Sei whales were nearly hunted to extinction in the 20th century and are recovering, but face ongoing threats from ship strikes and prey depletion as they expand their range.
Sei whales struck by ships suffer acute traumatic injuries from propeller strikes causing death or severe disability. Animals that survive ship strikes may have broken bones, internal injuries, and infections preventing normal feeding. Zooplankton distribution changes from climate warming force sei whales to travel further for food, increasing energetic expenditure. Small population size from historical whaling means inbreeding effects may be emerging in some ocean populations. Recovery from near-extinction requires sustained protection from all sources of human-caused mortality.