Aquatic species that embark on massive journeys through freshwater systems are facing a converging danger from dams, pollution, and overfishing hindering them from accessing their spawning sites.
Species like the golden mahseer and giant devil catfish are among thirty priority species which have now been selected for global protection by the United Nations in a new report.
"Freshwater fish provide for countless numbers of people worldwide, so for humans, they're crucially significant," stated a lead biologist on the report.
A group of international researchers evaluated more than 15,000 species of freshwater migratory fish – which represent 50% of all known fish – and determined their numbers had fallen by an staggering 81% in the past 50 years.
The researchers stated that for far too long, this category of species has been neglected but "are an vital part of community livelihoods."
Excessive Harvesting and Environmental Degradation
The priority group is made up of fish that are both at risk and also important for traditions for worldwide societies.
"As an instance, the golden mahseer is an revered fish of the Himalayan region. A great many individuals in that region cherish that fish for cultural and spiritual purposes that transcend economic worth," explained a conservation expert who worked on the report.
Similar to other fish on the list, it is facing two key pressures: overfishing and loss of home.
"Environmental degradation includes things like dams that break up a waterway, and can alter the seasonal patterns of a river, which leads to fish not being able to access their breeding grounds," the scientist added.
Disruption to migration is an challenge that is particularly common in Europe, where fish face a blockage to their journeys every kilometre.
In many cases the obstructions are small structures that are redundant and could be removed, noted an environmental science head.
But the collective effect on migratory fish is massive: "It can have a significant impact in terms of the energy reserves fish are using to pass the [barriers]."
That renders them more susceptible to disease. They're more inclined to get predated. They will reproduce in suboptimal grounds."
Road to Recovery
Most fish will traverse national boundaries on their mammoth migrations. This requires collaborative efforts between governments to tackle these threats and guarantee the restoration of national populations, explained a study lead author.
The global treaty on migratory species is a global UN treaty established in 1979 which commits countries to work together to conserve migrating species of every type.
The United Nations is now recommending that the 30 priority species be listed to the treaty at its annual meeting in the near future.
The distinctive antelope is an example of a species that has benefited from being included under the treaty.
Following a catastrophic decline, an global conservation effort was formed and since then numbers have rebounded significantly.
"The focus has often been on some of the more visible species, such as whales," commented a high-ranking UN representative.
She added it was now the turn of river fish to receive coordinated action.
