Testing an acoustic zooplankton fish profiler mounted on a glider: a spatial temporal acoustic survey of Trinity Bay

Richard, Kassandra (2023) Testing an acoustic zooplankton fish profiler mounted on a glider: a spatial temporal acoustic survey of Trinity Bay. Memorial University of Newfoundland. (Unpublished)

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (1MB)

Abstract

Gliders are autonomous underwater vehicles (AUVs) of approximately 2 m in length that are capable of long-term deployments on the scale of months. They move vertically through the water by altering their buoyancy. The glider’s wings convert the vertical force provided by its variable buoyancy device into forward motion, allowing them to also move in a horizontal fashion. Gliders have to operate with limited power-supplies, and therefore cannot replace conventional oceanographic survey cruises. Nevertheless, as more instrumentation options are adapted for gliders, they are rapidly contributing to important oceanographic observations at a fraction of the cost of regular surveys. An example of a low power instrument that can be used on a glider is the Acoustic Zooplankton Fish Profiler (AZFP), which is a multi-frequency echosounder that is used to detect marine species of various sizes. Its original purpose was to be attached to a stationary structure such as a mooring, but recently, the AZFP is being used to augment traditional vessel-based sampling by being attached to gliders. Integrated into gliders, AZFPs can collect data at greater depths, closer to the coast-line, and over longer time periods than vessel-based sampling. This report describes a glider deployment intended to test Memorial University’s AZFP mounted on a glider and visualize the water column in Trinity Bay. In this field experiment, we produce results that explore the attenuation of sound in seawater at specific frequencies, discuss whether a repeated acoustic signal is logically the bottom or a pycnocline, and talk about the practicalities of visualizing large bodies of water with the AZFP on a glider.

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