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10 Fun Facts About Migratory Fish

In celebration of the upcoming World Fish Migration Day on May 24, below are 10 fun facts about migratory fish:

Steelhead and rainbow trout are the same species of fish; rainbow trout (pictured) are the fresh water form.
Photo courtesy of Shutterstock

1. When most people think of migratory fish, they think of salmon and other anadromous species that are born in freshwater, migrate to the ocean, and return to their natal rivers to spawn. But catadromous fish, like the American eel, do just the opposite—they migrate from the ocean into freshwater where they spend most of their lives, and then back to the ocean to spawn.

2. The distance that migratory fish travel can vary wildly. A Chinook salmon tagged in the Aleutian Islands and recovered in Salmon River, Idaho, was determined to have traveled 3,500 miles to spawn.

3. In contrast, river herring on the East Coast typically do not travel far from the outlet of their natal stream. River herring often occur in schools of thousands of fish near these outlets.

4. Considering the long distances some migratory fish travel, their ability to navigate back to their natal stream to complete their life cycle is truly incredible. Scientific evidence suggests that these fish use magnetic fields, environmental cues and their olfactory memory (or sense of smell) to navigate to the precise stream where they were born.

5. Diadromous fish play a crucial role in nutrient transport that supports freshwater and inland ecosystems. They migrate out of streams when they are still small and grow large on the ocean’s nutrients. Since many species die shortly after returning to their natal stream, their bodies serve as an important input of nutrients in these freshwater ecosystems.

6. Chinook salmon are among the largest migratory fish in the U.S., with the largest ever recorded being 126 lbs., though most Chinook salmon weigh only about 30 lbs.

7. Dams are not the only barriers to fish migration that are causing major declines in fish populations. Less obvious barriers can cause just as much damage, including poorly constructed culverts that occur at many road crossings.

8. Some salmon can jump as high as 6.5 feet—a skill that helps them in their upstream swim to their spawning grounds. However, the depth of the landing pool following such a leap can be as important to fish migration as the height of potential barriers.

9. Steelhead and rainbow trout are the same species of fish—rainbow trout is the freshwater form, and steelhead trout is the migratory form. Steelhead, unlike many migratory fish, do not always die after spawning and can make several trips back and forth between the ocean and their natal stream during their life cycle.

10. The cost of declining fish populations is not just ecological, it is financial. The Columbia River basin in California is estimated to have averaged between 10 and 16 million fish in the 19th century. Today, only about 1.5 million salmon and steelhead enter the Columbia each year, and only about 400,000 of those are wild, river-spawned fish. The rest are born in hatcheries. The National Marine Fisheries Service estimated the cost of salmon fishery losses due to dams in the Colombia Basin to be $6.5 billion for the period between 1960 and 1980 alone.

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A volcano erupts on New Zealand's Whakaari/White Island on Dec. 9, 2019. Michael Schade / Twitter

A powerful volcano on Monday rocked an uninhabited island frequented by tourists about 30 miles off New Zealand's coast. Authorities have confirmed that five people died. They expect that number to rise as some are missing and police officials issued a statement that flights around the islands revealed "no signs of life had been seen at any point,", as The Guardian reported.

"Based on the information we have, we do not believe there are any survivors on the island," the police said in their official statement. "Police is working urgently to confirm the exact number of those who have died, further to the five confirmed deceased already."

The eruption happened on New Zealand's Whakaari/White Island, an islet jutting out of the Bay of Plenty, off the country's North Island. The island is privately owned and is typically visited for day-trips by thousands of tourists every year, according to The New York Times.

Michael Schade / Twitter

At the time of the eruption on Monday, about 50 passengers from the Ovation of Seas were on the island, including more than 30 who were part of a Royal Caribbean cruise trip, according to CNN. Twenty-three people, including the five dead, were evacuated from the island.

The eruption occurred at 2:11 pm local time on Monday, as footage from a crater camera owned and operated by GeoNet, New Zealand's geological hazards agency, shows. The camera also shows dozens of people walking near the rim as white smoke billows just before the eruption, according to Reuters.

Police were unable to reach the island because searing white ash posed imminent danger to rescue workers, said John Tims, New Zealand's deputy police commissioner, as he stood next to Prime Minister Jacinda Ardern in a press conference, as The New York Times reported. Tims said rescue workers would assess the safety of approaching the island on Tuesday morning. "We know the urgency to go back to the island," he told reporters.

"The physical environment is unsafe for us to return to the island," Tims added, as CNN reported. "It's important that we consider the health and safety of rescuers, so we're taking advice from experts going forward."

Authorities have had no communication with anyone on the island. They are frantically working to identify how many people remain and who they are, according to CNN.

Geologists said the eruption is not unexpected and some questioned why the island is open to tourism.

"The volcano has been restless for a few weeks, resulting in the raising of the alert level, so that this eruption is not really a surprise," said Bill McGuire, emeritus professor of geophysical and climate hazards at University College London, as The Guardian reported.

"White Island has been a disaster waiting to happen for many years," said Raymond Cas, emeritus professor at Monash University's school of earth, atmosphere and environment, as The Guardian reported. "Having visited it twice, I have always felt that it was too dangerous to allow the daily tour groups that visit the uninhabited island volcano by boat and helicopter."

The prime minister arrived Monday night in Whakatane, the town closest to the eruption, where day boats visiting the island are docked. Whakatane has a large Maori population.

Ardern met with local council leaders on Monday. She is scheduled to meet with search and rescue teams and will speak to the media at 7 a.m. local time (1 p.m. EST), after drones survey the island, as CNN reported.

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