Placopecten Magellanicus Research Articles

Inter-species comparison of life traits related to amnesic shellfish toxin kinetic in five pectinid species

Pectinid species (scallops) hold significant economic value, but their filtration activity makes them vulnerable to harmful algal blooms, particularly Pseudo-nitzschia species producing domoic acid (DA). Domoic acid contamination can lead to amnesic shellfish poisoning in humans, causing prolonged fisheries closures and sales bans. This study aimed to compare several pectinid species to investigate if inter-specific differences in energetic traits could be linked to their ability to depurate the toxin. Using Dynamic Energy Budget (DEB) theory and the AmP multi-species estimation procedure, we analysed five species: two slow depurators (Pecten maximus and Placopecten magellanicus) and three hypothesised fast depurators (Argopecten purpuratus, Mimachlamys varia, and Nodipecten subnodosus). Results showed differences among species in assimilation rates, somatic maintenance rates, and reserve mobilisation rates but only the reserve mobilisation rates (i.e. the energy conductance parameter) consistently increased along the “slow-to-fast” depuration gradient. This research lays the groundwork for developing toxin kinetics models to quantify the processes affecting DA accumulation and depuration, and to assess the retention time of DA. Our approach and results will therefore not only be of interest to the DEB community in terms of multi-species approaches, but are likely to have applications in pectinid aquaculture and fisheries management.

Assessing spatial structure in marine populations using network theory: A case study of Atlantic sea scallop (Placopecten magellanicus) connectivity.

Knowledge of the geographic distribution and connectivity of marine populations is essential for ecological understanding and informing management. Previous works have assessed spatial structure by quantifying exchange using Lagrangian particle-tracking simulations, but their scope of analysis is limited by their use of predefined subpopulations. To instead delineate subpopulations emerging naturally from marine population connectivity, we interpret this connectivity as a network, enabling the use of powerful analytic tools from the field of network theory. The modelling approach presented here uses particle-tracking to construct a transport network, and then applies the community detection algorithm Infomap to identify subpopulations that exhibit high internal connectivity and sparse connectivity with other subpopulations. An established quality metric, the coherence ratio, and a new metric we introduce indicating self-recruitment to subpopulations, dubbed the fortress ratio, are used to interpret community-level exchange. We use the Atlantic sea scallop (Placopecten magellanicus) in the northwest Atlantic as a case study. Results suggest that genetic lineages of P. magellanicus demonstrate spatial substructure that depends on horizontal transport, vertical motility, and suitable habitat. Our results support connectivity previously characterized on Georges Bank and Mid-Atlantic Bight. The Gulf of St. Lawrence genetic lineage is found to consist of five subpopulations that are classified as being a sink, source, permeable, or impermeable using quality metrics. This approach may be applied to other planktonic dispersers and prove useful to management.

Contrasting responses of commercially important Northwest Atlantic bivalve species to ocean acidification and temperature conditions

Modern calcifying marine organisms face numerous environmental stressors, including overfishing, deoxygenation, increasing ocean temperatures, and ocean acidification (OA). Coastal marine settings are predicted to become warmer and more acidic in coming decades, heightening the risks of extreme events such as marine heat waves. Given these threats, it is important to understand the vulnerabilities of marine organisms that construct their shells from calcium carbonate, which are particularly susceptible to warming and decreasing pH levels. To investigate the response of four commercially relevant bivalve species to OA and differing temperatures, juvenile Mercenaria mercenaria (hard shell clams), juvenile Mya arenaria (soft shell clams), adult and juvenile Arctica islandica (ocean quahog), and juvenile Placopecten magellanicus (Atlantic sea scallops) were grown in varying pH and temperature conditions. Species were exposed to four controlled pH conditions (7.4, 7.6, 7.8, and ambient/8.0) and three controlled temperature conditions (6, 9, and 12°C) for 20.5 weeks and then shell growth and coloration were analyzed. This research marks the first direct comparison of these species’ biological responses to both temperature and OA conditions within the same experiment. The four species exhibited varying responses to temperature and OA conditions. Mortality rates were not significantly associated with pH or temperature conditions for any of the species studied. Growth (measured as change in maximum shell height) was observed to be higher in warmer tanks for all species and was not significantly impacted by pH. Two groups (juvenile M. arenaria and juvenile M. mercenaria) exhibited lightening in the color of their shells at lower pH levels at all temperatures, attributed to a loss of shell periostracum. The variable responses of the studied bivalve species, despite belonging to the same phylogenetic class and geographic region, highlights the need for further study into implications for health and management of bivalves in the face of variable stressors.

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.

Offshore windfarm construction elevates metabolic rate and increases predation vulnerability of a key marine invertebrate

A global increase in offshore windfarm development is critical to our renewable energy future. Yet, widespread construction plans have generated substantial concern for impacts to co-occurring organisms and the communities they form. Pile driving construction, prominent in offshore windfarm development, produces among the highest amplitude sounds in the ocean creating widespread concern for a diverse array of taxa. However, studies addressing ecologically key species are generally lacking and most research is disparate, failing to integrate across response types (e.g., behavior, physiology, and ecological interactions), particularly in situ. The lack of integrative field studies presents major challenges to understand or mitigate actual impacts of offshore wind development. Here, we examined critical behavioral, physiological, and antipredator impacts of actual pile driving construction on the giant sea scallop (Placopecten magellanicus). Benthic taxa including bivalves are of particular concern because they are sound-sensitive, cannot move appreciable distances away from the stressor, and support livelihoods as one of the world's most economically and socially important fisheries. Overall, pile driving sound impacted scallops across a series of behavioral and physiological assays. Sound-exposed scallops consistently reduced their valve opening (22%), resulting in lowered mantle water oxygen levels available to the gills. Repeated and rapid valve adductions led to a 56% increase in metabolic rates relative to pre-exposure baselines. Consequently, in response to predator stimuli, sound-exposed scallops displayed a suite of significantly weaker antipredator behaviors including fewer swimming events and shorter time-to-exhaustion. These results show aquatic construction activities can induce metabolic and ecologically relevant changes in a key benthic animal. As offshore windfarm construction accelerates globally, our field-based study highlights that spatial overlap with benthic taxa may cause substantial metabolic changes, alter important fisheries resources, and ultimately could lead to increased predation.

Noise pollution causes parental stress on marine invertebrates, the Giant scallop example

In marine invertebrates, abiotic stresses on adults can act directly on gametes quality, which impacts phenotype and development success of the offspring. Human activities introduce noise pollution in the marine environment but still few studies on invertebrates have considered the impacts on adult or larval stages separately, and to our knowledge, never investigated the cross-generational effects of anthropogenic noise. This article explores parental effects of pile driving noise associated with the building phase of offshore wind turbines on a coastal invertebrate, Pecten maximus (L.). Adults were exposed to increasing levels of sound during gametogenesis, then their offspring were also exposed. The results highlight that anthropogenic noise experienced by the parents reduces their reproductive investment and modify larval response in similar conditions. Also, larvae from exposed adults grew 6-fold faster and metamorphosed 5-fold faster, which could be an amplified adaptive strategy to reduce the pelagic phase in a stressful environment.

Effects of Daily Consumption of Scallop Oil Prepared from Internal Organs of Japanese Giant Scallop (Patinopecten yessoensis) on Serum Lipid Composition and Its Safety: A Randomized, Double-blind, Placebo-controlled, Parallel Group Comparison Study.

Scallop oil (SCO) prepared from the internal organs of the Japanese giant scallop (Patinopecten yessoensis) contains eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and phospholipids (PL). It was previously shown that SCO consumption improves cholesterol and triacylglycerols (TG) contents in mice. The present study demonstrated the effects of daily SCO consumption (1.2 g/day, containing 376 mg of EPA, 63 mg of DHA, and 150 mg of PL) for 12 weeks in human subjects. In this randomized, doubleblind, placebo-controlled, parallel group comparison study, 70 Japanese subjects with serum TG levels ≥120 but < 200 mg/dL were recruited and randomly assigned to the SCO or placebo group. All subjects ingested six capsules per day for 12 weeks. We conducted medical interviews, body composition measurements, vital sign examinations, and blood sampling at weeks 0 (baseline), 4, 8, and 12, and measured peripheral blood flow at weeks 0 and 12. In the case of subjects with higher serum TG levels, SCO consumption decreased the changes in serum TG and malondialdehyde-low density lipoprotein (MDA-LDL) levels compared with the placebo group. Safety assessment revealed no medically significant changes due to continuous SCO consumption. The findings indicate that 1.2 g/day of SCO consumption may be beneficial for reducing serum TG and MDA-LDL levels in persons with higher TG levels.

Evaluating bycatch avoidance in the U.S. Atlantic sea scallop Placopecten magellanicus fishery

AbstractObjectiveThe effectiveness of bycatch avoidance programs relies on changes in fishing behavior in response to spatiotemporal information on bycatch patterns. A voluntary bycatch avoidance program in the U.S. sea scallop Placopecten magellanicus fishery designed to prevent triggering bycatch allocation of Yellowtail Flounder Limanda ferruginea was implemented and maintained concurrently with other management measures. Detecting bycatch avoidance behavior and relative effectiveness for bycatch mitigation presents an analytical challenge.MethodsWe evaluated effectiveness of the bycatch avoidance program over the course of 4 years based on fishing behavior relative to bycatch advisories. Using loglinear models to compare frequencies, we examined the relationship between bycatch reports from participating vessels and bycatch advisories throughout the year in each of the 4 years. We compared results from self‐reported catch to data from a mandatory observer program for participating and nonparticipating vessels in the bycatch avoidance program.ResultSignificant associations between bycatch advisories and fishing locations indicated bycatch avoidance behavior, while accounting for the effect of sea scallop density on fishing location decisions. Evidence of avoidance behavior was stronger in earlier years of the program and varied spatially. Decreasing avoidance behavior coincided with revised bycatch management measures, which appear to have altered the incentives for bycatch avoidance.ConclusionWe found differences in the fishing behavior of fishing captains who participated in the bycatch avoidance program when Yellowtail Flounder bycatch was perceived to threaten economic yield due to fishery closures. Bycatch mitigation program evaluations should consider the program objectives as well as incentives (and disincentives) in interpreting behavior.

Chromosome-level genome assembly of sea scallop Placopecten magellanicus provides insights into the genetic characteristics and adaptive evolution of large scallops

Placopecten magellanicus (Gmelin, 1791), a deep-sea Atlantic scallop, holds significant commercial value as a benthic marine bivalve along the northwest Atlantic coast. Recognizing its economic importance, the need to reconstruct its genome assembly becomes apparent, fostering insights into natural resources and generic breeding potential. This study reports a high-quality chromosome-level genome of P. magellanicus, achieved through the integration of Illumina short read sequencing, PacBio HiFi sequencing, and Hi-C sequencing techniques. The resulting assembly spans 1778 Mb with a scaffold N50 of 86.71 Mb. An intriguing observation arises – the genome size of P. magellanicus surpasses that of its Pectinidae family peers by 1.80 to 2.46 times. Within this genome, 28,111 protein-coding genes were identified. Comparative genomic analysis involving five scallop species unveils the critical determinant of this expanded genome: the proliferation of repetitive sequences recently inserted, contributing to its enlarged size. The landscape of whole genome collinearity sheds light on the relationships among scallop species, enhancing our broader understanding of their genomic framework. This genome provides genomic resources for future molecular biology research on scallops and serves as a guide for the exploration of longevity-related genes in scallops.

Depuration of ingested 14C-labelled polystyrene nanospheres in the Atlantic scallop (Placopecten magellanicus)

The presence of nano-plastics in marine bivalves is well established and may represent a risk to human consumption. The main objective of our work was to study the detailed tissue distribution of 14C-radiolabelled polystyrene nanospheres (PSNP; 325 nm) following their ingestion by commercial-size Atlantic scallop (Placopecten magellanicus) using whole-body autoradiography to assess their translocation, bioaccumulation and depuration mechanisms over a short-term exposure (6h) and a long-term exposure (2 weeks). Results showed that the nanospheres (PSNP) did not accumulate in scallop tissues despite the fact they were ingested and transported all along the digestive system. Elimination of the PSNP was virtually completed within 48 h and no radiolabeling appeared in the edible adductor muscle. This is indicative of the presence of an active depuration mechanism of particles without nutritional value as plastic PSNP. Our preliminary work indicates a rapid translocation of PSNP in scallops minimizing a possible transfer to human consumers.

Trace elements in bivalve shells: How “vital effects” can bias environmental studies

We report on the concentrations of rare earths (REE), Y, Mg, Mn, Cu, Zn, Sr, Ba, Pb and U in a series of wild scallops (Placopecten magellanicus) collected alive on the same day in Saint Pierre et Miquelon (a French archipelago located south of Newfoundland) and ranging in age from 2 to about 20 years. We analyzed representative fragments from the entire last annual shell growth increment of each animal to assess changes in trace element incorporation with age.No correlation with the age of the animals was obtained for Sr and Mn concentrations, which are quite variable from one individual to another, even of similar age. On the other hand, for REE, Y, Cu, Zn, Ba and U, the concentrations measured in the last annual growth increment formed by animals aged 2 to 7 years are similar. From 8 years of age, the concentrations of these elements increased very strongly (for example for Yb, almost by an order of magnitude between 8 and 20 years of age), and possibly with some variation between individuals of the same age. Two elements show a different behavior: Mg concentrations in the shell margins increase continuously with the age of the animals; Pb concentrations are scattered but seem to decrease with the age of the animals.This turning point in the behavior of the elements from 8 years of age coincides with major metabolic changes, since at this age wild P. magellanicus from Newfoundland reduce their growth, in favor of gamete production. Our results demonstrate that metabolic activity of the animals largely controls the incorporation of many trace elements into the shells. These results demonstrate that the age of the animals must be taken into account when their shells are used to study pollution or (paleo) environmental condition.

Partitioning spatial dynamics in abundance of marine fisheries stocks between fine- and broad-scale variation: A Bayesian approach

Fisheries stocks are often characterized by pronounced spatial patterning. This occurs at different scales, which may be driven by separate mechanisms. Regression kriging is often used to generate population estimates which may parse variation among these scales. A previous application of this and other frequentist methods to estimate the abundance of Atlantic sea scallops (Placopecten magellanicus) found that semi-parametric regression kriging performs best among model-based methods. We expanded upon these results by adapting the model structure for a Bayesian framework. This approach demonstrated the trade-off between abundance as a function of depth and broad spatial habitat features, and of fine-scale spatial aggregation. We applied our model to the 2015 belt transect survey of Atlantic sea scallops in Georges Bank and the Mid-Atlantic Bight off the eastern coast of the United States. The overall Bayesian predictions generally agreed with those of the frequentist method. However, the former favored broad spatial trends coupled with very fine-scale aggregation, while the latter favored finer trends and broad aggregation as the dominant driver of scallop abundance. Therefore, one can draw similar conclusions about abundance, yet disparate conclusions about the drivers. Careful consideration of the benefits and limitations of each approach is warranted.

Bacterial community trends associated with sea scallop, Placopecten magellanicus, larvae in a hatchery system

Atlantic sea scallops, Placopecten magellanicus, are the most economically important marine bivalves along the northeastern coast of North America. Wild harvest landings generate hundreds of millions of dollars, and wild-caught adults and juvenile spat are increasingly being cultured in aquaculture facilities and coastal farms. However, the last two weeks of the larval maturation phase in hatcheries are often plagued by large mortality events. Research into other scallop- and aquacultured-species point to bacterial infections or altered functionality of microbial communities which associate with the host. Despite intense filtering and sterilization of seawater, and changing tank water every 48 h, harmful microbes can still persist in biofilms and mortality is still high. There are no previous studies of the bacterial communities associated with the biofilms growing in scallop hatchery tanks, nor studies with wild or hatchery sea scallops. We characterized the bacterial communities in veliger-stage wild or hatchery larvae, and tank biofilms using the 16 S rRNA gene V3-V4 region sequenced on the Illumina MiSeq platform. Hatchery larvae had lower bacterial richness (number of bacteria taxa present) than the wild larvae and tank biofilms, and hatchery larvae had a similar bacterial community (which taxa were present) to both wild larvae and tank biofilms. Bacterial richness and community similarity between tank samples fluctuated over the trial in repeated patterns of rise and fall, which showed some correlation to lunar cycle that may be a proxy for the effects of spring tides and trends in seawater bacteria and phages which are propagated into hatchery tanks. These results along with future work, will inform hatcheries on methods that will increase larval survival in these facilities, for example, implementing additional filtering or avoiding seawater collection during spring tides, to reduce bacterial taxa of concern or promote a more diverse microbial community which would compete against pathogens.

Drivers of decadal-scale temporal change in epibenthic megafaunal assemblages on scallop fishing grounds in the Bay of Fundy

The Bay of Fundy presents a unique environment with extreme tidal range, strong currents, fresh-water river discharge, and diverse habitats that are also experiencing temperature increase at a faster rate than most of the world ocean. There is extensive commercial fishing, valuable beds of sea scallop (Placopecten magellanicus) being found in several areas, some of which have been fished for over a century. Previously, comparative analyses of data collected in 1967 and 1997 found that the epibenthic assemblage on the Digby scallop ground had become more homogenous over the 30 year interval, while species composition had changed significantly. Attached, fragile, epifaunal taxa declined, whereas scavengers and robust burrowing filter-feeders increased in frequency of occurrence, consistent with the physical impacts of fishing gears as a primary driver. The Digby ground along with the commercial scallop grounds around Grand Manan Island and on Lurcher Shoal were resampled in 2007–08 to determine whether the changes off Digby had continued and if they were also occurring in other parts of the Bay. Significant spatial differences among the three scallop grounds were observed. The leafy bryozoan, Flustra foliacea, which was expanding its local range through time, was the leading contributor to the spatial dissimilarity. Depth and mean tidal current speed were the most important environmental variables influencing species composition. Significantly more taxa were recorded per station in 1997 than in 2007–08, while assemblage compositions were significantly different between the two periods. Decadal-scale declines in the frequencies of occurrence of attached, epibenthic filter-feeders, including the polychaete Filograna implexa, were observed, continuing the trend previously reported and consistent with on-going impacts of bottom-contact fishing gears, despite decades of trawling and dredging. However, other and unknown drivers were also implicated in the observed changes.

Static adsorption and photocatalytic degradation of amoxicillin using titanium dioxide/hydroxyapatite nanoparticles based on sea scallop shells.

The objective of this study is to investigate the efficiency of two processes for the amoxicillin removal through static (batch) adsorption and photocatalytic degradation onto the prepared samples. Three solid materials as photocatalyst and/or adsorbent were synthesized viz. nanotitanium dioxide (NT) prepared by the sol-gel method, scallop shells-based nanohydroxyapatite (NP), and nanotitanium dioxide/nanohydroxyapatite composite (NTP). The physicochemical and morphological properties of the prepared samples were tested by TGA, XRD, DRS, ATR-FTIR, nitrogen adsorption/desorption isotherm, zeta potential, SEM, and TEM. The major operational conditions were optimized for catalyst or adsorbent mass, pH, shaking time, initial amoxicillin (AMX) concentration, power of UV lamp, and temperature. The results illuminated that NTP achieved the highest adsorption capacity (88.46mg/g) at 20 ℃ and AMX adsorption onto all the solid materials was well applied by Langmuir, Temkin, pseudo-second order, and Elovich models. The maximum desorption percent (98%) was attained by acetone. The degradation percent of AMX reached 85.3 and 99.5% for NT and NTP, respectively, using 0.9g/L of catalyst dosage through 90min. AMX photodegradation onto the catalysts' surface was well fitted by Langmuir-Hinshelwood, Arrhenius, and Eyring-Polanyi models with endothermic, physical, and nonspontaneous nature of photocatalysis process. NTP acts as a promising adsorbent and photocatalyst for the antibiotics' removal in wastewater.

Integrating habitat features into spatio-temporal biomass dynamics models for a better understanding of stock productivity: a case study of sea scallop in the Bay of Fundy

Abstract Recent efforts in ocean mapping of seafloor habitat have made data increasingly available. For bottom-dwelling and/or sessile species, there is often a strong relationship between population productivity and habitat, and stock assessment models are likely to be improved by the inclusion of habitat. Here, we extend a recently developed spatio-temporal biomass dynamics model to allow habitat to inform probabilities of non-zero tows and catchability. Simulation experiments demonstrate the ability of this new approach to reliably capture population trends over time and space, with the applicability of the method further demonstrated using data from the Canadian Maritimes Inshore Sea Scallop Fishery in the Bay of Fundy. This habitat-informed spatio-temporal biomass dynamics model better captures underlying processes, reduces uncertainty, thereby improving our understanding of stock status from which fisheries management decisions can be based.

Effects of warming and fishing on Atlantic sea scallop (Placopecten magellanicus) size structure in the Mid-Atlantic rotationally closed areas

Abstract The Atlantic sea scallop supports one of the most lucrative fisheries on the Northeast U.S. shelf. Understanding the interannual variability of sea scallop size structure and associated drivers is critically important for projecting the response of population dynamics to climate change and designing coherent fishery management strategies. In this study, we constructed time series of sea scallop size structures in three rotationally closed areas in the Mid-Atlantic Bight (MAB) and decomposed their total variances using the variance partitioning method. The results suggested that the interannual variances in sea scallop size structures were associated more with thermal stress in regions shallower than 60 m but more with fishing mortality in regions deeper than 60 m. The percentages of small (large) size groups increased (decreased) with elevated thermal stress and fishing pressure. We adopted a scope for growth model to build a mechanistic link between temperature and sea scallop size. Model results suggested a gradual decrease in maximum shell height and habitat contraction under warming. This study quantified the relative contributions of thermal stress and fishing mortality to the variance of scallop size structure and discussed the need for adaptive management plans to mitigate potential socioeconomic impacts caused by size structure changes.

Observations on a Reemerging Epizootic of the Sea Scallop, Placopecten magellanicus, Resource

The Anaskid nematode, Sulcascaris sulcata has a worldwide distribution and utilizes benthic molluscs as an intermediate host with sea turtles (Chelonioidea) serving as definitive hosts. During the spring of 2015, sea scallops (Placopecten magellanicus) harvested along the mid-Atlantic Bight (MAB) presented with rust-colored lesions on the surface of the adductor muscles. Morphological and molecular investigations determined that the lesions were caused by an infection by third- and fourth-stage larval S. sulcata. Seasonal monitoring from 2015 to 2018 delineated a stable spatial distribution of infected scallops that corresponded to a large 2013 year-class of scallops and persistent utilization of this habitat by seasonally resident loggerhead turtles. Given the life cycle and etiology of S. sulcata, the risk to human health via direct infection or allergic reaction appears to be low, however, the spatiotemporal scale of nematode-infected scallops resulted in fishery-level impacts with respect to the spatial distribution of fishing effort in response to product quality and depreciation of the value of landed scallops. The long-term trajectory of the epizootic remains unclear and continued monitoring of the spatiotemporal distribution of nematode-infected scallops is warranted as S. sulcata spatial distribution is likely dependent upon sea scallop abundance, which is currently trending toward more northerly portions of the MAB.

Evaluating simple measures of spatial-temporal overlap as a proxy for encounter risk between a protected species and commercial fishery

Spatial and temporal assessments of overlap are becoming increasingly popular as indicators of encounter risk. The overlap in distributions between protected species and commercial fishing effort is of interest for reducing bycatch. We explored overlap between the U.S. Atlantic sea scallop fishery and loggerhead turtles (Caretta caretta) using 2 metrics, and we assessed the ability of one of those metrics to track estimated fishery interactions over time. Moderate overlap occurred between June - September; mild overlap in the spring (May) and fall (October - November); and relatively little overlap from December to April. Qualitatively, there appeared to be some correspondence between the overlap values averaged across months for each calendar year and published annual loggerhead interaction estimates with fisheries, but the predictive performance of the overlap metric was low. When data on the relative distributions of commercial fishing effort and protected species are available, simple measures of spatial and temporal overlap can provide a quick and cost-effective way to identify when and where bycatch is likely to occur. In this case study, however, overlap was limited in helping to understand the relative susceptibility of protected species to commercial fishing (i.e., magnitude of interactions). We therefore caution against using overlap as a meaningful predictor of absolute risk unless there is direct evidence to suggest a relationship.

Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes

This study assessed the energy budget for juvenile Atlantic Sea Scallop,Placopecten magellanicus, during a natural drop in temperature (15.6°C to 5.8°C) over an 8-week time period during the fall at three different enrichment levels of carbon dioxide (CO2). Every 2 weeks, individuals were sampled for ecophysiological measurements of feeding activity, respiration rate (RR) and excretion rate (ER) to enable the calculation of scope for growth (SFG) and atomic oxygen:nitrogen ratios (O:N). In addition, 36 individuals per treatment were removed for shell height, dry tissue weight (DTW) and dry shell weight (DSW). We found a significant decrease in feeding rates as CO2increased. Those rates also were significantly affected by temperature, with highest feeding at 9.4°C. No significant CO2effect was observed for catabolic energy processes (RR and ER); however, these rates did increase significantly with temperature. The O:N ratio was not significantly affected by CO2, but was significantly affected by temperature. There was a significant interaction between CO2and temperature for ER and the O:N ratio, with low CO2levels resulting in a U-shaped response that was not sustained as CO2levels increased. This suggests that the independent effects of CO2and temperature observed at low levels are different once a CO2threshold is reached. Additionally, there were significant differences in growth estimators (shell height and DSW), with the best growth occurring at the lowest CO2level. In contrast to temperature variations that induced a trade-off response in energy acquisition and expenditure, results from this research support the hypothesis that sea scallops have a limited ability to alter physiological processes to compensate for increasing CO2.