Freshwater mussel conservation: A global horizon scan of emerging threats and opportunities

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus-building Delphi technique. Our 14 priority topics fell into five broad themes (autecology, population dynamics, global stressors, global diversity, and ecosystem services) and included understanding diets throughout mussel life history; identifying the drivers of population declines; defining metrics for quantifying mussel health; assessing the role of predators, parasites, and disease; informed guidance on the risks and opportunities for captive breeding and translocations; the loss of mussel–fish co-evolutionary relationships; assessing the effects of increasing surface water changes; understanding the effects of sand and aggregate mining; understanding the effects of drug pollution and other emerging contaminants such as nanomaterials; appreciating the threats and opportunities arising from river restoration; conserving understudied hotspots by building local capacity through the principles of decolonization; identifying appropriate taxonomic units for conservation; improved quantification of the ecosystem services provided by mussels; and understanding how many mussels are enough to provide these services. Solutions for addressing the topics ranged from ecological studies to technological advances and socio-political engagement. Prioritization of our topics can help to drive a proactive approach to the conservation of this declining group which provides a multitude of important ecosystem services.     

Fish remains from the Neolithic site of El Mirador cave (Atapuerca,Spain): Seasonality and resource management

Ichthyoarchaeological analyses of the freshwater fish remains from levels 19 and 20 in El Mirador cave (Atapuerca, Spain) have been conducted. Fish were always present as a source of animal protein, although their importance in the human diet was not fully exploited by people during the Neolithic on the Iberian Peninsula. Two principal goals are treated here: a taxonomic study of the fish remains and a characterization of the exploitation of this resource. The results show that the human community of El Mirador cave practiced fishing, and that fish was part of their diet and social life.     

Mitigating the effects of high-head dams on the Columbia River, USA: experience from the trenches

Worldwide, humans have tremendously altered freshwater ecosystems and arguably, construction of dams has had the greatest effect. Maintaining natural ecological processes and developing mitigation strategies that will maintain species while retaining dam benefits is challenging. In the Columbia River, USA, over the last 30 years more than US$7 billion has been spent on efforts to save historically large runs of salmon. These efforts have included improving passage conditions at dams through construction of efficient fish ladders for adult salmon, effective fish passage facilities for downstream migrating juvenile salmon, voluntarily spilling water to decrease the number of downstream migrants that pass through turbines, modifying dam operations to provide more constant flow and providing additional flow from storage reservoirs to create more natural flow through areas inundated by dams. Construction of hatcheries to offset losses in habitat for wild fish has also occurred. Further, for salmon from the Snake River, the largest tributary to the Columbia River, a large percent of juvenile salmon smolts are collected at upstream dams and transported in barges to the lower river to avoid passage through dams, turbines, and reservoirs. Experiences in the Columbia River suggest that the sum of all of these actions may keep salmon stocks from going extinct, but the technological fixes will not likely provide complete mitigation for altered freshwater ecosystems. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

A river-based approach in reconstructing connectivity among protected areas: Insights and challenges from the Balkan region

Global efforts to halt biodiversity loss mandate the establishment of protected areas. In the face of habitat loss and climate uncertainty, large-scale networks of protected areas connected by corridors are needed to increase the dispersal and persistence potential of biota. For example, the recent European Biodiversity Strategy for 2030 defines clear targets for identifying, establishing and integrating ecological corridors, as part of a Trans-European Nature Network. Here, we examined whether rivers could serve as such corridors, facilitating landscape connectivity (i.e. extent to which landscape facilitates or impedes species movement, exchange of genes, natal dispersal and metapopulation dynamics) among protected areas hosted within different countries in the Balkan Peninsula, southeastern Europe. To quantitatively address this question, we calculated the proportion of the river network enclosed within a protected area per country to detect patterns of protection coverage and explored the degree to which spatial connections between 1878 protected areas are supported by the river network. Acknowledging that dams hinder instream continuity, we further quantified potential loss of connections between protected areas caused by the existence of already implemented or planned dam projects upon critical river habitats of endangered fish species. Our results highlight that Balkan rivers have great potential in providing the spatial connections needed to establish landscape connectivity between most of protected areas in the region. Still, heedless hydropower growth and dissimilarities in river protection between neighboring countries remain key challenges for the evolution of a relative framework. Transnational cooperation and systematic planning of infrastructure development could be the only efficient steps towards supporting the establishment of a river-based network to reconstruct connectivity between protected areas and meet biodiversity goals.     

Significant association between SNPs in the superoxide dismutase 3, extracellular (SOD3) gene and resistance to Aeromonas hydrophila in the freshwater mussel Hyriopsis cumingii

Extracellular superoxide dismutase (SOD3) is a major antioxidant enzyme that protects organs from damage by reactive oxygen species (ROS). In this study, the SOD3 gene was identified and characterized from the freshwater mussel Hyriopsis cumingii (Hc‐SOD3). The cDNA sequence consists of 763 bp, encoding a protein of 208 amino acids. The amino acid sequence possesses two CuZnSOD signature sequences, and amino acids required for binding of Cu (His‐93, ‐95, ‐110 and ‐169) and Zn (His‐110, ‐118, ‐129 and Asp‐132) were conserved in Hc‐SOD3. The Hc‐SOD3 genomic sequence was 9165 bp in length, containing four exons and three introns. Eighteen single nucleotide polymorphisms were detected in the Hc‐SOD3 gene from resistant stock (RS) and susceptible stock (SS) of H. cumingii to Aeromonas hydrophila. The genotype and allele distribution were examined in resistant and susceptible stocks. Among them, a C/G substitution at the g.7994C>G locus and G/C substitution at the g.8087G>C locus were significantly associated with resistance/susceptibility of H. cumingii to A. hydrophila, both in genotype (P = 0.017, P = 0.004 respectively) and allele frequency (P = 0.021, P = 0.006 respectively). Linkage disequilibrium analysis revealed that g.7994C>G, g.8001A>G, g.8035G>A, g.8087G>C and g.8191T>A were in linkage disequilibrium. The results suggest that the two polymorphic loci, g.7994C>G and g.8087G>C, could be potential genetic markers for future molecular selection of strains that are resistant to diseases.     

Chromium and Selenium in Invertebrate Prey of Lesser Scaup

Abstract: The combined lesser scaup (Aythya affinis) and greater scaup (A. marila) population in North America has steadily declined from an average of 7.5 million breeding birds in the 1970s to an all-time low of 3.39 million in 2005. Bioaccumulation is widely known as the means of elevated levels of toxins in vertebrates. Our goal was to determine whether chromium and selenium were factors contributing to the continental scaup population decline by identifying wetlands used by scaup that potentially contain dangerous concentrations of chromium and selenium. We hypothesized that zebra mussels (Dreissena polymorpha) would contain the highest concentrations of selenium and chromium because they are filter feeders, whereas amphipods would contain the lowest concentrations because of their short life span. We collected zebra mussels, fingernail clams (Sphaerium transversum), chironomid larvae, snails (Gastropoda), and amphipods on randomly selected traditional lesser scaup staging and breeding wetlands. We found higher chromium concentrations in zebra mussels from Iowa, USA, than in those from Wisconsin, USA (P = 0.0074). In addition, selenium concentrations in zebra mussels from Wisconsin were higher than in those from Iowa (P < 0.0001). Higher selenium concentrations in amphipods were associated with sampled wetlands surrounded by developed land. Invertebrates with >5 μg/g selenium and >1 μg/g chromium are potentially hazardous for scaup. Chromium concentrations in Iowa were the highest for most species examined, whereas they were the lowest in Minnesota, USA. Based on our results, lesser scaup probably accumulate the highest concentrations of selenium on Lake Onalaska, Wisconsin, whereas they probably accumulate the lowest concentrations in Iowa. Waterfowl biologists are searching for explanations to the scaup decline; we propose chromium and selenium concentrations in amphipods and fingernail clams may be a factor.     

Bioaccumulation of Trace Elements in Roach, Silver Bream, Rudd, and Perch Living in an Inundated Opencast Sulphur Mine

The contents of Cd, Pb, Cu, Mn, Fe, and Sr were determined in bottom sediment and fish in Piaseczno lake (inundated opencast sulphur mine, southern Poland) from April 2001 to January 2002. To determine the mobility and availability of these elements in the 0–5 cm layer of the sediment, a 6-step sequential extraction procedure was applied. Generally, in the sediment the amounts of Cd were low, of Pb and Cu were elevated, but of Mn, Fe, and Sr were very high. Risk of contamination of water by Sr and Mn estimated using individual contamination factor was much higher than by Cd, Pb, Cu and Fe. A relationship was found between the contents of the metals in some fish tissues and their trophic habits. According to bioconcentration factor Sr and Mn, which posed the highest risks to water contamination were concentrated to a greatest degree in benthivorous fish.     

Effects of 254 nm UV irradiation on the mobility and survival of larvae of the invasive fouling mussel Limnoperna fortunei

In order to investigate the feasibility of using ultraviolet (UV) irradiation to prevent the invasive Asian mussel, Limnoperna fortunei, from colonizing components of the cooling systems of industrial and power plants, the mobility and mortality of its larvae were assessed after exposure to different doses of UVC (λ = 254 nm) in laboratory conditions. Total (100%) mortality was achieved with a dose of 149 mJ cm^?2 at 23?°C and 103 mJ cm^?2 at 25.8?°C. Immediately after exposure, larvae were alive but had reduced mobility. The proportion of active larvae increased after 24 h, but fell again at 48 and 72 h to levels similar to those immediately after exposure. The highest mortality rates were always recorded at the last observation, 72 h after exposure. These results indicate that the larvae of L. fortunei are highly sensitive to UVC, suggesting that UV irradiation has the potential to control fouling by this mussel when the water is relatively clear. However, application of UV-based technologies in plants that use cooling water from water bodies with high loads of suspended solids (eg the Paraná-Uruguay basin, with ca 160 mg l^?1 of suspended solids and absorbance values around 0.255) is unlikely to be effective without prior filtration of the water.