An Approximate Bayesian Method Applied to Estimating the Trajectories of Four British Grey Seal (Halichoerus grypus) Populations from Pup Counts
Table 2
Estimates (mean and 95% credibility intervals) of the total size of the grey seal populations in each region before breeding in 2007. The results for the two models are given along with those from simple (equally weighted) model averaging and applying the uniform prior across the two models. The numbers in italics are the equivalent estimates calculated from the best fitting state space models contained in the 2008 report of the UK Standing committee on Seals [18].
Model
2007 Regional Population (in thousands, mean value, and 95% CIs1)
North Sea
Orkney
Inner Hebrides
Outer Hebrides
Total2
Density dependent pup survival
20.9 (16.4–25.7)
46.1 (35.6–58.0)
8.0 (5.9–10.7)
34.3 (27.0–42.0)
109.4 (84.8–136.4)
17.1 (10.6–25.9)
60.9 (40.9–93.5)
8.3 (6.5–10.5)
31.3 (24.0–39.1)
117.6 (89.1–168.9)
Density dependent fecundity
24.1 (19.7–29.0)
124.6 (102.2–151.1)
24.7 (18.3–34.2)
69.6 (57.0–86.0)
243.3 (190.8–277.9)
27.2 (20.7–38.2)
103.0 (79.5–142.9)
21.4 (16.5–32.1)
88.1 (67.0–143.0)
239.7 (188.8–356.2)
Model averaged
22.5 (17.1–28.3)
85.4 (37.2–146.2)
16.4 (6.2–32.3)
52.1 (28.1–82.5)
177.3 (88.5–289.2)
20.5 (11.1–33.6)
75.4(40.4–130.0)
12.9 (6.5–27.2)
51.2 (23.8–111.5)
160.1 (84.5–304.5)
Uniform prior
22.5 (18.0–27.3)
85.78 (45.8–131.3)
16.3 (8.0–27.7)
52.1 (33.1–74.3)
176.8 (104.6–260.8)
1All the CIs include uncertainty in the population sex-ratio. 2The CIs are estimated conservatively by summing those of the individual models.
