GASKIN and WATSON: HARBOR PORI'OISE 



FiGl'RE 10. -Movements of scarred female on 30 August 1974 (solid circles at left of figure) and 29 August 1974 (solid circles in center of 

 tlgure). Solid squares show "patrolling" behavior of school of four animals recorded on 2 August 1974. Qualifying comments on position fixes 

 and surfacings in Figure 9 apply here also. 



mobile prey. That the harbor porpoises in this area 

 can shift tens of kilometers in a few hours cannot be 

 questioned (Read and Gaskin in press); if few fish are 

 present in one area, they may well move in a loosely 

 synchronized group to forage in other localities. This 

 degree of mobility and scanning ability is highly 

 adapted not only to the mobility of their prey species, 

 but also to the patchy nature of the distribution pat- 

 terns of such fish; there is probably a significant ran- 

 dom element in the dispersal of juvenile herring in 

 the Quoddy region (Jovellanos and Gaskin 1983). The 

 type of porpoise movement shown in Figure 9 was 

 presumed to indicate that prey were dispersed, since 

 the animal spent little time in any one location. In the 

 other movement pattern (Fig. 10) the same animal 

 was believed to be encountering prey in local concen- 

 trations that merited prolonged submergences in one 

 area. 



We have little evidence that the region might be 

 significant either as a mating area or a calving 

 ground. Females appear to have their calves off- 

 shore, since, although the latter may be very small in 

 late June and July, they already accompany females 

 sighted in the outer part of the Quoddy region (Smith 

 and Gaskin 1983). Many females with calves appear 

 to remain on tidal convergence streaks up to 20 km 



offshore in the outer Quoddy region (Read 1983) and 

 may not move into the coastal zone at all. It seems 

 more likely that the study area functioned as a signi- 

 ficant feeding area for this species rather than being 

 a zone favoured for reproductive activity. 



The demonstrated existence of "specific ranges" 

 and annual returns by individual harbor porpoises in 

 this study is not surprising. Rather similar patterns, 

 although sometimes on very different geographical 

 scales, have been recorded for Delphinus delphis by 

 Martin et al. (1971), Orcinus orca by Bigg (1982), 

 Tursiops trun^.atus by Wells et al. (1980) and Wiirsig 

 and Wiirsig (1979), and Lagenorhynchus obscurtis by 

 Wiirsig and Wiirsig (1980). Periodic disappearances 

 and abrupt reappearances of T. truncatics were also 

 recorded by Wiirsig (1978), while studying the 

 animal. 



With respect to the progressive decline in relative 

 abundance in the peak part of summer, lack of con- 

 sistent observations through late September-late 

 October (because of high winds) prevented us from 

 determining whether or not this resulted from a real 

 population decrease in the area, or simply a shift of 

 peak abundance from mid-August to mid-September 

 during the decade. Consequently we adopted an in- 

 direct approach to the problem, plotting sightings 



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