In the 12 years since Dudgeon et al. (2006) reviewed major pressures on freshwater ecosystems, the biodiversity crisis in
the world’s lakes, reservoirs, rivers, streams and wetlands has deepened. While lakes, reservoirs and rivers cover only
2.3% of the Earth’s surface, these ecosystems host at least 9.5% of the Earth’s described animal species. Furthermore,
using the World Wide Fund for Nature’s Living Planet Index, freshwater population declines (83% between 1970 and
2014) continue to outpace contemporaneous declines in marine or terrestrial systems. The Anthropocene has brought
multiple new and varied threats that disproportionately impact freshwater systems. We document 12 emerging threats
to freshwater biodiversity that are either entirely new since 2006 or have since intensified: (i) changing climates; (ii)
e-commerce and invasions; (iii) infectious diseases; (iv) harmful algal blooms; (v) expanding hydropower; (vi) emerging
contaminants; (vii) engineered nanomaterials; (viii) microplastic pollution; (ix) light and noise; (x) freshwater salinisation;
(xi) declining calcium; and (xii) cumulative stressors. Effects are evidenced for amphibians, fishes, invertebrates, microbes,
plants, turtles and waterbirds, with potential for ecosystem-level changes through bottom-up and top-down processes.
In our highly uncertain future, the net effects of these threats raise serious concerns for freshwater ecosystems. However,
we also highlight opportunities for conservation gains as a result of novel management tools (e.g. environmental flows,
environmental DNA) and specific conservation-oriented actions (e.g. dam removal, habitat protection policies,managed
relocation of species) that have been met with varying levels of success.Moving forward, we advocate hybrid approaches
that manage fresh waters as crucial ecosystems for human life support as well as essential hotspots of biodiversity and
ecological function. Efforts to reverse global trends in freshwater degradation now depend on bridging an immense gap
between the aspirations of conservation biologists and the accelerating rate of species endangerment.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/brv.12480

Emerging threats and persistent conservation challenges for freshwater biodiversity

Pearly mussels (Unionacea) are widespread, abundant, and important in freshwater ecosystems around the world. Catastrophic declines in pearly mussel populations in North America and other parts of the world have led to a flurry of research on mussel biology, ecology, and conservation. Recent research on mussel feeding, life history, spatial patterning, and declines has augmented, modified, or overturned long-held ideas about the ecology of these animals. Pearly mussel research has begun to benefit from and contribute to current ideas about suspension feeding, life-history theory, metapopulations, flow refuges, spatial patterning and its effects, and management of endangered species. At the same time, significant gaps in understanding and apparent paradoxes in pearly mussel ecology have been exposed. To conserve remaining mussel populations, scientists and managers must simultaneously and aggressively pursue both rigorous research and conservation actions.

/pdf/changing-perspectives-on-pearly-mussels-north-america-s-most-2ilbnkrueq.pdf

Changing Perspectives on Pearly Mussels, North America's Most Imperiled Animals

Impacts of climate change on fisheries

Preface.Acknowledgements.Introduction.Form and Function.Origin and Evolution.Nautilus: The Survivor.Biodiversity and Zoogeography.Life Cycle.Growth.Physiological Ecology.Reproductive.From Egg to Recruitment.Coastal and Shelf Species.Oceanic and Deep-Sea Species.Cephalopods as Predators.Cephalopods as Prey.Fishing Methods and Scientific Sampling.Fishery Resources.Fisheries Oceanography.Assessment and Management.Conclusions.Appendix A: Classification of Living Cephalopod Families.Appendix B: Synopsis of Living Cephalopod Families.References.Index.

Cephalopods: Ecology and Fisheries

Freshwater mussels of the Order Unionida provide important ecosystem functions and services, yet many of their populations are in decline. We comprehensively review the status of the 16 currently recognized species in Europe, collating for the first time their life-history traits, distribution, conservation status, habitat preferences, and main threats in order to suggest future management actions. In northern, central, and eastern Europe, a relatively homogeneous species composition is found in most basins. In southern Europe, despite the lower species richness, spatially restricted species make these basins a high conservation priority. Information on freshwater mussels in Europe is unevenly distributed with considerable differences in data quality and quantity among countries and species. To make conservation more effective in the future, we suggest greater international cooperation using standardized protocols and methods to monitor and manage European freshwater mussel diversity. Such an approach will not only help conserve this vulnerable group but also, through the protection of these important organisms, will offer wider benefits to freshwater ecosystems.

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Conservation status of freshwater mussels in Europe: state of the art and future challenges.

The spatial distribution patterns of freshwater pearl mussels, Margaritifera margaritifera (L.), in the River Kerry, north-western Scotland were investigated, together with their relationships to a number of physical parameters (distance from nearest bank, mean water depth, mean current velocity, substratum descriptors, aquatic vegetation cover). The mussels exhibited a highly contagious, non-random spatial distribution pattern. Adult and juvenile M. margaritifera were found to have broadly similar habitat `preferences', although adults were found over a wider range of physical conditions. Based on computed habitat suitability curves, optimum water depths of 0.3–0.4 m and optimum current velocities of 0.25–0.75 ms-1 at intermediate water levels were observed. River bed substratum characterisitics appear to be the best physical parameters for describing M. margaritifera habitat. Boulder-stabilised refugia, which contain enough sand for burrowing, are ideal microhabitats for juvenile mussels. Adults are able to tolerate silty or muddy conditions for unknown lengths of time, but juveniles are never found in this type of habitat. Substratum-based discriminant function models were used to predict the presence or absence of mussels, with a success rate of 76–92%.

Physical microhabitat requirements of freshwater pearl mussels, Margaritifera margaritifera (L.)

Cephalopods are highly sensitive to environmental conditions and changes at a range of spatial and temporal scales. Relationships documented between cephalopod stock dynamics and environmental conditions are of two main types: those concerning the geographic distribution of abundance, for which the mechanism is often unknown, and those relating to biological processes such as egg survival, growth, recruitment and migration, where mechanisms are sometimes known and in a very few cases demonstrated by experimental evidence. Cephalopods seem to respond to environmental variation both ‘actively’ (e.g. migrating to areas with more favoured environmental conditions for feeding or spawning) and ‘passively’ (growth and survival vary according to conditions experienced, passive migration with prevailing currents). Environmental effects on early life stages can affect life history characteristics (growth and maturation rates) as well as distribution and abundance. Both large-scale atmospheric and oceanic processes and local environmental variation appear to play important roles in species–environment interactions. While oceanographic conditions are of particular significance for mobile pelagic species such as the ommastrephid squids, the less widely ranging demersal and benthic species may be more dependent on other physical habitat characteristics (e.g. substrate and bathymetry). Coastal species may be impacted by variations in water quality and salinity (related to rainfall and river flow). Gaps in current knowledge and future research priorities are discussed. Key research goals include linking distribution and abundance to environmental effects on biological processes, and using such knowledge to provide environmental indicators and to underpin fishery management.

/pdf/a-review-of-cephalopod-environment-interactions-in-european-3pe6avzvy7.pdf

A review of cephalopod–environment interactions in European Seas

Margaritifera margaritifera Linn., the freshwater pearl mussel, is distributed from the arctic and temperate regions of western Russia, westwards through Europe to the northeastern seaboard of North America (Fig. 19.1; Jungbluth et al. 1985). Throughout most of its range it has become scarce or threatened, and is listed as “vulnerable” by IUCN (Wells et al. 1983). It is widely believed that it has now become even more threatened (Chesney and Oliver 1998; Young 1991) and the purpose of this chapter is to review evidence for its current status and to identify the causes of its decline.

The Extent of, and Causes for, the Decline of a Highly Threatened Naiad: Margaritifera margaritifera

The effects of a major flood on an endangered freshwater mussel population

Body size at sexual maturity, egg-size distributions, and potential reproductive output have been estimated for female and male squid, Loligo forbesi Steenstrup, off the west coast of Scotland. Two size modes at maturity were found in both sexes, but separation into size cohorts was more pronounced in males (180 and 350 mm mantle length, ML). Preliminary ageing studies based on statolith ring-counts suggest that these size modes are not due to different age groups at breeding. Females have a single size mode of mature eggs in the proximal oviduct, but may have at least two size modes of eggs within the ovary. This finding is interpreted as evidence of batch-spawning in this squid. There was a weak relationship between total egg numbers (range 1000 to 16000) and body size (range 196 to 318 mm ML) and between mature egg size and body size. Males showed a strong positive relationship between spermatophore length and body length but a weak relationship between total number of spermatophores and body size. The results are discussed in the context of flexibility of breeding strategies in the loliginids and variety of life-cycle patterns.

Lee C. Hastie

Papers

Physical microhabitat requirements of freshwater pearl mussels, Margaritifera margaritifera (L.)

A review of cephalopod–environment interactions in European Seas

The Extent of, and Causes for, the Decline of a Highly Threatened Naiad: Margaritifera margaritifera

The effects of a major flood on an endangered freshwater mussel population

Flexible reproductive strategies in the squid Loligo forbesi.