By: Heidi Ahonen, Christian Lydersen, Laura de Steur and Kit M Kovacs // Norwegian Polar Institute. Kathleen M Stafford // University of Washington, USA
Satellite-tracking studies have shown that narwhals occupy deep offshore areas in the winter and migrate into coastal areas over the continental shelves in summer. However, in the Barents Sea region, we see them only rarely in coastal areas around Svalbard, regardless of the time of year. They are capable of diving for an hour or more to great depths in search of giant squid and bottom-dwelling fish. They are quite shy and can hear ships at great distances, so they can easily escape detection by leaving the surface for long periods when they choose to “disappear”.
To learn more about the Red Listed population of narwhal in the Barents Region, we have been “listening” for them using Passive Acoustic Monitoring (PAM) devices. Recent analyses of several years of PAM records from the western Fram Strait have provided quite amazing results. Narwhal signals were detected year-round (year after year) at a mooring site that sits at the edge of the continental slope east of Greenland (west of Svalbard at about 79°N). Perhaps even more surprising was the fact that the narwhal sounds occurred more frequently when warm Atlantic Water influxes occurred in the area.
We certainly do not have all the answers (yet) to explain these results, but the presence of narwhal throughout the year in western Fram Strait is likely facilitated by the almost constant flow of drifting fields of Arctic ice, carried southward by the East Greenland Current, creating ideal habitat all months of the year. The increase in acoustic signalling when warm water influxes take place might be associated with the formation of frontal areas, which are created when warm currents meet cold currents. Such fronts likely concentrate narwhal prey.
Heidi Ahonen, Christian Lydersen, Laura de Steur and Kit M Kovacs // Norwegian Polar Institute
Kathleen M Stafford // University of Washington, USA
Ahonen H, Stafford KM, Lydersen C, de Steur L, Kovacs KM (2019) A multi-year study of narwhal occurrence in the western Fram Strait – detected via passive acoustic monitoring. Polar Research (forthcoming)