Fish nets to nests, from the shallow tropics to bathyal Antarctica.

Marine fish are found in all oceans on Earth, compose over half of the world’s vertebrates, and exhibit highly differing morphologies (Nelson et al., 2016). They occupy the deep hadopelagic to the shallowest coastal regions. As this group of animals are so diverse, the term ‘fish’ is not contained within a specific lineage. Fish occupy different ecosystems within the global ocean, being adapted to exploit their specific environments. Zonation occurs between areas of the global ocean due to different environmental conditions, mainly driven by depth; as light levels decrease, and temperatures reduce, species are evolved to exploit these environments. Broadly species diversity is higher in the shallow waters of the global ocean than in the deep sea; however, morphologically, the deep sea hosts greater diversity (Martinez et al., 2021). Fishes have different life histories that determine their development, and the challenges faced in development are dictated by their environment (Thorson et al., 2017). Species exploit niches which are unique to their specific habitat. A heterogeneous habitat allows for a wider range of niches, and as such, a higher species diversity (Brownscombe et al., 2019; Charton and Ruzafa, 1999). The different morphologies that species of fishes exhibit are specialised for their way of life, for example, fin design and use. Most fishes have some form of locomotion, either by swimming, or using their fins to walk (Lauder, 2000). Movement is widely used by fishes to complete daily and developmental activities such as migration between regions for food. Fishes, like most animals, are impacted by anthropogenic actions (Pauly et al., 2005). Humans have established fisheries to exploit and extract fishes from their habitats, something undertaken by all coastal countries and communities (Hicks et al., 2019). Fishing can be classed into three overall forms: recreational, commercial, and subsistence fishing (Cooke et al., 2016; Love, 2006). Fishes are an important source of protein for small island developing states (SIDS) as they have limited space for farming and other agricultural practices (Robinson et al., 2022; Sing Wong et al., 2022). Different types of fishing gear can be used to target different morphologies and movements (Eyo and Akpati, 1995). These fishing gears may be restricted by legislation. Fisheries departments in governments, local enforcements, and international treaties or organisations, such as the United Nations and the Convention on the Conservation of Antarctic Marine Living Resources, can enact levels of restrictions, as can local laws and traditions. Governments and local communities can establish marine protected areas, which have the power to protect marine resources from being extracted by abiding groups. This can offer recovery to a certain stock from stock depletion or provide an area for spill-over effects for fishing to occur beside it (Di Lorenzo et al., 2016; García-Rubies et al., 2013). This dissertation encompasses and has themes covering the movement, life histories, and governance of fishes. I present data from 1) a tropical island fishery and 2) a unique bathyal cryonotothenioid nesting site in Antarctica in two chapters.