Determining spatial and temporal scales for management: lessons from whaling

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 frcequently smaller than those typically employed in management. Overall, the evidence indicates that: (1) the time frame for management should be at most decadal in scope (i.e., <100 yr) and based on both genetic and nongenetic evidence of population substructure, and (2) at least some stocks should be defined on a smaller spatial scale than they currently are.

Emptying the Oceans: A Summary of Industrial Whaling Catches in the 20th Century

“…In addition, some populations of whales appear to have been completely extirpated (Clapham et al, 2008) or, in the case of eastern North Pacifi c right whales, nearly so (Ivashchenko et al, 2013). To paraphrase a famous quotation by John Gulland regarding fi sheries: whaling management in the 20th century was an interminable debate about the status of stocks until all doubt was removed.…”

Population structure and individual movement of southern right whales around New Zealand and Australia

“…Fidelity to calving grounds can be viewed as a type of cultural memory, and it seems the memory of the suitable calving ground can be lost along with the whales that formerly inhabited such areas (Clapham et al 2008). A loss of this cultural memory is thought to be a contributing factor to the absence of recovery in some southern right whale (e.g.…”

Factors affecting whale detection from large ships in Alaska with implications for whale avoidance

“…whale mortalities due to ship strikes (Acevedo et al 2006, Clapham et al 2008, Guzman et al 2012. Some whale populations are in recovery (e.g.…”