A recovery of harbour porpoises (Phocoena phocoena) in the southern North Sea? A case study off Eastern Frisia, Germany

Table 1 Estimation of g(0) for the porpoise-only flights

Date	Number of sightings^a	Individual surface time	Total surface time	N 1	N 1&2
02/17/03	24	0.44^b	10.56	5	2
05/07/03	11	0.45	4.95	7	1
06/07/03	16	0.39	6.24	7	5
07/10/03	26	0.41	10.66	12	8
02/16/04	27	0.44^b	11.88	1	1
05/03/04	50	0.45	22.50	7	4
07/22/04	16	0.41	6.56	1	1
Sum	170		73.35	40	22
Availability bias/average surface time=0.43				Perception bias/sighting probability = 0.55

Altitude 183 m; N1&2 duplicate sightings of control and principal observer between 20 and 45°, N1 sightings of control observer only
^aSightings of principal observer in valid transect sections
^bAverage after Teilmann (2000)

ISSN: 1438-3888