834 
Fishery Bulletin 95(4), 1997 
whales. The area is also a primary location for seine 
fishing for herring off New England. Herring seiners 
were observed fishing or transiting to or from areas of 
whale aggregation daily during summers 1992-94. 
Although herring stocks were increasing, our data 
indicated that prey available for whales on Stell- 
wagen showed a marked decrease, corresponding to 
a decrease in sand lance populations throughout the 
Northeast ecosystem (Sherman, 1992). This decrease 
in prey would be expected given the documented in- 
verse relation between sand lance and herring or 
mackerel stocks, primarily due to direct predation 
(Fogarty et al., 1991). Although we cannot assign a 
definitive prey type to our echo-sounder traces from 
Stellwagen, the documented importance of sand lance 
as a prey for whales on Stellwagen Bank through 
observations of prey in the mouths of feeding whales 
(Hain et al., 1982; Weinrich et al., 1992), the direct 
observation of sand lance on Stellwagen Bank (Hain 
et al., 1995), prey in fish stomachs, and the lack of 
other suitable prey records throughout the years 
suggest that sand lance remained the predominant 
prey type for whales in that location. 
We propose that humpback whales feeding in the 
Gulf of Maine ecosystem have shifted from their pri- 
mary distribution of the mid-1970s through the late- 
1980’s as a result of a shift in the abundance of avail- 
able prey. Although we have considered only a small 
portion of the Gnlf of Maine habitat, our findings 
correspond with other data from the same period. In 
the western side of the Great South Channel (an 
important area for whales from 1979 to 1991 where 
sand lance were the primary prey [Kenney and Winn, 
1986; Payne et al., 1990 J) humpback whale sightings 
were sporadic after July 1991 (Francis 9 ; Clapham 10 ; 
Mattila * 11 ). OffMt. Desert Rock, Maine, where hump- 
backs were virtually absent throughout the 1980’s, 
numbers of whale sightings increased to levels far 
above those of the mid-1970’s (Fernald 12 ). Surveys 
conducted in 1993 on Georges Bank by researchers 
from the YONAH (Years of the North Atlantic Hump- 
back) project also sighted large numbers of hump- 
backs, including many animals photographed on 
Stellwagen Bank in previous years (Clapham 10 ). 
If a resurgence of herring is responsible for shifts 
in distribution and in primary prey type, it suggests 
that the distribution of humpback whales through 
the late 1970’s and 1980’s may have been a human- 
9 Francis, L. 1995. Atlantic Cetacean Research Center, PO 
Box 1413, Gloucester, MA 01930. Personal commun. 
10 Clapham, P. 1995. Smithsonian Institution, Washington, 
DC. Personal commun. 
11 Mattila, D. 1995. Center for Coastal Studies, PO Box 1036, 
Provincetown, MA 02657. Personal commun. 
12 Fernald, T. 1995. Allied Whale, College of the Atlantic, Bar 
Harbor, ME 04609. Personal commun. 
induced consequence. The “explosion” of sand lance 
in the mid- to late 1970’s is thought to be primarily 
the result of the virtual elimination of herring due 
to overfishing. If this is true, we hypothesize that 
our observed distribution of whales from 1992 to 1994 
should remain relatively stable over the course of a 
fairly long period because the current situation would 
be closer to a “natural” ecosystem. 
Alternatively, fluctuations in primary prey may 
occur naturally, and may take place regardless of 
human interference. If this is true, we hypothesize 
that whale distributions will show fluctuations that 
may be cyclical. New England ground-fishermen have 
for years talked of regular cycles in sand lance abun- 
dance, although there are no scientific data to sup- 
port this often-made contention. 
Regardless of which hypothesis, if either, proves 
true, our data show a shift in both distribution and 
primary prey type for humpback whales in southern 
New England waters in recent years. Because this 
shift has been so complete, it will be interesting and 
illustrative to see whether, and how, other potentially 
prey-dependant humpback whale life history param- 
eters, such as reproductive patterns, social behav- 
ior, and demographics of whales, all well-documented 
during a period of explosive sand lance abundance 
(Clapham and Mayo, 1990; Weinrich, 1991; Weinrich 
and Kuhlberg, 1991; Clapham et al., 1992), change 
in response to these ecosystem alterations. 
Acknowledgments 
We would like to thank Cindy Belt, Tina Laidlaw, 
Joy Lapseritis, Laine Gonzales, Nancy Miller, Liz 
Phinney, Leo Axtin, Karla Bristol, and many interns 
at the Cetacean Research Unit for their assistance 
in gathering sighting data for this study. Staff of the 
Center for Coastal Studies, Provincetown, MA, and the 
Atlantic Cetacean Research Center, Gloucester, MA, 
were generous in sharing data on ages and sightings of 
individuals, especially mother-calf pairs. Portions of this 
study were funded by the Bruce J. Anderson Founda- 
tion, the Sudbury Foundation, the Fund for Preserva- 
tion of Wildlife and Natural Areas, the Norcross Wild- 
life Foundation, and the American Cetacean Society — 
Los Angeles Chapter. This work was conducted under 
Marine Mammal Research Permit no. 681. 
Literature cited 
Anthony, V. C., and G. Waring. 
1980. The assessment and management of the Georges 
Bank herring fishery. Rapp. P.-V. Reun. Int. Explor. Mer 
177:72-111. 
