TY - JOUR
T1 - Geographic, seasonal, and diurnal surface behavior of harbor porpoises
AU - Teilmann, Jonas
AU - Christiansen, Casper T.
AU - Kjellerup, Sanne
AU - Dietz, Rune
AU - Nachman, Gøsta Støger
PY - 2013/4
Y1 - 2013/4
N2 - During ship surveys harbor porpoises are only visible when breaking the sea surface to breathe, while during aerial surveys they may be seen down to 2 m below the surface. The fractions of time spent at these two depths can be used for correcting visual surveys to actual population estimates, which are essential information on the status and management of the species. Thirty-five free-ranging harbor porpoises (Phocoena phocoena) were tracked in the region between the Baltic and the North Sea for 25-349 d using Argos satellite transmitters. No differences were found in surface behavior between geographical areas or the size of the animals. Slight differences were found between the two sexes and time of day. Surface time peaked in April, where 6% was spent with the transmitter above surface and 61.5% between 0 and 2 m depth, while the minimum values occurred in February (3.4% and 42.5%, respectively). The analyses reveal that individual variation among porpoises is the most important factor in explaining variation in surface rates. However, the large number of animals documented in the present study covering a wide range of age and sex groups justifies the use of the seasonal average surface times for correcting abundance surveys.
AB - During ship surveys harbor porpoises are only visible when breaking the sea surface to breathe, while during aerial surveys they may be seen down to 2 m below the surface. The fractions of time spent at these two depths can be used for correcting visual surveys to actual population estimates, which are essential information on the status and management of the species. Thirty-five free-ranging harbor porpoises (Phocoena phocoena) were tracked in the region between the Baltic and the North Sea for 25-349 d using Argos satellite transmitters. No differences were found in surface behavior between geographical areas or the size of the animals. Slight differences were found between the two sexes and time of day. Surface time peaked in April, where 6% was spent with the transmitter above surface and 61.5% between 0 and 2 m depth, while the minimum values occurred in February (3.4% and 42.5%, respectively). The analyses reveal that individual variation among porpoises is the most important factor in explaining variation in surface rates. However, the large number of animals documented in the present study covering a wide range of age and sex groups justifies the use of the seasonal average surface times for correcting abundance surveys.
U2 - 10.1111/j.1748-7692.2012.00597.x
DO - 10.1111/j.1748-7692.2012.00597.x
M3 - Journal article
SN - 0824-0469
VL - 29
SP - E60-E76
JO - Marine Mammal Science
JF - Marine Mammal Science
IS - 2
ER -