FISHERY BULLETIN: VOL. 83. NO. 3 



per hour for each month of summer for each year 

 with sufficient data (Fig. 2). This suggests that the 

 decline resulted from a combination of both factors, 

 with a general overall decline in relative abundance 

 since about 1973 and a progressive retardation of the 

 peak of numbers since about 1975. Unfortunately 

 there is insufficient information in Department of 

 Fisheries and Oceans records to decide if any change 

 in food supply could have occurred during those 

 years, especially with respect to juvenile herring 

 abundance (T. D. Iles^). Nevertheless, our surface 

 temperature records for the inner Quoddy region 

 reveal a consistent decline in the mean summer value 

 (centered on mid-August) from above 12°C in 1971 

 to below 11°C in 1977 (Gaskin et al. 1979). The 

 temperature curve is compared with the pattern of 

 relative abundance in Figure 11; there is close cor- 

 respondence from 1972 onwards. Such a decline 

 might result from increase in relative dominance of 



''T. D. lies, Biological Station, Department of Fisheries and 

 Oceans, New Brunswick, EOG 2X0, Canada, August 1980. 



Nova Scotia current water in the Bay of Fundy 

 (Sutcliffe et al. 1976) and perhaps a significant 

 decline in the availability of zooplankton prey of 

 juvenile herring. Alternatively the slightly cooler 

 waters might be marginally less suitable for young 

 porpoise calves. 



ACKNOWLEDGMENTS 



The authors are very grateful to J. Hines and G. 

 Darlington of the Department of Mathematics and 

 Statistics at the University of Guelph for much 

 assistance and advice during the analysis of the en- 

 vironmental data. G. J. D. Smith and A. J. Read of 

 the Department of Zoology read the manuscript in 

 its several drafts, and along with two anonymous 

 referees gave much useful and constructive advice 

 regarding improvements. Many former and current 

 assistants and graduate students, too numerous to 

 name, helped to collect the laboriously obtained field 

 data. Marine Research Associates of Lords Cove and 

 the late R. Thurber of St. Andrews, N.B., provided 



7- 



6- 



C 



4- 



CO 



Figure 1 1 .- Comparison of midsummer (late 

 •July-early September) sightings per hour of har- 

 bor porpoises in the Fish Harbor region of New 

 Brunswick between 1970 and 1978 with surface 

 temperatures based on 8 stations (n = about 

 60/annum): Solid circles and dashed line (sight- 

 ings per hour), open circles and dotted line (°C). 

 Vertical dots and bars represent the standard 

 error about the mean. 



12.0 

 .9 

 .8 

 .7 

 .6 

 .5 

 .4 

 .3 

 .2 

 .1 



1 1.0- 

 .9 

 .8' 



I. \ 

 I . \ 



\ ?. 



< . 



 I 



9 





2. 



4. 



: \ 



■■•, y 

 ■» 



6 



T. \ 



i'- 



11 



— I 1 1 1 — I 1 — 



1970 1971 1972 1973 1974 1975 



— I I 



1976 1977 



1978 



Year 



440 



