A stranded humpback whale in Germany’s Baltic Sea is looking weaker after rescue attempts earlier this week, and officials said on March 29 that hopes of the animal finding its way back to the Atlantic have dimmed. The decision came after experts described a marked decline in the whale’s activity and breathing as it remained stuck near the eastern German coast.

Officials enforced a 500-meter restricted area around the whale so it could get some rest and, if possible, free itself. Mecklenburg-Pomerania environment minister Till Backhaus said authorities decided to leave the whale alone in the zone to allow it to set off and successfully leave it, while also acknowledging that the animal appears weakened and sick.

Backhaus also said the whale may have injuries after coming into contact with a fishing net. He described the situation as one in which the restricted area was intended to balance the need to avoid disruption with the aim of giving the whale a chance to move on its own.

Earlier efforts to rescue the whale included attempts off a sandbank near Timmendorfer Strand beach and in the Wismar Bay, with officials using an excavator and boats to create large waves that could help the whale swim free. The progress during the rescue phase drew sustained attention in Germany, with media updates and even live streaming from the scene, and with people across the country exchanging messages about the efforts.

Experts said by then that the whale’s decline was noticeable. Stefanie Groß, of the Institute for Terrestrial and Aquatic Wildlife Research at the University of Veterinary Medicine Hannover, said the whale’s respiratory rate had dropped considerably and that the animal was not moving; she also said it did not react even when researchers drove closer.

It was not immediately clear why the whale entered the Baltic Sea in the first place. Some experts said it may have lost its way while following a shoal of herring during migration, and it was described as most likely a male.

Officials and researchers said the Baltic Sea is not suitable for long-term survival because the salt concentration is too low, and they reported the whale had already developed a skin disease. They also said the whale appeared unable to find the right kind of nutrition it needs, while noting that whales can often go without food for weeks.

The next step, if the whale can survive and continue its movement, would be a return to the Atlantic via the North Sea. Burkard Baschek, director of the German Maritime Museum in Stralsund, said the journey depends on navigating narrow straits and that there were still about 500 kilometers to go, describing the chances of success as relatively slim.

The whale was first spotted swimming in the Baltic Sea on March 3, and reports that it had become stranded surfaced last week. By late March 29, officials said the animal’s weakened condition meant the rescue outlook continued to worsen.