Mussel Length Research Articles

Genetics and ontogeny are key factors influencing thermal resilience in a culturally and economically important bivalve

Increasing seawater temperatures coupled with more intense and frequent heatwaves pose an increasing threat to marine species. In this study, the New Zealand green-lipped mussel, Perna canaliculus, was used to investigate the effect of genetics and ontogeny on thermal resilience. The culturally and economically significant mussel P. canaliculus (Gmelin, 1971) has been selectively-bred in New Zealand for two decades, making it a unique biological resource to investigate genetic interactions in a temperate bivalve species. Six selectively-bred full sibling families and four different ages, from early juveniles (6, 8, 10 weeks post-fertilisation) to sub-adults (52 weeks post-fertilisation), were used for experimentation. At each age, each family was exposed to a three-hour heat challenge, followed by recovery, and survival assessments. The shell lengths of live and dead juvenile mussels were also measured. Gill tissue samples from sub-adults were collected after the thermal challenge to quantify the 70 kDa heat shock protein gene (hsp70). Results showed that genetics, ontogeny and size influence thermal resilience in P. canaliculus, with LT50 values ranging between 31.3 and 34.4 °C for all studied families and ages. Juveniles showed greater thermotolerance compared to sub-adults, while the largest individuals within each family/age class tended to be more heat sensitive than their siblings. Sub-adults differentially upregulated hsp70 in a pattern that correlated with net family survival following heat challenge, reinforcing the perceived role of inducible HSP70 protein in molluscs. This study provides insights into the complex interactions of age and genotype in determining heat tolerance of a key mussel species. As marine temperatures increase, equally complex selection pressure responses may therefore occur. Future research should focus on transcriptomic and genomic approaches for key species such as P. canaliculus to further understand and predict the effect of genetic variation and ontogeny on their survival in the context of climate change.

Temporal variability in biochemical composition and morphometric parameters of cultivated Mediterranean mussels (Mytilus galloprovincialis) in Çanakkale, Türkiye

In recent years, there has been a growing interest in bivalve and gastropod species (Mollusca phylum) due to their high nutritional value compared to terrestrial organisms. Bivalve species, in particular, hold significant potential for both aquaculture and fishing industries worldwide. Among shellfish, mussels play a crucial role in aquatic ecosystems. Parameters such as meat yield and condition index are essential for determining consumption strategies of bivalve species. Thus, this study focused on monthly collections of Mediterranean mussels (Mytilus galloprovincialis) from Çanakkale Gelibolu Ilgardere Mediterranean Mussel Cultivation Farmers between March 2019 and February 2020. During this period, analyses were conducted for condition index, meat yield, shell component index, as well as protein, carbohydrate, lipid, and ash content. The temperature variations in the study area aligned with seasonal changes maximum value and minimal value were recorded as 8.7 °C in March and 27.3 °C in July. Salinity values ranged from 15.2 ‰ in November and January to 24.01 ‰ in December. The length of mussels ranged from 52.54 mm to 68.53 mm, with total weights ranging from 11.18 g to 25.37 g. The length-weight relationship of Mediterranean mussels was determined as Weight = 0.0002 * Length2.806. Condition index, meat yield, and shell component index exhibited significant variations across months (P < 0.05). There was no relationship between these parameters and environmental factors. Fluctuations in protein content were observed, with the lowest recorded in May (41.88 %) and the highest in November (61.19 %). Lipid, carbohydrate, and ash content ranged between 12.49 % and 18.59 %, 9.69 % and 34.31%, and 6.95 % and 18.06 %, respectively. Overall, it can be concluded that aside from the summer months, the harvesting and consumption of cultivated mussels are more suitable in terms of meat quality and biochemical profile.

Mussels with luggage: the influence of artificially attached “backpack” devices on mussel movement behavior

BackgroundFreshwater mussels are important keystone and indicator species of aquatic ecosystems. Recent advances in sensor technology facilitate applications to individually track mussels and to record and monitor their behavior and physiology. These approaches require the attachment of sensor devices as “backpacks” to the outer shell surface. The interpretation of such data makes it necessary to understand the influence of these attachments on the horizontal and vertical movement behaviors of freshwater mussels. Over a series of mesocosm experiments, this study systematically investigated the effects of three size- and wiring-specific variants of artificially attached backpacks on the horizontal and vertical movement behavior of Anodonta anatina.ResultsAcross all experiments, equipping mussels with backpacks did not result in a significant influence on horizontal movement for any of the backpack variants. In contrast to this finding, the big backpacks with a high ratio between backpack volume and mussel length resulted in a significantly negative effect on vertical movement, indicating a potential for adverse effects of such devices on mussels, especially in natural settings.ConclusionsThe findings of this study show that assessing the effects of attached devices on mussels requires a species-specific evaluation of potential impacts on the endpoints of interest. Especially for vertical movement patterns, selection of the smallest available devices appears mandatory.

Transitioning from wild seed fishery to Seed Mussel Collectors (SMCs): Reviewing the efficiency of collectors for seed provisioning in mussel bottom culture

The availability of mussel seed is a critical aspect in mussel farming. Since 2009, the Dutch mussel sector has been transitioning from wild seed fishery to suspended seed collectors (Seed Mussel Collectors, or SMCs). Collector systems using either ropes or nets as settlement substrate are placed in Oosterschelde Bay, the Wadden Sea, and the North Sea annually. We analyzed detailed harvest data from 2010 until 2022, to investigate the efficiency of different systems, identify differences between years and areas, and assess how production can be optimized. Additionally, numerical density, biomass, and shell lengths of mussels from 0.375 mm shell length were recorded on SMC ropes at one SMC location during a full growth season to evaluate biomass-density relations and assess the process of self-thinning on the ropes. Total harvest of SMC mussel seed increased over the period 2010–2022, from 8.0 ×106 kg to 21.0 ×106 kg fresh weight. Harvest per unit substrate was remarkably stable over the years across sites, with a lower mean in Oosterschelde Bay (∼2.56 kg m−1) than in the Wadden Sea (∼3.28 kg m−1). Ropes were found to provide a greater yield per unit area than nets, but nets are less labor-intensive to use. Occurrence of density-dependent growth on the ropes was indicated by the allometric relation between mussel biomass and mussel density. A positive relation between density and growth rate suggested that competition increased with growth rate. In the growth data covering a full SMC season, we first observed a rapid numerical increase as newly settled mussels continued to grow into the measured size range. This was followed by a period of rapid numerical reduction and increasing biomass, indicating self-thinning. Finally numerical reduction stabilized and biomass increase accelerated coupled with comparatively slower shell length increase. The self-thinning occurred between approximately 2.3 mm and 11.6 mm mean shell length. Our analysis of 12 years of production data shows that SMC seed is a robust and annually more reliable alternative to wild capture fishery as a seed provisioning resource for mussel culture. Production per unit substrate does not appear to be easily amenable to further improvement. Production per unit area showed no indication of overstocking on the scale of the SMC plots, suggesting that production gains could be made by increasing substrate density.

Effects of microalgae diets on growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis

AbstractThis study evaluates the growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis fed four marine microalgae (Pavlova lutheri, Nannochloropsis oculata, Diacronema vlkianum and Rhinomonas reticulata) diets for 21 days. Black mussel is a common bivalve species that has been recognized as important for marine aquaculture with increasing production in the last two decades. The mussel group fed N. oculata showed a significantly lower survival rate than the other groups (p &lt; 0.05). Shell height, length, and width of mussels were measured. The height and length of the mussel group fed N. oculata were statistically higher than other experimental groups (p &lt; 0.05). Shell width did not show any significant differences among groups (p &gt; 0.05). The microalgae N. oculata showed the highest protein content whereas P. lutheri had the highest crude lipid content among dietary treatments. The group fed P. lutheri showed significantly higher protein, lipid, and ash contents among experimental groups (p &lt; 0.05). The D. vlkianum diet enhanced the highest docosahexaenoic acid level in black mussels. Black mussel fed P. lutheri showed the highest eicosapentaenoic acid and polyunsaturated fatty acid levels. Arachidonic acid was found to be similar among experimental groups. In our study, P. lutheri and D. vlkianum had outstanding results on survival, growth, and essential fatty acid accumulation in mussel culture.

Study of Green Mussel Eating Habits (Perna Viridis) in Aleu Naga Waters, Banda Aceh

Alue Naga waters is one of the coastal areas that have been used by the community as a residential area, a place for tourism, shrimp ponds, fish and fishing ground for oysters, green mussels and fish. Green mussels are one of the groups of the phylum molluscs in the class bivalves of the genus Perna and live attached to hard objects. This study aimed to analyze the food habits of the digestive tract of green mussels in the waters of Alue, Naga, Banda Aceh. This research was conducted from February to April 2022 in Alue Naga waters. Determination of the sampling location was carried out by purposive sampling with 3 stations. The method used for sampling green mussels was done by Random Sampling method and the number of samples taken was 45 samples, then preserved with 4% formalin. Food analysis was carried out at Marine Biology Laboratory, Faculty of Marine and Fisheries, Syiah Kuala University. The study, found that the food composition of green mussels consisted of 7 classes, namely: Baccillariophyceae class 45%, Chlorophyceae class 16%, Cyanophyceae class 19%, Dinophyceae class 3%, Coscinosiscophyceae class 10%, Zygnematophyceae class 3% and Euglenoidea 3%. Based on the highest IP (preponderance index) value, the main food of green mussels was obtained from the Baccillariophyceae class. The total length of green mussels was 79.56 mm and the average of intestinal length was 108.10 mm, the relative length of gut was 1.36. Based on the relative length of the intestine with a value of 1, green mussels are classified as omnivorous fish.Keywords: Green mussel, Food Habits, Gut

Influence of Urbanization on Patterns of Variability of Mytilus galloprovincialis Populations

Urbanization is currently one of the most widespread disturbances urgently requiring empirical data regarding its effects on coastal ecosystems. The aim of this study was to compare patterns of variability in populations of the Mediterranean mussel, Mytilus galloprovincialis, between urban and non-urban intertidal rocky shores, over a temporal scale of 12 months and multiple spatial scales (from cm to 10 s of km). For this, variance components associated with percentage cover, spat and total density, condition index, shell length and clump thickness of mussels were compared. Different patterns emerged depending on the response variable and the spatial and temporal scale. There was in general, a higher variability in urban than in non-urban shores, particularly for shell length, spat and total density that can be interpretated as a first stage of degradation, before noticing changes in mean values of these variables. Moreover, the most relevant scales of variability of total and spat density changed with urbanization (10 s of km in urban; 10 s of cm/m in non-urban). Results highlight the need for adopting proper management plans that should include the relevant spatial and temporal scales of variability; otherwise, they will fail in ameliorating urbanization effects on intertidal ecosystems.

INTENSITAS DAN PREVALENSI EKTOPARASIT Balanus sp. PADA KERANG HIJAU YANG DIBUDIDAYAKAN DALAM BAGAN TANCAP DI PERAIRAN BANYUURIP, UJUNGPANGKAH, GRESIK

Green mussels, as one of several food source in Indonesia and cultured by stake cultures, are susceptible to barnacles Balanus sp. The purpose of this study was to analyze the population of Balanus sp. related to the amount of them attached to the clam shells in various length classes of green mussels, determine the intensity and prevalence of Balanus sp. on green mussels, and analyzed the correlation between length and total weight of green mussels Perna viridis to Balanus sp. The study was conducted at Banyuurip Beach, Ujungpangkah District, Gresik Regency in June-July 2021. The sampling interval was set once every 20 days on each stake culture. The selected stake culture was determined by purposive sampling; with the sample are green mussels and Balanus sp. The variable of this research is the number of Balanus sp. attached to the shell on various classes of mussel length, intensity, prevalence, biometry and correlation between length and weight, correlation between height and total weight, correlation of width and total weight of green mussels attached by Balanus sp. Data analysis was done by the T-test and correlation. The results showed that The 1st stake culture was dominated by barnacles Balanus sp. in class VII of green mussel length (47.7 – 55.4)mm. The 2nd stake culture was dominated by barnacles in class VII green mussel length (47.7 – 55.4)mm. The 3rd stake culture was dominated by barnacles Balanus sp. in the green mussel length class VI (39.9 – 47.6)mm. The intensity of attack by Balanus sp. on green mussels showed an average value of 7±3.54 individual/tail on 1st stake, and 8±7.78 individual/tail on 2nd stake. Both are considered to be a moderate intensity. The highest prevalence of barnacles Balanus sp. was in the 1st stake, with the score of 51%±46.67, and was included in the very frequent category. As the conclusion, this results showed that the presence of the ectoparasite Balanus sp. has a moderate effect on green mussels growth, which shown a disturbance in the length and the width of green mussels.

Effects of seasonal changes and depth on growth parameters of the Mediterranean mussel (Mytilus galloprovincialis) on a shipwreck in the Eastern Mediterranean Sea

AbstractThe study was conducted between July 2018 and May 2020 to compare seasonal changes in growth parameters of the Mediterranean mussel (Mytilus galloprovincialis) at different depths in two different areas of the Northeastern Mediterranean Sea (Aegean Sea). In a preliminary study, mussels were placed in cages at different depths of an artificial reef (AR – shipwreck) and natural reef (NR). Temperature, salinity, pH, and dissolved oxygen were determined seasonally at both sites at a depth of 37 m (deepwater) and 25 m (midwater). Linear increases in length and width of mussels at the AR site were recorded, while no consistent changes were observed for mussels at the NR. There was negative correlation between the specific growth rate (SGR) and salinity (r2= 0.5098) and temperature (r2= 0.1470) at the AR site. Negative correlations were also recorded between pH and the commercial condition index (CCI) at both the AR (r2= 0.3869) and NR (r2= 0.3600) sites. Our findings show that depth had a significant effect (p&lt; 0.05) on theCCIof mussels at the NR site, while its effect was insignificant for this index at the AR site (p&gt; 0.05). This study indicates that natural reefs provide more suitable conditions for the growth of Mediterranean mussels than shipwrecks used as artificial reefs.

BIOACCUMULATION OF METALS AND EVALUATION OF GOLDEN MUSSELS ENCRUSTED ON DIFFERENT SCREENS OF NET CAGES

This study aimed to evaluate the characterization and bioaccumulation of metals of the golden mussel encrusted in the screens of net cages installed in the reservoir of Itaipu Binacional. The experimental design was completely randomized, composed of two types of screens (PVC and Bezinal) distributed on four sides (Sides I, II, III, and IV) of the net cage. The total mass, the average mass, and the dimensions (width, height, and length) of the mollusks were evaluated. The mussels adhered to the Bezinal screen presented a higher average mass, length, height, and width than those colonized on the PVC screen (p &lt;0.05). However, the PVC screen provided a greater (p &lt;0.05) total mass of encrusted mussels. Regardless of the screen used, the average mass and length of mussels had higher values on Side I (p &lt;0.05) than to the Sides II and IV, but not different from Side III. The mussels evaluated showed high levels of metals, and those encrusted in the Bezinal screen presented higher levels of Al, Zn and Cr than the individuals on the PVC screen (p &lt;0.05). The use of a Bezinal screen is more efficient than a PVC screen, as an antifouling material. Mussels with shorterlengths had a higher incidence on the PVC screen. The mussels encrusted in the Bezinal screen bioaccumulate higher content of Al, Zn, and Cr. The type of screen used in the net cages influences the mass and size of adhered mussels, as well as can interfere with the metal accumulation in the golden mussel.

Abundance data applied to a novel model invertebrate host shed new light on parasite community assembly in nature.

Understanding how environmental drivers influence the assembly of parasite communities, in addition to how parasites may interact at an infracommunity level, are fundamental requirements for the study of parasite ecology. Knowledge of how parasite communities are assembled will help to predict the risk of parasitism for hosts, and model how parasite communities may change under variable conditions. However, studies frequently rely on presence-absence data and examine multiple host species or sites, metrics which may be too coarse to characterise nuanced within-host patterns. We utilised a novel host system, the freshwater mussel Anodonta anatina, to investigate the drivers of community structure and explore parasite interactions. In addition, we aimed to highlight consistencies and inconsistencies between PA and abundance data. Our analysis incorporated 14 parasite taxa and 720 replicate infracommunities. Using Redundancy Analysis, a joint species distribution model and a Markov random field approach, we modelled the impact of both host-level and environment-level characteristics on parasite structure, as well as parasite-parasite correlations after accounting for all other factors. This approach was repeated for both the presence and abundance of all parasites. We demonstrated that the regional species pool, individual host characteristics (mussel length and gravidity) and predicted parasite-parasite interactions are all important but to varying degrees across parasite species, suggesting that applying generalities to parasite community construction is too simplistic. Furthermore, we showed that PA data fail to capture important density-dependent effects of parasite load for parasites with high abundance, and in general performs poorly for high-intensity parasites. Host and parasite traits, as well as broader environmental factors, all contribute to parasite community structure, emphasising that an integrated approach is required to study community assembly. However, care must be taken with the data used to infer patterns, as presence-absence data may lead to incorrect ecological inference.

Density and characteristics of Green mussels (Perna viridis) in Percut Sei Tuan coastal, North Sumatra, Indonesia

Percut Sei Tuan is a coastal area on the east coast of North Sumatra which has a lot of natural resource potential, one of them which is green mussels (Perna viridis). Green mussels have many benefits, namely for consumption, cultivation and bioindicator. This study aimed to determine the density, habitat location, growth pattern, frequency distribution of green mussels, physical-chemical parameters of water, a substrate of the bottom waters, and the relationship of green clams density to water and substrate parameters. The study was conducted in July-September 2020. Data analysis included density, the relationship of total length and weight of green mussels, the frequency distribution of shell lengths, and Principal Component Analysis (PCA). The results showed that the density of green mussels at stations I, II, and III were 352 ind/m2, 3 ind/m2, and 1 ind/m2, respectively. The relationship between the length and weight of green shells shows that the growth was negative allometric. The water condition, seen from the physical, chemical, and substrate parameters, was still suitable for P. viridis. Water and substrate parameters that were positively related to the density of green mussels were water temperature, nitrate, phosphate, C-organic, percentage of silt and clay. Parameters that were negatively related were salinity, pH, and percentage of sand in the bottom substrate. The present study suggested that Station I was an appropriate area for the growth and reproduction of green mussels.

The role of urbanisation in affecting Mytilus galloprovincialis.

Urbanisation is considered as one of the most critical and widespread threats to coastal marine ecosystems. The aim of this study was to compare the density, percentage cover, thickness of clumps, condition index and size-frequency distribution of Mytilus galloprovincialis between urban and non-urban shores, at nested spatial scales, in the Northern Portuguese coast. M. galloprovincialis was selected as model because it is economically and ecologically relevant. Moreover, the relationship between mussel size and the other variables (i.e. density, percentage cover, thickness and condition index) were investigated. Mussels on urban shores showed a smaller density and a greater frequency of larger individuals. A significant negative correlation between mussel length with density and with thickness of clumps was also found. Our results seem to indicate that recruitment has declined on urban shores and, as a result, intraspecific competition is also smaller, leading to more resources being available for a fewer individuals which can reach larger sizes. As mussel beds support a great biodiversity of invertebrates and provide many ecosystem services, urbanisation may have indirect effects on communities associated with mussels. Understanding the vulnerability of mussel beds to urbanisation could inform management.

Depth effect on growth and fatty acid profile of Mediterranean mussel (Mytilus galloprovincialis) produced on a longline off south Portugal

Mytilus galloprovincialis is one of recent bivalve species produced in Portugal offshore. The growth, condition index, and the fatty acid composition of the mussel produced at 2 and 13 m depth was compared in longline on the south coast of Portugal. For each depth, a monitoring of several water quality parameters such as temperature, turbidity, nutrients, and chlorophyll-a was carried out. There were no significant differences between mussel growths at different depths. On the first sampling, shell length mean was 24 mm, reaching 50 mm 9 months after. High dispersion of mussel length was observed due to slow growers. The condition index shows a typical seasonal variation, with high values in autumn and late spring and minimum values in January. Analysis of fatty acids did not reveal differences at both depths and DHA levels (8.71 mg/g) were generally higher than EPA (5.90 mg/g). The water quality revealed few differences in the environmental conditions in the water column, which may explain the similarities between the quality of mussels produced at different depths. Based on these data, the mussel offshore production in that area can be done at this range of profundities 2 and 13 m, without affecting growth and fatty acid composition.

Die‐offs of the endangered pearl mussel Margaritifera margaritifera during an extreme drought

Abstract Droughts may be responsible for important ecological impacts in freshwater ecosystems, including the death of rare species. This study assessed the mortality of the endangered pearl mussel Margaritifera margaritifera (Linnaeus, 1758) in the Mente, Rabaçal and Tuela rivers (north west of the Iberian Peninsula) during the extreme summer drought of 2017. Mortality occurred as a result of the low river flow, which led to mussel stranding near the banks and consumption (by predation or scavenging) by wild boar Sus scrofa (Linnaeus, 1758). Mortality differed across sites. The shell lengths of live mussels (measured before the drought) and dead mussels significantly differed in the Rabaçal River, but not in the Mente and Tuela rivers. Extreme droughts are predicted to increase in number and intensity in the future, and possible impacts on rare species such as M. margaritifera should be carefully monitored. Several M. margaritifera populations in Iberia (and elsewhere) may now be at increased risk, and measures should be implemented in order to mitigate the impacts of future extreme droughts.

On the banks of the Red Cedar: toward socio-ecologically robust riparian management in an iconic Michigan river

Land use is continually evolving in river watersheds and riparian zones, particularly in areas containing dense human populations requiring infrastructure development. Land use planners in south-central Michigan, USA, are challenged to balance infrastructure needs with the ecological integrity of the iconic Red Cedar River, which flows through the Michigan state capital (Lansing) and surrounding suburban and rural areas and supports freshwater diatoms, mussels, fishes, and other organisms. Although land use goals in the Red Cedar River watershed include protecting riverine biodiversity, decision-makers need a systematic method for predicting and mitigating effects of land use change on the river ecosystem. We developed a framework for evaluating habitat associations of diatoms and native unionid mussels in the Red Cedar River using field collections and mixed-effects modeling to facilitate socio-ecologically informed riparian management. Diatoms were significantly more abundant and genus-rich in riffles and pools than runs, whereas mussels were more abundant in riffles than pools, with intermediate run abundance. Diatom relative abundance was most affected by pH (+ effect), depth (+), and water temperature (+), similar to diatom genus richness (pH and depth +). Mussel relative abundance was best explained by depth (–), pH (+), and percent forest cover (+), similar to mussel length (depth +, pH –). Results from this study underscore riparian management strategies for optimizing forest cover, depth, and pH to promote ecologically favorable conditions for diatoms and mussels in the Red Cedar River (e.g. stable, near-neutral pH; diverse tree species with ≥60% forest cover). Advancing understanding of aquatic biota and their habitats, this research provides a foundation for socio-ecologically balanced land use planning in the Red Cedar River and other riverine ecosystems.

Food Habits of Flightless American Eiders (Somateria mollissima dresseri) in Québec, Canada

Abstract We provide the first quantitative study on the diet of Somateria mollissima dresseri (American Eider) undergoing the flightless wing molt. Twenty-nine adult females in wing molt were collected in the St. Lawrence Estuary and Gulf of St. Lawrence, QC, Canada. We identified a total of 510 prey items comprising 6 species of molluscs, echinoderms, and crustaceans from the esophagus and proventriculus of 15 birds. Mytilus edulis (Blue Mussel) was the most important prey for eiders as it occurred in 80% of the gullets and represented nearly 95% of the total aggregate prey mass, confirming the importance of this prey item for American Eiders throughout the annual cycle. The mean length of mussels consumed by eiders in the Estuary was nearly 4 times that of mussels ingested by birds in the Gulf; factors driving this difference remain unknown. Accordingly, we suggest that future work on the foraging ecology of flightess American Eiders examine how the size of mussels consumed by birds may be influenced by...

Estimation of Apparent Survival, Detectability, and Density of Three Federally Threatened Mussel Species in a Small Watershed

Almost half of the mussel species in North America are imperiled, and eight species found in the eastern Gulf Coastal Plain drainages were recently federally listed. Information regarding the status of known populations of these species is either limited or outdated. Three sites in the Choctawhatchee River watershed (southeast Alabama), where federally threatened mussel species were known to occur, were sampled for mussels eight times each over 4 mo. Three federally threatened species, Fusconaia burkei, Hamiota australis, and Pleurobema strodeanum, and one common species, Elliptio pullata, were individually tagged and released using a robust mark-recapture sampling design. Each species-site combination having sufficient sample sizes was analyzed using a set of six candidate mark-recapture models chosen a priori, and estimates of apparent survival, detectability, and density were derived using the computer program MARK to average models. A total of 820 mussels, 427 of which are listed as federally threatened or endangered, were tagged over eight sampling occasions at three sites. Apparent survival of E. pullata varied among sampling occasions (0.96–0.99), while threatened species tended to have nearly constant survival. Detectability increased with mussel length for E. pullata at all sites (0.07–0.82), but with the exception of P. strodeanum at 8M1, length did not affect detectability of threatened species (0.11–0.52). Densities of threatened species (0.05–1.0 individuals/m2) were typically lower than those of E. pullata (0.15–1.78 individuals/m2) at each site. These data offer insights into the current status of known populations of threatened species at three sites in the Choctawhatchee watershed and will serve as a baseline against which the future status of these populations can be measured. These data also demonstrate the potential viability of using these methods for long-term monitoring of these populations.

Quantification of Freshwater Pearl Mussel Entrainment Velocities and Controlling Factors; a Flume Study

Increased flood frequency and magnitude are predicted for Scotland, and the country contains several of the world's largest recruiting populations of freshwater pearl mussel (Margaritifera margaritifera). This study provides a unique flume experiment to measure the near-bed velocities required for freshwater pearl mussel entrainment and factors affecting their movement. It represents the first quantitative attempt at examining the precise water velocities at which freshwater pearl mussel become vulnerable to displacement during high flow events. Measurement of the near-bed velocities at which the mussels moved was undertaken using an indoor recirculating flume. The effect of the different parameters (bed substrate, mussel burial depth, mussel curvature, mussel alignment, shell curvature and the presence of a simulated foot) on entrainment velocity was tested in the flume and their significance was verified using Kruskal–Wallis and Mann Whitney tests. Bed substrate was found to have the biggest influence on mussel entrainment velocities with averages of 0.86 ms−1, 0.95 ms−1, 1.01 ms−1 and 1.42 ms−1 for sand, gravel, mixed bed and boulder beds respectively. Stepwise logistic regression showed that bed substrate, foot presence, mussel length, mussel burial depth and shell curvature were sufficient to explain mussel entrainment velocity. These findings provide valuable information for the modelling of freshwater pearl mussel dynamics in streams systems and assessing the vulnerability of endangered mussel populations to higher flows associated with climate change in Scotland. Copyright © 2015 John Wiley & Sons, Ltd.

Size-dependent changes in toxicity of Perna viridis mussels exposed to natural populations of Pyrodinium bahamense var. compressum

The mussel Perna viridisis used in the Philippine saxitoxin monitoring program as an indicator organism for the presence of saxitoxin in shellfish in an effort to assess concentration beyond a level considered safe for public consumption. Saxitoxin bioaccumulates in mussels through ingestion of saxitoxin-producing algae Pyrodinium bahamense var. compressum(Pbc). This study focuses on the relationship between mussel length and mussel toxicity in mussels exposed to a natural bloom of Pbc. Mussel toxicity was assessed weekly in a 134-day sampling period using Receptor Binding Assay (RBA). Smaller mussels are more toxic than larger mussels at low Pbc cell density (≈102 cells/L) and the reverse is true at higher Pbc cell density (≈5×103 cells/L). These results can be useful in developing strategies for the collection of mussel samples in a toxic algal bloom monitoring program.