Seipt et al Identification of Balaenoptera physalus in Massacfiusetts Bay 



277 



It is clear, however, that many of the gaps in our 

 sighting histories of individual whales represent real 

 absences from the area. Resightings of individuals out- 

 side our study area confirm that the summer ranges 

 of these whales are often, if not regularly, extensive. 

 In a preliminary analysis of photographs from the 

 North Atlantic Fin Whale Catalogue, Agler et al. (1990) 

 report a number of instances of movement of indivi- 

 duals between Massachusetts Bay and the waters of 

 Maine and the Bay of Fundy. It is possible that some 

 individuals undertake extensive movements outside the 

 Gulf of Maine, but the current lack of observer effort 

 beyond this region precludes investigation of this idea. 



From the regional perspective of this study, it is 

 tempting to compare the results reported here with the 

 much more complete information available on Gulf of 

 Maine humpback whales and to conclude that the two 

 populations are broadly similar in their patterns of 

 occurrence and distribution. The annual return rate of 

 humpback whales to Massachusetts Bay is extremely 

 high, with as many as 85% of individuals observed in 

 one year returning the next (Mayo 1983, Mayo et al. 

 1988). While no individual humpback remains in Mas- 

 sachusetts Bay for an entire season, many appear to 

 spend prolonged periods in the area between making 

 wider forays elsewhere in the Gulf of Maine (Clapham 

 and Mayo 1987, Mayo et al. 1988). Other humpbacks 

 are observed less often, and presumably frequent other 

 habitats for much of the year, a fact which reflects con- 

 siderable variation among individuals. It is also clear 

 that overall individual fidelity to the Gulf of Maine is 

 maternally directed (Clapham and Mayo 1987). 



It is not unreasonable to expect that fin whales might 

 exhibit similar patterns of occurrence. Given that the 

 distribution of fin and humpback whales in high lati- 

 tudes must be predominantly related to the distribu- 

 tion of their prey (Payne et al. 1986), it is to be expected 

 that the occurrence of both species should be character- 

 ized by individuals returning repeatedly, both during 

 a season and from year to year, to consistently produc- 

 tive habitats such as Massachusetts Bay. From the 

 standpoint of energetics, it would make little sense for 

 an individual to abandon an area of high productivity 

 and search elsewhere if the resources found in the 

 former habitat were adequate for its needs, although 

 it is possible that, as suggested by Watkins et al. (1984), 

 social imperatives play an important role in the move- 

 ment of individuals. 



Overall, the data presented here suggest that there 

 are more similarities than differences in the high- 

 latitude population characteristics of humpback and fin 

 whales, although data from other sources suggest that 

 significant differences between the two species do 

 exist. In addition to the above-mentioned studies which 

 documented extensive movements on the parts of 



individuals (Brown 1962, Mitchell 1974, Watkins et al. 

 1984), other observers have noted evidence for spatial 

 segregation by length in certain areas (Mackintosh 

 1942, Mitchell 1974, Rorvik etal. 1976, Sergeant 1977), 

 a phenomenon that has not been demonstrated for 

 humpbacks. Our own data are regional in nature and 

 do not permit us to address these broader questions 

 of population structure at the oceanic level. However, 

 with increased photographic effort in other areas, 

 studies based upon the identification of individual fin 

 whales should provide clearer insights into the popula- 

 tion biology of this species in the North Atlantic. 



Acknowledgments 



The authors are grateful to the staff of the Center for 

 Coastal Studies who, by ignoring humpback and right 

 whales as often as possible, helped to provide the 

 photographic data upon which this paper is based. We 

 also thank Bill Rossiter for additional photographs and 

 data, and for his consistent support of fin whale studies 

 over the years. We are grateful to the captains and 

 crew of the Dolphin Fleet for all their assistance in the 

 field; we are particularly indebted to Captain Aaron 

 Avellar, who initially suggested that variations in the 

 blaze and chevron patterns of fin whales might be 

 useful in the recognition of individuals. The manuscript 

 benefitted from a thoughtful review by Scott Baker. 

 This study was funded in part by the National Marine 

 Fisheries Service, Northeast Region, under contract 

 number 50-EANF-6-00059. Additional support from 

 the International Wildlife Coalition and the Seth 

 Sprague Educational and Charitable Foundation is 

 gratefully acknowledged. 



Citations 



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 S.E. Frohock, M.P. HawTermale, S.K. Katona, S.S. Sadove, 

 and I.E. Seipt 



1990 Finback whale. Balaenoptera physalus, photographic 

 identification: Methodology and preliminary results from the 

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 press). 

 Brown, S.G. 



1962 The movements of fin and blue whales within the Antarc- 

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 CeTAP 



1982 A characterization of marine mammals and turtles in the 

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