The harbour porpoise (Phocoena phocoena) in the central German Bight: phenology, abundance and distribution in 2002–2004

Table 1 Estimation of g(0) for the porpoise-only flights (altitude = 152/183 m)

Date	Number of sightings^a	Individual surface time	Total surface time	N1	N1&2
07/28/02	24	0.41	9.84	8	2
02/14/03	32	0.44^b	14.08	7	5
05/26/03	23	0.45	10.35	17	9
06/22/03	13	0.39	5.07	2	1
07/28/03	10	0.41	4.10	7	2
09/13/03	18	0.39	7.02	9	5
03/06/04	15	0.55	8.25	3	2
Sum	135		58.71	53	26

N1&2 = duplicate sightings of control and principal observer between 20° and 45°, N1 = sightings of control observer only
Availability bias/average surface time = 0.43
Perception bias/sighting probability = 0.49
^aSightings of principal observer in valid transect sections
^bAverage after Teilmann ( 2000 )

ISSN: 1438-3888