Investigators say the animals are being held in freezing water and cramped pens.
The U.S.-made Catalina seaplane crashed in 1945, but it was not piloted by an American.
In 2017, Russia's warships spent four times longer on deployment and drills in the Pacific Oceans than they were planning to.
The Kremlin has vowed it will not be caught off guard if war breaks out.
Moscow was flexing its muscles in the border regions in recent months.
One of the most time-consuming areas to guard in 2017 has been Primorye—the only Russian region to border North Korea.
Russian marines are training in field combat in North Korea, bordering Primorye.
Two ships in Russia's Pacific Fleet practiced amphibious landing in Primorye, Russia, and more drills in the country's east will follow.
Russia is on a courtship mission around the Pacific, and its troops are making their presence known near its short but tense North Korean border.
Russian ground, air and sea forces have held a series of drills in the Primorye region bordering North Korea in recent weeks.