Scientists who spent the summer studying monk seals in the Northwestern Hawaiian Islands rescued nine of the animals caught in fishnets and other marine debris.

Charles Littnan, the National Oceanic and Atmospheric Administration’s program leader for monk seal research, said Tuesday one seal was a female pup entangled in a 800-pound mess of buoys, fishing nets and clothes baskets off Kure Atoll.

The rescues are among the work researchers do to protect the species, which is the most critically endangered marine mammal in U.S. waters.

The Hawaiian monk seal population numbers only about 1,100 and is declining about 4 percent per year. Scientists say the species could disappear in 50 to 100 years if the trend is not reversed.

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