tuary, Maine, as determined by daily growth increments 

 in otoliths. Fish. Bull., U.S. 79:123-130. 



UCHIYAMA, J. H., AND P. STRUHSAKER. 



1981. Age and growth of skipjack tuna, Katsuwonus 

 pelamis, and yellowfin tuna, Thunnus albacares, as indi- 

 cated by daily growth increments of sagittae. Fish. Bull., 

 U.S. 79:151-162. 



WILD, A., AND T. J. FOREMAN. 



1980. The relationship between otolith increments and 

 time for yellowfin and skipjack tuna marked with tet- 

 racycline. [In. Engl, and Span.] Inter-Am. Trop. Tuna 

 Comm. Bull. 17:509-560. 



RICHARD RADTKE 



Hawaii Institute of Marine Biology 

 P.O. Box 1346 

 Kaneohe, HI 96744 



YEARLY CHANGES IN ABUNDANCE OF 



HARBOR SEALS, PHOCA V1TULINA, AT 



A WINTER HAUL-OUT SITE IN MASSACHUSETTS 



Information on the abundance of the harbor seal, 

 Phoca vitulina concolor, population in New 

 England consists of outdated estimates in the lit- 

 erature (King 1964; Maxwell 1967; Hewer 1974; 

 Bonner 1976). A more recent series of unpublished 

 reports (Richardson 1 ; Knapp and Winn 2 ; Kraus 3 ; 

 Gilbert and Stein 4 ) suggests a harbor seal popula- 

 tion which is increasing in numbers from its 

 present breeding range north of Massachusetts 

 southward into southern New England. A primary 

 research need identified by Prescott et al. 5 was 

 confirmation of this suspected increase in the har- 

 bor seal population throughout New England. 



'Richardson, D. T. 1973. Distribution and abundance of 

 harbor and gray seals in Acadia National Park. Final report to 

 National Park Service and Maine Department of Sea and Shore 

 Fisheries, State of Maine Contract No. MM4AC009, 59 p. 



2 Knapp, C. L., and H. E. Winn. 1978. Harbor seals, New 

 Hampshire to Long Island. Unpubl. rep., University of Rhode 

 Island, Graduate School of Oceanography, Kingston, RI 02881, 

 36 p. 



3 Kraus, S. 1980. The population of harbor seals (Phoca vit- 

 ulina) in southern New England. Unpubl. rep. of harbor seal 

 workshop, 5 March 1980, Boston, Mass. New England 

 Aquarium, Boston, MA 02109, 9 p. 



••Gilbert, J. R., and J. L. Stein. 1981. Harbor seal popula- 

 tions and marine mammal fisheries interactions. University of 

 Maine, Department of Forestry and Wildlife Resources, Orono, 

 Maine. Annual Report to NEFC/NMFS/NOAA, Contract No. 

 NA-80-FA-C-00029, 55 p. 



^ 5 Prescott, J. H.,S. D. Kraus, and J. R. Gilbert. 1980. East 

 Coast/Gulf Coast cetacean and pinniped workshop. Final Re- 

 port for Marine Mammal Commission, contract 79/02. Avail- 

 able National Technical Information Service, Springfield, VA 

 22151 as PB80-160104, 142 p. 



This study summarizes available data on annual 

 fluctuations in seal numbers since 1972 at one site 

 in southeastern Massachusetts. 



The study was conducted at Stage Point, Man- 

 omet, Mass. (lat. 41°55'N, long. 70°32'W). Harbor 

 seals occur seasonally at Stage Point from late 

 October through May (Schneider and Payne 1983). 

 A rapid decrease in numbers occurs at this site in 

 May (Schneider and Payne 1983 ), prior to the pup- 

 ping season which occurs mid-May to mid-June in 

 Maine (Richardson footnote 1; Wilson 6 ). A few 

 seals are reported throughout the summer but 

 most move northward out of the study area by 

 June. 



The study site consists of a shoreline with a 

 sandy cliff to 25 m. Sand, rock, and cobble extend 

 from the base of the cliff into the water. Seals haul 

 out exclusively on the larger rocks in the im- 

 mediate subtidal zone from about 1-2 h before to 

 1-2 h after low tide (Schneider and Payne 1983). 

 A similar haul-out pattern has been described 

 at other rock-ledge sites in New England 

 (Richardson footnote 1; Wilson footnote 6). Be- 

 cause of the synchronized haul out observed at 

 Stage Point, the number of seals seen on the rocks 

 is considered representative of the number of seals 

 in the immediate vicinity (Schneider and Payne 

 1983) and, therefore, a useful index for monitoring 

 changes in the abundance of harbor seals at this 

 location. 



Methods 



Counts at Stage Point were made by direct ob- 

 servation within 2 h of low tide from the cliffs 

 above the haul-out site. Schneider and Payne 

 (1983) found that during 1979-80 the average 

 number of seals observed at Stage Point peaked in 

 January; therefore, the average number of seals 

 ( ±SE) seen per daily count in January of each year 

 was used in analyses among years. We trans- 

 formed the January averages into logarithmic 

 values, and the coefficient of correlation (r) from 

 the linear regression was used to describe the rela- 

 tionship between the average number of seals seen 

 per daily count in January 1972 and 1983. 



In addition, air temperature, wave intensity, 

 and human disturbance influence the total 

 number of seals seen per daily count at Stage Point 



6 Wilson, S. C. 1978. Social organization and behavior of 

 harbor seals Phoca vitulina concolor in Maine. Final Report to 

 Marine Mammal Commission, Contract No. GPO PB 280- 

 3188. Available National Technical Information Service, 

 Springfield, VA 22151 as PB 280 188, 103 p. 



440 



FISHERY BULLETIN: VOL. 82, NO. 2, 1984. 



