropriate terrain attributes for ecological studies may be a challenging process that can lead users to select a subjective, potentially sub-optimal combination of attributes for their applications. The objective of this paper is to assess the impacts of subjectively selecting terrain attributes for ecological applications by comparing the performance of different combinations of terrain attributes in the production of habitat maps and species distribution models. Seven different selections of terrain attributes, alone or in combination with other environmental variables, were used to map benthic habitats of German Bank (off Nova Scotia, Canada). 29 maps of potential habitats based on unsupervised classifications of biophysical characteristics of German Bank were produced, and 29 species distribution models of sea scallops were generated using MaxEnt. The performances of the 58 maps were quantified and compared to evaluate the effectiveness of the various combinations of environmental variables. One of the combinations of terrain attributes–recommended in a related study and that includes a measure of relative position, slope, two measures of orientation, topographic mean and a measure of rugosity–yielded better results than the other selections for both methodologies, confirming that they together best describe terrain properties. Important differences in performance (up to 47% in accuracy measurement) and spatial outputs (up to 58% in spatial distribution of habitats) highlighted the importance of carefully selecting variables for ecological applications. This paper demonstrates that making a subjective choice of variables may reduce map accuracy and produce maps that do not adequately represent habitats and species distributions, thus having important implications when these maps are used for decision-making.

Identifying patterns of dispersal, connectivity and selection in the sea scallop,Placopecten magellanicus,usingRADseq‐derivedSNPs

Understanding patterns of dispersal and connectivity among marine populations can directly inform fisheries conservation and management. Advances in high‐throughput sequencing offer new opportunities for estimating marine connectivity. We used restriction‐site‐associated DNA sequencing to examine dispersal and realized connectivity in the sea scallop Placopecten magellanicus, an economically important marine bivalve. Based on 245 individuals sampled rangewide at 12 locations from Newfoundland to the Mid‐Atlantic Bight, we identified and genotyped 7163 single nucleotide polymorphisms; 112 (1.6%) were identified as outliers potentially under directional selection. Bayesian clustering revealed a discontinuity between northern and southern samples, and latitudinal clines in allele frequencies were observed in 42.9% of the outlier loci and in 24.6% of neutral loci. Dispersal estimates derived using these clines and estimates of linkage disequilibrium imply limited dispersal; 373.1 ± 407.0 km (mean ± SD) for outlier loci and 641.0 ± 544.6 km (mean ± SD) for neutral loci. Our analysis suggests restricted dispersal compared to the species range (>2000 km) and that dispersal and effective connectivity differ. These observations support the hypothesis that limited effective dispersal structures scallop populations along eastern North America. These findings can help refine the appropriate scale of management and conservation in this commercially valuable species.

Gray meat in the Atlantic sea scallop, Placopecten magellanicus, and the identification of a known pathogenic scallop apicomplexan

Atlantic sea scallop (Placopecten magellanicus) meats are normally firm and creamy white. However, scallops with small, darkened and stringy adductor muscle (gray meat) episodically occur along the Eastern Seaboard, most recently in the rotational management areas of Georges Bank after extended fishing closures. These gray meat scallops are associated with reduced harvestable biomass and mass mortality events. We tested age, nutritional stress and disease as causative agents for this condition. Adult scallops of different shell heights (SH) ranging from (90–145mm) were collected from Georges Bank and analyzed for meat quality and the presence of pathogens using biochemical, histopathological and molecular methods. Gray meat occurrence was weakly correlated with shell height only explaining 8.49% of the variance in a generalized additive model (GAMS). Gray meat weights were lower than white meat (p<0.001) and there was a dramatic reduction in protein content (p<0.05) in gray meat scallops associated with extensive myodegeneration. Amino acid profiles confirmed the breakdown of muscle tissue with an increase in free hydroxyproline in gray meat scallops. Infection by an apicomplexan parasite was detected in the muscle tissue of all gray meat scallops tested. An intermediate pathology stage (brown meat) was also identified. As the parasitic infection increased, meat quality decreased. Numerous developmental stages of the parasite were present in various organs of the scallops. This apicomplexan has an identical SSU rDNA sequence to a novel parasite occurring in the Iceland scallop during a recent mass mortality event. The range of this parasite in Atlantic sea scallops and the effect of abiotic/biotic stressors on pathogenicity are currently unknown. Results from this study link an apicomplexan species, known to be highly pathogenic in scallops, to gray meat occurrence with a potentially high impact on the fishery.

Prophylactic effect ofHaslea ostreariaculture supernatant containing the pigment marennine to stabilize bivalve hatchery production

This paper explores the possibility of using the supernatant of Haslea ostrearia culture containing marennine, a natural microalgal pigment, as an antimicrobial in bivalve hatcheries. The blue mussel Mytilus edulis and the scallop Placopecten magellanicus were used as model animals, and the pathogenic marine bacteria Vibrio splendidus was used to induce larval mortality. The hypothesis tested was that V. splendidus pathogenicity in larval rearings can be controlled by using marennine-containing culture supernatants. The effect of three marennine concentrations was tested on a larval rearing over 20 days for M. edulis and 9 days for P. magellanicus. At a low dose (0.1 mg L-1), survival and physiological condition were both higher than in the control. In bacterial challenges, larvae were exposed to V. splendidus for 72 h, with or without marennine. The bacterial challenge caused significant mortality when compared to controls, while the marennine-treated larvae showed significantly higher survival. Results show that marennine is an interesting molecule for pathogen control in hatcheries as it is active at low concentrations and significantly enhanced larval survival and physiological condition. -- Keywords : Bivalve hatcheries ; microalgal by-products ; Haslea ostrearia ; Mytilus edulis ; Placopecten magellanicus ; Vibrio splendidus.

Application of Seasonal Closures to Reduce Flatfish Bycatch in the U.S. Atlantic Sea Scallop Fishery

ABSTRACT The U.S. Atlantic sea scallop fishery has a bycatch allocation of Georges Bank yellowtail flounder that has in some cases limited the ability of the scallop fleet to fully optimize harvest of the scallop allocation. One strategy used to mitigate bycatch in the Georges Bank sea scallop fishery is time/area closures of scallop access areas. The original access area closure period, established in 1999, ran from February 1 through June 15, and it was primarily based on historical yellowtail spawning data at a broad spatial resolution. Beginning in 2011, data on yellowtail bycatch rates in the scallop fishery were collected during a dedicated seasonal bycatch survey in and around the scallop access areas of Closed Area I and Closed Area II on Georges Bank. Examination of seasonal trends in this data resulted in managers eliminating seasonal closures starting in 2013 in the Nantucket Lightship and Closed Area I access areas, and changing the dates for the seasonal closure in the Closed Area II access a...

Mortality Assessment of Atlantic Sea Scallops (Placopecten magellanicus) from Gray-Meat Disease

ABSTRACT The sea scallop Placopecten magellanicus (Gmelin, 1791) fishery is the most valuable wild scallop fishery in the world. Landings are primarily adductor muscles, which are ideally creamy white and firm. Recently, an increasing number of dark brown to gray, flaccid, and stringy meats have been caught in areas of Georges Bank and the mid-Atlantic, causing concern in industry and management. The mortality of gray-meat scallops was investigated, and an anesthetization procedure was developed allowing assessment of meat color in live scallops for laboratory experiments. The mortality rate of gray-meat scallops compared with white-meat scallops was tested. Gray-meat infection was swift and fatal; 26 of the original 28 gray-meat scallops died, whereas only 1 of 28 white-meat scallops died. The gray-meat condition was clearly associated with apicomplexan parasite infection intensity. Gray-meat scallops were identified visually, with image analysis computer software, and cell counts of apicomplexan nuclei....

The Influence of Temperature - Food Availability on the Shell Growth of Sea Scallop Placopecten magellanicus (Gmelin, 1791)

A study of the growth of the sea scallop, Placopecten magellanicus, under suspended culture conditions was carried out over a seven month period at a culture site in Graves Shoal, Mahone Bay,Nova Scotia – Canada. Scallop spat were cultivated in pearl nets at a density of 30-35 per net set at four locations corresponding to the surface (7 m) and bottom (14 m) at the outer edge and the center of the site. Shell height was measured at monthly intervals. Environmental conditions represented as temperature and food availability at the surface and bottom over the same period were also monitored. Shell Height growth rate was slightly greater at the surface than at the bottom. At the surface sites growth was greater at the outside (SUROUT) than at the center locations, but at the bottom growth was greater at the centre location (BOTIN). The only significant relationship between shell growth and temperature - food variables was chlorophyll a concentration. Key words: temperature, food availability, shell height, sea scallop

Measuring scallop fertilization success in the field: chamber design and tests

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 551:141-154 (2016) - DOI: https://doi.org/10.3354/meps11684 Measuring scallop fertilization success in the field: chamber design and tests Skylar R. Bayer*, Richard A. Wahle, Peter A. Jumars, Damian C. Brady Darling Marine Center, University of Maine, 193 Clark’s Cove Road, Walpole, ME 04573, USA *Corresponding author: skylar.bayer@maine.edu ABSTRACT: We developed and tested a method to field test fertilization success, measured as the proportion of eggs fertilized, in the giant sea scallop Placopecten magellanicus, a commercially valuable and sedentary broadcast spawner in the northwest Atlantic. A laboratory sperm dilution series determined maximum fertilization success expected in the field and assessed gamete longevity. We also developed and flume-tested a fertilization chamber to assess ambient water-column sperm loads near field populations. We then conducted a series of dockside field trials using these chambers over the course of the late summer spawning season in coastal Maine, USA. Chambers were deployed among manipulated populations of scallops to assess effects of local spawner abundance and location on time-integrate fertilization success. In dilution-series experiments, maximum fertilization success occurred at sperm concentrations >107 sperm ml-1. Egg longevity fell to zero between 8 and 24 h at ambient temperatures of 12°C, and sperm half-life shortened from 2 h to 9 min with a 10-fold dilution from a sperm concentration of 107 cells ml-1. Flume trials demonstrated chamber artifacts: fertilization was lower inside the chamber and the effect was greater at higher flow rates, but chamber orientation to flow had no effect. Increasing the numbers of eggs tended to reduce fertilization efficiency. In dockside tests, a 30-fold difference in spawner numbers had a significant effect on fertilization success. Notwithstanding acknowledged chamber artifacts due to flow impedance, this study establishes the feasibility of time-integrated fertilization experiments with scallops and sets the stage for further investigations of fertilization dynamics in natural scallop populations. KEY WORDS: Giant sea scallop · Placopecten magellanicus · Fertilization success · Fertilization ecology · Population density effect · Allee effects · Fisheries · Depensation Full text in pdf format PreviousNextCite this article as: Bayer SR, Wahle RA, Jumars PA, Brady DC (2016) Measuring scallop fertilization success in the field: chamber design and tests. Mar Ecol Prog Ser 551:141-154. https://doi.org/10.3354/meps11684 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 551. Online publication date: June 09, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Assessing the use of a camera system within an autonomous underwater vehicle for monitoring the distribution and density of sea scallops (Placopecten magellanicus) in the Mid-Atlantic Bight

Assessing the use of a camera system within an autonomous underwater vehicle for monitoring the distribution and density of sea scallops (Placopecten magellanicus) in the Mid-Atlantic Bight

Implications of extremely high recruitment events into the US sea scallop fishery

Implications of extremely high recruitment events into the US sea scallop fishery

Identification of a Mycobacterium sp. as the causative agent of orange nodular lesions in the Atlantic sea scallop Placopecten magellanicus.

The Atlantic sea scallop Placopecten magellanicus is an economically important species in the offshore fisheries on the east coast of the USA. Recently, animals collected from waters ranging from Massachusetts to Maryland have shown variably sized (up to 1 cm in diameter) orange nodular foci, predominantly in the adductor muscle tissue, but also in other organs. Histological evaluation of the nodular lesions showed rod-shaped bacteria that stain acid-fast positive and Gram-positive. PCR methodology was employed to identify the causative organism of the nodules as a Mycobacterium sp. using analysis of the partial 16S gene and the 16S-23S internal transcribed spacer region. Based upon genotypic findings, the causative bacterium fits well into the genus Mycobacterium.

Особенности активности ферментов энергетического обмена в тканях черноморских моллюсков разной подвижности в норме и при патологии

Одним из важнейших показателей метаболизма у моллюсков является активность ферментов энергетического обмена ― лактатдегидрогеназы (ЛДГ, 1.1.1.27) и малатдегидрогеназы (МДГ, 1.1.1.37), неизменно участвующих в адаптационных перестройках. Целью работы было сравнение активности ферментов энергетического обмена в тканях черноморских моллюсков с различными эколого-физиологическими особенностями. Объектами исследования служили половозрелые моллюски Mytilus galloprovincialis, Flexopecten glaber ponticus, Аnadara kagoshimensis и Rapana venosa в нерестовый период. Длина раковины мидии составляла 50–55 мм, анадары ― 25–33 мм, рапаны ― 50–80 мм, флексопектена ― 35–54 мм. Активность ферментов измеряли спектрофотометрически (при 340 нм and 25 ºC) по скорости окисления НАД-Н в цитоплазме тканей. Максимальная активность ЛДГ и МДГ у мидии, анадары и рапаны установлена в мышечной ткани, минимальная ― в гепатопанкреасе. Уровень активности МДГ в ноге, аддукторе, жабрах и гепатопанкреасе двустворчатых моллюсков-фильтраторов мидии и анадары достоверно выше, чем ЛДГ. Наибольшей активностью МДГ характеризовались ткани устойчивой к гипоксии анадары. Активность ЛДГ и МДГ в однотипных тканях хищного моллюска рапаны существенно не различалась. Показано, что активность ЛДГ в гепатопанкреасе, жабрах и мышечной ткани пропорциональна подвижности вида и увеличивается в ряду мидия ― анадара ― рапана. У Flexopecten glaber ponticus, собранного в зоне сброса воды с рисовых чеков и пораженного перфораторами, тканевая специфика активности ЛДГ и МДГ была нарушена, уровень активности ферментов понижен и не соответствовал естественной подвижности вида. Обсуждено состояние здоровья черноморского гребешка, находящегося под угрозой исчезновения в дикой природе.