. The Canadian field-naturalist. 528 The Canadian Field-Naturalist Vol. 102 -1°C, counts began hours before low tide, counts were conducted at a lower altitude (50-100 m) and only large groups of seals were photographed. One group entered the water before it could be counted or photographed. This group was estimated at 100 seals (30 October 1984). Results Flight dates (August to January) and numbers of seals seen for both sets of surveys are shown in Figure 1. The data were examined to determine whether the departures and arrivals were occurring at a linear rate (Terhune 1985). To compare
. The Canadian field-naturalist. 528 The Canadian Field-Naturalist Vol. 102 -1°C, counts began hours before low tide, counts were conducted at a lower altitude (50-100 m) and only large groups of seals were photographed. One group entered the water before it could be counted or photographed. This group was estimated at 100 seals (30 October 1984). Results Flight dates (August to January) and numbers of seals seen for both sets of surveys are shown in Figure 1. The data were examined to determine whether the departures and arrivals were occurring at a linear rate (Terhune 1985). To compare the rates of emigration from the north and immigra- tion to the south (Figure 1), the northern data were inverted using the formula Y = 238 + (979 - Z), where Y is the inverted number of seals and Z is the number actually sighted per survey (maxi- mum = 979, minimum = 238). The equation for the northern 1984 inverted data (as plotted in Figure 1) is Y = + where X is the survey date (first date = 0). The correlation coefficient (R = ) is significant (F = , P < ). The equation for the southern 1983 data (Figure 1) is Y = + (r = , F = , P ). The overall changes in numbers and the rates of change per day are presented in Table 1. The southern data presented include the survey dates immediately prior to and following the northern 1984 survey period. Discussion Although the northern and southern surveys were conducted independently, they shared many similar features. The differences in methodology mentioned above are not thought to be significant. The linear nature of the decrease in seal numbers (as opposed to a rapid, short-duration exodus) on 16 14 12 .10 ) ) 'â â 8 ) I 1 6 ) 4 H. O N DATE D Figure \. Changes in numbers of Harbour Seals on haul-out sites during autumn in the southern New England region (solid circles, 1983; open circles, 1984) and in the Bay of Fundy (Xs, 1984, inverted data, see text). The straight line equat
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