Journal Article

Vast assembly of vocal marine mammals from diverse species on fish spawning ground

Wang, Delin, Yi, Dong Hoon, Tran, Duong D., Gong, Zheng, Huang, Wei, Jech, J. Michael, Garcia, Heriberto, Jain, Ankita D., Makris, Nicholas C., Godø, Olav Rune, Ratilal, Purnima

2016

Overview

Vocalizations were recorded for over eight distinct whale species as they converged on a shoal of herring to feed; the predators divided the shoal into overlapping but species-specific foraging sectors and the activities of the whales changed between day and night. Marine predators at prey Using a combination of passive and active ocean acoustic waveguide remote sensing in an important northwestern Atlantic marine mammal autumn foraging ground, Purnima Ratilal and colleagues have mapped the movement and distribution of more than ten marine mammal species simultaneously with that of their fish prey. The vocalizations of humpback, blue, fin, minke and other marine mammal species were recorded across an area of roughly 100,000 square kilometres as they converged onto dense herring shoals, dividing them into overlapping but species-specific foraging sectors, which were maintained for more than two weeks. This snapshot of marine life reveals how predators moved through the huge shoal, indicating how the activities of the predators varied as day moved into night. The results will increase understanding of marine-mammal behaviour and inform conservation efforts. 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 species 1 , 2 , 3 , 4 , 5 , 6 . Here we use passive ocean acoustic waveguide remote sensing (POAWRS) 7 , 8 in an important North Atlantic feeding ground 9 , 10 to instantaneously detect, localize and classify MM vocalizations from diverse species over an approximately 100,000 km 2 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-time 11 , 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 species 1 , 2 , 3 , 4 , 5 , 17 , 18 .

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/158/2445 / 704/158/2446 / Acoustics / Analysis / Animal communication / Animal populations / Animals / Anthropogenic factors / Aquatic Organisms - physiology / Atlantic Ocean / Diet - veterinary / Distribution / Ecosystem / Feeding Behavior / Fish / Fishes - physiology / Foraging behavior / Humanities and Social Sciences / letter / Male / Mammals - physiology / Marine ecology / Marine ecosystems / Marine mammals / multidisciplinary / Plankton / Population density / Predation / Predatory Behavior / Prey / Remote sensing / Science / Shoals / Spawning / Species diversity / Time Factors / Vocalization, Animal / Whales & whaling / Whales - physiology