http://hdl.handle.net/1893/12 This community contains the ePrints and eTheses produced by the Aquaculture staff and students. Sat, 24 Oct 2026 14:33:15 GMT 2026-10-24T14:33:15Z http://hdl.handle.net/1893/38414 Title: Plasticity in a bacterial global regulatory switch that drives a shift in antibiotic resistance and virulence Author(s): Correia, Annapaula; Manners, Emma J; Evans, Benjamin A; Malone, Jacob G; O’Grady, Justin; Mavrogiorgou, Eleni; Arminu, Sergio; Usai, Manuela; Naik, Dixita; McMillan, Stuart; Kay, Gemma L; Hill, Claire; Sudhakar, Padhmanand; Meader, Emma; Desbois, Andrew P Abstract: Antibiotic resistance and expression of virulence factors impact the outcome of infection by Pseudomonas aeruginosa. Pathogenesis is often modelled using the PAO1 reference strain but laboratory lineages vary in the sequence and activity of MexT, a global regulator impacting virulence, biofilm formation, and ciprofloxacin resistance. We defined the impact of active versus inactive MexT in PAO1 and observed transcriptomic changes affecting the expression of ~900 genes. Phenotyping revealed altered metabolism, antibiotic resistance, and virulence, resulting in striking variation across a ‘single’ model organism. We propose that antibiotic resistance promotes plasticity in mexT accounting for variation across lineages. We introduced antibiotic resistance into clinical P. aeruginosa isolates and observed mutations in mexT when selective pressure was removed, supporting the proposed evolutionary pathway. Overall, we have demonstrated the transcriptomic basis of MexT as a phenotypic switch in PAO1 and implicated antibiotic resistance as a cause of changes in mexT. Furthermore, MexS/MexT-regulated efflux is implicated in the antibiotic stress response and virulence, helping identify the mechanisms for rapid phenotypic switching through mexT and confirming that PAO1 is unlike most isolates. Improved understanding of the regulatory changes linked to antibiotic resistance is particularly relevant to P. aeruginosa where cycles of antibiotic treatment are common. Thu, 08 Jan 2026 00:00:00 GMT http://hdl.handle.net/1893/38414 2026-01-08T00:00:00Z http://hdl.handle.net/1893/38412 Title: Revealing potential Atlantic salmon bycatch hotspots from pelagic fisheries landings across the Northeast Atlantic Author(s): Borland, Aislinn; Elliott, Sophie; Gillson, Jonathan P; Utne, Kjell; Banas, Neil; Toms, Simon; Tyldesley, Emma; Bárðarson, Hlynur; Bull, Colin Abstract: Atlantic salmon (Salmo salar) marine survival has declined markedly over the past five decades, leading to concerns about future population viability. While many studies have explored the impacts of stressors such as climate change and predation, less is known about bycatch from pelagic fisheries targeting finfish species. This study, focused on the first few months of the salmon marine migration period, narrows down the space-time domains where pelagic fisheries bycatch is most likely to occur. Landings from an International Council for the Exploration of the Sea led data call were used to assess bycatch exposure. Temporal patterns of monthly landings of six commercially important pelagic finfish species (mackerel Scomber scombrus, herring Clupea harengus, horse mackerel Trachurus trachurus, sardine Sardina pilchardus, capelin Mallotus villosus, and chub mackerel Scomber colias) within the Northeast Atlantic region from 2000 to 2022 were considered alongside reconstructed salmon migration regions. This study indicated that bycatch exposure from herring and mackerel fisheries was higher than that of other pelagic fisheries along the shared salmon migration corridor between April and August, with cumulative exposure highest over time for the herring fishery. Southern salmon populations were also exposed to the horse mackerel and sardine fisheries in April. Temporal patterns of monthly pelagic landings were compared with patterns of marine return rates in salmon index populations, but no consistent relationships were present. Quantifying salmon bycatch rates at sea remains challenging due to highly variable and sparse data but, given the severity of declines across their range, conservation measures that address factors affecting marine survival of salmon are urgently needed. Future investigations using emerging technology in the pelagic fisheries identified in this study could provide opportunities to develop more robust information on bycatch risk to Atlantic salmon stocks and to direct appropriate mitigation measures. Thu, 15 Oct 2026 00:00:00 GMT http://hdl.handle.net/1893/38412 2026-10-15T00:00:00Z http://hdl.handle.net/1893/38366 Title: Producing Affordable Tilapia in Sub-Saharan Africa by Replacing Feed with Farm-Produced Black Soldier Fly Larvae Author(s): Newton, Richard W; Bostock, John; Messeder, Tim; Immink, Anton; Little, David C Abstract: Fish remains unaffordable for communities in many parts of Sub-Saharan Africa where malnutrition is common. High aquaculture production costs due to feed and labour prevent the production of affordable fish. Substitution of commercial with farm-made feed can lower production costs. In this study, on a small-scale Ugandan tilapia farm, commercial feed was substituted with black soldier fly larvae (BSFL), grown using fruit and vegetable waste. Data on the cost of establishing larvae production facilities, operating costs and fish production were used to test the economic feasibility of substituting feed with BSFL to produce affordable tilapia. We found that feed could successfully be substituted with up to 66% BSFL with no effect on fish production. Economic analysis revealed that 55% substitution was needed to produce tilapia at US$2.00/kg with a Feed Conversion Ratio of 2.4. Profitability improves if fish sales are supplemented with sales of frass (used substrate) and any leftover BSFL. Substitution of feed with BSFL grown on local low-cost waste materials provides a sustainable and circular approach to tackling food security in some of the world's poorest communities. Wed, 23 Sep 2026 00:00:00 GMT http://hdl.handle.net/1893/38366 2026-09-23T00:00:00Z http://hdl.handle.net/1893/38363 Title: Diatom–lipid–copepod nexus under threat by global change Author(s): Jonasdottir, Sigrun; Broughton, Richard; Visser, André Abstract: The central role of lipids in the ecology of high-latitude and temperate seas is under threat by global change. This hinges on the tight ecological links between diatoms and copepods of the genus Calanus and similar (e.g. Neocalanus, Calanoides) that produce and accumulate energy-rich lipids. Strongly coupled through seasonal water-column stability, nutrient supply, spring-bloom succession, and overwintering life strategies, this nexus is foundational to the highly productive food webs of these regions. We experimentally tested how a change in phytoplankton type from diatoms to flagellates, along with 2°C warming, affects lipid accumulation of the subarctic copepod Calanus finmarchicus. We report that the ability of C. finmarchicus to accumulate lipids is seriously impaired by a changing diet, being threefold higher on diatoms than flagellate-based diets, whereas within diet types, up to a sevenfold reduction in lipids is associated with a 2°C temperature rise. This, together with higher specific respiration rates, smaller size, and reduced diatom productivity, suggests the ability of Calanus to overwinter may be compromised, threatening their contribution to regional productivity and to sequestered carbon via the lipid pump. Similar lipid-mediated couplings are prevalent throughout seasonal environments, casting uncertainty on their future provision of ecosystem services. Wed, 30 Sep 2026 00:00:00 GMT http://hdl.handle.net/1893/38363 2026-09-30T00:00:00Z