Despite the seemingly low annual harvest, two factors must be taken into consideration when discussing the decline and later (nearly) complete disappearance of right whales in the region: one, the preference of Basque whalers to target mother-calf pairs; and two, exploitation of the species outside the Bay of Biscay.
Unatoč naizgled niskom godišnjem žetvi, dva faktora moraju se uzeti u obzir kada se raspravlja opadanje i kasnije (gotovo) potpuni nestanak pravih kitova u regiji: jedan, sklonost baskijskih kitolovaca ciljanju parova majka-mladunče i dva, eksploatacija vrsta izvan Biskajskog zaljeva .