Archival pop-off tag tracking of Greenland sharks Somniosus microcephalus in the High Arctic waters of Svalbard, Norway

摘要

ABSTRACT: The Greenland shark Somniosus microcephalus is the largest fish in Arctic waters and a significant predator that is likely numerous, but little is known about its movement patterns or habitat preferences. In June 2008 and 2009, 20 archival pop-off tags were deployed on Greenland sharks in coastal waters in Svalbard, Norway (~80°N), to address this knowledge gap. Over the period June to December, 14 of the tags reported data. The swimming depth of the sharks was 111 ± 74 m (mean ± SD), but they occupied waters from the surface down to a depth of at least 1560 m (the depth limit of the tags), which is the deepest confirmed record for this species. The sharks displayed a wide range of depths within each 6 h time bin collected by the tags, with no obvious diel movement pattern. They experienced temperatures from −1.5 to 7.4°C (mean ± SD = 3.8 ± 1.4°C). The average depth of swimming increased and temperatures experienced by the sharks decreased from June through December. Most individuals moved north from the tagging area, and travelled a range of distances during their variable deployment times, but most tags popped off 500 km from the tagging site. The average distance travelled varied from 0.6 to 16.6 km d−1. Two sharks travelled 725 and 980 km, respectively, representing the most northerly (82.4°N) and easterly (40.8°E) locations documented for this species. The movements of the tagged sharks suggest that this species likely ranges broadly in northern waters and likely hunts throughout the water column in Arctic seas.