SPECIES-HABITAT RELATIONSHIPS AND COMMUNITY STRUCTURE OF REEF FISHES ASSOCIATED WITH TEMPERATE HARDBOTTOM REEFS OF NORTH CAROLINA, USA

Numbers of human-made, artificial structures in coastal oceans are increasing. Humans deploy these artificial structures for a variety of purposes, including to protect shorelines, harness energy resources, create and restore habitat, and foster tourism, fishing, and diving opportunities. Because the introduction of artificial structures to coastal oceans has the potential to drive ecological change, understanding how species use these artificial structures as habitat is important. Along the southeastern USA continental shelf, shipwrecks and intentionally sunk artificial reefs provide an opportunity to determine how reef fish communities rely on artificial structures, especially in comparison to naturally-occurring rocky reefs. Here, I investigated five applied research questions on artificial reefs, shipwrecks, and rocky reefs of North Carolina, USA using methods ranging from diver-conducted surveys and fisheries acoustics to time-lapse videography and audio recordings. First, I tested how reefs that vary in topographic complexity function to support reef fishes (Chapter 1). I discovered that flat reefs, which are often difficult to detect, provide similar support for reef fishes as more easily detectable complex, high-relief reefs. Second, I examined how reefs support fishes with different thermal affinities and determined that because tropical and subtropical fishes occurred in higher abundances on artificial structures than rocky reefs that deploying additional human-made reefs may help warm-water fishes move poleward from the tropics (Chapter 2). Third, I examined spatial relationships between planktivorous fishes, zooplankton (prey), and piscivorous fishes (predators) around artificial structures (Chapter 3). I found that aggregations of planktivorous fishes around artificial structures related to spatial patterns across adjacent trophic levels, suggesting that artificial structures influence multiple trophic levels. Fourth, I documented how reef fishes reacted to underwater noises typically emitted when searching for oil and gas beneath the seafloor, finding that fish abundance decreased 78% during evening hours when exposed to these loud noises, raising conservation concerns (Chapter 4). Fifth, I assessed how quickly newly established artificial reefs create fish habitat and discovered that newly deployed human-made reefs can provide fish habitat comparable to 20-year old artificial reefs within five months (Chapter 5). Taken together, these results demonstrate that differences exist between fish communities residing on artificial structures versus natural reefs (Chapters 1 & 2). These differences are driven largely by higher abundances of planktivorous fishes (Chapter 3), as well as tropical and subtropical highly-reef associated species, on artificial structures than on natural reefs (Chapter 2). When considering future installation of human-made structures, artificial reefs can quickly establish fish habitat comparable to previously established artificial structures (Chapter 5), yet effects from exploration prior to installation of these structures, such as underwater noises, can disrupt how fish use reefs (Chapter 4). Artificial structures clearly serve as fish habitat, and as artificial structures continue to be deployed, conservation and management efforts must recognize that species-habitat relationships differ between artificial structures and naturally occurring rocky reefs and that artificial structures can have both ecological benefits and impacts.Doctor of Philosoph