STORRE Community: This community contains the ePrints and eTheses produced by the Aquaculture staff and students.

Combined Surface‐Bottom Aeration: A Pathway to Improved Water Quality and Productivity in Pond‐Based Tilapia Farming

2026-10-01T00:00:00Z

Title: Combined Surface‐Bottom Aeration: A Pathway to Improved Water Quality and Productivity in Pond‐Based Tilapia Farming Author(s): Roy, Mithun; Asaduzzaman, Md; Saha, Debasish; Islam, Md Rakeb‐Ul; Little, David C; Newton, Richard; Ahmed, Abu Tweb Abu; Islam, Faruk‐Ul; Asadujjaman, Md; Chowdhury, Muhammad Tanvir Hossain; Mamun, Abdullah‐Al Abstract: Pond-based aquaculture demands effective management of dissolved oxygen (DO) for sustainable intensification to improve productivity. This study evaluated surface aeration (SA), bottom aeration (BA) and combined surface-bottom aeration (SBA) against a non-aerated control during a 120-day monoculture of Nile tilapia (Oreochromis niloticus) stocked at 400 fish/decimal. Water quality and DO dynamics were monitored throughout the culture period, and aeration was initiated on Day 59 when biomass reached 0.58 ± 0.05 kg/m2 and morning DO declined below 4 mg/L. Aerated ponds maintained more stable DO regimes than the NA control, whereas SBA achieved comparatively improved DO concentrations across water depths. SBA exhibited significantly (p < 0.05) higher total production (16.47 ± 0.195 MT/ha), faster specific growth (4.39% ± 0.035%), higher survival (96.88% ± 0.22%) and a lower feed conversion ratio (1.41 ± 0.017), whereas treatment NA showed the lowest performance across growth and feed efficiency parameters. Economic analysis aligned with these results, whereas SBA showed favourable cost–benefit ratios (1.14 ± 0.02) and return on investment (13.60% ± 1.36%). However, because SBA involved a higher installed power input than single-mode aeration systems, the observed benefits reflect the performance of the combined aeration configuration under the applied operational conditions rather than a strictly energy-normalized comparison. By simultaneously evaluating spatial oxygen distribution, operational aeration thresholds, biological performance and economic outcomes, this study provides practical evidence supporting integrated SBA as an effective strategy for sustainable intensification of pond-based Nile tilapia farming.

Plasticity in a bacterial global regulatory switch that drives a shift in antibiotic resistance and virulence

2026-01-08T00:00:00Z

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.

Revealing potential Atlantic salmon bycatch hotspots from pelagic fisheries landings across the Northeast Atlantic

2026-10-15T00:00:00Z

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.

Producing Affordable Tilapia in Sub-Saharan Africa by Replacing Feed with Farm-Produced Black Soldier Fly Larvae

2026-09-23T00:00:00Z

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.