A beam trawler is a net suspended from a beam that keeps the net open as it is dragged through the ocean. Beam trawlers require no bait and catch far more fish than hook-and-line fishing. Once beam trawlers were combined with engine-powered ships in the late 19th century, fishing became so efficient that it began to noticeably deplete fish populations.

Biodiversity, an elision of “biological diversity,” refers to the variety and interactions of all living things on earth. Life depends on this variety, and the fewer species that exist in an ecosystem, the less biodiversity there is and the harder it will be for the remaining species to survive. The disappearance of fish species due to overfishing is a threat to biodiversity that has cumulative effects on the entire natural order.

Commercial extinction is distinct from biological extinction. While biological extinction means that there are no surviving members of a given species, commercial extinction occurs when there are so few left of a species that fishing for them is no longer profitable.