FISHERY BULLETIN: VOL. 83. NO. 4 



Radio-tagged porpoises exhibiting the high activity 

 state expressed two ventilation patterns; these are 

 described using the terminology of Watson and 

 Gaskin (1983). Most data recorded in this activity 

 state consisted of Pattern B, a series of long dives, 

 each followed by a sequence of several rolls (see 

 Figure 5). Less commonly observed was Pattern A, 

 in which single rolls followed relatively short 

 submergences (seldom exceeding 30 s in duration). 

 Pattern A was exhibited for brief periods only (5-16 

 min) and comprised <4% of all signals recorded dur- 

 ing high activity sequences. 



Ventilation data recorded from RT-2 and RT-4 were 

 dominated by low activity sequences. However, low 

 activity sequences were not recorded from either 

 RT-3 or RT-7. Although RT-3 was frequently observed 

 resting at the surface, the loose transmitter package 

 (see above) caused the antenna to reflect backwards, 

 allowing signal reception only during rolls. Thus, it 

 was not possible to accurately monitor the duration 

 of resting periods for this porpoise Data from RT-7 

 were acquired only during periods of high winds and 

 heavy seas which precluded surface resting behavior. 



Because surface resting was the criterion on which 

 determinations of activity levels were based, it was 

 impossible to ascertain the activity level of radio- 

 tagged porpoises in periods of high vdnds and heavy 

 seas. Tb construct an activity budget, therefore, it 

 was necessary to exclude data recorded during 

 periods when surface resting was not possible A 

 total of 10.5 h of ventilation sequences were record- 

 ed under such conditions. In addition, data acquired 

 from RT-3 were excluded because of the bias imposed 

 by the transmitting system. After these data had 

 been deleted, 24.5 h of ventilation sequences record- 

 ed from RT-2 and RT-4 remained. 



Both RT-2 and RT-4 were relatively inactive from 

 midnight until 0600, spending over 90% of this 

 period in the low activity state Both porpoises spent 

 a considerable portion of this time resting at the sur- 

 face (Ikble 2). During this period of reduced activity, 

 the porpoises were seldom located in nearshore 

 areas, although they frequented such areas during 

 other periods. The two porpoises were highly active 

 for 35% (RT-2) and 36% (RT-4) of daylight and even- 

 ing hours (0600 until midnight) (Ikble 2). 



DISCUSSION 



Movements and Ranges 



Radio-tagged harbor porpoises demonstrated con- 

 siderable mobility within the study area, often 

 moving distances of 15-20 km in a 24-h period. These 



results are similar to those previously reported from 

 radio-tagged harbor porpoises in the region (Gaskin 

 et al. 1975). Other inshore odontocete species exhibit 

 daily movements of a similar magnitude For exam- 

 ple, dusky dolphins, Lagenorhynchus obscurus, track- 

 ed by Wiirsig (1982), travelled a "mean minimum 

 distance" of 19.2 km each day. However, pelagic 

 species apparently travel over much greater 

 distances. A pelagic spotted dolphin, Stenella at- 

 tenuata, tracked by Leatherwood and Ljungblad 

 (1979), travelled over 100 km in a 12-h period, while 

 common dolphins, Delphintcs delphis, may cover 

 distances of 70-140 km each day (Evans 1971). 



The mobility exhibited by the majority of radio- 

 tagged porpoises suggest that the ranges of these 

 animals were similar to that calculated for RT-2 (210 

 km^). Only one other study has examined the areas 

 of home ranges utilized by odontocete cetaceans. 

 Wells et al. (1980) used resightings of naturally mark- 

 ed animals to estimate the size of bottlenose dolphin, 

 Tursiops truncatus, ranges in the coastal waters of 

 western Florida. The mean home ranges of these 

 dolphins varied with age and sex, and ranged from 

 15 to 41 km^. It is possible that the apparent dif- 

 ference in the size of home ranges of these two 

 species reflects the exploitation of different prey 

 species. In the Bay of Fundy, harbor porpoises feed 

 predominantly on juvenile herring, Clupea harengvs 

 (Smith and Gaskin 1974), which exhibit a high degree 

 of mobility (Jovellanos and Gaskin 1983). In contrast, 

 Florida bottlenose dolphins are opportunistic 

 predators on species such as mullet Mugil cephalus, 

 which may be more sedentary in nature (Irvine et 

 al. 1981). 



Patterns of Activity 



The patterns of activity observed in the present 



Table 2.— Activity patterns of radio-tagged harbor porpoises RT-2 

 and RT-4 in the western Bay of Fundy. The low activity state was 

 characterized by frequent surface resting periods, which were in- 

 frequent or absent in the high activity state. Only data recorded dur- 

 ing calm conditions have been included. 



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