sophisticated navigational training required by 

 young animals. 



Andersen (1974) concluded, on the basis of 

 parasitic infestation, that about 907c of the 50 harbor 

 porpoises he examined from Danish pound nets were 

 "sick." Most of the yearlings autopsied from our weir 

 sample were only lightly parasitized and appeared to 

 be in good health. Older harbor porpoises were heavily 

 infected with pseudaliid lung worms and campulid 

 liver flukes, but in our experience this is typical of the 

 adult population in general (Arnold and Gaskin 1974). 



Many of the harbor porpoises we examined had 

 empty stomachs, indicating either a lack of available 

 fish in the weir or refusal to feed while trapped. Har- 

 bor porpoises observed inside weirs usually ap- 

 peared to be stressed, breathing rapidly and 

 swimming quickly (1.5 m/s) in a regular circular or 

 figure- eight pattern. These animals rarely demon- 

 strated any behavior that might have been inter- 

 preted as feeding or foraging activity. 



Weir Entrapment Questionnaire 



The 36 respondents reported 59 trapped harbor 

 porpoises over the 5-yr period, 1975-79. Of these 

 animals, 23 (39%) were shot or died accidentally, 

 usually by drowning after becoming entangled in the 

 seine net while being removed. The majority of weir 

 fishermen {727c) indicated that they endeavored to 

 release the animals unharmed, either by seining and 

 releasing them, or by waiting for the animals to es- 

 cape on their own. One respondent who shot en- 

 trapped harbor porpoises indicated that the meat was 

 used for human consumption. In general, weir fisher- 

 men displayed a favorable attitude towards harbor 

 porpoises, in contrast to their attitude towards har- 

 bor seals, Phoca vitulina. Harbor seals are generally 

 considered pests, as they swim freely in and out of 

 weirs and may chew holes in the netting. 



Fourteen respondents indicated that harbor por- 

 poises became trapped in weirs during the summer 

 months (July-September), while only one reported 

 entrapment at other times (September-October). 

 This is in agreement with our own observations and 

 reflects the seasonal abundance of both harbor por- 

 poises and herring in inshore waters (Gaskin 1977). 



Many responses (12 of 18) indicated that harbor 

 porpoises usually entered herring weirs at night. This 

 suggests that visual detection of the weir is important 

 in avoiding entrapment. Busnel et al. (1965) found 

 that a captive harbor porpoise using only echoloca- 

 tion had difficulty avoiding transparent nylon mono- 

 filament 3.5 mm in diameter. Since the netting on 

 weirs is constructed from synthetic material, it may 



not be readily detectable by echolocating harbor 

 porpoises. 



Herring tend to be closer to the surface at night than 

 during daylight hours (Brawn 1960) and thus are 

 more susceptible to the weir fishery during this period. 

 Harbor porpoises may follow schools of herring into 

 the weirs and then become trapped. However, ques- 

 tionnaire respondents indicated that large numbers 

 of herring were not always present when entrapment 

 occurred. Some harbor porpoises, therefore, pre- 

 sumably became trapped as a result of foraging on 

 small schools of herring or other prey species. 



Impact of the Fishery on the Population 



If the annual bycatch per weir (0.328) calculated 

 from the questionnaire returns is representative of 

 all 216 licensed weirs, some 70 harbor porpoises 

 become trapped in Charlotte County each year. Of 

 these animals, 27 die as a result of entrapment, 



Gaskin (1977), using uncorrected sighting per unit 

 effort data, estimated the harbor porpoise popula- 

 tion in the lower Bay of Fundy as 4,000 during mid- 

 August. Prescott et al. (1981) estimated the August 

 population in the "western half of the Bay of Fundy" 

 as 3,456, using aerial strip census methodology. The 

 annual mortality inflicted on the harbor porpoise 

 population by weirs in Charlotte County would ap- 

 pear to be < 1 7c of these population estimates. An un- 

 known number of individuals from this population 

 are trapped in weirs in northern Maine (Prescott and 

 Fiorelli 1980) and a few scattered weirs along the 

 Digby, Nova Scotia, shore and in Saint John County, 

 New Brunswick (incomplete data from questionnaire 

 returns). 



Subsistence hunting for harbor porpoises is at a 

 very low level in Charlotte County at the present 

 time, although one native hunter claimed to have 

 taken approximately 50 animals in 1979 (Prescott et 

 al. 1981). Based on our own observations, however, 

 native hunters from Maine take only 5-10 harbor por- 

 poises each summer in the area. Harbor porpoises 

 used for human consumption by New Brunswick fish- 

 ing families are almost invariably from herring weirs 

 or gill nets. 



Entanglement in gill nets has a much greater poten- 

 tial for impact on the P. phocoena population since 

 there is no opportunity for live release. About 20 

 fishermen actively gill net in the county (A. B. 

 Cross 1 ), but we have little information on the level of 



'A. B. Cross, Fisheries and Oceans Canada, Lord's Cove, Deer 

 Island, New Brunswick, Canada E0G 2J0, pers. commun. August 

 1982. 



661 



