Abstract,- Between 1980 and 

 1987 in Massachusetts Bay, 156 in- 

 dividual fin whales Balnenoptera 

 physalus were photographically iden- 

 tified using variations in natural 

 markings and scars. Of these, 98 

 (62.8%) were observed more than 

 once, and 70 (44.9%) were photo- 

 graphed in 2 to 8 different years. On 

 average, 49.2% of whales seen in a 

 year were resighted at least once 

 during that year, and 44.5% were 

 observed the following year. Within 

 a year, the observed occupancies (the 

 period between first and last sight- 

 ing) of resighted individuals varied 

 from 1 to 197 days (mean 46.1), while 

 the number of separate days on 

 which individuals were sighted ranged 

 from 1 to 12 days (mean 2.5). How- 

 ever, given the strong bias in photo- 

 graphic effort towards other species 

 in the region, it is likely that rates 

 of within-season occurrence and an- 

 nual return are considerably under- 

 represented in the data. Overall, the 

 results suggest some similarity be- 

 tween the population characteristics 

 of fin whales and those of the sym- 

 patric humpback whale Megaptera 

 novaeangliiie, although data from 

 whaling catches and from radio tele- 

 metry point to the existence of major 

 differences between the two species. 



Population Characteristics of 

 Individually Identified Fin Whales 

 Balaenoptera physalus in 

 Massachusetts Bay 



Irene E. Seipt 

 Phillip J. Clapham 

 Charles A. Mayo 

 Mary P. Hawvermale 



Cetacean Research Program, Center for Coastal Studies 

 Box 1036, Provincetown, Massachusetts 02657 



Manuscript accepted 11 December 1989. 

 Fishery Bulletin, U.S. 88:271-278. 



In recent years, techniques for the 

 identification of individual cetaceans 

 using variations in natural markings 

 and scars have permitted investiga- 

 tions of the biology and behavior of 

 many species (recently summarized 

 in Hammond et al. 1990). Some of 

 these studies have yielded detailed 

 descriptions of the structure and 

 patterns of migratory movement of 

 some populations. Until recently, 

 similar studies of fin whales Bnlae- 

 noptera physalus had been hampered 

 by the lack of a technique with which 

 to reliably identify individual whales, 

 and by the tendency of observers to 

 concentrate on more accessible spe- 

 cies whose ranges overlap that of the 

 fin whale. 



As a result, the high-latitude distri- 

 bution of the fin whale remains poor- 

 ly understood despite extensive hunt- 

 ing this century. On the one hand, 

 whaling data and information from 

 some radio telemetry studies have 

 shown that fin whales sometimes un- 

 dertake extensive movements. For 

 example, a whale radio-tagged by 

 Watkins et al. (1984) travelled 1700 

 km across the Irminger Sea in 9.5 

 days. Discovery tag returns suggest 

 that Antarctic fin whales, at least 

 over the course of several seasons, 

 may have high-latitude ranges that 

 encompass as much as 90 degrees of 

 longitude (Brown 1962), In contrast 

 to this, a whale tagged by Watkins 



et al. (1981) in Prince William Sound, 

 Alaska, exhibited short-term site fidel- 

 ity, remaining in a restricted area for 

 at least 28 days. At a broader level, 

 whaling data led Sergeant (1977) to 

 characterize the composition of the 

 North Atlantic fin whale population 

 as a "patchy continuum," Mitchell 

 (1974) believed that some spatial sep- 

 aration of stocks existed, but that dif- 

 ferent populations moved latitudinal- 

 ly with the seasons, with some whales 

 moving south in winter to occupy the 

 summering areas of others. Data 

 from CeTAP (1982) generally sup- 

 port this idea of a seasonal shift in the 

 population. 



Mayo (1982) and Mayo et al. (1985) 

 presented a technicjue for the identi- 

 fication of individual fin whales using 

 variations in natural features as well 

 as prominent scars. This technique 

 has since been adopted by a number 

 of observers in the western North 

 Atlantic (Clapham 1987, Agler et al. 

 1990), and has been used by us to 

 study the population characteristics 

 of fin whales observed in Massachu- 

 setts Bay during the period 1980-87. 

 We present here the results of this 

 study, including evidence that fin 

 whales on a high-latitude feeding 

 ground exhibit patterns of seasonal 

 occurrence and annual return that 

 are in some respects similar to those 

 shown for humpback whales Megap- 

 tera no vaeangliae.y 



271 



