🔗 Share this article

Aquatic species that embark on massive migrations through inland waterways are grappling with a multifaceted threat from dams, pollution, and overfishing preventing them from arriving at their reproductive areas.

Examples including the Himalayan mahseer and goonch catfish are among 30 key fish species which have now been prioritised for global preservation by the United Nations in a new report.

"Migratory fish support many millions of people globally, so for people, they're incredibly vital," said a lead researcher on the report.

A panel of global researchers examined over 15,000 species of migrating freshwater species – which represent 50% of all fish species – and determined their populations had fallen by an staggering 81% in the last half century.

The scientists stated that for an extended period, this group of species has been neglected but "are an essential part of human survival."

Excessive Harvesting and Environmental Degradation

The focused group is consists of fish that are both at risk and also important for traditions for global societies.

"For example, the tiger of the river is an revered fish of the Himalayan region. Many individuals in that region esteem that fish for cultural and spiritual reasons that go far beyond economic values," commented a freshwater specialist who contributed to the report.

Similar to other fish on the list, it is experiencing two major pressures: overfishing and environmental destruction.

"Habitat loss encompasses things like dams that divide a river system, and can change the normal water flow of a river, which results in fish not being able to connect to their spawning grounds," the scientist said.

Interruption to migration is an problem that is particularly widespread in Europe, where fish come across a blockage to their journeys every kilometre.

In many cases the barriers are minor structures that are redundant and could be eliminated, noted an conservation charity head.

But the combined effect on migratory fish is immense: "It can have a massive impact in terms of the resources fish are expending to pass the [barriers]."

That renders them more susceptible to illness. They're more inclined to get hunted. They will breed in suboptimal areas."

Road to Recovery

The majority of species will cross country boundaries on their lengthy journeys. This necessitates collaborative work between states to address these threats and ensure the recovery of local populations, argued a study contributor.

The global treaty on migratory species is a worldwide United Nations agreement signed in 1979 which obligates signatories to work together to protect migratory species of many kinds.

The United Nations is now recommending that the 30 fish species be added to the agreement at its yearly conference in the near future.

The Saiga antelope is an example of a species that has benefited from being included under the convention.

Following a population crash, an international conservation initiative was established and since then numbers have recovered significantly.

"Conservation efforts has traditionally been on some of the more charismatic species, such as large mammals," commented a senior conservation representative.

She noted it was now the turn of migratory freshwater fish to gain from international efforts.