Fig. 2From: A recovery of harbour porpoises (Phocoena phocoena) in the southern North Sea? A case study off Eastern Frisia, GermanyDetection probability function for harbour porpoises during seven of 12 porpoise-only aerial surveys (altitude = 183 m; model = hazard rate key function with simple polynominal series expansion; n = 170 sightings)Back to article page