A humpback whale. (Photo by werner22brigitte /Pixabay)

A humpback whale that had been splashing around Alameda for more than three weeks seems to have moved into the harsher waters of the Bay.

Scientists at the Marin Headlands-based Marine Mammal Center have been monitoring the whale since May 27, when they first received reports of its presence in the water off of Alameda, center spokesman Giancarlo Rulli said.

Though the adult female humpback, nicknamed Allie, short for Alameda, appeared sickly when it first arrived, it “showed more energetic behavior” as the weeks passed, Rulli said.

Allie entertained spectators by breaching and slapping its tail as it circled the Seaplane Lagoon beside the former Alameda Naval Air Station.

On June 14, scientists at the center saw Allie nearing the exit of the lagoon, then lost sight of it. The whale was spotted the following day near Islais Creek along the San Francisco waterfront, and then again four hours later leaving Alameda, Rulli said.

Experts at the center believe Allie braved the choppier waters of the Bay because the whale’s condition improved over the course of its stay in the sheltered lagoon rich with food, according to Rulli.

They assume the animal remains in the Bay but are unsure because they did not attach a tracking device, and hope it will swim toward the Golden Gate.

Center officials have asked ferries and local shipping companies to notify them if they see the whale so that it can ascertain Allie’s status and location, Rulli said.

Boaters who witness a whale in distress or suffering harassment are asked to call the Marine Mammal Center at 415-289-SEAL.