Observing marine mammal (MM) populations continuously in time and space over the immense ocean areas they inhabit is challenging but essential for gathering an unambiguous record of their distribution, as well as understanding their behaviour and interaction with prey species1,2,3,4,5,6. Here we use passive ocean acoustic waveguide remote sensing (POAWRS)7,8 in an important North Atlantic feeding ground9,10 to instantaneously detect, localize and classify MM vocalizations from diverse species over an approximately 100,000 km2 region. More than eight species of vocal MMs are found to spatially converge on fish spawning areas containing massive densely populated herring shoals at night-time11,12,13,14,15,16 and diffuse herring distributions during daytime. We find the vocal MMs divide the enormous fish prey field into species-specific foraging areas with varying degrees of spatial overlap, maintained for at least two weeks of the herring spawning period. The recorded vocalization rates are diel (24 h)-dependent for all MM species, with some significantly more vocal at night and others more vocal during the day. The four key baleen whale species of the region: fin, humpback, blue and minke have vocalization rate trends that are highly correlated to trends in fish shoaling density and to each other over the diel cycle. These results reveal the temporospatial dynamics of combined multi-species MM foraging activities in the vicinity of an extensive fish prey field that forms a massive ecological hotspot, and would be unattainable with conventional methodologies. Understanding MM behaviour and distributions is essential for management of marine ecosystems and for accessing anthropogenic impacts on these protected marine species1,2,3,4,5,17,18.
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Permission for this National Oceanographic Partnership Program experiment was given in the Office of Naval Research document 5090 Ser 321RF/096/06. This research was supported by the US National Science Foundation, the US Office of Naval Research (Ocean Acoustics Program), the National Oceanographic Partnership Program, the US Presidential Early Career Award for Scientists and Engineers, the Alfred P. Sloan Foundation, the Census of Marine Life, and Northeastern University. The authors thank J. R. Preston for assistance with GOM 2006 experiment, D. H. Cato and P. L. Tyack for discussions.
The authors declare no competing financial interests.
Extended data figures and tables
a–h, Beamformed spectrograms of typical repetitive vocalizations from diverse MM species observed using the POAWRS receiver array in the Gulf of Maine from 19 September to 6 October 2006.
a, b, Compare single hydrophone measured spectrogram (a) with spectrogram after coherent beamforming (b) with 64-element sub-aperture of POAWRS 160-element hydrophone array. The song vocalization from a humpback individual roughly 35 km away from the POAWRS receiver array recorded on 2 October 2006 at 23:48:45 EDT is enhanced by 18 dB above the background noise after beamforming in b where whale bearing is −64.16° from array broadside.
a, Pitch-tracks of repetitive mysticete vocalizations in the 10 to 100 Hz range. Thick solid curves are the means of roughly 500 to 1,000 vocalizations of each type. Mean instantaneous bandwidth of the pitch-tracks are indicated by the dashed curve. Even though blue and sei type I calls have some overlapping bandwidth, they can be well separated using the upper frequency fU and slope df/dτ features (Extended Data Table 2). b, Mean pitch-track and instantaneous bandwidth of repetitive odontocete downsweep vocalizations in the 1 to 4 kHz range.
a, b, MM vocalization bearings from diverse species measured by POAWRS receiver array on 1 October 2006 (a) and 2 October 2006 (b). The bearings are measured from true North in clockwise direction with respect to the instantaneous spatial locations of the receiver array centre. The techniques used here for resolving source bearing ambiguity about the horizontal line-array axis are provided in Methods section 3. The shaded bars on the x axis indicate the operation time periods of the receiver array.
a–c, Bearings and repertoire of humpback vocalizations measured by POAWRS receiver array on 1 October 2006 (a), 2 October 2006 (b), and 3 October 2006 (c). The ‘meow’, ‘bow’, and ‘feeding’ call characteristics are provided in ref. 7.
Measured herring shoaling areal population densities (ranging from 0.2 fish per m2 to over 10 fish per m2) determined from OAWRS12,13 survey in the Gulf of Maine from 26 September 2006 to 6 October 2006, upon calibration with tens of thousands of coincident and co-located conventional ultrasonic fisheries echosounding measurements, combined with trawl sampling for identity and biological–physiological characterization of fish populations15,16. The mean diffuse herring density of 0.053 fish per m2 is determined from conventional ultrasonic fisheries echosounding. The bathymetric data (contours shown in grey) were obtained from the US National Centers for Environmental Information.
Mean diel call rates for sei whales and odontocetes in general are not correlated to the diel Atlantic herring shoal mean areal population density. The error bars indicate standard deviations obtained from averaging the time series over multiple diel cycles from 26 September 2006 to 6 October 2006. The period from roughly 2–6 EDT contains a data gap.
Cumulative diurnal MM vocalization rate distribution and azimuthally-averaged POAWRS MM POD as a function of minimum distance from diurnal herring shoaling areas. The e-folding distances of the cumulative MM vocalization rate distributions decrease from day (shown here) to night (in Fig. 3b) by 27.3 to 7 km (blue), 9.3 to 3.9 km (fin), 51.7 to 3.5 km (humpback), 22.5 to 0 km (minke), 11.2 to 8.1 km (sei), and 22.4 to 5.5 km (odontocetes). The percentage of vocalizations that fully overlap with herring shoaling areas increase from day to night by 0% to 18% (blue), 14% to 40% (fin), 6% to 44% (humpback), 0% to 71% (minke), and 5% to 24% (sei), but decrease by 36% to 29% (odontocetes).
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Wang, D., Garcia, H., Huang, W. et al. Vast assembly of vocal marine mammals from diverse species on fish spawning ground. Nature 531, 366–370 (2016). https://doi.org/10.1038/nature16960
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