Schilling et al,: Behavior of Balaenoptera boreahs during episodic influx 



753 



II I 



II I M I, Ml I 



I .11 



I I I I I I 



II II 



July 



August 



September 



DATE 



Figure 3 



Occurrence of individual sei whales Balaenoptera horealis in the southern Gulf of Maine 

 during 1986. Individual whales are ordered (top to bottom) by date of first sighting; each 

 row of marks represents the dates on which one individual was seen during the year. 

 Vertical marks represent single whales. 



vidual associations were trans- 

 ient, generally lasting less than 

 24 hr. 



Of 13 cow/calf pairs, 3 (23.0%) 

 were associated with 1 or more 

 other whales, while 48 (51.6%) of 

 the 93 non-calf groups involved 

 2 or more whales. Frequency of 

 association with another whale 

 was not statistically significant 

 between groups with and with- 

 out mother-calf pairs (x^ 3.7, p 

 0.06, 1 df). Cow/calf pairs were 

 never seen with more than one 

 associate. 



Comparisons with 

 other data sets 



S 60:64 





10 20 30 10 50 60 70 80 90 100 130 160 200 300 500 



Seconds Between Respirations 



Figure 4 



Histogram showing the distribution of breath intervals (see) 

 from sei whales Balaenoptera borealis recorded during 52 

 sightings in the 1986 season on northern Stellwagen Bank. 

 Note the scale change for the longer breath intervals due to 

 their infrequent occurrence. 



northern and southern Stellwagen Banks, where most 

 observations took place (two-tailed i-test, p 0.93, 1 df). 

 Resightings of individual animals on successive days 

 were recorded 14 times. In cases where all members 

 of an associated group were photoidentified, only one 

 pair of animals was seen together on two days; one 

 whale from this pair was later sighted with a different 

 associate two days later. These data indicate that indi- 



Sei whales identified in the south- 

 ern Gulf of Maine in 1986 were 

 compared with one 1984 photo- 

 graph from Georges Bank (At- 

 lantic Cetacean Research Center), 

 one from Stellwagen Bank in 

 1987 (Plymouth Marine Mammal 

 Center), one from Jeffrey's Ledge in 1988 (Cetacean 

 Research Unit), three from the Scotian Shelf in 1988 

 (Atlantic Cetacean Research Center and Nancy Miller), 

 and four from the Scotian Shelf in 1989 (New England 

 Aquarium). There were two matches. Sei whale 33 was 

 photographed on 11 June 1984 between Wilker's and 

 Oceanographer's Canyon on the southern edge of 

 Georges Bank (40°05'N, 68°19'W), 176nmi from the 

 1986 sighting; sei whale 19 was photographed on 28 

 August 1989 on the Nova Scotian Shelf (42°57'N, 

 65°09'W), 211nmi from its 1986 sighting. 



Discussion 



Photoidentification of individual animals has been ac- 

 complished for numerous baleen and toothed whales 

 (Katona et al. 1980, Dorsey 1983, Agler et al. 1990, 

 Seipt et al. 1990). Our results indicate that some sei 

 whales can be identified using variations in natural 

 markings. Dorsal-fin shape, natural pigment patterns, 

 and scarring were all useful features. The presence of 

 circular scars along the flank— hypothesized to be 

 caused by small sharks (Shevchenko 1977), lampreys, 

 or pathogenic microorganisms (Tomilin 1957, Rice 

 1977)— and dorsal-fin notches (unknown origin) both 

 facilitated identification of the individuals. While these 

 techniques work within a single season, the possibility 

 of acquiring new dorsal-fin notches, new scars, or 



