1
|
Oestreich WK, Benoit-Bird KJ, Abrahms B, Margolina T, Joseph JE, Zhang Y, Rueda CA, Ryan JP. Evidence for seasonal migration by a cryptic top predator of the deep sea. MOVEMENT ECOLOGY 2024; 12:65. [PMID: 39313840 PMCID: PMC11421108 DOI: 10.1186/s40462-024-00500-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 08/20/2024] [Indexed: 09/25/2024]
Abstract
BACKGROUND In ecosystems influenced by strong seasonal variation in insolation, the fitness of diverse taxa depends on seasonal movements to track resources along latitudinal or elevational gradients. Deep pelagic ecosystems, where sunlight is extremely limited, represent Earth's largest habitable space and yet ecosystem phenology and effective animal movement strategies in these systems are little understood. Sperm whales (Physeter macrocephalus) provide a valuable acoustic window into this world: the echolocation clicks they produce while foraging in the deep sea are the loudest known biological sounds on Earth and convey detailed information about their behavior. METHODS We analyze seven years of continuous passive acoustic observations from the Central California Current System, using automated methods to identify both presence and demographic information from sperm whale echolocation clicks. By integrating empirical results with individual-level movement simulations, we test hypotheses about the movement strategies underlying sperm whales' long-distance movements in the Northeast Pacific. RESULTS We detect foraging sperm whales of all demographic groups year-round in the Central California Current System, but also identify significant seasonality in frequency of presence. Among several previously hypothesized movement strategies for this population, empirical acoustic observations most closely match simulated results from a population undertaking a "seasonal resource-tracking migration", in which individuals move to track moderate seasonal-latitudinal variation in resource availability. DISCUSSION Our findings provide evidence for seasonal movements in this cryptic top predator of the deep sea. We posit that these seasonal movements are likely driven by tracking of deep-sea resources, based on several lines of evidence: (1) seasonal-latitudinal patterns in foraging sperm whale detection across the Northeast Pacific; (2) lack of demographic variation in seasonality of presence; and (3) the match between simulations of seasonal resource-tracking migration and empirical results. We show that sperm whales likely track oceanographic seasonality in a manner similar to many surface ocean predators, but with dampened seasonal-latitudinal movement patterns. These findings shed light on the drivers of sperm whales' long-distance movements and the shrouded phenology of the deep-sea ecosystems in which they forage.
Collapse
Affiliation(s)
| | | | - Briana Abrahms
- Center for Ecosystem Sentinels, Department of Biology, University of Washington, Seattle, WA, USA
| | | | | | - Yanwu Zhang
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - Carlos A Rueda
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - John P Ryan
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| |
Collapse
|
2
|
Chenoweth EM, Boswell KM, Friedlaender AS, McPhee MV, Burrows JA, Heintz RA, Straley JM. Confronting assumptions about prey selection by lunge‐feeding whales using a process‐based model. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13852] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ellen M. Chenoweth
- University of Alaska Fairbanks Fairbanks AK USA
- University of Alaska Southeast Sitka AK USA
| | | | - Ari S. Friedlaender
- University of California Santa Cruz Santa Cruz CA USA
- Oregon State University Newport OR USA
| | | | | | | | | |
Collapse
|
3
|
Blasi MF, Caserta V, Bruno C, Salzeri P, Di Paola AI, Lucchetti A. Behaviour and vocalizations of two sperm whales (Physeter macrocephalus) entangled in illegal driftnets in the Mediterranean Sea. PLoS One 2021; 16:e0250888. [PMID: 33914839 PMCID: PMC8084192 DOI: 10.1371/journal.pone.0250888] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Accepted: 04/15/2021] [Indexed: 11/18/2022] Open
Abstract
Illegal driftnetting causes each year several entanglements and deaths of sperm whales in different Mediterranean areas, primarily in the Tyrrhenian Sea. In summer 2020, during the June-July fishing season, two sperm whales were found entangled in illegal driftnets in the Aeolian Archipelago waters, Southern Italy. These two rare events were an exceptional chance to collect behavioural and acoustics data about entangled sperm whales. We analysed 1132 one-minute sets of breathing/behavioural data and 1575 minutes of acoustic recording, when the whales were found entangled, during the rescue operation, immediately after release, and in the days thereafter. The first whale was generally quiet showing a general status of debilitation/weakness, numerous skin lesions, and low breathing rate (0.31 (0.60)); it collaborated during rescue operations. On the contrary, the second whale showed a high level of agitation with a high breathing rate (1.48 (1.31)) during both the entanglement period and the net cutting operations, vigorously moving its fluke and pectoral fins, opening its mouth, sideway rolling or side fluking and frequently defecating. Acoustically, the first whale produced mainly single clicks in all phases except for two series of creaks during rescuing operations while the second whale produced a wide range of vocalizations (single clicks, likely either slow clicks or regular clicks, creaks, and codas). Our observations indicate that acoustics, respiratory and behavioural parameters may be useful to monitor the physical/physiological status of sperm whales during disentanglement operations.
Collapse
Affiliation(s)
- Monica Francesca Blasi
- Filicudi WildLife Conservation, Località Stimpagnato, Filicudi, Lipari (ME), Italy
- * E-mail:
| | - Valentina Caserta
- Filicudi WildLife Conservation, Località Stimpagnato, Filicudi, Lipari (ME), Italy
| | - Chiara Bruno
- Filicudi WildLife Conservation, Località Stimpagnato, Filicudi, Lipari (ME), Italy
| | - Perla Salzeri
- Filicudi WildLife Conservation, Località Stimpagnato, Filicudi, Lipari (ME), Italy
| | - Agata Irene Di Paola
- Filicudi WildLife Conservation, Località Stimpagnato, Filicudi, Lipari (ME), Italy
| | - Alessandro Lucchetti
- Centro Nazionale Ricerca - Istituto per le Risorse Biologiche e le Biotecnologie Marine (CNR-IRBBM), Ancona, Italy
| |
Collapse
|
4
|
Richard G, Samaran F, Guinet C, Bonnel J. Settings of demersal longlines reveal acoustic cues that can inform toothed whales where and when to depredate. JASA EXPRESS LETTERS 2021; 1:016004. [PMID: 36154091 DOI: 10.1121/10.0003191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Fishing boats produce acoustic cues while hauling longlines. These acoustic signals are known to be used by odontocetes to detect the fishing activity and to depredate. However, very little is known about potential interactions before hauling. This article describes the acoustic signature of the setting activity. Using passive acoustic recorders attached to the buoys of longlines, this work demonstrates an increase in the ambient sound of ∼6 dB re 1 μPa2 Hz-1 within 2-7 kHz during the setting activity. This could also be used as an acoustic cue by depredating species, suggesting that predators can detect longlines as soon as they are set.
Collapse
Affiliation(s)
- Gaëtan Richard
- Laboratoire des Sciences et Techniques de l'Information, de la Communication et de la Connaissance, Unité Mixte de Recherche 6285, École Nationale Supérieure de Techniques Avancées Bretagne, 2 rue François Verny, 29806 Brest Cedex 9, France
| | - Flore Samaran
- Laboratoire des Sciences et Techniques de l'Information, de la Communication et de la Connaissance, Unité Mixte de Recherche 6285, École Nationale Supérieure de Techniques Avancées Bretagne, 2 rue François Verny, 29806 Brest Cedex 9, France
| | - Christophe Guinet
- Centre d'Études Biologiques de Chizé, Unité Mixte de Recherche 7372, Centre National de la Recherche Scientifique and La Rochelle Université, 79360 Villiers-en-Bois, France
| | - Julien Bonnel
- Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, USA , , ,
| |
Collapse
|
5
|
Wild LA, Mueter F, Witteveen B, Straley JM. Exploring variability in the diet of depredating sperm whales in the Gulf of Alaska through stable isotope analysis. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191110. [PMID: 32269781 PMCID: PMC7137980 DOI: 10.1098/rsos.191110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 01/27/2020] [Indexed: 06/11/2023]
Abstract
Sperm whales interact with commercially important groundfish fisheries offshore in the Gulf of Alaska (GOA). This study aims to use stable isotope analysis to better understand the trophic variability of sperm whales and their potential prey, and to use dietary mixing models to estimate the importance of prey species to sperm whale diets. We analysed tissue samples from sperm whales and seven potential prey (five groundfish and two squid species). Samples were analysed for stable carbon and nitrogen isotope ratios, and diet composition was estimated using Bayesian isotopic mixing models. Mixing model results suggest that an isotopically combined sablefish/dogfish group, skates and rockfish make up the largest proportion of sperm whale diets (35%, 28% and 12%) in the GOA. The top prey items of whales that interact more frequently with fishing vessels consisted of skates (49%) and the sablefish/dogfish group (24%). This is the first known study to provide an isotopic baseline of adult male sperm whales and these adult groundfish and offshore squid species, and to assign contributions of prey to whale diets in the GOA. This study provides information to commercial fishermen and fisheries managers to better understand trophic connections of important commercial species.
Collapse
Affiliation(s)
- Lauren A. Wild
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 12101 Point Lena Loop, Juneau, AK 99801, USA
| | - Franz Mueter
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 12101 Point Lena Loop, Juneau, AK 99801, USA
| | - Briana Witteveen
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 12101 Point Lena Loop, Juneau, AK 99801, USA
| | - Janice M. Straley
- Department of Biology, University of Alaska Southeast, 1332 Seward Ave, Sitka, AK 99835, USA
| |
Collapse
|
6
|
Richard G, Bonnel J, Tixier P, Arnould JPY, Janc A, Guinet C. Evidence of deep-sea interactions between toothed whales and longlines. AMBIO 2020; 49:173-186. [PMID: 31055794 PMCID: PMC6889101 DOI: 10.1007/s13280-019-01182-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 01/31/2019] [Accepted: 04/03/2019] [Indexed: 06/01/2023]
Abstract
Toothed whales (odontocetes) feeding on fish caught on hooks in longline fisheries is a growing issue worldwide. The substantial impacts that this behaviour, called depredation, can have on the fishing economy, fish stocks and odontocetes populations, raise a critical need for mitigation solutions to be developed. However, information on when, where and how odontocete depredation occurs underwater is still limited, especially in demersal longline fisheries (fishing gear set on the seafloor). In the present study, we investigated depredation by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) on demersal longlines in the French Patagonian toothfish fishery (Southern Ocean). Using a combination of animal-borne behavioural and longline-attached data loggers, we demonstrated that both species are able to depredate longlines on the seafloor. This study, therefore, suggests that odontocetes whales-longline interaction events at depth may be unrecorded when assessing depredation rates from surface observations during hauling phases only. This result has implications for the management of fisheries facing similar depredation issues as underestimated depredation rates may result in unaccounted fish mortality in fish-stock assessments. Therefore, while further research should be conducted to assess the extent of deep-sea whale-longline interaction events during soaking, the evidence that depredation can occur at any time during the whole fishing process as brought out by this study should be considered in future developments of mitigation solutions to the issue.
Collapse
Affiliation(s)
- Gaëtan Richard
- Present Address: Centre d’Études Biologiques de Chizé, UMR 7372 – CNRS & Université de La Rochelle, 79360 Villiers-en-Bois, France
- Lab-STICC UMR 6285, ENSTA Bretagne, 2 rue François Verny, 29806 Brest Cedex 9, France
- School of Life and Environmental Sciences (Burwood Campus), Deakin University, Geelong, VIC Australia
| | - Julien Bonnel
- Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543-1050 USA
| | - Paul Tixier
- School of Life and Environmental Sciences (Burwood Campus), Deakin University, Geelong, VIC Australia
| | - John P. Y. Arnould
- School of Life and Environmental Sciences (Burwood Campus), Deakin University, Geelong, VIC Australia
| | - Anaïs Janc
- Present Address: Centre d’Études Biologiques de Chizé, UMR 7372 – CNRS & Université de La Rochelle, 79360 Villiers-en-Bois, France
| | - Christophe Guinet
- Present Address: Centre d’Études Biologiques de Chizé, UMR 7372 – CNRS & Université de La Rochelle, 79360 Villiers-en-Bois, France
| |
Collapse
|
7
|
Fais A, Johnson M, Wilson M, Aguilar Soto N, Madsen PT. Sperm whale predator-prey interactions involve chasing and buzzing, but no acoustic stunning. Sci Rep 2016; 6:28562. [PMID: 27340122 PMCID: PMC4919788 DOI: 10.1038/srep28562] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 06/07/2016] [Indexed: 11/09/2022] Open
Abstract
The sperm whale carries a hypertrophied nose that generates powerful clicks for long-range echolocation. However, it remains a conundrum how this bizarrely shaped apex predator catches its prey. Several hypotheses have been advanced to propose both active and passive means to acquire prey, including acoustic debilitation of prey with very powerful clicks. Here we test these hypotheses by using sound and movement recording tags in a fine-scale study of buzz sequences to relate the acoustic behaviour of sperm whales with changes in acceleration in their head region during prey capture attempts. We show that in the terminal buzz phase, sperm whales reduce inter-click intervals and estimated source levels by 1-2 orders of magnitude. As a result, received levels at the prey are more than an order of magnitude below levels required for debilitation, precluding acoustic stunning to facilitate prey capture. Rather, buzzing involves high-frequency, low amplitude clicks well suited to provide high-resolution biosonar updates during the last stages of capture. The high temporal resolution helps to guide motor patterns during occasionally prolonged chases in which prey are eventually subdued with the aid of fast jaw movements and/or buccal suction as indicated by acceleration transients (jerks) near the end of buzzes.
Collapse
Affiliation(s)
- A Fais
- BIOECOMAC. Dept. of Animal Biology, La Laguna University, Spain.,Zoophysiology, Department of Bioscience, Aarhus University, Denmark
| | - M Johnson
- Scottish Ocean Institute, University of St. Andrews, Scotland
| | - M Wilson
- Zoophysiology, Department of Bioscience, Aarhus University, Denmark.,Institute of Biology, University of Southern Denmark, Denmark
| | - N Aguilar Soto
- BIOECOMAC. Dept. of Animal Biology, La Laguna University, Spain.,CREEM, University of St. Andrews, Scotland
| | - P T Madsen
- Zoophysiology, Department of Bioscience, Aarhus University, Denmark.,Murdoch University Cetacean Research Unit, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia
| |
Collapse
|
8
|
Skarsoulis EK, Dosso SE. Linearized two-hydrophone localization of a pulsed acoustic source in the presence of refraction: Theory and simulations. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 138:2221-2234. [PMID: 26520304 DOI: 10.1121/1.4930937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This paper develops an efficient three-dimensional localization method for transient acoustic sources, with uncertainty estimation, based on time differences between direct and surface-reflected arrivals at two hydrophones. The localization method accounts for refraction caused by a depth-dependent sound-speed profile using a ray-theoretic approach for calculating eigenray travel times and partial derivatives. Further, the method provides localization error estimates accounting for uncertainties of the arrival times and hydrophone locations, as well as for depth-dependent uncertainties in the sound-speed profile. In the first of two steps, source depth and range to each hydrophone are estimated using an iterative, linearized Gauss-Markov inversion scheme. In the second step, the estimated source ranges are combined with the hydrophone locations to obtain the source location in the horizontal. Localization performance is analyzed in a simulation study, and the linearized localization estimates and uncertainties are validated by comparison with a fully nonlinear (but numerically intensive) Markov-chain Monte Carlo inversion.
Collapse
Affiliation(s)
- E K Skarsoulis
- Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas, GR-711 10 Heraklion, Crete, Greece
| | - Stan E Dosso
- School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
| |
Collapse
|
9
|
Schakner ZA, Lunsford C, Straley J, Eguchi T, Mesnick SL. Using models of social transmission to examine the spread of longline depredation behavior among sperm whales in the Gulf of Alaska. PLoS One 2014; 9:e109079. [PMID: 25272019 PMCID: PMC4182800 DOI: 10.1371/journal.pone.0109079] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 09/08/2014] [Indexed: 11/19/2022] Open
Abstract
Fishing, farming and ranching provide opportunities for predators to prey on resources concentrated by humans, a behavior termed depredation. In the Gulf of Alaska, observations of sperm whales depredating on fish caught on demersal longline gear dates back to the 1970s, with reported incidents increasing in the mid-1990s. Sperm whale depredation provides an opportunity to study the spread of a novel foraging behavior within a population. Data were collected during National Marine Fisheries Service longline surveys using demersal longline gear in waters off Alaska from 1998 to 2010. We evaluated whether observations of depredation fit predictions of social transmission by fitting the temporal and spatial spread of new observations of depredation to the Wave of Advance model. We found a significant, positive relationship between time and the distance of new observations from the diffusion center (r(2) = 0.55, p-value = 0.003). The data provide circumstantial evidence for social transmission of depredation. We discuss how changes in human activities in the region (fishing methods and regulations) have created a situation in which there is spatial-temporal overlap with foraging sperm whales, likely influencing when and how the behavior spread among the population.
Collapse
Affiliation(s)
- Zachary A. Schakner
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA, United States of America
- * E-mail: (ZS); (SM)
| | - Chris Lunsford
- Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, Auke Bay Laboratories, Juneau, AK, United States of America
| | - Janice Straley
- University of Alaska Southeast, Sitka, AK, United States of America
| | - Tomoharu Eguchi
- Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, La Jolla, CA, United States of America
| | - Sarah L. Mesnick
- Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA, La Jolla, CA, United States of America
- * E-mail: (ZS); (SM)
| |
Collapse
|
10
|
Tran DD, Huang W, Bohn AC, Wang D, Gong Z, Makris NC, Ratilal P. Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 135:3352-3363. [PMID: 24907798 DOI: 10.1121/1.4874601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing, and classified using a single low-frequency (<2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. Multiple concurrently vocalizing sperm whales, in the far-field of the horizontal receiver array, were distinguished and classified based on their horizontal spatial locations and the inter-pulse intervals of their vocalized click signals. The dive profile was estimated for a sperm whale in the shallow waters of the Gulf of Maine with 160 m water-column depth located close to the array's near-field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the horizontal array. By accounting for transmission loss modeled using an ocean waveguide-acoustic propagation model, the sperm whale detection range was found to exceed 60 km in low to moderate sea state conditions after coherent array processing.
Collapse
Affiliation(s)
- Duong D Tran
- Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115
| | - Wei Huang
- Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115
| | - Alexander C Bohn
- Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115
| | - Delin Wang
- Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115
| | - Zheng Gong
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Nicholas C Makris
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Purnima Ratilal
- Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115
| |
Collapse
|
11
|
Straley JM, Schorr GS, Thode AM, Calambokidis J, Lunsford CR, Chenoweth EM, O’Connell VM, Andrews RD. Depredating sperm whales in the Gulf of Alaska: local habitat use and long distance movements across putative population boundaries. ENDANGER SPECIES RES 2014. [DOI: 10.3354/esr00595] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
12
|
Thode AM, Wild L, Mathias D, Straley J, Lunsford C. A comparison of acoustic and visual metrics of sperm whale longline depredation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 135:3086-3100. [PMID: 24926504 DOI: 10.1121/1.4869853] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Annual federal stock assessment surveys for Alaskan sablefish also attempt to measure sperm whale depredation by quantifying visual evidence of depredation, including lip remains and damaged fish. A complementary passive acoustic method for quantifying depredation was investigated during the 2011 and 2012 survey hauls. A combination of machine-aided and human analysis counted the number of distinct “creak” sounds detected on autonomous recorders deployed during the survey, emphasizing sounds that are followed by silence (“creak-pauses”), a possible indication of prey capture. These raw counts were then adjusted for variations in background noise levels between deployments. Both a randomized Pearson correlation analysis and a generalized linear model found that noise-adjusted counts of “creak-pauses” were highly correlated with survey counts of lip remains during both years (2012: r(10) = 0.89, p = 1e-3; 2011: r(39) = 0.72, p = 4e-3) and somewhat correlated with observed sablefish damage in 2011 [r(39) = 0.37, p = 0.03], but uncorrelated with other species depredation. The acoustic depredation count was anywhere from 10% to 80% higher than the visual counts, depending on the survey year and assumptions employed. The results suggest that passive acoustics can provide upper bounds on depredation rates; however, the observed correlation breaks down whenever three or more whales are present.
Collapse
|
13
|
Miller B, Dawson S, Vennell R. Underwater behavior of sperm whales off Kaikoura, New Zealand, as revealed by a three-dimensional hydrophone array. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:2690-2700. [PMID: 24116407 DOI: 10.1121/1.4818896] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Observations are presented of the vocal behavior and three dimensional (3D) underwater movements of sperm whales measured with a passive acoustic array off the coast of Kaikoura, New Zealand. Visual observations and vocal behaviors of whales were used to divide dive tracks into different phases, and depths and movements of whales are reported for each of these phases. Diving depths and movement information from 75 3D tracks of whales in Kaikoura are compared to one and two dimensional tracks of whales studied in other oceans. While diving, whales in Kaikoura had a mean swimming speed of 1.57 m/s, and, on average, dived to a depth of 427 m (SD = 117 m), spending most of their time at depths between 300 and 600 m. Creak vocalizations, assumed to be the prey capture phase of echolocation, occurred throughout the water column from sea surface to sea floor, but most occurred at depths of 400-550 m. Three dimensional measurement of tracking revealed several different "foraging" strategies, including active chasing of prey, lining up slow-moving or unsuspecting prey, and foraging on demersal or benthic prey. These movements provide the first 3D descriptions underwater behavior of whales at Kaikoura.
Collapse
Affiliation(s)
- Brian Miller
- Department of Marine Science, Otago University, P.O. Box 56, Dunedin, New Zealand
| | | | | |
Collapse
|
14
|
Mathias D, Thode AM, Straley J, Andrews RD. Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:2446-2461. [PMID: 23968042 DOI: 10.1121/1.4816565] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Between 15 and 17 August 2010, a simple two-element vertical array was deployed off the continental slope of Southeast Alaska in 1200 m water depth. The array was attached to a vertical buoy line used to mark each end of a longline fishing set, at 300 m depth, close to the sound-speed minimum of the deep-water profile. The buoy line also served as a depredation decoy, attracting seven sperm whales to the area. One animal was tagged with both a LIMPET dive depth-transmitting satellite and bioacoustic "B-probe" tag. Both tag datasets were used as an independent check of various passive acoustic schemes for tracking the whale in depth and range, which exploited the elevation angles and relative arrival times of multiple ray paths recorded on the array. Analytical tracking formulas were viable up to 2 km range, but only numerical propagation models yielded accurate locations up to at least 35 km range at Beaufort sea state 3. Neither localization approach required knowledge of the local bottom bathymetry. The tracking system was successfully used to estimate the source level of an individual sperm whale's "clicks" and "creaks" and predict the maximum detection range of the signals as a function of sea state.
Collapse
Affiliation(s)
- Delphine Mathias
- Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0238, USA.
| | | | | | | |
Collapse
|