276 
Fishery Bulletin 106(3) 
the same fashion (Fig. 5). The center of right whale oc- 
currence tended to remain relatively consistent across 
the season, and there was no statistically significant 
variability in mean latitude or longitude (for the 2- 
week intervals, weighted by SPUE) across the periods 
(Kruskal-Wallis, P-0.210 for latitude, P=0.580 for lon- 
gitude). Similarly, there was no significant interan- 
nual variability in mean latitude (P=0.063) or mean 
longitude (P=0.797). 
The timing of the SPUE maximum varied markedly 
between years: late February-early March in 1998, 
early to mid-April in 1999, late March-early April in 
2000, early March to mid-April in 2001, and late Feb- 
ruary-early March in 2002. This interannual varia- 
tion was responsible for the apparent bimodal pattern 
seen over the season when data were pooled across 
all five years (Table 3). The within-season temporal 
variation was statistically significant in each of the five 
years (P<0.001 for each). The duration of right whale 
occurrence also varied substantially between years: 
January-April in 1998 (no December 1997 surveys), 
December-April in 1999, mid- January-mid-April in 
2000, and at least late December-mid-April in 2001 
(no surveys were undertaken during the first two weeks 
of December 2000), and only late January-late March 
(and a second brief period in early April) in 2002. The 
numbers of consecutive two-week periods when right 
whales were observed were 9 in 1998, 9 in 1999, 7 in 
2000, 9 in 2001, and 5 in 2002. 
Approximately 97% of the right whales sighted within 
the study area by aerial survey were within the criti- 
cal habitat boundaries (Fig. 3). The critical habitat 
included approximately 75% of the total ocean area 
within our defined study area. The majority of cells 
within which right whales were sighted were inside the 
critical habitat, but 17 cells with SPUE >0 fell partially 
or entirely outside the critical habitat (Fig. 4). SPUE 
did vary significantly among the three areas (Kruskal- 
Wallis, P=0.009). However, the mean values for the 
cells east of the critical habitat (11.1 unweighted, 10.9 
weighted by effort and by the proportion of cell area 
for the five cells straddling the eastern boundary) fell 
between the area inside the critical habitat (18.5 un- 
weighted, 23.1 weighted) and the aa outside to the west 
(2.3 unweighted, 2.0 weighted). Pairwise nonparametric 
comparisons (Wilcoxon rank sum tests, weighting was 
not possible) showed statistically significant differences 
between the areas east and west of the critical habitat 
(P=0.023) and between the areas inside and to the west 
(P- 0.003), but not between the areas inside and to the 
east (P=0.669). 
Discussion 
The spatial pattern of right whale distribution observed 
during this study was largely similar to that described 
by Hamilton and Mayo (1990); most sightings were 
concentrated toward the eastern side of the bay (Fig. 3). 
The majority of the data collected by Hamilton and Mayo 
Table 3 
Mean (±standard error [SE] ) and maximum number of 
sightings of North Atlantic right whales ( Eubalaena gla- 
cialis) per unit of effort (no. of whales/1000 km of survey 
effort) in Cape Cod Bay, Massachusetts, summarized by 
two-week periods across the entire study, 1998-2002. 
Period 
Mean 
SE 
Maximum 
n 
1-14 Dec 
4.21 
3.53 
417.3 
121 
15-28 Dec 
4.47 
4.47 
339.9 
76 
29 Dec-11 Jan 
7.70 
2.87 
789.4 
328 
12-25 Jan 
4.53 
1.34 
288.3 
378 
26 Jan-8 Feb 
10.98 
2.67 
554.4 
417 
9-22 Feb 
14.08 
2.40 
510.8 
407 
23 Feb-8 Mar 
23.15 
4.60 
729.8 
333 
9-22 Mar 
14.79 
3.14 
625.7 
395 
23 Mar-5 Apr 
23.54 
3.47 
575.7 
410 
6-19 Apr 
14.70 
2.51 
552.1 
412 
20 Apr-3 May 
6.63 
1.67 
293.1 
380 
4-17 May 
0.00 
0.00 
0.0 
305 
(1990) was derived from opportunistic sightings recorded 
by researchers working aboard commercial whale watch- 
ing vessels departing from Provincetown multiple times 
per day, bound for Stellwagen Bank to the north of Cape 
Cod, from mid-spring through early fall. Aerial survey 
effort in our study was systematic, consistent across 
years, and spatially uniform throughout the study area 
and thus provided the first complete representation of 
the spatial and temporal distribution of right whales 
in Cape Cod Bay during winter and spring. The SPUE 
analysis provided a more refined interpretation of raw 
sighting data than have earlier analyses by reducing 
bias caused by uneven allocation of effort. 
During the seasonal expansion of right whale distri- 
bution in the bay (Fig. 5), right whales may be particu- 
larly at risk from collisions with ships traveling between 
the mouth of the Cape Cod Canal at the southwest and 
ports to the northeast of the bay (Fig. 1; Ward-Geiger 
et al., 2005). The above risk should be considered when 
implementing routing measures for shipping traffic. 
The boundaries of the Cape Cod Bay critical habitat 
encompassed the areas of highest SPUE values when 
pooled across all years and periods, and therefore the 
existing boundaries appear to service as a good man- 
agement unit. Despite the low number of sightings east 
of Cape Cod, the area- and effort-weighted statistics 
indicated that the waters east of the critical habitat 
may be important habitat for right whales, providing 
some support for existing fishery management measures 
in place east of the critical habitat (SAM West; Fig. 1) 
and the proposed Off Race Point Seasonal Management 
Area for shipping activity, which includes the portion 
of SAM West within the boundaries of this analysis 
(Federal Register, 2006). 
