The following has just been published online: Clapham, P.J., Aguilar, A. and Hatch, L.T. 2007 (in print 2008). Determining spatial and temporal scales for the management of cetaceans: lessons from whaling. Marine Mammal Science doi: 10.1111/j.1748-7692.2007.00175.x. ABSTRACT Selection of the appropriate management unit is critical to the conservation of animal populations. Defining such units depends upon knowledge of population structure and upon the timescale being considered. Here, we examine the trajectory of eleven subpopulations of five species of baleen whales to investigate temporal and spatial scales in management. These subpopulations were all extirpated by commercial whaling, and no recovery or repopulation has occurred since. In these cases, time elapsed since commercial extinction ranges from four decades to almost four centuries. We propose that these subpopulations did not recover either because cultural memory of the habitat has been lost, because widespread whaling among adjacent stocks eliminated these as sources for repopulation, and/or because segregation following exploitation produced the abandonment of certain areas. Spatial scales associated with the extirpated subpopulations are frequently smaller than tho se typically employed in management. Overall, the evidence indicates that: i) the timeframe for management should be at most decadal in scope (i.e. less than 100 years) and based on both genetic and non-genetic evidence of population substructure, and ii) at least some stocks should be defined on a smaller spatial scale than they currently are. The paper is available free from: http://www.blackwell-synergy.com/toc/MMS/0/0 Phil Clapham National Marine Mammal Lab, Seattle