Nichols et ai. : Spatial and temporal distribution of Eubalaena glacialis in Cape Cod Bay 
275 
70° 40' W 70° 30' W 70° 20' W 70° 10' W 70° 00' W 69° 50’ W 
- 42° 00' N 
42° 10' N 
41°50'N 
41° 40’ N 
> 69.04 (top 5%) 
= 28.95-69.03 (75th— 95th percentile) 
= 12.31-28.94 (50th— 75th percentile) 
= 5.37-12.30 (25th— 50th percentile) 
= 0.01-5.36 (< 25th percentile) 
= 0 (effort > 0) 
no effort 
Figure 4 
Overall mean North Atlantic right whale ( Eubalaena glacialis) 
sightings per unit of effort (SPUE; number of whales/1000 km 
of survey effort) in Cape Cod Bay, 1998-2002. SPUE values are 
separated by quartiles, representing the top, second highest, third, 
and bottom quarters of the distribution. The upper quarter is 
further partitioned by identifying the top 5% of all values. 
trated in a band extending across Cape Cod Bay from 
the southwest to the northeast (Fig. 3). 
The overall 5-year mean SPUE value for all 101 
sampled cells was 11.9 whales per 1000 km of sur- 
vey effort (i.e., one right whale every 84 km of accept- 
able survey flown; Table 2). The maximum SPUE in 
a single cell during any two-week period was 789.4 
right whales/1000 km (i.e., one whale every 1.3 km) 
during 29 December 1997-11 January 1998. An area 
of high-SPUE cells extended along the eastern side of 
the bay from the south to the tip of the Cape (Fig. 4). 
Distinct areas of lower SPUE values radiated out from 
the highest-value cells, and a gradient of decreasing 
SPUE values extended to the west. 
Annual mean SPUE was highest in 2000 and lowest 
in 2002 (Table 2), and the difference was almost an 
order of magnitude. The interannual variability was 
statistically significant (Kruskal-Wallis nonparametric 
ANOVA, P<0.001). When 2002 data was eliminated, 
the interannual variability remained statistically sig- 
nificant (Kruskal-Wallis, P= 0.033). When we tested for 
differences among the annual means with a parametric 
Duncan’s multiple range test, using either unweighted 
or effort-weighted means, 2002 was found to be sig- 
nificantly different from all other years. Using the un- 
weighted means, we found that 1998 and 2000 were 
not different from one another, and neither were 1998, 
1999, and 2001. Using the effort-weighted means, we 
found that 1998, 1999, and 2001 did not differ, but that 
2000 was significantly different from all other years. 
When separated into two-week periods pooled across 
all years, mean SPUE values varied considerably. 
SPUE values were low in December and January, in- 
creased during February, exhibited two peaks in late 
February-early March and late March-early April, and 
declined to low values by the end of April and to zero 
in May (Table 3). The within-season temporal vari- 
ability was statistically significant (Kruskal-Wallis, 
.PcO.OOl). The area occupied by right whales expanded 
and then contracted over the course of the season in 
