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Shrimp are the most economically valuable internationally-traded seafood commodity, and wild-caught, trawled shrimp make up almost half of the ~6.6 million metric tons of annual global production. Shrimp trawling is responsible for one-third of the world’s total fisheries bycatch, leading many to consider shrimp trawling to be the single most destructive fishing practice in the world. Though the bycatch of large marine animals can be significantly reduced by use of turtle excluder devices (TEDs) on shrimp trawls, current TED designs are ineffective at reducing the capture of smaller organisms which represent a large portion of the total bycatch. To further reduce bycatch in the United States Gulf of Mexico shrimp trawl fleet, a variety of bycatch reduction devices (BRDs) are currently being used in conjunction with TEDs. I evaluated the efficiency of a new TED design, intended to reduce bycatch and maintain target shrimp catch. The new TED model is characterized by 5-cm spacing between flat bars, as opposed to the current industry standard of 10-cm spacing between round bars. Comparative towing experiments under standard commercial shrimp trawling operations in waters off of Georgia, Texas and Mississippi during the summer of 2012 demonstrated shrimp losses or gains of -4.32%, +6.07%, -1.58% respectively and an overall reduction in the capture weight of sharks (41.1-99.9%), rays and skates (76.5-93.4%) and horseshoe crabs (100%). These experiments were limited in time and space, and therefore not fully representative of fishing conditions throughout the year, but this study demonstrates the new TED’s effect on the catch rates of target shrimp and bycatch. This thesis research should lead to a broader understanding of the benefits of using reduced spacing flat bar TEDs in the U.S. shrimp trawl industry.

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The main subject of my papers has been the phylum Tardigrada, with particular emphasis on the Antarctic fauna. While this is one of the ‘lesser known phyla’ the group forms an important element of Antarctic non-marine ecosystems. My work has centred on four interrelated themes: i) taxonomy, predominantly Tardigrada and with an Antarctic bias though including wider global species and high taxon groupings (I have also worked on other taxa such as Fungi-imperfecti and freshwater invertebrates); ii) biodiversity of tardigrades, particularly Antarctic habitats; iii) data-based studies based on the terrestrial Tardigrada and Antarctic freshwater crustaceans; and iv) biogeographic analysis of these databases. The thesis presented consists of papers published in major, peer-reviewed journals, along with book chapters published and in press. Several of my papers have been cited 10-30 times according to the ISI Web of Science citation system. Highlights of my work include being the first to publish a paper on the global terrestrial biogeography of a phylum and showing the extant limno-terrestrial tardigrade fauna reflect the early tectonic break-up of the Laurasia, West and East Gondwana super continents between 65 and 135 million years ago.

The extensive acidification of fresh waters across Europe and North America during the 20th century led to extensive and widespread loss of species, which fundamentally changed the structure of resident communities. While attempts to limit or halt acidifying emissions have been successful in reversing the chemical consequences of acidification, any corresponding biological recovery has been patchy at best. The main aim of this thesis was to investigate potential ecological constraints on this biological recovery, ranging from interactions between individuals to ecosystem-level processes, using a model stream system that has been extensively studied for over 40 years. I used a combination of long-term survey data and experiments, both in the field and the laboratory, to provide evidence that the lag in recovery of acidified aquatic communities is due to intrinsic resistance to re-colonisation by acid-sensitive species, as a result of both direct and indirect interactions between predators and prey. However, there is also evidence of recovery at an ecosystem level, with rates of microbial decomposition increasing – a key link in the transfer of energy to higher trophic levels, which could be facilitating population increases in large-bodied predators. These findings increase our understanding of the drivers which govern the structure and function of ecological networks in response to an important climatic stressor. This is especially relevant given the rapid industrialisation of countries such as India and China, which could well soon experience anthropogenic acidification on a significant scale.

Following a call from Linton (2010) to think more relationally about water this thesis seeks to explore the infolding and unfolding relations that take-form between bodies around particular characteristics of freshwater. There is a tradition of exploration regarding the sustainability, quality, monitoring and management of water when we encounter research on human associations with fluvial hydrology, and whilst this work is important, this project looks to enrol more nascent and contemporary geographical themes to broaden our understanding of encounters with freshwater landscapes, and take a more relational approach to fluvial geographies. These works then shall address a gap in the geographical literature and describe the personal, pre-personal and affective worlds that emerge when bodies become down by the river. Whilst this is not specifically a walking project, walking the course of the River Severn serves as a trajectory along which processual ideas of bodies on the move shall be mobilised. A series of creatively written segues will link together a sequence of theoretical and conceptually driven site ontologies (Marston et al 2005; Woodward et al 2010) and relations associated with the Severn and freshwater more broadly. The flow and form of the thesis will reflect the multivariant characteristics of water and its varying speeds and slownesses. The chapters will step into puddles, mooch about in a ships graveyard, rethink the source of a river, paddle a coracle and set the scene for how an ontological, relational approach to fluvial landscapes can contribute to geographical thinking. The works will focus on human-nonhuman relations, vibrant materialities and elemental mobilities, in so doing enable further understanding of how we can apprehend sites as moments of coherence in a turbulent world, and contribute to broadening our scope of knowledge of the more-than-human.