272 



Fishery Bulletin 88(2). 1990 



Figure 1 



Fin whale study area. 



Methods 



The observations in this study were conducted in the 

 coastal region dominated by Massachusetts Bay and 

 Cape Cod Bay (Fig. 1) between the years 1980 and 1987 

 inclusive. Observations were made from 30-m commer- 

 cial v^rhalewatching vessels operating between April 

 and October of each year from Provincetown, Massa- 

 chusetts. Beginning in the autumn of 1983, additional 

 cruises were made from a 12-m diesel-powered re- 

 search vessel and, beginning in the autumn of 1985, 

 from a 14-m auxiliary ketch. The total number of 

 cruises conducted during the study period was 5979, 

 97% of which were made by whalewatching vessels. 

 Search patterns were in most cases non-random and 

 non-systematic. This was particularly true of the whale- 

 watching vessels, where search tracks were decided by 

 the captains based upon where most whales had been 

 seen the previous day or trip. Search effort directed 

 specifically at fin whales varied considerably. Because 

 humpback and (during the spring) right whales Euba- 

 laena glacialis were preferred by the whalewatching 

 vessels, opportunities to obtain usable photographs of 

 fin whales occurred only incidentally except during 



periods when the preferred species were less abundant 

 or absent. An exception were four fin whales that ex- 

 hibited large, permanent scars that were easily notice- 

 able from a distance of 100 m or more. Because these 

 whales were among the few that could be readily 

 recognized by all observers in the field, they were much 

 more likely to be photographed, and confirmation of 

 identity could be achieved with poorer quality photo- 

 graphs than those taken of unscarred whales. 



Individual fin whales were identified using variations 

 in natural markings, as described in Clapham (1987), 

 Hawvermale (1987), and Agler et al. (1990). Major 

 features used included the shape of the dorsal fin, the 

 light-colored wash of pigment on the right side of the 

 head (the "blaze"), and the V-shaped pattern of light 

 pigment behind the blowholes and extending down both 

 sides of the whale (the "chevron"). Scars were also 

 used. A full definition of features and a description of 

 the technique can be found in Agler et al. (1990). 



Fin whales exhibit asymmetry in their coloration, 

 with greater variability in features on the right side 

 of the head than the left; consequently, while some 

 whales were identified using both right and left sides, 

 an individual was not considered matchable if only the 



