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Geoacoustic inversion in shallow waterCox, Benjamin Timothy January 1999 (has links)
No description available.
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iSAT: The Integrated Satellite and Acoustic Telemetry system for tracking marine megafaunaDe La Torre, Pedro R. 05 1900 (has links)
In this dissertation an innovative technology to study whale sharks, Rhincodon typus is presented.
The Integrated Satellite and Acoustic Telemetry project (iSAT) combines underwater
acoustic telemetry, autonomous navigation and radio frequency communications into a standalone
system. The whale shark, a resident of the Saudi Arabian Red Sea, is the target of
the study. The technology presented is designed to help close current gaps in the knowledge of
whale shark biology; these are gaps that prohibit the design of optimal conservation strategies.
Unfortunately, the various existing tracking technologies each have limitations and are unable
to solve all the unanswered questions. Whale shark populations are increasingly threatened by
anthropogenic activities such as targeted and indirect fishing pressure, creating an urgent need
for better management practices.
This dissertation addresses the current state-of-the-art of relevant technologies, including
autonomous surface vehicles (ASVs), sensors for research in the ocean and remote monitoring
of wild fauna (biotelemetry). iSAT contains components of all of these technologies, but the
primary achievement of this dissertation is the development of iSAT’s Acoustic Tracking System
(ATS). Underwater, the most efficient way of transmitting energy through long distances is
sound. An electronic tag is attached to an animal and works as its acoustic identifier. iSAT’s
hydrophone array detects the presence and direction of the acoustic signal generated by the tag.
The expected performance, range, and capacity to tell the direction to the tag are explained and
compared to the actual measured values. The first operational iSAT ATS is demonstrated.
This work represents significant advancement towards a fully autonomous iSAT system. Developments
on the power electronics, navigation, renewable energy harvesting, and other modules
are included in this research. With the recent integration of digital acquisition systems, iSAT’s
capabilities were increased to minimize its size and allow it to communicate with other acoustic
systems. Future engineering works are still necessary to achieve a fully automated system, but
the current developments with the ATS have immediate applications.
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A biogeography of the mesopelagic communityProud, Roland Hudson January 2016 (has links)
There are a large number of research vessels and fishing vessels equipped with echosounders plying the world ocean, making continual observations of the ocean interior. Developing data collation programmes (e.g. Integrated Marine Observing System) and automated, repeatable analyses techniques enable the upper c. 1,200 meters of the world ocean to be sampled routinely, and for their characteristic deep scattering layers (DSLs) to be compared. Deep scattering layers are comprised of zooplankton (e.g. euphausiids) and fish, particularly myctophids or lantern fish, and comprise the majority of sub-surface biomass. Here we present, by the analysis of a global acoustic dataset, a mesopelagic biogeography of the sea. This was accomplished by (i) the collation and processing of a global active acoustic dataset, (ii) the development of a standardised and automated method of sound scattering layer (SSL) extraction and description, (iii) the derivation of the environmental drivers of DSL depth and biomass, (iv) the definition of a mesopelagic biogeography based on the drivers of DSL metrics and (v) the prediction, using output from the NEMO-MEDUSA-2.0 coupled model, of how the metrics and biogeography may change by 2100. Key findings include, the development of the Sound Scattering Layer Extraction Method (SSLEM) the inference that primary production, water temperature and wind stress are key drivers in DSL depth and biomass and that mesopelagic fish biomass may increase by 2100. Such an increase is a result of increased trophic efficiency from the shallowing of DSLs and rising water temperatures, suggesting, that as the climate warms the ocean is becoming more efficient. The biophysical relationships and biogeography derived here, serve to improve our understanding of mesopelagic mid-trophic level dynamics in open-ocean ecosystems. This will aid both fisheries and conservation management, which now adopt more holistic approaches when monitoring and evaluating ecosystem health and stability.
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