In 1990, it was a rare sight in the Hauraki Gulf. Now it is common. Octopus tetricus is a warm-water species expanding its range southward as New Zealand's seas warm. Originally found in northern waters, it is now established as far south as Wellington. It is smaller than the Maori octopus, with a more compact body and shorter arms. Like its cousin, it is intelligent and capable of rapid colour change. It hunts crabs and small fish in rocky reefs and estuaries, using its beak to crush shells. It is a daytime hunter, often visible in shallow water. The expansion of its range is a clear indicator of climate change. As waters warm, tropical and subtropical species move south, altering local ecosystems. The common octopus competes with native species for food and shelter. Its impact on local biodiversity is still being studied. For fishers, it is both a pest and a prize. It empties pots but provides good eating. For scientists, it is a warning. The ocean is changing. The creatures within it are moving. This becomes expensive for established species. The common octopus is just one sign of a larger shift. It adapts faster than expected. No one told it otherwise.