Thermidor anyone?: An official of the Kanagawa Prefectural Fisheries Technology Center in Miura shows off an American lobster caught in Tokyo Bay in July. KYODO

YOKOHAMA — An American lobster, chiefly found along the upper Atlantic coast of North America, was caught in Tokyo Bay, a fisheries research center said Thursday, calling it the first such catch.

"Someone might have mistakenly dropped an imported lobster into the sea, or released it intentionally," said a researcher at Kanagawa Prefectural Fisheries Technology Center in Miura, Kanagawa Prefecture, noting American lobsters are rarely found in seas around Japan.

According to the center, a fishing boat caught the 30-cm-long, 1.2-kg lobster about 8 km off Hakkeijima in Yokohama.

The researcher expressed concern that the ecosystem of Tokyo Bay could be affected, as the American lobster, or Homarus americanus, is an alien species that would have few natural enemies there.