Passive acoustic monitoring on the North Atlantic right whale calving grounds

Abstract

North Atlantic right whales Eubalaena glacialis calve during winter off Florida and Georgia, USA, a region of high shipping traffic, and ship-strike risk is a concern. Passive acoustic monitoring (PAM) of right whales on their foraging grounds increases detection opportunities to inform mariners of right whale presence and reduce the likelihood of ship strike. This study evaluates the effectiveness of PAM on right whale calving grounds by documenting the occurrence of right whale call detections on 2 types of acoustic instruments deployed off the coasts of Savannah, GA, and Jacksonville, FL, and comparing results with visual sightings and ambient noise conditions. Over 400 right whale calling events were detected on archival marine acoustic recording units (MARUs) at 2 sites across 2 seasons, and 92% of these calling events included right whale upcalls. Daily detections on archival MARUs and near-real time Autobuoys, which automatically detect upcalls, were significantly correlated and occurred on up to 25% of days off Savannah and 46% of days off Jacksonville. Visual aerial surveys detected right whales within 20 km of each acoustic site on a similar proportion of days with visual survey effort (15 to 33% off Savannah and 34 to 43% off Jacksonville). Acoustic methods enabled greater temporal effort, yielding a 2-to 10-fold increase in days with right whale detections over visual methods. Shipping noise and fish chorusing likely mask right whale call detections. However, considering the high number of right whale calling event detections by PAM during this study the results indicate that this is an effective method to augment detection of right whales in this environment, especially at night when they cannot be seen.

Have whales returned to a historical hotspot of industrial whaling? The pattern of southern right whale Eubalaena australis recovery at South Georgia

“…The most commonly heard call types were upcalls < 200 Hz; some gunshot calls were also detected. These 2 call types have previously been described for North Pacific and North Atlantic right whales on calving and feeding grounds and for SRWs on calving grounds; upcalls (but not gunshots) have also been described from SRWs on feeding grounds (Širović et al 2006, Mellinger et al 2007, Munger et al 2008, Parks et al 2011, Matthews et al 2014, Soldevilla et al 2014, Webster et al 2016, Crance et al 2017, Dombroski et al 2017. Call rates were generally low, with periods of silence of several hours, making triangulation using multiple buoys challenging.…”

Vocalizations produced by southern right whale (Eubalaena australis) mother-calf pairs in a calving ground off Brazil

“…The size of repertoires recorded in different areas and contexts may vary in relation to this repertoire description and therefore other call types may be found. Studies have been investigating the vocal behavior of right whales' surface-active groups (SAG), but little is known about the repertoire and vocal behavior of mothercalf pairs (Kraus and Hatch, 2001;Trygonis et al, 2013;Soldevilla et al, 2014). When comparing vocal activity of mother-calf pairs and SAGs, some variance in the relative proportion of recorded calls is expected due to differences in groups' behavioral context and in the assumed functions of certain call types .…”

“…Upcalls were the most frequent call type detected in SRW wintering grounds off Brazil where predominant whale group were mother-calf pairs as well as NARW wintering areas (Soldevilla et al, 2014). The upcall hypothesized function is to announce presence of one individual to other(s) and for contact maintenance (Clark, 1983;.…”

Marine mammal conservation: over the horizon

“…For such applications, real-time sound might be transferred through cables or via satellite or cellular networks (Lee et al 2018). Realtime acoustic monitoring of right whales on the east coast of the USA is used to notify mariners of their location, thus reducing the risk of ship strikes (Soldevilla et al 2014). The high-frequency and cryptic nature of many marine mammal signals, however, mean that sophisticated data compression and automated detectors are re quired (Gillespie et al 2009).…”