Copepods

Copepods are tiny, oil-rich animals whose abundance helps determine whether a bay can support whales. Their importance appears at two scales: researchers count them as part of the food supply that may keep whales in a habitat, while the book suggests that parasites on a whale may help it locate that same food.

Food Supply and Habitat

In late winter and early spring, the research vessel Shearwater surveys zooplankton in the bay. The count is used as an indicator of whether the habitat can support whales: above 3,750 organisms per cubic metre, the density of copepods and other small animals is considered sufficient to sustain the population. The threshold concerns the combined abundance of these organisms, not copepods alone.

The survey gives this measurement a practical consequence. If the food supply falls short, a whale arriving at the historic feeding ground may find it inadequate and move on. On the expedition described in the book, six hours of searching yielded empty sample nets, indicating that there was not enough food for whales in the surveyed water. The result made the absence of whales legible not simply as a matter of chance, but as a possible response to the habitat’s available food.

Whales, Lice, and Copepods

Copepods also connect whales to the small organisms living on their bodies. The book notes that whale lice feed on the same copepods that whales do. It proposes, cautiously, that the lice might act as minute sensors, helping lead their hosts toward food. This remains a possibility rather than a demonstrated account of how whales find prey, but it makes the whale’s body part of a wider feeding relationship: organisms associated with the whale may also register its food environment.

Ecological Significance

The account places the great scale of whales beside the minute scale of their food. A habitat’s capacity to sustain these large animals depends on counting tiny organisms in seawater, and the survey’s numerical threshold turns that dependence into a testable measure. Copepods therefore matter not as incidental plankton, but as part of the conditions that can keep whales in a feeding ground—or make them leave it.