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In this study, we investigated the impact of water temperature on pearl formation and the molecular mechanisms underlying this biomineralization process in the mussel Hyriopsis cumingii. In the laboratory experiment, recipient mussels received saibo grafts from donor mussels and then were cultivated at five temperatures (16, 20, 24, 28, and 32 °C) for 1 month. We found that speed of pearl formation varied with water temperature: there was no visible pearl granules at 16 and 20 °C, tawny pearl granules were collected at 24 °C and lustrous pearl granules were collected at 28 and 32 °C. The expressions of several nacreous layer matrix protein genes (hic22, hic24, HcTyr Hc-upsalin and Hcperlucin) at 28 °C and 32 °C were peaked on day 28, and the expressions of other nacreous layer matrix protein genes (hic52 and hic74) on day 28 were significant higher than day 14. In the natural environment, pearl deposition rate also increased as water temperature rose, and the optimum range for pearl growth in H. cumingii was between 28.3 and 30.3 °C. Expression of the prismatic layer-related matrix protein genes hic31 and both prismatic and nacreous layer-related matrix protein gene silkmapin was significantly high in winter, and expressions of the nacreous layer-related matrix protein genes (hic24, hic74, HcTyr, Hc-upsalin and Hcperlucin) were always higher during higher temperature seasons compared with winter. These results indicate that high water temperature can speed up pearl formation and further regulate matrix protein secretion to accelerate pearl nacre deposition.

Understanding dreissenid mussel population dynamics and their impacts on lake ecosystems requires quantifying individual growth across a range of habitats. Most dreissenid mussel growth rates have been estimated in nutrient rich or nearshore environments, but mussels have continued to expand into deep, cold, low-nutrient habitats of the Great Lakes. We measured annual quagga mussel (Dreissena rostriformis bugensis) growth at 15 m, 45 m, and 90 m in Lake Ontario using caged mussels near Oswego, New York, USA from June 2018 to May 2019. Quagga mussel growth (starting size 12 mm) was greatest at 15 m (mean shell length increase = 10.2 mm), and was lower at 45 m (5.9 mm) and 90 m (0.7 mm). Caged mussels were obtained from near the 90-m site and those reared at 15 and 45 m developed thicker shells than those that were caged at 90 m. We observed relatively high colonization by quagga and, to a lesser degree, zebra mussels (Dreissena polymorpha) at 15 m, very few colonizers at 45 m, and none at 90 m. Higher growth potential, but low natural mussel densities observed at 15 m and 45 m suggest factors other than growth limit dreissenid abundance at these depths. The relatively slow dreissenid growth rates observed in offshore habitats are consistent with the gradual abundance increases documented in these zones across the Great Lakes and suggest new mussels that become established in these habitats may contribute to ecosystem effects for decades.

Uroporphyrinogen III synthetase (UROS) is an important enzyme involved in the structural formation of porphyrin, which is responsible for color intensity. A UROS homolog was isolated and characterized from the pearl mussel, Hyriopsis cumingii (HcUros). The HcUros cDNA was 858 bp in length with an open reading frame that encoded a 285 amino acid protein, which contained a conserved HemD domain. HcUros exhibited widespread tissue distribution, displaying particular enrichment in the mantle and haemolymph of purple mussels, compared to white mussels. In situ hybridization of HcUros in mantle tissue demonstrated that it was specifically expressed in the dorsal epithelial cells of the mantle pallia. Additionally, HcUros expression was upregulated following implantation of the pearl sac to produce pearls. The data suggest that HcUros contributes to shell pigmentation, and nacre formation and coloring in H. cumingii.

Funder: Corpus Christi College, University of Cambridge; doi: http://dx.doi.org/10.13039/501100000591, Funder: St Catharine's College, University of Cambridge; doi: http://dx.doi.org/10.13039/501100008101, Biological early warning systems (BEWSs) monitor the behaviour or physiology of living organisms as an indirect mechanism to sense local environmental changes, and have become a widely established tool for monitoring water pollution. Complementary to conventional chemical and physical techniques, their strength lies in the ability to continuously monitor water quality, providing direct and rapid warning of toxic discharges. Bivalve molluscs (mussels and clams) are ideal sensing organisms for BEWSs, owing to their: high water filtration capacity; sensitivity to numerous, diverse pollutants; considerable longevity; high abundance; and wide range of physical responses to environmental change. Two behavioural metrics of bivalves have dominated in ecotoxicological studies, and consequently spawned development into BEWSs: valve movements, typically measured using electromagnetic techniques; and bivalve cardiac activity, typically measured using infrared photoplethysmography. However, other, less studied bivalve behaviours may exhibit pollutant impacts, including shell growth and dissolution, premature egg/larval release, horizontal movement, and burial. Such metrics may, with further research, provide bases for future BEWSs, some through current valve movement monitoring technology, others potentially through acoustic telemetry. Future bivalve-based BEWSs may become more informative and sensitive through the greater nuance that lies in integration of different metrics simultaneously and/or multi-species monitoring. Future directions may seek techniques that reduce disturbance to bivalves and enable observation of a more natural mode of behaviour, through using untethered, or entirely unequipped, specimens. With rigorous controls for individual- and population-level variation, bivalves have great power as biosensors and, bolstered by the scope for future advancements, this field has the potential to make significant contributions to future water quality management.

Mytella strigata (Hanley, 1843) is an invasive mussel species that has rapidly spread in China in recent years. Here, we tested the utility of three mitochondrial gene fragments, COI, 12S, and 16S, and two nuclear gene fragments, D1 28S and 18S-ITS1, for characterizing the levels of genetic diversity among and within populations using 191 M. strigata specimens collected in China to aid ongoing efforts to identify the origin of the invasion as well as molecular genetic studies. M. strigata exhibited two sex-associated haplogroups according to the COI and 12S sequences. The ratio of female-lineage to male-lineage COI and 12S sequences was 149:22 and 72:7, and the genetic distances between haplogroups were 6.56 and 9.17, respectively. Only one haplotype was detected among the 18S-ITS1 sequences (413 bp), and three haplotypes were detected among the D1 28S sequences (296 bp). The haplotype diversity of both the female-lineage COI and 12S sequences was greater than 0.5, and the nucleotide diversity of the 12S, 16S, D1 28S, and 18S-ITS1 sequences was less than 0.005 in all six populations in China. Our findings indicated that COI is the most useful gene fragment for genetic diversity studies of M. strigata populations; D1 28S and 18S-ITS1 sequences would be useful for species identification because of their low intraspecific diversity. Our genetic analysis of the COI sequences revealed Colombia as the most likely origin of M. strigata in China and showed that the invasive populations in China have recently experienced or are currently experiencing a population bottleneck.

12 pages, 6 figures.-- Under a Creative Commons license, As filter-feeding bivalves, mussels have been traditionally studied as possible vectors of different bacterial or viral pathogens. The absence of a known viral pathogen in these bivalves makes it particularly interesting to study the interaction of the mussel innate immune system with a virus of interest. In the present work, mussels were challenged with viral haemorrhagic septicaemia virus (VHSV), which is a pathogen in several fish species. The viral load was eliminated after 24 h and mussels evidenced antiviral activity towards VHSV, demonstrating that the virus was recognized and eliminated by the immune system of the host and confirming that mussels are not VHSV vectors in the marine environment. The transcriptome activating the antiviral response was studied, revealing the involvement of cytoplasmic viral sensors with the subsequent activation of the JAK-STAT pathway and several downstream antiviral effectors. The inflammatory response was inhibited with the profound downregulation of MyD88, shifting the immune balance towards antiviral functions. High modulation of retrotransposon activity was observed, revealing a mechanism that facilitates the antiviral response and that had not been previously observed in these species. The expression of several inhibitors of apoptosis and apoptosis-promoting genes was modulated, although clear inhibition of apoptosis in bivalves after severe viral infection and subsequent disease was not observed in this study. Finally, the modulated expression of several long noncoding RNAs that were correlated with genes involved in the immune response was detected, This work was supported by the Ministerio de Ciencia e Innovación (PID2021-124955OB-I00) and Xunta de Galicia (IN607B 2022/13). AS was supported by a Spanish AEI/EU-FSE predoctoral contract PRE2019-090760

Invasive dreissenid mussels (Dreissena polymorpha and Dreissena bugensis) have a profound effect on the total phosphorus (TP) budget in Lake Ontario, which in turn influences ecological processes such as the resurgence of the benthic alga Cladophora. A validated three-dimensional integrated hydrodynamic and ecological modeling framework is applied to quantify the impact that dreissenids have on the spatial and species distribution of TP in the lake. Model results for April to September 2013 show that dreissenids decrease TP in the water column by about 1812 metric tonnes, which is about 60% of the tributary TP loading to the lake. This reduction in TP affects other processes controlling its distribution. Physical transport of TP from nearshore to offshore waters is reduced, and the amount of TP involved in chemical reactions is reduced, while TP processed by biological transformations is increased. This study provides the first attempt to quantify the TP budget changes in Lake Ontario by dreissenids using numerical modeling, and findings of this study can be generalized to other lakes with similar conditions.

Recently, there is a greater interest for the development of mussel Mytilus edulis hatcheries, particularly for the production and commercialization of triploid bivalves. The aims of this study wer...

Conservation of ecosystem engineers, which modulates the surrounding habitat by causing physical state changes in biotic or abiotic materials, is important for maintaining the functional integrity of ecosystems. This study examined the effects of endangered freshwater pearl mussels (Margaritifera laevis and M. togakushiensis) on channel morphology and flow in a low-gradient sandy river. For this, we performed a field removal experiment of mussels using three treatments in twelve 10-m reaches. Mussel abundance and biomass, and three physical variables were measured before, immediately after, and two months to one year after the treatments. Mussel removal resulted in channel degradation with a 60% increase in flow depth, a 30% decrease in current velocity, and a 50% reduction in the width-to-depth ratio two months after the treatments, whereas minimal changes were measured in reaches with mussels. The results indicated that pearl mussels act as an ecosystem engineer affecting the channel morphology and flow of sandy rivers. The conservation of the pearl mussel populations is key to preserving their far-reaching benefits in ecosystem integrity including habitats for other various organisms.

Analysis of long-term data (1987–2019) was carried out on the morphology and autecology of the benthic colonial large-cell species Striatella unipunctata (Lyngbye) C. A. Agardh, 1832 in the microphytobenthos of the Black Sea and Sea of Japan, including water areas of specially protected natural areas of Russia. The species is widely found on natural and artificial substrates in the Black Sea year-round, and in the Sea of Japan, at a water temperature down to −1.5 °C. St. unipunctata quantitative data were determined by direct cell counting in the Goryaev camera under light microscopes (LMs) Biolam L-212, Axioskop 40, and Olympus BX41. Species morphology, phytogeography, and ecology are described. The cell size range of populations is presented: for the Black Sea, valves 25–148 µm long, 8–22 µm wide, frustules 36.3–50.4 µm wide, 18–24 fibulae in 10 µm, and 7–8 girdle bands in 10 µm; for the Sea of Japan, valves 85–125 µm long, 12–21 µm wide, 7–8 girdle bands in 10 µm, 20–25 fibulae in 10 µm, frustules 32.0–34.3 µm long, 10–11 µm wide, and 25 fibulae in 10 µm. For the first time, St. unipunctata valves and frustules were studied in vivo under LMs, and frustule ultrastructure, under a scanning electron microscope (SEM). For the first time, quantitative indicators of the species populations from the Black Sea and Sea of Japan were compared. The morphology of the frustule ultrastructure of St. unipunctata was studied under a Hitachi SEM, model SU3500 (Japan), in Leica EM ACE200 gold-palladium-coated samples. In the Kazachya Bay of the Black Sea near the Oceanarium, the absolute maximum abundance was recorded – 41.6·10³ cells·cm−2 with a biomass of 1.73 mg·cm−2 in January (t = +6.9 °C) in the epizoon of the cultured mussel Mytilus galloprovincialis Lamarck, 1819 at a depth of 0.5 m at excessive organic pollution of water. The minimum values were of 0.26·10³ cells·cm−2 and 0.011 mg·cm−2, respectively, in July (t = +23.5 °C) at a depth of 2.5 m. In the Paris Bay (Russky Island) of the Sea of Japan in the water area of the Marine Mammal Research Base of the Primorsky Oceanarium (Vladivostok), the abundance in the asbestos plates periphyton was of 207·10³ cells·cm−2 in the summer. For the first time, unique micrographs of the species in vivo were obtained under a LM, and of purified frustules – under a SEM.

Mussels are a group of bivalves that includes the dominant species of shallow-sea, freshwater, and deep-sea chemosynthetic ecosystems. Mussels cling to various solid underwater surfaces using a proteinaceous thread, called the byssus, which is central to their ecology, physiology, and evolution. Mussels cluster using their byssi to form “mussel beds,” thereby increasing their biomass per unit of habitat area, and also creating habitats for other organisms. Clustered mussels actively filter feed to obtain nutrients, but also ingest pollutants and suspended particles; thus, mussels are good subjects for pollution analyses, especially for microplastic pollution. The byssus also facilitates invasiveness, allowing mussels to hitchhike on ships, and to utilize other man-made structures, including quay walls and power plant inlets, which are less attractive to native species. Physiologically, mussels have adapted to environmental stressors associated with a sessile lifestyle. Osmotic adaptation is especially important for life in intertidal zones, and taurine is a major component of that adaptation. Taurine accumulation systems have also been modified to adapt to sulfide-rich environments near deep-sea hydrothermal vents. The byssus may have also enabled access to vent environments, allowing mussels to attach to “evolutionary stepping stones” and also to vent chimneys.

Larvae (glochidia) of Unionida mussels form obligate symbiotic associations with host fish to complete their life-cycle. To identify previously unknown host fish associations for the threatened New...

Horse mussels Modiolus modiolus can occur in dense aggregations and form areas of ecological and biological significance. In the Bay of Fundy, Canada, aggregations of horse mussels are associated with flow parallel bedforms, and this area is under consideration for designation as a sensitive benthic area which would provide protective measures. Basic demographic information is required to inform the development of effective conservation and management strategies and although general life-history characteristics of M. modiolus are known, detailed quantitative demographic information on this population is limited. The objective of this study was to characterize the population structure of horse mussels in the Bay of Fundy and assess change in key demographic characteristics since the last study in this area in 1997/1998. There have been significant changes in the population since 1998: the 2017 population contains larger, older, mature individuals, with significantly more females; 35% of the current population is over 20 yr of age. Direct evidence that this population has been impacted by bottom-contact fishing gear was also observed. Consistent with M. modiolus populations worldwide, this population demonstrates life-history traits (e.g. slow growth rates, late age of maturity, long lifespan) that make it sensitive and susceptible to disturbance. Coupled with the knowledge that this population overlaps with significant fishing activity, this study supports the assumption that this population is vulnerable to bottom-contact fishing and that recovery from adverse impacts would be slow and uncertain.

In Brazil, Anodontites trapesialis is a mussel species that occurs spontaneously in fish breeding sites. This species feeds on the remains of cultural treatments of other aquaculture species. The objective of the work is to understand the bromatological composition of mussel A. trapesialis. Individuals were selected to compose three samples of 500 g each of A. trapesialis for chemical composition, with viscera and viscera + shells being evaluated. The species presented 40.42 to 62.76 g of viscera per individual with a moisture content of 5.16% for viscera + shells and 86.5% for viscera. The mussel contains 42.6 and 12.96% crude protein, 3.16 and 1.76 of ether extract, 0.76 and 2.5% of crude fiber for viscera and viscera + shells. The total digestible nutrients were 74.16 and 36.96% for viscera and viscera + shells and 18.43 and 52.83% of mineral material for viscera and viscera + shells. A. trapesialis has relevant characteristics in its chemical composition as high protein content that gives the species potential for the human, animal, and other byproducts production.

This study is designed to monitor the zootechnical performance of the African mussel "Perna perna" in submerged longline at the Boutalha area in Dakhla Bay, for two production cycles carried out during the years 2019 and 2020. The first rearing cycle started on March the 26th, 2019 with a spat of mean size 19.1±3.23 mm, and a mean weight of 0.79±0.32 g. While the second cycle was launched on January the 6th, 2020 by rearing the spat of mean size 22.31 ± 3.12 mm and mean weight of 2.24±1.52 g. A sampling of mussels was done monthly for the growth monitoring and the daily monitoring of physicochemical parameters of the farming medium. The results showed that the growth rate was almost similar for both rearing cycles, with a gain in length/ weight of about 6.57mm/2.75g and 5.98mm/2.86g, respectively for the first and second cycles. The live weight/growing rates recorded respectively for the first and second cycles, once the commercial size (60mm) was obtained, were 20.01±5.24g/ 19.97% and 22.28±6.65g/16.83% achieving a filling rate of 38.07%/37.94%, thereafter the rearing period was 6.5 months/7 months. Regarding the production and biomass, the results revealed that the biomass per longline exceeded the value of 9.5 tons for both cycles.

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

Considering the importance of hemocyte characterization for immunological studies, this work aimed to characterize the hemocyte types of Perna perna mussels combining transmission electron microscopy and flow cytometry with the classical optical microscopy. The results indicated four type of hemocytes: hyalinocytes, semigranulocytes, granulocytes and blast-like cells.

Studies of climate change effects on individuals and populations are mostly couched in terms of lethal temperature limits, but 2 other elements make predictions difficult: the effects of sublethal stress and intraspecific variability. Sublethal stress, such as exposure to highly variable temperatures, can cause carryover effects that influence how an animal responds to subsequent events and its long-term fitness. Additionally, intra-specific genetic variability can allow more complex species responses to climate change. We used 2 genetically distinct lineages of the intertidal mussel Perna perna to investigate the effects of sublethal temperature variability and genetic identity on thermal sensitivity estimates derived from standard metabolic rate measurements. Mussels were exposed to one of 3 acclimation treatments: measurements done immediately after collection (i.e. field fresh), or exposure to 2 wk of either constant temperature or fluctuating temperatures. The mussels were then exposed to rising temperatures within the range normally experienced in the field while oxygen consumption was recorded. We found no effect of lineage or treatment on the aerobic standard metabolic rate of mussels, but Q10, a proxy for thermal sensitivity, was influenced by treatment. While Q10 values under constant temperature did not differ significantly from those for field-fresh mussels, both were significantly lower than for fluctuating temperatures. Thus, temperature variability increased thermal sensitivity, but our results indicate that this was independent of genetic identity. Chronic increased temperature variability and repeated exposure to high (but sublethal) temperatures under climate change are likely to increase mussel temperature sensitivity and decrease performance. Such alterations to fitness are expected to occur before animals are exposed to lethal temperatures.

Mussels provide important ecological functions in freshwater ecosystems but the associations between Amazonian mussels, macroinvertebrate assemblage and habitat quality remain poorly understood. We investigated whether changes in macroinvertebrate assemblage structure and ecological functioning were associated with mussel presence. We compared sites with and without mussels, with similar habitat conditions, in an eastern Amazonian river, using field measurements of macroinvertebrate structure, hydrological variables and sediment organic matter, and laboratory experiments of mussel clearance rate and biodeposition. Sites with mussels were associated with higher macroinvertebrate abundance and number of taxa, especially for trichopterans Marilia (shredder), Oecetis (predator) and Antarctoecia (collector). Decreased chlorophyll-a in the water column and increased sediment organic matter were positively associated with mussel presence. Laboratory experiments corroborated these patterns, which were stronger with higher mussel density. Mussel filtration and biodeposition may be associated with habitat quality for other invertebrates by lowering phytoplankton density in the water column and increasing inputs of sediment organic matter. This suggests a potential role of freshwater mussels in ecosystem function associated with high taxonomic and functional diversity in the macroinvertebrate assemblages of an eastern Amazon river, enhancing the already high mussel conservation priority.

A sample of 30 thick-shelled river musselsUnio crassusPhilipsson (Unionida: Unionidae) was collected from the River Sauer in Luxembourg to acquire data on parasitic infestations of the mussels. Among other parasites, different development stages of freshwater mites were collected from the gills and the mantle of the mussels and were documented with bright-field, stereo, and confocal laser scanning microscopy and microscopic X-ray computed tomography. The retrieved data allowed a morphological description of larvae and female adults of the mites and assigning them to the genusUnionicolaHaldeman (Trombidiformes: Unionicolidae) and the subgenusPentataxThor. Additionally, adult stages and larvae were barcoded by sequencing a section of the mitochondrialCOIand18SrRNA genes. This resulted in 4 new, similarUnionicolalineages from the adult stages, which differ in at least 14.7% (uncorrectedpdistance) from those already published. Barcoding of larval DNA was not successful. The comparison with known European species of the genusUnionicolaand analysis of the barcoding results allowed the proposal of a new species of the genusUnionicola.The species was namedUnionicola sauerensissp. nov. after the River Sauer in Luxembourg, where the infested mussels were collected.

Modiolus kurilensis F. R. Bernard, 1983 (Mollusca, Bivalvia) can be found in Peter the Great Bay (the Sea of Japan) both on soft and hard substrates, often together with the mussel Crenomytilus grayanus (Dunker, 1853); it is a promising commercial species. This mollusc is a by-catch when catching C. grayanus. The aim of the work was to assess M. kurilensis resources and settlement structure in Peter the Great Bay. The research was carried out in 2007–2018 by scuba-diving methods of hydrobiological research at the depths of down to 20 m. In total, the data were analyzed for 2,409 stations; M. kurilensis was found at 308 stations. Sampled molluscs were measured and weighed. The material was processed statistically and cartographically; the mean biomass and distribution density of M. kurilensis settlements were calculated. In total, 870 horsemussels were analyzed for studying the settlement structure. The following indicators were estimated: index of settling (ratio of the abundance of juvenile molluscs with a shell length of 1–30 mm (spat, yearlings) to the abundance of adults with a shell length of > 50 mm); index of maturation (ratio of the abundance of pre-reproductive molluscs with a shell length of 35–50 mm to the abundance of adults with a shell length of > 50 mm); index of replenishment of the commercial stock (ratio of the abundance of molluscs with a shell length of 95–100 mm (recruits) to the abundance of molluscs of commercial length of > 100 mm). The state of M. kurilensis population in Peter the Great Bay is stable: the ratio of molluscs of non-commercial length varies 52 to 86 % in most settlements, which indicates active natural reproduction and regular replenishment of the benthic part over many years. Replenishment of settlements with settling of both spat and yearlings depends on the presence of pelagic larvae in the plankton, while replenishment of the mature molluscs depends on favorable conditions for juvenile survival. In 2007–2018, the mean values of the indices of settling and maturation in M. kurilensis settlements in Peter the Great Bay were of (0.18 ± 0.07) and (0.05 ± 0.01), respectively. M. kurilensis resources are estimated at 27.1 thousand tons, and the commercial stock – at 16.4 thousand tons. The annual replenishment of the commercial stock of M. kurilensis in Peter the Great Bay is possible in a volume of more than 3 thousand tons. The mean value of the index of replenishment of the commercial stock is of (0.21 ± 0.03).

The irregular supply of natural mussel seed for aquaculture has seen an increase in the establishment of hatcheries to produce a reliable source of mussel seed. While many of the factors influencing fertilisation and early survival of hatchery-produced mussel larvae have been explored, little is known about the factors influencing the success of larvae during settlement and development under hatchery conditions. This study examines the effects of feed concentration, airflow rate, rope type and larval stocking density on the growth, settlement and development of Australian blue mussel larvae under hatchery conditions. Manipulation of feeding concentration at the time of settlement (25,000 cell ml−1, 50,000 cell ml−1, 100,000 cell ml−1 and no feed) had little effect on growth, settlement and development of larvae, due to reduced feeding behaviour during this period. In contrast, high airflow rates were found to increase settlement and larval development but did not influence growth. Larvae also show significantly greater settlement rates on more filamentous ropes compared with those on less filamentous rope types. We also detected a strong inverse relationship between larval density and size at settlement, suggesting density-dependent competition may reduce growth under hatchery conditions. These results indicate optimal conditions for settlement and development of mussel larvae in hatcheries may be achieved by decreasing feed concentration during the settlement phase, increasing airflow rates and maintaining moderate densities of larvae. These optimised hatchery conditions have the potential to improve yields while simultaneously reducing production costs.

Environmental DNA (eDNA) sampling is a powerful tool for monitoring aquatic organisms and has the potential to make significant contributions to the conservation of freshwater mussels. Conv...

Freshwater drum (Aplodinotus grunniens) may be a predator of the invasive zebra mussel (Dreissena polymorpha), which established in Lake Winnipeg in 2013. In this study, the diets, trophic position, and growth of 51 freshwater drum collected in 2019 (six years post-zebra mussel invasion) were compared to 64 freshwater drum sampled in 2000. Benthic insect larvae were the dominant food items in both years. Although mollusks occur in high densities in Lake Winnipeg, they were only consumed by a few freshwater drum in either sample year. Zebra mussels were not a frequent prey item in 2019 as they were only consumed by four of the sampled freshwater drum. Stable isotope analysis of white muscle tissue yielded similar δ13C and δ15N values in both years and were consistent with a benthic, insectivorous diet. Length-at-age data derived from otoliths revealed that the 2019 population had at least an equal growth rate to the 2000 population. Weight-at-length data suggested that fish condition was greater in 2019 than in 2000, which coincided with increased benthic macroinvertebrate density in Lake Winnipeg. Based on these findings, Lake Winnipeg freshwater drum continue to feed predominantly on insect larvae and not zebra mussels.

Assessing effects of species identity and richness on ecosystem function for globally imperiled fauna is imperative to understand how species loss affects freshwater ecosystems. Here, we ex...

Large-scale losses of spat are commonplace during the early stages of mussel aquaculture costing the industry millions in lost production. The dominant cause of this poor spat retention is thought to be secondary settlement behavior, whereby spat detach from farming substrata in an effort to relocate to another site. One approach that could be used to reduce these spat losses is to use natural substrates, such as macroalgae, to which wild mussel spat commonly attach. These natural substrates are often associated with chemical and morphological settlement cues. In New Zealand, the majority of mussel spat used by the aquaculture industry are harvested from the wild while attached to a range of species of macroalgae and other general debris (referred to as Kaitaia spat material). The filamentous morphology and chemicals released by some of these macroalgal species, including the rhodophyte Pterocladia lucida, have been shown to improve mussel settlement. Therefore, in this study, the spat of the green-lipped mussel, Perna canaliculus, were seeded onto aquaculture grow ropes with and without P. lucida to determine whether the presence of the macroalgae would improve the retention of the mussel spat. The presence of P. lucida increased spat retention by 33% relative to a control over 12 weeks and also increased the proportion of spat (by 16%) that successfully migrated away from biodegradable seeding substrata onto the permanent structure of the grow rope. The timing of spat losses relative to the breakdown of seeding substrata is consistent with the macroalga producing chemical cues that encourage spat settlement. In contrast, no spat attached directly to the P. lucida suggesting morphology of the macroalga was not playing a role in the observed increase in spat retention. These results suggest that there may be chemical cues present in P. lucida that may have the potential to be used to help resolve the problem of poor spat retention in green-lipped mussel aquaculture.

The metabolic activity of unionid mussels influences the oxygen fluxes and other physical and chemical characteristics in aquatic systems. Unionid oxygen consumption rate during digestion and its dependency on food availability is understudied. In laboratory conditions, we quantified the oxygen consumption rate of Anodonta anatina and Unio pictorum in response to algal concentration—0.05, 6.0 and 12.0 mg of Ash Free Dry Mass of Chlorella vulgaris L−1—and mussel dry soft-tissue mass at 19 ± 1°C. Following a 5-h feeding-period, the oxygen consumption rate (mg O2 h−1) increased with algal concentration and mussel dry mass in both species during a 2-h digestion-period. The mean oxygen consumption per gram of dry mass (mg O2 gDM−1 h−1) increased with the algal concentration in both species. The oxygen consumption rate of A. anatina was significantly greater than that of U. pictorum at a given algal concentration. The A. anatina oxygen consumption per gram of dry mass decreased with increasing dry mass. Oxygen consumption rate during digestion shows inter-specific differences and is dependent on food availability. The findings inform the species-specific quantification of oxygen consumption, and validation is required in in situ conditions.

Many freshwater mussel species are highly endangered. Knowledge of their occurrence and distribution is a crucial prerequisite for their conservation. The use of environmental DNA (eDNA) is...

Mytilus galloprovincialis, a globally successful marine alien invasive species, occupies all artificial hard substrata in the embayment of the Knysna estuary, South Africa. The current study compar...

Biofouling has been reported to be both harmful and innocuous on the growth and survival of cultured bivalves. If harmful, it could increase the operational cost substantially in an attempt to mitigate it. The study investigated the effect of sedentary biofoulers on the growth and survival of Crassostrea tulipa cultured on coconut shell and oyster shell cultches in the Densu Delta, Ghana, from December 2017 to July 2018. Physico-chemical parameters were monitored. Environmental temperature (26.4 ± 0.07 °C–29.5 ± 0.50 °C) and pH (7.2 ± 0.01–8.8 ± 0.01) were found to be within optimum levels for oyster propagation. The low levels of salinity (0.2 ± 0.01 ‰) and DO (0.6 ± 0.01 mg/l) and high turbidity (31.4 ± 2.91 NTU) could explain the observed high mortality of cultured oysters in July 2018. The observed fouling organisms were Fistubalanus pallidus (barnacle), Brachidontes sp. (mussel), Ficopomatus sp. (tube worm), Chaetomorpha antennina (green alga), and sea anemone. Oysters cultured on the undersurface of biofouled oyster shell cultches exhibited significantly faster growth than their cleaned counterparts but comparable on the upper surfaces of the cultches. The growth of cultured oysters on biofouled coconut shell cultches exhibits faster but insignificant growth than the oysters on cleaned cultches. There was no significant difference between the survival of oysters cultured on biofouled and cleaned coconut shell and oyster shell cultches. Marketable size oysters (≥ 6 cm shell height) are attainable in 7 to 8 months for both treatments. It was concluded that biofouling had no deleterious effect on the growth and survival of oysters. Besides, given the preferred shucked oysters in the Ghanaian market, it is inessential to incur further cost to control biofoulers.

In the context of food sovereignty, it is essential to distinguish and give value to national products, especially those from artisanal production. Argentina and Chile mussel production occurs at d...

The production of blue mussels is currently reliant upon supply of wild larvae, which is a limiting factor to upscaling production. A potential solution to address this limiting factor is to develop a larval hatchery; however, costs associated with microalgal cultivation to feed the larvae account for around 30% of total costs. Microalgae are classically considered to be photoautotrophic and are cultured under light, in seawater with additional nitrate and phosphate. Many microalgae can be cultured mixotrophically, or heterotrophically, on an organic carbon source which results in an enhanced cell density and altered biochemical profile. Over the course of two feeding trials this study compares larval growth and survival employing current “industry standard” and mixotrophic “designer” microalgal feeds as diets. The “designer” feed employed proved to be as effective as the standard feed and subsequent optimisation demonstrated that a diet tailored towards the development of the larvae performs the most effectively in terms of larval growth. A sequential diet of mixotrophically cultured microalgae, where the primary component of the diet changed as the larvae increased in size, resulted in the greatest larval growth (174.35 μm) and total fatty acid content (7.20% dry weight). First-order modelling indicates that approximately ten times lower volume of mixotrophically cultivated microalgae was required to produce sufficient larval feed. Thus, mixotrophic culture has the potential to reduce the costs of microalgal cultivation and increase the profitability of a mussel larval hatchery.

The aim of this study was to determine the stock density effect on size and biomass on mussel Mytilus edulis platensis, at growth up phase ropes. These ropes were made using three initial stocking densities: 200, 300 and 400 mussels m-1 and hung on in a longline at Belvedere site on San Jorge gulf, Argentina. Stock density showed no influence on individual mussel biomass. Higher growth length was obtained at higher densities. According to these results, when the mussels are in the fattening or thinning out phase, the optimum stocking density would be 300 to 400 mussels m-1.

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