1999 

 OUR LIVING OCEANS 



1994). Seven of 35 live-captured bottlenose dol- 

 phins (20%) from Matagorda Bay, Texas, in 1992, 

 tested positive for previous exposure and it is pos- 

 sible that other cstuarine resident dolphin com- 

 mimities have been exposed as well. Ihe relatively 

 high number of bottlenose dolphin deaths which 

 occurred during these mortality events suggests 

 that these populations may be physiologically 

 stressed, possibly from nearshore pollution and 

 chemical contamination or other causes. For these 

 reasons, and because the PBR tor most of these 

 relatively small provisional stocks would be ex- 

 cecdeci with the incidental capture ot a single dol- 

 phin, each is recognized as a strategic stock. 



HARBOR PORPOISE: 

 GULF OF MAINE- 

 BAY OF FUNDY STOCK 



Stock Definition and 

 Geographic Range 



rhis harbor porpoise stock is found in U.S. 

 and C'anadian Atlantic waters. During the sum- 

 mer duly to September), harbor porpoises are con- 

 centrated in the northern Gulf of Maine-south- 

 ern Bay of Fundy region, generally in waters less 

 than 1 50 meters (m) deep (Palka et al., 1996). [dur- 

 ing hill ((October to necember) and spring (April 

 to |une), harbor porpoises are widely dispersed 

 from North Carolina to Maine, though in much 

 lower densities than that seen during the summer. 

 No specific migratory routes to the northern Gulf 

 of Maine-lower Bay of Fundy region have been 

 documented. Animals are seen from the coastline 

 to the middle of the Gulf of Maine (>200 m deep) 

 in both spring and tall. During winter (December 

 to March), some harbor porpoises have been re- 

 ported in waters ott the Mid-Atlantic (trom New 

 Jersey to North C^arolina). Two stranding records 

 trom Florida occurred during the 1980's. 



Ciaskin ( 1984. 1992) proposed that there were 

 tour separate populations in the western North 

 Atlantic: the Gulf of Maine-Bay of Fundy, Gult 

 ot St. Lawrence, Newfoundland, and Greenland 

 populations. Recent analy.ses involving mitochon- 

 drial DNA (Wang et al., 1996), organochlorine 

 contaminants (Westgate et al., 1997), heavy met- 

 als (Johnston, 1995), and life history parameters 



(Read and Horn, 1 995) support G.iskin's proposal. 

 In particular, there is a suggestion that the Gulf ot 

 Maine-Bay ot Fundy females are different than 

 Gulf of St. Lawrence females, but males were sta- 

 tistically indistinguishable (Palka et al., 1 996). Re- 

 search on microsatellites, a potentially powerful 

 genetic tool, is currently being conducted to re- 

 analyze existing genetic data and analyze new 

 samples in order to resolve the larger scale stock 

 structure question. 



Population Size 



Line-transect surveys were conducted during 

 1991, 1992, and 1995 to estimate the population 

 size of harbor porpoises aggregated in the Gulf of 

 Maine-Bay of Fundy region during the summer. 

 The next scheduled survey is in the summer ot 

 1999. The abundance estimated trom the 1991 

 survey was 37,500 (CV- = 0.29, 95% C! = 

 26,700-86,400) (Palka, 1995a), 67,500 from the 

 1992 survey (CV = 0.23, 95% CI = 32,900- 

 104,600) (Smith et al., 1993) and 74,000 harbor 

 porpoises from the 1995 survey (CV = 0.20, 95% 

 CI =40,900-109,100) (Palka, 1996). The inverse 

 variance weighted-average abundance estimate 

 from all three survevs (Smith et al., 1993) was 

 54,300 harbor porpoises (CV = 0.14, 95% CI = 

 41 ,300-71,400). Possible reasons tor inter-annual 

 differences in abundance and distribution include 

 experimental error and inter-annual changes in wa- 

 ter temperature and availability ot primary prey 

 species (Palka, 1995b). Ihe minimuiii population 

 estimate calculated tor this popuLitimi is 48,289 

 (CV = 0.14). 



Current Population Trend 



Data are not sufficient to determine the popu- 

 lation trends tor this species. Previous abundance 

 estimates tor harbor porpoises in the Cult ot 



-C'oc-KiLicni of varidiion ((-V) is a statisiic.ll measure used to 

 calculate confidence iniervais (CI), which gauge the accuracy' 

 of popuhuion estimates. An accurate population estimate is 

 characterized by a low CV and a narrow CI. CI is often given 

 a percentage likelihootl of being correct (e.g. 95% means thai 

 if the data were rcsampled and the CI were recalculated 10(1 

 times, then 95 times it would contain the true value. 



252 



