VOA慢速英语[科技报道]伊利诺斯州放生鱼类活化石

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2017-8-9 15:17

VOA慢速英语[科技报道]伊利诺斯州放生鱼类活化石

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VOA慢速英语

2017-08-09


Ancient Fish Returns to Illinois Waters


The Illinois Department of Natural Resources is returning a fish called the alligator gar to the state’s rivers.

Some people call the fish a “living fossil.“ Experts believe the fish first appeared during the Early Cretaceous period more than 100 million years ago.

Randy Sauer is an Illinois state fisheries biologist. He says the fish disappeared from the state’s rivers in the 1990s, although they have continued to do well in southern states.

Sauer says biologists want to bring the fish back to northern rivers “because it is important to have top predators to balance the species below them,“ he said.

Sport fishermen like to try to catch the alligator gar. Alligator gar are the second-largest freshwater fish in North America. They can grow as large as 2.7 meters and weigh more than 136 kilograms. Sauer says their large size is one reason they disappeared in the 1990s.

Experts say alligator gars are “opportunistic feeders.“ This means they will eat almost anything -- including small turtles or ducks. They also eat invasive species such as Asian and silver carp. Sauer hopes the re-introduction of the alligator gar will help the state’s efforts to control the carp.

Because gar can live up to 60 years, the program will continue to increase for many years.

Sauer notes that female alligator gars do “not sexually mature until 11 years, and the male not till 6 or 7 years.“

That means the biologists will try to raise and release a lot of fish early in the program to re-introduce them.

“We’re probably going to stock more heavily than 10 or 20 years down the road when hopefully these fish will find each other and start doing the job on their own,“ Sauer says.

伊利诺斯州放生鱼类活化石

Small devices have been placed in 7,000 of the fish so they can be observed after they are released into the waterways of Illinois. As it rains and floods, biologists expect some of the fish will follow the rivers into the states of Louisiana and Texas.

I’m Mario Ritter.

Correspondent Erika Celeste reported this story from the Kasaskaskia River State Fish and Wildlife Area in Illinois. Christopher Jones-Cruise adapted the report for Learning English. Mario Ritter was the editor.

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