Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6
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The long-term goals of this program are to (1) instantaneously detect, image and spatially chart fish populations over continental-shelf scales, and (2) continuously monitor the areal densities and behavior of these fish populations over time using a novel audible frequency acoustic system (300- 5000Hz) referred to as Ocean Acoustic Waveguide Remote Sensing (OAWRS). This new method is being applied to explore the abundance, temporal and spatial distributions and behavior of fish populations in the Gulf of Maine on and near Georges Bank, a marine ecosystem being studied in the Census of Marine Life program. OAWRS is a valuable conservation tool for rapid imaging and enumeration of large scale fish populations over thousands of square kilometers to effectively monitor and manage the national fish stock.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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The goal of this effort was to provide use of the Flextensional Sea Test (FST) Array assembled under the Office of Naval Research (ONR) Multistatic ASW Capability Enhancement Program (MACE) as the source of underwater sounds to support active bi-static sonar capabilities for monitoring fish populations and behaviors during a September/October 2006 sea test off the coast of Maine. That sea test will be designated here as the Gulf of Maine (GoM) sea test. As the FST array hardware already existed and was suitable for the bi-static, active fish monitoring procedure planned for the GoM test, the approach for SSC-SD participation was primarily to arrange shipment of the array and support hardware to the Woods Hole Oceanographic Institute (WHOI), to install the system aboard R/V Endeavor as its operational-platform vessel, and to provide personnel for: installing the array-control equipment, operating and maintaining the installed transmission system, and removing the array-control equipment from the vessel after the sea test's end.
Author: Dong Hoon Yu
Publisher:
ISBN:
Category :
Languages : en
Pages : 194
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The recent fish population decline due to increased human presence has led to calls for predictive methods to help reverse or stabilize the situation. It has been difficult, however, to establish such methods primarily due to the technical obstacles in observing fish populations in natural habitats. Here we use acoustics to observe the ocean environment and study fish behavior during the critical spawning period over continental-shelf scales. Fish are known to be one of the main sources of strong natural returns in the continental-shelf environment, and so identified as a major source of clutter for wide-area undersea surveillance. The first continental-shelf scale acoustic measurements of Atlantic cod over thousands of square kilometers using towed source and receiver arrays were made by an international, multi-disciplinary team led by MIT researchers including myself in the historic Lofoten cod spawning ground in Norway during the peak spawning period in Winter 2014, where extensive but spatially discrete groups of spawning cod were successfully imaged. These initial instantaneous wide-area observations of cod aggregations suggest that these observed spawning groups have quantifiable properties that are linked to essential collective behavioral functions. We find that the mean group population per annual spawning season of Northeast Arctic cod over the entire spawning ground in Lofoten Norway is remarkably invariant across the available 30 years of line-transect survey data. The marked stability of the annual mean spawning group size in contrast to the large variations in total spawning population across years supports the interpretation of the expected spawning group size over the 30-year data set as the group behavioral quantum empirically expected for reliable spawning. Time series of the total Atlantic cod spawning population for major spawning regions across the North Atlantic show that once the total spawning population declined below a quantum, recovery to preindustrial levels did not occur in that region even after decades, which is an apparent consequence of large difference between the pre-industrial level and one quantum level. Quantized group behavior during spawning is also investigated for the Atlantic herring species. We find that the daily herring spawning group population is stable over the peak annual spawning period from wide-area acoustic measurements of spawning herring in the Gulf of Maine in Fall 2006. This supports the quantum concept that the mean spawning group population has evolved to a stable optimal size to fulfill the essential behavioral function of reliable spawning for Atlantic herring. As with cod, time series of the Atlantic herring spawning population for major spawning grounds across the North Atlantic show that when total spawning population declined below the empirically determined quantum level, return to pre-industrial levels required decades. Our findings show that to be sustained at pre-industrial levels the total spawning population must greatly exceed the mean spawning group size found at pre-industrial levels for any oceanic fish population we investigated, and likely many others. The migration of extensive social groups towards specific spawning grounds in vast and diverse ocean environments is an integral part of the regular spawning process of many oceanic fish species. Oceanic fish in such migrations typically seek locations with environmental parameters that maximize the probability of successful spawning and egg/larval survival. The 3D spatio-temporal dynamics of these behavioral processes are largely unknown due to technical difficulties in sensing the ocean environment over wide areas. Here we use ocean acoustic waveguide remote sensing (OAWRS) to instantaneously image immense herring groups over continental-shelf-scale areas at the Georges Bank spawning ground. Via multi-spectral OAWRS measurements, we capture a shift in swimbladder resonance peak correlated with the herring groups' up-slope spawning migration, enabling 3D spatial behavioral dynamics to be instantaneously inferred over thousands of square kilometers. We show that herring groups maintain near-bottom vertical distributions with negative buoyancy throughout the migration. We find a spatial correlation greater than 0.9 between the average herring group depth and corresponding seafloor depth for migratory paths along the bathymetric gradient. This is consistent with herring groups maintaining near-seafloor paths to both search for optimal spawning conditions and reduce the risk of predator attacks during the migration to shallower waters where near-surface predators are more dangerous. This analysis shows that multi-spectral resonance sensing with OAWRS can be used as an effective tool to instantaneously image and continuously monitor the behavioral dynamics of swimbladder-bearing fish group behavior in 3 spatial dimensions over continental-shelf scales. Recent research has found a high spatial and temporal correlation between certain baleen whale vocalizations and peak annual spawning processes of Atlantic herring in the Gulf of Maine. These vocalizations are apparently related to feeding activities of baleen whales with suggested functions that include communication, prey manipulation, and echolocation. Here the feasibility of the echolocation function is investigated. Physical limitations on the ability to detect large herring shoals and the seafloor by acoustic remote sensing are determined with ocean acoustic propagation, scattering, and statistical theories given baleen whale auditory parameters. Detection is found to be highly dependent on ambient noise conditions, herring shoal distributions, baleen whale time-frequency vocalization spectra, and geophysical parameters of the ocean waveguide. Detections of large herring shoals are found to be physically feasible in common Gulf of Maine herring spawning scenarios at up to 10 ± 6 km in range for humpback parameters and 1 ± 1 km for minke parameters but not for blue and fin parameters even at zero horizontal range. Detections of the seafloor are found to be feasible up to 2 ± 1 km for blue and humpback parameters and roughly 1 km for fin and minke parameters, suggesting that the whales share a common acoustic sensation of rudimentary features of the geophysical environment. No effect of anthropogenic sound on marine mammal vocalization behavior was found during our measurements. Some published statistical tests assessing the impact of anthropogenic sound on marine mammal behavior were found to have 98-100% false positive biases with no true positive confirmation, and so lack statistical significance.
Author: John Michels (Journalist)
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 644
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A weekly record of scientific progress.
Author: Felix Piavsky
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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Book Description
Accurately tracking multiple fish shoals can help understand fish migration patterns, better estimate fish populations, and lead to better decisions regarding fishery routines and preservation of the related marine ecosystems. Previously, fish shoals and their characteristics were identified manually for each shoal. Here we present techniques to automatically detect, track, and predict small fish shoal characteristics using Ocean Acoustic Waveguide Remote Sensing (OAWRS) over large areas and extended time periods. OAWRS system allows us to instantaneously map, image, and monitor fish populations over continental shelf-scale areas of thousands of square kilometers. Conventional fishery sonars operate at much higher frequencies and so have detection ranges limited the immediate vicinity of research vessels. The methods presented here can provide near real-time analysis during experiments or later analysis. In this work, we continuously tracked the migration of multiple fish schools during the 2014 Norwegian Sea experiment and 2003 Atlantic US coast experiment. Each shoal goes through image processing, tracking, feature extraction, and track management analysis. We take into account special cases such as splitting or merging of shoals. The results of this work can provide reliable tracking of small fish shoals, marine mammals, and underwater vehicles.
Author: Mark Andrews
Publisher:
ISBN: 9781124321295
Category :
Languages : en
Pages : 171
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Abstract : Underwater acoustic imaging and surveillance systems often transmit broadband pulses and process the scattered returns with a correlation matched filter in order to achieve high spatial resolution in range localization. When imaging distributed groups of scatterers, such as schools or shoals of fish, bubble clouds and swarms of AUVs, large numbers of individuals, ranging from tens to hundreds of thousands, are often present within each resolution cell of the imaging system. To estimate population density, spatial distribution, scattering cross-section and other parameters of the scatterer group and their error bounds, it is essential to understand the statistical nature and composition of the broadband matched filtered scattered returns. Here, using a combination of theoretical model development and experimental data analysis, we investigate (1) the statistics of broadband acoustic propagation in temporally and spatially varying shallow water waveguides, (2) the statistics and mechanisms for scattering from distributed groups, and (3) the effects of multiple scattering and waveguide dispersion in predicting the level and duration of the broadband matched filtered scattered intensities. The analysis is applied to two types of underwater acoustic imaging systems for mapping fish distributions. (a) The ocean acoustic waveguide remote sensing (OAWRS) system that allows instantaneous wide area continental-shelf scale imaging by utilizing muti-modal waveguide propagation, and (b) the conventional ultrasonic echosounder using direct-path propagation to image scatterer groups over water depth.Using experimental data acquired in the US east coast continental shelf, the scintillation statistics of one-way propagated broadband waveforms are quantified as a function of signal bandwidth, center frequency, and range. The received broadband intensity is shown to follow the Gamma distribution implying the central limit theorem has led to a fully saturated Gaussian field. An efficient numerical approach is developed to estimate the broadband transmission loss in a fluctuating, range-dependent ocean waveguide using spatial averaging of a time-harmonic stochastic propagation model. This approach is essential for rapidly detrending OAWRS imagery to make real time population density estimates.Theoretical models are then developed to determine the statistical moments of the broadband matched filtered scattered returns from distributed groups. For the ultrasonic echosounder, a numerical Monte-Carlo model that includes multiple scattering is developed and implemented to determine the conditions for when multiple scattering is significant. The model is implemented for Atlantic herring schools found in the Gulf of Maine, imaged with a conventional fisheries echosounder. Our analysis indicates that the single-scatter approximation is valid even for dense Atlantic herring schools at ultrasound frequencies. For direct-path imaging systems, an analytic model is also developed to efficiently estimate the scattered field statistics from the group by applying a single scatter approximation. The model can be used to compare the levels of the coherently and incoherently scattered intensities. It provides an explanation for how high spatial resolution is acheived with incoherently scattered fields with the coherent matched filter.We examine the effects of multiple scattering, attenuation, and waveguide dispersion on population density imaging with the OAWRS imaging system by implementing a numerical Monte-Carlo model. The model determines the statistical moments of the matched filtered multiply scattered returns from a distributed group of discrete scatterers, and incorporates propagation through a fluctuating range-dependent ocean environment. Results of the model are applied to interpret OAWRS imagery of shoaling Atlantic herring populations acquired during the NOPP-funded 2006 Experiment in the Gulf of Maine. Our analysis indicates that multiple scattering and attenuation were mostly negligible at OAWRS frequencies employed and for herring densities observed.
Author: Acoustical Society of America
Publisher:
ISBN:
Category : Architectural acoustics
Languages : en
Pages : 1052
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Author:
Publisher:
ISBN:
Category : Aquatic sciences
Languages : en
Pages : 1436
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Author: Thomas Rossing
Publisher: Springer Science & Business Media
ISBN: 0387304460
Category : Science
Languages : en
Pages : 1179
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Book Description
This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.
Author: Babin, Marcel
Publisher: UNESCO
ISBN: 9231040421
Category : Nature
Languages : en
Pages : 880
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Book Description
The proliferation of harmful phytoplankton in marine ecosystems can cause massive fish kills, contaminate seafood with toxins, impact local and regional economies and dramatically affect ecological balance. Real-time observations are essential for effective short-term operational forecasting, but observation and modelling systems are still being developed. This volume provides guidance for developing real-time and near real-time sensing systems for observing and predicting plankton dynamics, including harmful algal blooms, in coastal waters. The underlying theory is explained and current trends in research and monitoring are discussed.Topics covered include: coastal ecosystems and dynamics of harmful algal blooms; theory and practical applications of in situ and remotely sensed optical detection of microalgal distributions and composition; theory and practical applications of in situ biological and chemical sensors for targeted species and toxin detection; integrated observing systems and platforms for detection; diagnostic and predictive modelling of ecosystems and harmful algal blooms, including data assimilation techniques; observational needs for the public and government; and future directions for research and operations.
