Presence of ribbon seal vocalizations are related to sea ice extent in the Nemuro Strait, the Okhotsk Sea

Abstract

Vocalizations of ice-breeding ribbon seals Histriophoca fasciata were recorded using underwater passive acoustic methods from November 2012 to March 2014 off the Nemuro Strait, Japan. Seal presence in the strait was examined in relation to the sea ice extent in the Okhotsk Sea. Ribbon seal downsweeps were only detected when sea ice was present in the strait (February and March), with more detections in March leading up to the spring breeding season. Since ribbon seals require ice for breeding, underwater communication for breeding could be needed during the sea ice presence in this strait. Northeasterly winds were another indirect driver of ribbon seal occurrence, since winds from this direction likely transport sea ice from the central Okhotsk Sea into the Nemuro Strait. Downsweep detections decreased in the middle of the day, which is consistent with observations that seals hauled out on the ice during this time, and thus were producing fewer underwater vocalizations. Our results suggest that a decrease in the sea ice extent in the Okhotsk Sea may change the distribution of ribbon seals and impact their breeding behaviour since the Nemuro Strait region of the Okhotsk Sea is likely the southern limit of their breeding range.