FISHERY BULLETIN: VOL. 83 NO. 3 



Figure 9. - Movements of scarred mother during 2 h 12 min period of 10 August 1973 accompanied by calf (57 position fixes). On some occa- 

 sions they resurfaced close to an immediately previous position; about 75 surfacings are represented by these positions. Reverse arrow in- 

 dicates initial contact point (just outside Lords Cove), solid arrow point where tracking was abandoned, and white circles position of a medium- 

 sized animal which briefly joined the pair. 



we found relative abundance of porpoises conversely 

 to be greatest during neap tides. About 63% of the 

 sightings in 1973-75 were of mothers and calves. 

 Possibly these animals stay out of semi-enclosed 

 areas during periods of maximum water transport, 

 especially in areas with turbulent shallows such as 

 the Fish Harbour region. On the other hand, if there 

 are larger numbers of herring schools moving into 

 the outer part of the Quoddy region it may not be 

 necessary to forage in inshore waters. Once the 

 animals are in the study area however, the observed 

 changes in distribution during the tidal cycle confirm 

 the earlier subjective comment (Watson 1976) that 

 porpoises seemed to move inshore with the flood tide 

 and offshore with the ebb. 



The distribution of porpoise activity in the region 

 appeared to be closely related to subsurface 

 topography, particularly the margins of the basins 

 and channels in areas of restricted water flow, the 

 lee of islets, especially Fish Island and the Nub, and 

 blind trench heads such as that just north of Hath- 

 away Head. Because our meager acoustic records 

 revealed fish traces in all these sites at one time or 

 another (Fig. 3), we speculate that these may be 

 areas of fish accumulation which the porpoises have 



learned to exploit. Each may have subsurface eddies 

 or areas of relatively slack water against the lee side 

 of the slope or near the bottom, in which fish can 

 shelter from strong currents, and in which zooplank- 

 ton might also accumulate. In such areas fish could 

 not only avoid being carried further inshore, but 

 could also feed (Hamner and Hauri 1977). Dispersal 

 from offshore areas into the coastal belt is likely to be 

 augmented by onshore winds, which can increase 

 significantly the flow of water in the immediate sur- 

 face layers. Local fishermen believe that offshore 

 winds serve to hold "feed" away from the coast, while 

 coastwise winds might reduce the possibility of entry 

 into Fish Harbour by increasing surface flow past 

 the relatively narrow passages. We conclude that 

 light or moderate winds are unlikely to affect any 

 small cetacean directly; when winds were strong 

 enough that behavior might conceivably be affected, 

 we were not usually operating. 



Large variation always occurs in data such as 

 these, and it is to a large extent unpredictable. Such 

 variation in relative abundance can be explained 

 quite simply; these animals are large, highly mobile 

 predators with sophisticated adaptations both for ac- 

 tive and passive acoustic scanning for their equally 



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