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Migrating fish: species in danger worldwide

 

Between 1970 and 2016, the average size of wild vertebrate populations fell by 68%. This is the alarming observation issued recently by WWF in the framework of its new report “Living Planet 2020”  which measures the state of the planet’s biodiversity. The situation of migrating fish is especially disquieting. The full current situation of these migrating species and the challenges of protecting them …


A 76% decrease in the population in less than 50 years

 

Salmon, eel, sturgeon, lamprey, shad and other species all pass from seawater to freshwater to fulfil their lifecycles. To reproduce and grow, they evolve from one end of a river to the other or between the sea and rivers. We already knew that these fish populations have undergone a considerable and continuous decline. In addition, some of them are on the IUCN’s red list of threatened species. The report on the global situation published at the end of July is the result of collaboration gathering 15 organisations (including the World Fish Migration Foundation, the International Union of Conservation of Nature, WWF and the Zoological Society of London). It presents a dramatic figure: between 1970 and 2016, the migrating fish population declined by 76%. What is more, this figure could be an underestimation, since data are lacking for tropical regions.

The accused: pollution, overfishing and habitat loss

 

Due to their movement in different habitats, migrating fish are exposed to a greater number of risks. The foremost of these are the degradation, alteration and loss of their habitat and spawning grounds. Overfishing is responsible for a third of the decline, mostly at sea, but also in rivers for certain species such as the European eel. Pollution, the presence of invasive species and climate change all represent other threats.

In geographic terms, Europe has undergone the most dramatic fall (-96 %), versus -28% in North America, according to the study. The large number of structures on European streams and rivers, which hinder the free circulation of migrating fish, is the principle reason.

Projet SAMARCH

Aware of the criticality of the situation and the role played by migrating fish in biodiversity, European actors have started to cooperate internationally to better preserve these species (with in particular project the DiadEs and SAMARCH projects for the Salmonidae of Manche, endowed with €2.2 million and €7.8 million respectively).


The time to act is now

 

According to Herman Wanningen, founder of the World Fish Migration Foundation, the situation is critical for biodiversity, food security, and the millions of people who depend on fish for their food. But she doesn’t’ despair:

The statistics are shocking but we know that migrating fish populations can bounce back. We must act now before their populations reach a tipping point when they’ll no longer be able to reconstitute. It’s time to valorise migrating fish and the rivers that give them life”.

Among the 247 species studied in the framework of this report, more than half (56%) are in decline, while the populations of 43% of them have increased, due to monitoring, conservation and fish migration restoration measures. The recommendations issued involve several actions:

  • Develop and improve monitoring;
  • Collect more data;
  • Protect free-flowing rivers and implement planning at the basin scale, by eliminating obsolete dams (estimated at 15% in this report), by creating conservation areas and restoring ecosystems;
  • Confront existing threats by acknowledging the interaction between stress factors and the accumulative effects caused by, for example, pollution, and climate change. The report recommends recourse to nature-based solutions to mitigate the impact of climate change;
  • Encourage public and private decision-makers to take action, by getting them to recognise from the outset that migrating fish are the guarantors of ecological continuity;
  • Adhere to ongoing conservation initiatives.

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