Why abundance alone cannot assess sustainability in long-finned pilot whales (Globicephala melas): population structure, genetic uncertainty, and management implications

Long-finned pilot whales (Globicephala melas) are widely distributed across the North Atlantic and are often assessed for management as a single, abundant population. However, the species exhibits strong social organisation, stable matrilineal structure, and reproduction that occurs within social units, characteristics that shape demographic connectivity. These features raise questions about whether abundance alone provides a sufficient basis for assessing the sustainability of recurrent removals from a socially structured marine mammal population. Recent genetic and ecological studies indicate broad-scale differentiation and suggest regional structuring within the North Atlantic, yet sampling remains uneven and datasets linked directly to harvested individuals are limited. Consequently, it is not currently possible to determine how removals in the Faroe Islands are distributed across potential demographically independent populations (DIPs), matrilines or family lineages. This Mini Review synthesises current evidence on population structure, identifies key uncertainties, and evaluates post-mortem genetic sampling as a practical approach to reducing uncertainty and improving sustainability assessments for North Atlantic long-finned pilot whales.