Genetics is also a valued assessment method because genetic differences indicate reproductive isolation, which is in turn often proof of demographic isolation.
Stock structure can be assessed using population trends, tagging, photoidentification, differences in parasites and contaminant loads, or morphological and demographic data collected on harvested animals ( Taylor, 1999 Dizon et al., 1992 Gorbics and Bodkin, 2001).
The identification and delineation of such units, whose recruitment is primarily affected by local births and deaths in comparison to immigration and emigration, are a key to successful management. Accordingly, it has been suggested that management of large whales should be based on units that would not recover within a given time frame if extirpated ( Clapham et al., 2008). Dispersal rates between theorized stocks, though high enough to mask genetic differences, may not be sufficient for enough recruits to migrate from an area experiencing little to no anthropogenic removal to an area subject to high mortality to prevent the decline or extirpation of the latter. In this paper, the word “stock” is used in a management context to refer to groups of individuals of the same species that are demographically, but not necessarily genetically, isolated ( Taylor, 1999 Taylor, 2005 Clapham et al., 2008). Song structure analysis could therefore provide a useful and cost-efficient tool for defining conservation units over temporal and geographical scales relevant to management objectives in fin whales.Įffective management of marine mammals requires a working knowledge of their stock structure. The results are consistent with those derived from other stock structure assessment methodologies, such as chemical signature and photoidentification analysis, suggesting that fin whales in these areas may form separate management stocks. Classification trees showed that GSL songs differ significantly from those in the GoM. 6257 pulse intervals corresponding to 19 GSL and 29 GoM songs were measured to characterize songs from both areas. Recordings were made from September 2005 through February 2006 in the GSL and intermittently between January 2006 and September 2007 at two locations in the GoM. Lawrence (GSL) and Gulf of Maine (GoM) was compared. In this study the structure of songs recorded at two geographically close feeding aggregations in the Gulf of St. Their highly stereotyped interpulse interval has been shown to vary between geographic areas and to remain stable over time in some areas.
Fin whale ( Balaenoptera physalus) songs present a unique opportunity to determine interstock differences. Passive acoustic data are increasingly being used as a tool for helping to define marine mammal populations and stocks.
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