We used satellite tags to record the patterns of depth utilisation for four ocean sunﬁsh (Mola mola) and two leatherback turtles (Dermochelys coriacea) moving in broadly the same area off South Africa. Individuals were tracked for between 2 and 8 months and dive data relayed via satellite. For all the sunﬁsh and one of the turtles, we received binned data on depth distribution, while for the second turtle we received individual dive proﬁles along with the proportion of time spent diving. Leatherback turtles dived almost exclusively within the upper 200 m, spending only 0.6 and 0.2% of their time N200 m. There were times when sunﬁsh likewise occupied these relatively shallow depths. However, there were also protracted periods when sunﬁsh spent the majority of their time much deeper, with one individual remaining around 500 m for many hours at a time. These results suggest that sunﬁsh sometimes exploit deeply distributed prey which is beyond the foraging range of leatherback turtles. We conclude that while both species are believed to feed predominantly on gelatinous zooplankton, the fact that sunﬁsh do not need to come to the surface to breathe means that they can occupy an expanded vertical niche compared to the leatherback turtle.
|Autori:||HAYS G.C; FARQUHAR M.R; LUSCHI P; TEO S.L.H; THYS T.M|
|Titolo:||Vertical niche overlap by two ocean giants with similar diets: Ocean sunfish and leatherback turtles|
|Anno del prodotto:||2009|
|Appare nelle tipologie:||1.1 Articolo in rivista|