Aquatic species that embark on massive migrations through rivers, lakes, and ponds are confronting a combined threat from dams, pollution, and overfishing preventing them from reaching their spawning areas.
Examples including the Himalayan mahseer and giant devil catfish are among 30 key species which have now been selected for worldwide conservation by the United Nations in a new study.
"Freshwater fish provide for many millions of communities globally, so for humans, they're very important," said a lead researcher on the report.
A team of global researchers evaluated over 15,000 types of freshwater migratory fish – which make up 50% of all fish species – and determined their numbers had dropped by an staggering 81% in the last half century.
The scientists argued that for too long, this class of species has been ignored but "are an crucial part of community livelihoods."
Excessive Harvesting and Environmental Degradation
The focused selection is comprises fish that are both threatened and also important for traditions for many populations.
"To illustrate, the golden mahseer is an iconic fish of the Himalayas. Many people in that area esteem that fish for cultural and spiritual purposes that transcend financial values," commented a freshwater specialist who contributed to the report.
Similar to other fish on the list, it is experiencing two primary dangers: excessive fishing and habitat loss.
"Environmental degradation includes things like obstructions that divide a waterway, and can disrupt the normal water flow of a river, which causes fish not being able to access their spawning areas," the scientist added.
Disruption to migration is an problem that is especially prevalent in Europe, where fish come across a barrier to their journeys every kilometre.
Often the obstructions are minor structures that are no longer needed and could be taken out, noted an environmental charity lead.
But the combined impact on migrating fish is immense: "It can have a massive impact in terms of the energy reserves fish are consuming to pass the [barriers]."
That makes them more prone to disease. They're more likely to get hunted. They will breed in less-than-ideal locations."
Conservation Success
The majority of species will pass over country borders on their extensive migrations. This necessitates collaborative work between states to tackle these issues and secure the restoration of local stocks, explained a study lead author.
The international conservation agreement is a international UN convention created in 1979 which requires signatories to work together to protect migrating species of every type.
The United Nations is now proposing that the 30 priority species be listed to the agreement at its annual conference in the coming years.
The Saiga antelope is an example of a species that has seen improvement from being protected under the treaty.
Following a population crash, an international conservation team was formed and since then population levels have recovered dramatically.
"Attention has traditionally been on some of the more visible species, such as whales," commented a high-ranking conservation official.
The official said it was now the time of these aquatic migrants to gain from coordinated action.
