Aquatic species that make massive migrations through freshwater systems are facing a converging threat from human-made barriers, contaminants, and excessive harvesting stopping them from reaching their breeding sites.
Examples including the Himalayan mahseer and goonch catfish are among 30 priority fish species which have now been recommended for worldwide protection by the UN in a new assessment.
"These aquatic species support hundreds of millions of communities around the world, so for humans, they're very important," stated a co-author biologist on the study.
A group of global experts assessed over 15,000 types of migrating freshwater species – which represent half of all known fish – and found their populations had declined by an estimated 81% in the previous five decades.
The researchers said that for far too long, this group of species has been overlooked but "are an essential part of human survival."
Excessive Harvesting and Environmental Degradation
The focused group is consists of fish that are both endangered and also valued culturally for global societies.
"As an instance, the golden mahseer is an symbolic fish of the Himalayas. A great many communities in that region esteem that fish for traditional and sacred purposes that extend well past monetary worth," explained a conservation expert who contributed to the report.
Similar to other fish on the roster, it is confronting two key dangers: overfishing and loss of home.
"Environmental degradation includes things like dams that divide a waterway, and can alter the seasonal patterns of a river, which causes fish not being able to access their spawning areas," the spokesperson said.
Obstruction to migratory routes is an issue that is particularly prevalent in Europe, where fish encounter a barrier to their paths every kilometre.
In many cases the obstructions are unnoticed culverts or weirs that are no longer needed and could be removed, explained an conservation science head.
But the cumulative effect on migratory fish is massive: "It can have a profound effect in terms of the energy reserves fish are consuming to pass the [barriers]."
That leaves them more susceptible to illness. They're more prone to get predated. They will reproduce in less-than-ideal grounds."
Conservation Success
Most species will traverse country boundaries on their extensive journeys. This requires joint work between states to combat these issues and secure the restoration of local stocks, argued a report co-author.
The global treaty on migratory species is a international United Nations treaty signed in 1979 which commits countries to collaborate to safeguard migratory species of many kinds.
The UN is now suggesting that the thirty priority species be listed to the agreement at its annual meeting in the near future.
The Saiga antelope is an case study of a species that has benefited from being protected under the convention.
Following a population crash, an international anti-poaching team was established and since then numbers have recovered substantially.
"The focus has clearly been on some of the more well known species, such as big cats," stated a senior UN representative.
The official added it was now the opportunity of migratory freshwater fish to benefit from coordinated action.
