Investigating the Anthropocene influence on temperate fish assemblages through Baited Remote Underwater Video Stations (BRUVS)

Author: Sasha Whitmarsh

Whitmarsh, Sasha, 2019 Investigating the Anthropocene influence on temperate fish assemblages through Baited Remote Underwater Video Stations (BRUVS), Flinders University, College of Science and Engineering

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The ever increasing human population and subsequent pressure this places on the marine environment has been the focus of studies for many years, with effects from some potential stressors receiving widespread attention, e.g. climate change. The global use of our marine resources has led to various detrimental effects including population declines, local species extinctions, and a loss of ecosystem services, with these events now being referred to as Anthropocene defaunation. Fish assemblages play a key role in the functioning of many marine ecosystems and are an integral part of most human societies through fishing or recreational activities (e.g. snorkelling/diving). However, research has often focused on commercial, tropical, or reef species, while temperate areas, soft sediment habitats, and non-commercially targeted species have typically been less often investigated. The objective of my thesis is to describe such under-studied fish assemblages and assess the effects of increasing anthropogenic activities in South Australia through use of a contemporary non-extractive monitoring method. I conducted over 600 deployments using Baited Remote Underwater Video Stations (BRUVS) to answer three broad aims: 1) describe temperate fish communities and their natural variations; 2) determine how fish assemblages respond to differing anthropogenic stressors; and 3) investigate how BRUVS assess fish assemblages and ways it may be improved as a method. Through a thorough literature review, I was able to highlight variations about the BRUVS method that cause discrepancies across studies, and the potential impacts of underreporting such variation. From my studies, I found a wide variety of fish assemblages inhabiting South Australian waters, which were often site-specific and varied by habitat type, season, and across years. My anthropogenic case-studies showed varying levels of influence from potential stressors and began an understanding of cumulative stressors, which has previously been difficult to untangle. Specifically, I found some areas were responding to early protection from fishing with increases in the abundance of certain fisheries species; no evidence of an influence of brine outfall from desalination processes; limited influence from bait and berley input from tourism activities at the Neptune Islands group; and influences from effluent and oyster leases on the fish assemblages observed in Coffin Bay. I was also able to determine the impact of additional viewpoints on the abundance and assemblages observed and use these additional viewpoints to reduce some of the biases inherent with using BRUVS in a traditional manner. My results are relevant to future studies using BRUVS to provide a comprehensive species list and to quantify nighttime fish assemblages. Findings from my thesis will also enable a better understanding of fish assemblages in temperate Australia with a view to inform management decisions.

Keywords: BRUVS, fish assemblages, anthropogenic, stressors, impacts, baited video, temperate, temporal change, MaxN, 360

Subject: Biology thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Peter Fairweather