Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Marine Science

Major Professor

David F. Naar, Ph.D.

Committee Member

Steven A. Murawski, Ph.D.

Committee Member

Kendra Daly, Ph.D.

Committee Member

Mark E. Luther, Ph.D.

Committee Member

Chad Lembke, Ph.D.

Committee Member

Kevin M. Boswell, Ph.D.

Keywords

EK60, NASC, Seafloor morphology, Target Strength

Abstract

The advancement and application of non-invasive fisheries survey technologies, such as the scientific echosounder, have significantly enhanced our understanding of fish populations and their habitats, more recently in regions where traditional sampling methods are limited, such as complex reef habitats. This research, conducted as part of the Continental Shelf Characterization, Assessment, and Mapping Project (C-SCAMP) on the West Florida Shelf, leverages acoustic and visual technologies to investigate the distribution of fish densities, fish target strength and length relationships, and the relationship between seafloor topography and fish biomass distribution.

The first study compared reef fish densities estimated from near-concurrent acoustic (Simrad EK60 split-beam echosounder, 38 kHz) and towed video methods across varying bathymetry and habitat types. The findings highlight the complementary strengths of these technologies in estimating fish densities, although their efficiency varied with habitat relief. The second study focused on gray snapper (Lutjanus griseus), examining its in-situ target strength (TS) and length relationships using a split-beam echosounder and stereo video systems. Two TS-Length models were developed, demonstrating the potential for accurate TS estimation without physical fish capture, showing potential for more efficient and non-invasive fishery assessments. The third study explored the relationship between seafloor rugosity and fish biomass in the Elbow region on the West Florida Shelf, using acoustic backscatter (Nautical Area Scattering Coefficient) as a proxy for biomass. The results indicated that more complex, rugose seafloor areas supported higher fish biomass, underscoring the importance of detailed acoustic surveys.

Collectively, these studies demonstrate the value of integrating advanced acoustic and visual survey methods in marine ecological research, providing efficient, non-invasive, and critical insights for the sustainable management of fisheries resources on the West Florida Shelf and potentially elsewhere.

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