Thunnus abalunga

Actinopterygii: The Actinopterygii, or ray-finned fishes, constitute a class or subclass of the bony fishes. The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii. In terms of numbers, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. (Wikipedia)

Pelagic: Any water in a sea or lake that is neither close to the bottom nor near the shore can be said to be in the pelagic zone. (Wikipedia)

Oceanodromous: Oceanodromous fish, which occur widely throughout the world’s oceans, live and migrate wholly in the sea. They differ mainly from one another by the method and extent of their migration. (Britannica)

Subtropical: The subtropics are geographic and climate zones located roughly between the tropic circle of latitude (the Tropic of Cancer and Tropic of Capricorn) and the 38th parallel in each hemisphere. Subtropical climate regimes can exist at high elevations within the tropics, such as across the Mexican Plateau and in Vietnam and Taiwan. (Wikipedia)

Curved: The overall shape of the ichthyolith curves in one direction.

Cavity: The ichthyolith has a central nerve cavity. This is a base keyword included whenever an ichthyolith has a cavity, even when the cavity is further categorized with an additional keyword.

Triangular: The base of the ichthyolith is the widest part.