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We investigated trophic transfer of cadmium (Cd) through an Arctic marine food web in Hudson Bay and compared it with mercury (Hg), a metal known to strongly biomagnify. We evaluated blue mussel, sea urchin, common eider, sculpin, Arctic cod, and ringed seal for the influence of dietary and biological variables on variation in Cd and Hg concentrations. Age and size influenced metal concentrations among individuals within a vertebrate species. Consumer carbon and sulfur isotope values were correlated with their Cd and Hg concentrations, indicating habitat-specific feeding influenced metal bioaccumulation. Trophic transfer patterns for Cd depended on the vertebrate tissue, with food web biodilution observed for the muscle but not the liver. Liver Cd concentrations were higher in ringed seal and some common eider relative to prey. In contrast, we observed mercury biomagnification for both tissues. Tissue- and species-specific physiology can explain discrepancies of Cd trophic transfer in this Arctic marine food web. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PST) in shellfish products have led to severe risks to human health. To monitor the risk, the Canadian Shellfish Sanitation Program has been collecting longitudinal PST measurements in blue mussel (Mytilus edulis) and soft-shell clam (Mya arenaria) samples in six coastal provinces of Canada. The spatial distributions of major temporal variation patterns were studied via Functional Principal Component Analysis. Seasonal increases in PST contamination were found to vary the most in terms of magnitude along the coastlines, which provides support for location-specific management of the time-sensitive PST contamination. In British Columbia, the first functional principal component (FPC1) indicated the variance among the magnitudes, while FPC2 indicated the seasonality of the PST levels. The temporal variations tended to be positively correlated with the abundance of dianoflagellates Alexandrium spp., and negatively with precipitation and inorganic nutrients. These findings indicate the underlying mechanism of PST variation in various geographical settings. In New Brunswick, Prince Edward, and Nova Scotia, the top FPCs indicated that the PST contamination differed mostly in the seasonal increase of the PST level during summer. • Multi-decade Paralytic Shellfish Toxins (PST) in Canada were analyzed. • Shellfish harvesting sites differed the most in seasonal elevation of PST levels. • The spring-to-autumn period of increased PST was found in BC, QC, NB, and NS. • Rainfall, Alexandrium spp., nitrate/nitrite, and phosphate correlated with PST. • Higher seasonal increases tended to occur at locations of strong water mixing. [ABSTRACT FROM AUTHOR]

Shellfish poisonings have posed severe risks to human health globally. The Canadian Shellfish Sanitation Program was established in 1948 to monitor the toxin levels at shellfish harvesting sites along the coast of six provinces in Canada. Domoic acid has been a causal toxin for amnesic shellfish poisoning, and a macro-scale analysis of the temporal and spatial variation of domoic acid along Canada's coast was conducted in this study. We aggregated the toxin levels by week in blue mussel (Mytilus edulis) and soft-shell clam (Mya arenaria) samples, respectively, over a one-year scale. The subsequent application of Functional Principal Component Analysis unveiled that magnitudes of seasonal variation and peaked DA levels around early summer, spring, or mid-fall formed the largest variation in the toxin levels in blue mussels along the coastlines of British Columbia and Prince Edward Island and in soft-shell calms along those of New Brunswick and Nova Scotia. In Quebec, the DA levels were low and varied mostly in terms of the overall magnitude from spring to fall. Downstream correlation analyses in British Columbia further discovered that, at most sites, the strongest correlations were negative between precipitation as well as inorganic nutrients (including nitrate, nitrite, phosphate, and silicate) on one side and DA a few weeks afterward on the other. These findings indicated associations between amnesic shellfish poisoning and environmental stresses., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier B.V. All rights reserved.)

We assess the financial performance of an Atlantic salmon (Salmo salar) monoculture versus an Atlantic salmon, blue mussel (Mytilus edulis), and sugar kelp (Saccharina latissima) Integrated Multi-Trophic Aquaculture (IMTA) operation. Using updated methods and models, we improve on earlier studies of IMTA economics. A discounted cash-flow analysis was used to assess the profitability of hypothetical monoculture and IMTA operations over a 10-year period in the Bay of Fundy, New Brunswick, Canada. The IMTA operation was more profitable, even when no price premium was included for its products. A 10% price premium for IMTA salmon and mussels resulted in a substantially higher net present value for the IMTA operation than for salmon monoculture. However, uncertainty related to IMTA's financial and environmental performance, as well as IMTA's increased operational complexity, may be barriers to IMTA adoption in Canada at present. As a result, it is likely that IMTA must generate substantially greater profits than salmon monoculture to stimulate investment. Alternatively, declining salmon production in recent years may encourage IMTA adoption in the future since it can provide crop diversification and economic stability benefits. IMTA research may benefit from alternative assessment methods such as the real options approach that explicitly incorporate uncertainty. [ABSTRACT FROM AUTHOR]

• Mussel tissues accumulated a mean of 26 µg STX eq. 100 g–1 after a 120 h exposure to cultured A. catenella. • Regardless of saxitoxin concentration or immune cell type, most cells remained alive and non-apoptotic. • The neutral lipid content of mussel immune cells decreased by a factor of two with A. catenella exposure. • A. catenella exposure affected the energy metabolism and osmolyte composition of mussel immune cells. The increasing occurrence of harmful algal blooms, mostly of the dinoflagellate Alexandrium catenella in Canada, profoundly disrupts mussel aquaculture. These filter-feeding shellfish feed on A. catenella and accumulate paralytic shellfish toxins, such as saxitoxin, in tissues, making them unsafe for human consumption. Algal toxins also have detrimental effects upon several physiological functions in mussels, but particularly on the activity of hemocytes – the mussel immune cells. The objective of this work was to determine the effects of experimental exposure to A. catenella upon hemocyte metabolism and activity in the blue mussel, Mytilus edulis. To do so, mussels were exposed to cultures of the toxic dinoflagellate A. catenella for 120 h. The resulting mussel saxitoxin load had measurable effects upon survival of hemocytes and induced a stress response measured as increased ROS production. The neutral lipid fraction of mussel hemocytes decreased two-fold, suggesting a differential use of lipids. Metabolomic 1H nuclear magnetic resonance (NMR) analysis showed that A. catenella modified the energy metabolism of hemocytes as well as hemocyte osmolyte composition. The modified energy metabolism was reenforced by contrasting plasma metabolomes between control and exposed mussels, suggesting that the blue mussel may reduce feed assimilation when exposed to A. catenella. [ABSTRACT FROM AUTHOR]

The common blue mussel ( Mytilus edulis ) was introduced to British Columbia, Canada, in the 1980s as an aquaculture alternative to native mussel species. Since then, the mussel industry in Pacific Canada has expanded and includes operations utilizing traditional methods of broodstock selection based on visual qualitative and quantitative traits. The impacts of hatchery propagation on genetic diversity and implications for animal fitness have been previously studied for other aquatic species, and this study further examines the effect of hatchery production on three M. edulis aquaculture populations in relation to a wild originator population. Prior to microsatellite genetic analysis, animals were identified to species using nuclear markers and were found to contain varying proportions of pure M. edulis as well as other pure species and hybrids from the ‘ Mytilus edulis complex’. Subsequently seven microsatellite markers were used to genotype 166 pure adult M. edulis individuals, all of which exhibited high levels of polymorphism. Allele frequencies at multiple loci did not conform to Hardy–Weinberg expectations and substantially less genetic diversity and very low effective population size estimates ( N e , calculated from linkage disequilibrium) were observed in farmed populations compared to the wild reference population. All populations were found to be genetically distinct based on F ST estimates. Mean allelic richness was approximately three times higher in the wild reference population than the three farmed populations (21 compared to 7.51, 7.91 in the two populations selecting for size and 8.24 in the population selecting for a colour morph). Observed heterozygosity was not significantly decreased in the cultured colour morph population, but was significantly different in the two other culture populations in comparison to the wild group. Reduced genetic diversity of the aquaculture populations is likely at least partially due to small effective breeding groups during hatchery propagation, creating genetic drift over successive generations. Speculations about the influence of broodstock selection practices are tentative and should be addressed in further temporal studies. These results indicate the need for the effective management of hatchery operations, the importance of rigorous site inventory, genetic broodstock characterization, and that ideally pedigree programs should be developed to help maintain healthy and productive shellfish culture populations with adaptive fitness capacity. Statement of relevance Hatchery methods impact species purity and genetic diversity. [ABSTRACT FROM AUTHOR]

During autumn 2012 and spring 2013, blue mussels Mytilus edulis (L.) with strongly deformed (L-shaped) posterior shell margins and green spots in soft tissue (microalgae) were collected from intertidal zone along the south shore of the Lower St. Lawrence Estuary near Rimouski (Québec, Canada). Identification of algal cells infesting mussels as Coccomyxa sp. was confirmed by rRNA sequencing and HPLC pigment analysis. Flow cytometric analysis revealed the presence of algal cells in the hemolymph and extrapallial fluid in mussels with deformed and non-deformed shells; concentrations of algal cells were ranged from about 200 mL-1 in mussels with actually non-deformed shells to concentrations reaching up to 3.8 × 107 mL-1 in mussels with heavily deformed ones. Chemical analyses of soft tissues led us to conclude that butyltin compounds and trace metals cannot be considered among factors responsible for the shell deformity observed. Using scanning electron microscopy, the biogenic nature of the erosion on the external shell surface and aragonitic lenses of prisms in the curvature zone of deformed shells (in sections) were recorded. The sequence of the green algae from M. edulis of the Lower St. Lawrence Estuary was closely related to Coccomyxa sp. infecting M. edulis from the Flensburg Fjord (North Sea) and Modiolus modiolus (L.) from the Vityaz Bay (Sea of Japan). [ABSTRACT FROM AUTHOR]

Abstract: The blue mussels Mytilus edulis are widely cultured in the coastal regions of Canada. However, their production on sleeves attached to long lines in the water column suffers from fall-offs due to byssus weakening, especially during the spawning period. Thus, we tested in laboratory the hypothesis that the spawning event changes the chemical and biochemical composition of byssal threads, resulting in a significant modification of their mechanical properties. Metal composition of byssus is interesting, as the proteins are cross-linked by complexation with metals influencing the breaking force. Our results show that the filaments' diameter and breaking force significantly decreased after spawning, as compared to unspawned individuals. However, no differences in the stress-at-break and strain-at-break were observed between the two experimental groups. Analysis of the lipid composition of the fibers' distal region indicates a very low concentration of total lipids, i.e. <0.05% in both groups. Some amino acid and lipid classes showed significant differences in relation to the spawn, but as their specific concentration or differences were very low in the byssal threads, their influence on mechanical properties seems negligible. The metal composition of the distal section of the byssus did not show substantial changes induced by the spawning event. Altogether, our results show that the weakening of the byssal thread force resulting from the spawning event of the mussels M. edulis in laboratory conditions was mainly due to a reduction of the fiber diameter, and cannot be related to changes in lipids, amino acid or metal composition. [Copyright &y& Elsevier]

Abstract: Integrated Multi-Trophic Aquaculture (IMTA) is a recycling concept in which waste nutrient discharges from high trophic levels become an additional energetic input for extractive organisms such as bivalves. The aim of this study was to measure the seston levels and absorption efficiency of mussels reared in the proximity of fish net-pens. The absorption efficiency of mussels Mytilus galloprovincialis and Mytilus edulis cultured at sites adjacent to red sea bream (Pagellus bogaraveo) and salmon (Salmo salar) cages was assessed on site, using natural seston diets and compared with mussels reared distant from the cages in the Ría de Ares-Betanzos (Galicia, N.W. Spain) and the Bay of Fundy (S.W. New Brunswick, Canada), respectively. Total particulate matter and the organic and the inorganic fractions of the seston were measured simultaneously. Seston parameters were generally similar at the mussel sites close to the fish cages and at the reference sites. However, significantly higher particulate inorganic matter coupled with lower food quality (seston organic content) observed at the sites close to the fish cages suggested occasional sediment resuspension events in the Ría de Ares-Betanzos and the Bay of Fundy. Owing to the reduced food quality, 20% lower absorption efficiency was measured for mussels in the proximity to the cages during the resuspension events. No significant differences in absorption efficiency were detected between the fish cages and the reference sites outside the resuspension events. Consequently, differences in absorption efficiency were attributed to natural variations in seston organic content, and absorption increased with increasing food quality. The results showed no evidence of increased organic content of the seston resulting from proximity to the fish-farm. It was concluded that proximity of cultured mussels to the fish cages did not result in an enhancement of the absorption efficiency. [Copyright &y& Elsevier]

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

Abstract: Previous studies on heavy metal contamination of the Baie des Chaleurs focus only on industrial centers and overlooked the ecosystem as a whole. To fill this gap, the objective of this study is to establish a baseline of the spatio-temporal distribution of heavy metals in mussels from the Baie des Chaleurs based on the ecosystem approach. Our results show, for the first time, a cadmium contamination in mussels across the south coast of the Baie des Chaleurs and not only in industrial centers. Our results also confirm previous studies showing heavy metal contamination of the Belledune area. This study demonstrates that the use of the ecosystemic approach is essential to obtain a comprehensive picture of environmental contamination in marine ecosystems. [Copyright &y& Elsevier]

Abstract: The St. Lawrence maritime estuary (Quebec, Canada) is subjected to mixed inputs of pollutants and the study of the induction of metallothionein in species of economic and ecologic importance such as Mytilus edulis and Mya arenaria was pertinent to assess the consequences of pollution in this northern estuary. Bivalves from an area devoid of anthropogenic influences but characterized by background metal contamination (Franquelin) were actively transplanted within this location and in a site contaminated by urban, industrial and endogenous pollutants, Baie-Comeau (Baie-des-Anglais). Spatial differences in metal concentrations were shown between sites. Cu and Zn concentrations were higher in mussels from Baie-des-Anglais at the beginning of the transfer and after 1 and 2 months. In clams, Zn concentrations were significantly higher in gills and digestive gland tissues for organisms transplanted in Baie-des-Anglais thus showing that spatio-temporal variations of metal concentrations were different between the two species studied. Mussels and clams partitioning of metals were shown to be different depending of the species, metal and/or tissue studied. In mussels, Cd and Cu concentrations decreased in both organs and both groups after the 3-month transfer in the polluted site. In mussels, total metal and metallothionein (MT) concentrations were positively correlated in digestive gland while in clams a positive correlation was only observed in gills. [Copyright &y& Elsevier]

Abstract: The effects of increased biodeposition within mussel (Mytilus edulis) farms on the benthic environment were investigated using surface sediment samples collected from 11 coastal embayments in Prince Edward Island (PEI), Canada. The degree of organic enrichment, determined using geochemical indicators (total free sulfides (S), redox potentials (EhNHE), water content (WC) and organic matter (OM)), was significantly greater in mussel leases compared to reference sites located both outside lease boundaries and in inlets not used to culture mussel (MANOVA, p <0.001). Post-hoc tests showed that mean WC and OM, EhNHE potentials and S concentration were all significantly different between lease and reference sites (p ≤0.009). Temporal changes in organic enrichment conditions were detected by comparing our 2001 data to those previously reported from a 1997 survey of the same sampling sites (MANOVA, p <0.001). This multivariate effect resulted primarily from a 39% increase in mean S concentration between 1997 and 2001 (p =0.029). Surface sediment variables at reference sites were similar between years. Benthic conditions were discriminated along an oxic–anoxic enrichment gradient using multidimensional scaling analysis. Mussel lease sites sampled in 1997 were clustered within predefined oxic sediment classifications along with the majority of reference sites, but were grouped farther along the enrichment gradient in 2001. The significant increase in hypoxic and sulfidic sediments within mussel farms between 1997 and 2001 is consistent with the 43% increase in PEI mussel production—a classic response to excessive organic biodeposition in shallow coastal inlets with relatively low dispersive capacity. [Copyright &y& Elsevier]

Abstract: Previous studies have suggested that a large proportion of the more heterozygous mussels are lost while in suspension culture. Such a reduction in multi-locus heterozygosity (MLH) could impact mussel production because more heterozygous individuals have better growth and survival than more homozygous ones. The present study followed the changes in MLH over a year in two different cohorts and found a reduction in MLH during the culture cycle for both cohorts. This reduction did not occur during the early phases of the culture operations, such as sleeving (= socking), or during the first weeks in suspension culture, but took place during the following growing season starting in early summer for both cohorts. The MLH decrease was not associated with different environmental conditions at the growing site. It is hypothesized that mussels characterized by high MLH are more mobile than those with lower MLH and migrate out of the mesh tubes faster after sleeving to get access to better growing conditions (space and food). However, being at the periphery of the sleeves, these more heterozygous individuals are more vulnerable to fall-offs due to turbulence and/or self-thinning. We suggest that the MLH decrease on the sleeves is not caused by the selective mortality of more heterozygous individuals but rather by higher losses through fall-offs. [Copyright &y& Elsevier]

Abstract: This paper describes the historical development of blue mussel (Mytilus edulis) farming in Tracadie Bay (Prince Edward Island, Canada) and relates the spacing of suspended sleeves (S S) on longlines to seston uptake. From 1990 to 2001, mussel biomass in Tracadie Bay increased by a factor of four (from 1137 to 4743 t). By 2001, seston uptake rates were approximately three-fold water renewal rates, and harvest yields (kg sleeve−1) were significantly lower than in the early 1990s. A one-year field experiment was carried out to determine whether a change in S S could restore harvest yields. We found that S S (10, 20, 40, 60, 80 cm) had no significant effect on the condition index of mussels. However, high S S positively affected shell growth and abundance for small seeds that were densely packed within sleeves. A complete husbandry shift toward high S S and high seeding densities (within sleeves) may enhance farm productivity (production per unit of effort) and curtail seston uptake at the bay scale. [Copyright &y& Elsevier]

Abstract: In suspended aquaculture, the size of mussel seed and the density at which these mussels are placed in socks are two important factors affecting mussel production. However, the effect of these two factors has yet to be examined simultaneously. We conducted two large-scale field experiments to assess the effect of seed size and initial density on growth, tissue-to-shell ratio and survival of blue mussels (Mytilus edulis) grown on longlines. Experimental mussel sites were set up during the autumn of two consecutive years in two bays on the north shore of Prince Edward Island, Canada. At each site, socks containing combinations of three seed sizes (small, medium and large) at two initial densities (low and high) were deployed and monitored over time. Small seed grew faster than large seed and often reached commercial size in the same time period. Furthermore, initial density generally did not affect shell growth. During the pre-spawning period following the autumn deployment, seed at low initial density had a higher tissue-to-shell ratio than seed at high initial density, especially for large seed. This effect of initial density disappeared in early summer. Early in the experiments (10 months), there appeared to be an interaction between seed size and initial density on mussel survival: survival of small seed generally decreased with increasing initial density, while survival of large seed was not affected by initial density. Since large seed tended to be packed at lower initial density than small seed, lack of crowding was likely responsible for the absence of density-dependent loss. Our study thus assessed different seeding strategies, and results were generally consistent across years and sites. [Copyright &y& Elsevier]

Abstract: Sediments and macroinvertebrate diversity underneath suspended mussel lines were examined in a shallow water system in Prince Edward Island, Canada. The objectives of the study were to describe the benthic environment in a typical mussel farm from eastern Canada and to underline various relationships between benthic parameters and husbandry practices. Benthic parameters included granulometry of the sediments, organic matter and sulfide contents as well as redox potential and common macroinvertebrate diversity indices. Husbandry operation parameters investigated were the number of years of operation and mussel culture density for a given lease. The results did not show any particular spatial patterns. The sediments'' mud content varied between 96 and 100%. Redox potential varied between −150 and 250 mV while sulfide concentration ranged between 100 and 9500 μM. Organic matter content varied between 1 and 16%. A total of 31 species were identified. Diversity indices were small throughout the study site. The number of years of operation for a given site varied between 0 (control sites) and 16 years while mussel culture densities ranged between 0 (control sites) and 0.70 kg/m2. Overall, no strong relationship was underlined between benthic parameters and studied husbandry practices. BIOENV analyses showed that culture density explained a small proportion of the benthic assemblages variability underneath mussel lines when using the macroinvertebrate abundance data set (r =0.137). Similar analyses showed that water depth better explained the variability observed under mussel lines when using the macroinvertebrate presence/absence data set (r =0.263). The absence of a strong relationship between husbandry practices and the studied benthic parameters might be related to the oceanographic characteristics and land-based activities associated with the water system rather than direct and cumulative effects of mussel culture. [Copyright &y& Elsevier]

Development of mariculture in Canadian waters has outpaced the ability of regulators to adequately assess environmental impacts and coexistence with other resource users. In eastern Canada, suspended longline culture of blue mussels (Mytilus edulis) leads to depletion of seston and subsequent biodeposition of feces and pseudofeces. Based on the need to evaluate aquaculture effects over multiple farms, a model was developed to compare the rate of mussel egestion with the scale of culture and tidal flushing of particulate waste from estuarine waters. Egestion was calculated using a bioenergetic submodel, and tidal flushing was determined with a tidal prism method. A short-term field program of particle sensing and sediment trapping was undertaken in Tracadie Bay and Savage Harbour (Prince Edward Island) to examine model assumptions and for validation. A finite element model was used to verify tidal prism calculations. Expressing model output as sedimentation rate, predicted biodeposition in Tracadie Bay was less than that estimated from field results but within the range of estuary-wide variation. In Savage Harbour, the egestion model overestimated biodeposition, likely because culture density on leased areas was sparse. A ranking of sites based on susceptibility to culture impacts was devised for multiple culture sites. [ABSTRACT FROM AUTHOR]

This report examines mercury concentrations in the marine environment of the Restigouche River, near a mercury cell chlor-alkali plant operated by Pioneer Chemicals Canada Inc. (PCI) in Dalhousie, New Brunswick. The PCI plant is a known point source of mercury in the area, but the extent of marine contamination in the Baie des Chaleurs as a result of those discharges has not been recently evaluated. Marine sediments (five transects), mussel tissue (six locations) and effluent samples (four locations) were obtained in the vicinity of the PCI plant and analyzed for total mercury. Mussel tissues were also analyzed for condition index, metallothioneins and zinc in the digestive gland and gonad as well as gonad vitellin-like proteins and digestive gland lipid peroxidation. Results indicated that the area of the Restigouche River around the PCI plant had elevated concentrations of mercury in sediment and mussel tissue compared with local background concentrations. Mercury concentrations in sediments decreased with distance from the chlor-alkali plant. Concentrations in sediments ranged from 0.03 mg/kg at a distance of 4.6 km to 1.96 mg/kg at a distance of 20 m from the shoreline at the plant. Nine sites had mercury concentrations exceeding the CCME Interim Sediment Quality Guideline (0.13 mg/kg), the furthest of which was 1090 m from PCI. Mercury concentrations in water discharges from four of the five observed outfalls ranged from 0.84 to 4.32 µg/L. Mercury concentrations in mussel tissue ranged from 0.02 mg/kg at a distance 4.6 km from the plant to 1.40 µg/kg directly in front of the plant. Condition index and zinc concentrations in mussels close to the plant were correlated with mercury levels; however, some abnormal biomarker results were found at locations far from the plant as well, indicating other sources of contaminants. Further studies are recommended to define the area of contamination near the PCI plant, as well as to determine the potential impact of other sources of mercury in the area. The environmental risk of the mercury contamination should also be more clearly established. [ABSTRACT FROM AUTHOR]

Abstract Consumer demand for fish and shellfish has led to an increase in aquatic species movement for aquaculture purposes. One potential drawback to the successful transplantation of animals for aquaculture is unpredictable performance due to local adaptation effects. This study used a common environment experiment to examine the potential for local adaptation in Mytilus trossulus (Lamark) on the east coast of Vancouver Island, British Columbia (BC). Newly settled mussels were collected from two sites, Chemainus and Quadra Island (approximately 150 km apart), reared in cages at the Quadra collection site, and mortality and shell length were monitored. Mussels were cage-reared for 384 days with an overall survival of 59% (Quadra) and 39% (Chemainus). The Quadra mussels were initially smaller (5.07 mm) than the Chemainus mussels (5.90 mm), but the two were similar at the end of the experiment (23.5 and 23.6 mm). Transplanted mussels had a significantly higher mortality over the course of the experiment, primarily due to a severe episode in the early summer, and had significantly lower relative growth rates at three of 11 measurement dates. Overall, the local mussels performed better than the transplanted mussels. This study demonstrates the potential for local adaptation effects between populations of mussels separated by only a relatively small geographic distance. [ABSTRACT FROM AUTHOR]

The advent of polymerase chain reaction (PCR)-based DNA markers, which claim to identify species diagnostically in the Mytilus edulis complex (M. edulis, M. galloprovincialis and M. trossulus) presents a possible method for simple, rapid species identification of Mytilus larvae. This study examines the inheritance of the Me 15/16 nuclear-DNA locus, which has previously been shown to produce three alleles diagnostic for M. edulis, M. galloprovincialis and M. trossulus. The Me 15/16 genotype was determined for pure species and hybrid larvae from 13 laboratory crosses between these three species and for adult mussels from five natural populations from which the parents of the crosses were selected. Genotype frequencies in the parent populations were generally as expected for M. edulis and M. galloprovincialis, but M. trossulus populations from eastern Canada and the Baltic Sea gave unexpected results. The marker was readily detected in individual larvae sampled 72 h and 2 weeks after fertilization, but amplification from 3 h old larvae was less reliable. Each cross produced larvae of all the expected genotypes and the results demonstrate that each of the three alleles can be inherited from either sex. The marker appears to be inherited in a Mendelian manner and should be of potential use in the future study of larvae in the M. edulis complex. [ABSTRACT FROM PUBLISHER]

Studies the reproductive isolation and output in sympatric mussel species, Mytilus edulis and Mytilus trossulus and their hybrids from Newfoundland. Sex ratio; Reproductive cycle; Gondosomatic index.

• Experimental study of the effects of A. catenella on M. edulis physiology and behaviour. • Average saxitoxin accumulation in tissues reached 52 µg STXeq 100 g–1 after one week. • Short-term responses include significant weight loss, increased oxygen consumption. • Valve opening amplitude was also lower and closure duration longer in exposed mussels. • No clear long-term differences were observed in comparison to non-exposed mussels. The effects of harmful algae on bivalve physiology are complex and involve both physiological and behavioural responses. Studying those responses is essential to better describe and predict their impact on shellfish aquaculture and health risk for humans. In this study we recorded for two months the physiological response of the blue mussel Mytilus edulis from Eastern Canada to a one-week exposure to a paralytic shellfish poisoning producing dinoflagellate strain of Alexandrium catenella , isolated from the St Lawrence estuary, Canada. Mussels in a 'control' treatment were fed continuously with a non-toxic diet, while mussels in a 'starvation' treatment were fed the same non-toxic diet the first week and subsequently starved for seven weeks. Mussels in a 'toxic' treatment received A. catenella for one week before being starved until the end of the experiment. Over a two-month experiment we monitored shell and tissue growth, filtration capacity, respiration rate, byssal attachment strength, valve opening behaviour, and toxin content in tissues. Mussels fed normally on the toxic dinoflagellate and accumulated an average of 51.6 µg STXeq 100 g–1 after one week of exposure. After seven weeks of depuration, about half of the specimen showed levels around 18 µg STXeq 100 g–1. The condition index of exposed mussels ('toxic' treatment) decreased rapidly from the start as compared to mussels that received a one-week non-toxic diet ('starvation' treatment). Oxygen consumption rates increased in the 'toxic' treatment before leveling out with that of mussels from the 'starvation' treatment. Valve opening amplitude was lower in the 'toxic' treatment during and following the exposure. Average valve closure duration was higher right after the exposure, during the peak of mussel tissue intoxication. No significant change in byssal thread strength was observed through time in each treatment but less force was required to detach mussels from the 'toxic' and 'starvation' treatments. The number of byssus threads produced by mussels exposed to the toxic dinoflagellate was also lower than in the control group. These results represent advancements in our understanding of the impacts of harmful algae on bivalves and contribute to the development of mitigation measures necessary to both the safety of consumers and the sustainability of aquaculture operations. [ABSTRACT FROM AUTHOR]

Examines Mytilus edulis suspended in the water column in 1994 and 1995 for the monitoring of oil drilling operations off Sable Island, Nova Scotia for hydrocarbon profiles, particularly aliphatic hydrocarbons. Planktonic origin of the biogenic hydrocarbons in the mussel; Effect of the occurrence of an unusual phytoplankton bloom during the suspension period.

As evidenced from literature, exposure to non-lethal concentrations of dissolved copper (Cu2+) and copper nanoparticles (CuO NPs) promotes blue mussels susceptibility to various bacterial infections. We study whether pre-exposure (3.5 h) with CuSO 4 (100 μg Cu L−1) and CuO NPs (1000 μg Cu L−1) will result in infection of M. edulis L. with pathogenic microalga Coccomyxa sp. under field conditions. In May – September 2019, cages were installed in the site Metis-sur-Mer, St. Lawrence Estuary (QC, Canada) where the native mussel population is known to be infected with the pathogen. Untreated and pre-exposed mussels were grown for up to 130 days. Only the mussels pre-exposed to copper were infected by Coccomyxa. This finding allows proposing that occurrences of Coccomyxa -infected mussels worldwide might have an association with water pollution with xenobiotics. Pre-exposure of caged mussels to copper, as a protocol monitoring for other infectious agents, can be recommended to test. [Display omitted] • Experimental infection of blue mussels with Coccomyxa alga is possible. • Pre-exposure with Cu2+ and CuO NPs results in alga transmission in field conditions. • Mussels susceptibility to Coccomyxa alga can be affected by aquatic pollution. • Pre-exposure of mussels to CuSO4 is recommended for monitoring of other infectious agents. [ABSTRACT FROM AUTHOR]

Bivalve aquaculture is an important component of the economy in eastern Canada. Because of current social, environmental, economic, and resource constraints, offshore mussel cultivation seems to be a promising strategy. With the objective of optimizing farming strategies that support the sustainability and development of the mussel industry at a microgeographic scale, we evaluated, after a traditional two year production cycle, the commercial performance of spat from several mussel (Mytilus edulis) stocks originating from sites separated by less than 65 km and cultivated at two different grow-out sites (shallow lagoon and offshore waters). The spatiotemporal variation in spat performance was studied through a multiyear in situ "stock-site" spat transfer design. The spat supply originating from the Bassin du Havre-Aubert lagoon systematically exhibited a larger size at sleeving time when compared to other stocks, and a better productivity level when harvested. Nevertheless, an alternative strategy would be to collect spat from the Havre-aux-Maisons lagoon, mostly because of the important commercial volumes of spat that can be collected there. Commercial performance (net income) was three times higher in the deep offshore grow-out site than in the shallow lagoon site. This better productivity in the open sea confirms the highly valuable strategy of offshore mussel farming in this area, where it was hypothesized that the less stressful environmental conditions positively influence reproduction, survival, and growth trends. [ABSTRACT FROM AUTHOR]

As evidenced from literature, exposure to non-lethal concentrations of dissolved copper (Cu 2+ ) and copper nanoparticles (CuO NPs) promotes blue mussels susceptibility to various bacterial infections. We study whether pre-exposure (3.5 h) with CuSO 4 (100 μg Cu L -1 ) and CuO NPs (1000 μg Cu L -1 ) will result in infection of M. edulis L. with pathogenic microalga Coccomyxa sp. under field conditions. In May - September 2019, cages were installed in the site Metis-sur-Mer, St. Lawrence Estuary (QC, Canada) where the native mussel population is known to be infected with the pathogen. Untreated and pre-exposed mussels were grown for up to 130 days. Only the mussels pre-exposed to copper were infected by Coccomyxa. This finding allows proposing that occurrences of Coccomyxa-infected mussels worldwide might have an association with water pollution with xenobiotics. Pre-exposure of caged mussels to copper, as a protocol monitoring for other infectious agents, can be recommended to test., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Non-indigenous species are often identified as threats to native species and communities. Yet, the mechanisms that enable many of these invaders to thrive and alter their newly invaded habitats are still not fully understood. This applies to habitats such as widespread sedimentary shorelines characterized by the presence of scattered biogenic clumps of blue mussels (Mytilus edulis) structurally more complex than bare sediments. In Atlantic Canada, some of these shorelines are numerically dominated by native mud crabs (Dyspanopeus sayi) but have been gradually invaded by the European green crab (Carcinus maenas). This study describes between-habitat (mussel clump vs. bare sediment) differences in density and diversity of invertebrates. It also tests the impact of juvenile green crabs in comparison to native mud crabs using two approaches: First, measuring habitat-related differences in these crabs' feeding rates on a common prey (soft-shell clams, Mya arenaria). Second, measuring their influence on invertebrate communities associated with mussel clumps. The results show that mussel clumps hold higher invertebrate density and diversity than surrounding sedimentary bottoms. In the laboratory, the feeding rates of native mud crabs were dependent on the type of habitat (sand flat > mussel clump), whereas those of green crabs were significantly higher and unrelated to the habitat in which predation occurred. In field experiments, juvenile green crabs were also the only predators that changed community structure in the mussel clump habitat. These results indicate that green crabs can cause a significant impact on native species and communities. Moreover, they suggest that the ability of this species to overcome the refuge provided by complex biogenic habitats for prey may represent an unexplored mechanism to explain this invader's expansion here and elsewhere., Competing Interests: The authors have declared that no competing interests exist.

During summer 2014-2017, wild mytilid mussels, highly infested with the pathogenic Coccomyxa-like microalgae, were collected along the Estuary and northwestern part of Gulf of St. Lawrence (Québec, Canada). Molecular identification showed that algae can be assigned to a single taxon, Coccomyxa sp. (KJ372210), whereas hosts are represented by Mytilus edulis, M. trossulus and hybrid between these two species. This is the first record of M. trossulus and hybrid among hosts of this pathogenic alga. Our results are indicative of a possible widespread distribution of Coccomyxa sp. in the Lower St. Lawrence Estuary and along coastal waters of Canadian Maritime provinces., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The article discusses a practical method for repeated extrapallial fluid extraction (EPF) from bivalve molluscs. The study used the mature blue mussels, Mytilus edulis, grown at the Laboratoire Aquicole of Institut des Sciences de la Mer de Rimouski (ISMER, UQAR) in Saint Lawrence Estuary, Canada. The study found that physiological mechanism has not shown any lethal effect or any inconvenience to the mussels and has no effect on the quality of extracted EPF.

Aim We performed the first test of predictions from the abundant-centre model using north-west Atlantic coastal organisms. We tested the hypotheses that the density of intertidal mussels (Mytilus edulis and M. trossulus) and dogwhelks (Nucella lapillus) and mussel age and size would peak at an intermediate location along their distribution range. We also assessed the latitudinal variation in critical aerial exposure time. Location North-west Atlantic coast between Newfoundland (Canada) and New York (USA), covering 1800 km of shoreline. Methods Using a nested design, we measured mussel density, age and size and dogwhelk density in 60 wave-exposed rocky intertidal sites spread evenly in six regions. Critical aerial exposure times were determined using online data. Results Mytilus edulis peaked in abundance in Maine and was much less abundant in the other regions. Mytilus trossulus peaked in abundance in southern Nova Scotia and Maine, was less abundant in the other regions to the north, and was absent in the southernmost region (New York). Both mussel species were least abundant in a northern region (Cape Breton), although not in the northernmost region (Newfoundland). Critical aerial exposure times were negatively correlated with overall mussel density. Mussel age and size were similar among regions. Dogwhelks peaked in abundance in Maine and were much less abundant in the other regions, being positively correlated with overall mussel density across regions. Main conclusions Density data for M. edulis and N. lapillus provide limited support for an abundant-centre pattern, while M. trossulus shows a clear rampedsouth distribution. Critical aerial exposure times suggest that physiological stress during summer and winter low tides may be lowest in Maine and southern Nova Scotia, which might partially explain mussel predominance in those regions. Winter ice scour in Cape Breton may explain the abundance trough observed there. Mussel size and age may be more limited by wave exposure at our sites (as they all face open waters) than by regional differences in environmental stress. Dogwhelks, which prey on mussels, seem to respond positively to prey density at the regional scale. Our study supports the notion that, while the abundant-centre model is a useful starting point for research, it often represents an oversimplification of reality. [ABSTRACT FROM AUTHOR]