This Weekend, Celebrate the World’s Weird and Wonderful Migratory Fishes

The first annual World Migratory Fish Day is making a splash with hundreds of outdoor, fish-centric events

The American paddlefish, which makes spawning migrations up the Yellowstone and Missouri Rivers. Photo: Zeb Hogan
The golden dorado, which migrates in rivers throughout the Parana-Paraguay basin. Photo: Zeb Hogan
The giant freshwater stingray, from the Mekong River, whose life history is a mystery. Photo: Zeb Hogan
The critically endangered Pangasius sanitwongsei migrates up the Mekong to spawn in northern Thailand and Laos in April and May. Photo: Zeb Hogan
The green sturgeon spends most of its life in coastal waters but spawns in freshwater, migrating up at three rivers in the Pacific Northwest. Photo: Zeb Hogan
The goonch catfish is a predatory, migratory species that lives throughout South and Southeast Asia. Photo: Zeb Hogan
Europe's Danube salmon. Photo: Zeb Hogan
The beluga sturgeon's Danube River migration is currently blocked by the Iron Gate Dam. Photo: Zeb Hogan
The goliath catfish lives in South America and is exceptional in that it migrates the entire length of the Amazon River. Photo: Zeb Hogan

Whether you live in Reykjavik, Christchurch or Portland, this Saturday you have the chance to head outdoors, get wet and learn about some fish. Hundreds of events are planned around the world in honor of the first annual World Fish Migration Day.

This global initiative, created by the Nature Conservancy, IUCN, World Wildlife Fund and other groups, seeks to raise awareness about migratory fishes, many of which are imperiled by dams and developments along their river routes. Events include ceremonial openings of fish ladders, sturgeon releasing, family-friendly guided tours of rivers, underwater photography workshops, a race called the “smolt bolt” and more.

There’s no sure estimate of how many of the 27,000 known fish species migrate, although it’s likely a lot—perhaps even a majority. Some researchers put the number at around 50 percent for all Canadian fishes, for example, and up to 70 percent of all fishes in the Mekong River.

Throughout the year, numerous species of migratory fishes are doing their thing all over the world. Right now, for example, lake sturgeon are spawning in the Fox and Wolf Rivers in Wisconsin, and in other offshoots of the Mississippi and Great Lakes. At the time of spawning, eggs account for about a third of a 150-pound female’s body weight.

“I find these fish remarkable because of how long they have been able to persist—150 million years—outliving the dinosaurs,” Ryan Koenigs, a senior fisheries biologist at the Wisconsin Department of Natural Resources, said in an email. Lake sturgeon “can also live to be 100 to 150 years old.” 

Migratory fishes have a number of ways of going about their lifecycle business. Lake sturgeon are straightforward, they migrate into rivers with flowing water to spawn. Others, however, have more elaborate rituals. Some, such as salmon, are born in freshwater and then make their way to salt water, only to eventually return to the stream or river of their birth to spawn—either as a final stop before death, or else repeating the process each year. Some—including several species of European and American eels—do the opposite, hatching in salt water but then migrating to spend most of their in fresh. And some fish species—for instance, capelin—migrate with the seasons, just as birds do, to find food. Still others, like the Mekong giant freshwater stingray, migrate for reasons completely unknown.

As conservationists well know, it’s hard enough protecting a species that stays in one place, let alone one that traverses an entire river system, sea or both. As a result, many migratory fish species are teetering precariously close to extinction. The Mekong giant catfish, for example, migrates along 1,600 square miles of Southeast Asia’s Mekong River and is down to just an estimated few hundred individuals.

That charismatic megafish is far from an isolated example, unfortunately; beluga sturgeon, Chinese paddlefish, Chinese sturgeon are all critically endangered. Development along rivers, including dams and pollution, coupled with over fishing, are often to blame.

While furry and feathered animals tend to inspire a lot of conservation efforts and media attention, fish often slip through our net of awareness and interest. So when the World Migratory Fish Day organizers first got the idea for scheduling an event dedicated to traveling fishes, they expected just a handful of organizations to step up. But the enthusiasm, they say, has been overwhelming, and the events listings are now pushing 300.

"The topic has struck a chord," Zeb Hogan, an aquatic ecologist at the University of Nevada, Reno, wrote in an email. "Perhaps because this is one of the first organized endeavors to celebrate migratory fish worldwide, and nearly every river—and every migratory fish—has a story to tell." 

Get the latest Science stories in your inbox.