Why do freshwater migratory fish need ‘safe passage’ as numbers decline globally?

Dorado catfish have no problems with long travel days.

This species, a large freshwater fish native to the Amazon, migrates from the Amazon mouth in northern Brazil to the foothills of the Andes Mountains in Colombia, Ecuador, Peru, Bolivia and parts of Brazil.

It’s the trip of a lifetime for these catfish — Which can run up to 11,000 kilometers.

But the dorado catfish and many other migratory freshwater fish like it are in danger – their journeys are increasingly disrupted Habitat destruction, overfishing and dams are blocking their path.

“If you stop these migrations … the stocks will disappear and, in some cases, the species will become extinct,” said Zeb Hogan, a biologist at the University of Nevada. day 6 Host Brent Bambury.

Hogan led a global assessment on migratory freshwater fish species, Published in March By the World Wildlife Fund, the Convention on the Conservation of Migratory Species of Wild Animals and the University of Nevada.

It found that there are 325 species of migratory fish crossing international borders that require deliberate action to survive.

“These are species where populations are either declining or in some cases at risk of extinction that require international cooperation to manage and protect them,” Hogan said.

What is the reason for the decline?

As the dorado catfish makes its long journey toward the Andes foothills, it faces many obstacles.

Dams are a big problem, Hogan said, noting that they prevent upstream migration, as well as prevent fish from moving back downstream after spawning.

But dorado catfish also have to contend with habitat degradation, such as having their breeding grounds turned into gravel or sand mines, Hogan said, in addition to floodplains being used for agriculture and overfishing leading to unsustainable harvests.

And these challenges affect more than just Amazonian catfish.

The American eel is among the other species listed in last month’s report, said Canadian fisheries biologist Steven Cook of Carleton University in Ottawa. Whereas The federal government decided not to list the eel as a threatened species.Cook, who is also the Canada Research Chair in Fish Ecology and Conservation Physiology, said there is cause for concern.

American eels breed in the Sargasso Sea near Bermuda. The larvae then make their way to the St. Lawrence and Great Lakes.

Cook said that getting there is not a problem. Getting back to those rendezvous near Bermuda proves challenging.

“They’re tall animals,” Cook said. “On their way downstream they encounter hydroelectric facilities and … their length doesn’t help them when they’re trying to get between the turbine blades, (so) we see quite a high level of mortality.”

benefits of migratory fish

These fish provide enormous value to people and the ecosystems they migrate through, Cook said. Some nutrients are cycled from the ocean into fresh water, which can promote forest growth, and in some places they are important for food security.

“Here in North America we take it for granted because we can go to the store and buy fish, but there are many places in the world where that’s not the case,” Cook said.

“So these seasonal pulses of migratory fish really help support low-income people and communities,” he said. “It was really a safety net for food insecure people.”

In Canada, some migratory fish, such as salmon and eel, have significant connections to Indigenous communities.

“They’re also iconic,” Cook said. “The Pacific salmon migration, the Atlantic salmon migration, some of the sturgeon we have in Canada, the American eel, these are all iconic species that make really epic migrations.”

finding solutions

There are several ways to protect these fish, Cook said.

“There are some conservation problems where we scratch our heads and say, ‘Hmm, we don’t know what to do.’ But when it comes to migratory fish, it is very simple, and it is to give them safe passage,” he said.

But, this is easier said than done. For fish crossing international borders, full cooperation is needed between all countries along the migratory path.

“It doesn’t matter how many jurisdictions do a good job, if there’s one place where things are going poorly it’s game over, because these animals need to get from A to B to C to complete their life cycle,” Cook said.

When it comes to American eels, he said, there is strong joint cooperation between Canada and the U.S., as well as between individual states and provinces. But it is not so everywhere.

Cook said some countries lack the political will, while others don’t have the money to make the changes needed to protect fish.

Another important part of these fish’s survival is awareness, Hogan said, especially given that many of these journeys take place underwater unseen.

“I love sharing the stories of these fish with people,” said Hogan, who used to host the TV documentary series, monster fish.

“Part of the solution is to share the stories of these incredible fish, 600-pound catfish, you know, stingrays that are 14 feet long in fresh water, and share some of these stories to get people engaged and caring.”

Hogan has reason to be optimistic. on a Last month a UN conference in Brazil focused on the conservation of migratory speciesCountries along the Amazon River agreed to take steps to protect the dorado catfish.

“We have a road map for action, we have countries that have come together to take action to help these fish,” Hogan said.

“I hope that five to 10 years from now we will be in a much better place than we are now.”