A massive rescue effort took place on Tuesday afternoon that lasted until sunset after five whales were discovered marooned on the shores of the west coast beach. The whales were discovered dead the morning after massive efforts by locals to save them.

The female seal pup — estimated to be around six months old — was seen swimming “erratically” near the shore in Sitka last month, according to a press release from the center. Worried Sitka residents then reported the pup to the center’s 24-hour stranding hotline.

A whale that washed ashore in the island of Kauai over the weekend likely died in part because it ate large volumes of fishing traps, fishing nets, plastic bags and other marine debris, scientists said Thursday, highlighting the threat to wildlife from the millions of tons of plastic that ends up in oceans every year.