Many large aquatic vertebrates, referred to as freshwater megafauna, cover long distances between their breeding and feeding grounds. To ensure their safe passage, they are dependent on free-flowing waters. However, this makes them vulnerable to the increasing fragmentation of river catchments caused by damming. The Russian sturgeon, for example, has lost 70 per cent of its spawning grounds in the Caspian Sea basin and its entire Black Sea basin spawning grounds over the last 60 years due to dam construction.
Yet, freshwater megafauna species play key roles in their respective ecosystems: owing to their size, most are at the top of the food chain, meaning that a large proportion of creatures in the local ecosystem would be affected by their extinction.
According to the authors, megafauna species are highly susceptible to external factors owing to their long lifespan, large body size, late maturity and low fecundity. Despite the fact that many megafauna species are under great threat, they have been largely neglected in previous research and conservation actions. Fengzhi He and his co-authors call for research focusing on the distribution patterns, life history and population dynamics of freshwater megafauna.
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Citation: He, F., Zarfl, C., Bremerich, V., Henshaw, A., Darwall, W., Tockner, K. and Jähnig, S. C. (2017), Disappearing giants: a review of threats to freshwater megafauna. WIREs Water, e1208. doi:10.1002/wat2.1208 http://onlinelibrary.wiley.com/doi/10.1002/wat2.1208/full