The Secret to Pacific Cod's Survival Lies in a Chilly Nursery

Why have Pacific cod catches risen in some Korean waters while plummeting in others? The answer, it seems, lies in the species’ very first days of life. At the southern edge of their habitat, these commercially vital fish are acutely sensitive to ocean temperature during their early life stages as eggs and larvae.

A recent study reveals a critical temperature window for survival. Experiments showed that cod eggs struggle to hatch below 3°C and above 10°C, while the resulting larvae fare better in cooler waters. Scientists used these findings to create a 'habitat suitability index'—a score showing how favourable an area is.

This modelling explains the regional picture perfectly. The eastern coast, with its persistent cool bottom waters, remains a favourable nursery, supporting rising cod catches. In contrast, widespread warming has made much of the southern coast unsuitable. These insights offer a powerful new basis for managing fisheries in our warming world.