The importance of determining and maintaining migration corridors for the Hilsa Shad fishery in Myanmar Inland Rivers.

The hilsa shad (Tenualosa spp) fisheries are one of the most important commercial fisheries in the Bay of Bengal region, being the national fish of Bangladesh, and playing an essential cultural and economic role in the lives of Myanmar people. More recently, the availability of Hilsa has declined across this region, due to a number of anthropogenic pressures, mainly intensive fishing and river obstruction by dams and barrages. Hilsa are known to be anadromous moving from the sea to the brackish or freshwater to spawn, however very little is very little is known about the lifecycle requirements of Hilsa in Myanmar waters and their migratory routes. River engineering and irrigation infrastructure is increasing in Myanmar rivers, wetlands and estuary systems and this has the potential to significantly negatively impact the Hilsa fisheries in Myanmar. With very little information on the migration patterns of Hilsa in Myanmar, it limits the ability for planning and positioning of infrastructure or remediation works such as fish passage. Leading on from other preliminary World Fish studies, Delta Flows is utilizing otolith microchemistry to determine the movements of adult Hilsa from the sea to the brackish or freshwater, where spawning might occur, and the movements of the juveniles back to the sea. Preliminary catch data has found adult Hilsa hundreds of kilometres inland including young-of-year, so it is suspected that at least a proportion of the population is spawning in freshwater. The next stage is analysis of the otolith microchemistry and this will help to better understand the lifecycle requirements of Hilsa in Myanmar waters, and improve informed decision making in relation to infrastructure planning

Control of globally invasive common carp: a 10 year commercial trial of the Williams\u27 carp separation cage in a Murray River fishway

Common carp Cyprinus carpio, are a highly migratory pest fish in Australia, North America, New Zealand and parts of Europe. Fishways built to facilitate native fish passage also benefit invasive carp. The Williams’ cage was developed to separate carp from native fish as they pass through fishways by exploiting their unique jumping behaviour. We report on a 10-year commercial application in a fishway on the lower Murray River (SE Australia) where a high biomass of carp resides. Between November 2007 and April 2017, the automated Williams’ cage was installed and operated at Lock 1 by a collaborative team of river managers, weir keepers, commercial fishers and researchers. To date, over 700 tonnes of adult carp, (approx. 350,000 fish) have been removed at a maximum rate of 5 tonnes per day. The income generated from the sale of the fish has far exceeded set up costs. Catches and separation efficiencies were highest in spring (Austral) when fish were migrating to spawn. During the cage design phase, refinements helped reduce bycatch of non-target native fish to practically zero (0.03%) and informed future designs, application and operation. The Williams’ cage has now successfully moved from an experimental idea to full commercial viability and could play a key role in controlling the dispersal and abundance of carp where high abundances preside and collaborative management alliances can be formed

Diel foraging and shelter use of large juvenile brown trout (Salmo trutta) under food satiation

The diel partitioning of juvenile brown trout Salmo trutta foraging behaviour is controlled by a number of factors including predation risk, competition, temperature and food availability. The present study uses PIT-tagging and visual observation to asses the use of shelter and foraging behaviour of Danish wild juvenile brown trout (13.5–15.6 cm). The experiment was conducted in a fluvarium and the fish were fed to satiation. It was hypothesised that food satiation would promote nocturnal foraging and increase daytime shelter use. Our results showed a significant difference in diel shelter use between day and night with a significant increase in shelter use during daytime conditions. Visual observations showed a significant preference for nocturnal feeding. Together with the significantly reduced shelter use during the night, our results support the hypothesis that young stream living trout only feed during the day to the extent needed to sustain growth

Daytime habitat selection for juvenile parr brown trout (Salmo trutta) in small lowland streams

Physical habitat is important in determining the carrying capacity of juvenile brown trout, and within freshwater management. Summer daytime physical habitat selection for the parr lifestage (7–20 cm) juvenile brown trout (Salmo trutta) was assessed in 6 small lowland streams. Habitat preference was determined for the four variables; water velocity, water depth, substrate and cover, and the preferences for physical habitat selection were expressed in terms of habitat suitability indices (HSI’s). The statistical confidence of HSI’s was evaluated using power analysis. It was found that a minimum of 22 fish observations was needed to have statistical confidence in the HSIs for water depth, and a minimum of 92 fish observations for water velocity during daytime summer conditions. Generally parr were utilising the deeper habitats, indicating preference for deeper water. Cover was also being selected for at all sites, but selection was inconsistent among sites for the variables substrate and velocity. The results indicate that during daytime summer conditions water depth is a significant variable for parr habitat selection in these small lowland streams, with cover also being important. Therefore, daytime refugia may be a critical limiting factor for parr in small lowland streams, and important for stream management actions under the Water Framework Directive

SLIDES: Environmental Flow Case Studies: Southern and Eastern Africa

Presenter: Rebecca Tharme, Riverfutures Ltd. 17 slide

SLIDES: Environmental Flow Case Studies: Southern and Eastern Africa

Presenter: Rebecca Tharme, Riverfutures Ltd. 17 slide

Supporting evidence-based decision-making: Capacity Building through Research

Lack of data inhibits informed decision-making and is a critical challenge in developing countries, many of which are under-resourced in financial, technical and institutional capacity to collect and analyse the required data. This limits the countries’ ability to achieve development goals and keeps them dependent on the provision of external resources. Development initiatives often treat capacity building and research as two separate tracks of development. While efforts have been made in the health sector to combine these through project-based learning, this approach is relatively unexplored in the water sector which by its inter-sectoral nature stands to benefit significantly from a more collaborative and solution-oriented development strategy. Capacity Building through Research (CBtR) facilitates data collection and analysis by local researchers, mentored by international experts, strengthening local capacity to produce credible evidence able to inform sustainability-related decision-making. Five case studies piloting CBtR are discussed here and evaluated through criteria of the Dutch Strategy Evaluation Protocol framework. CBtR is shown to be a long-term strategy that requires the strengthening of cross-disciplinary networks to enhance the capacity of water management institutions, which likely contributes to more efficient evidence collection and analysis suitable for decision-makers, leading to greater national resilience and reduced need for external support

Integrating fish into irrigation infrastructure projects in Myanmar: rice-fish what if…?

With rapidly increasing investment in water control infrastructure (WCI) and a recently ratified agriculture development strategy that promotes integrated farming of high-value products such as fish, agricultural production, already fundamental to Myanmar’s economy, will be central to driving the countries’ socioeconomic transformation. Water planners and managers have a unique opportunity to design and manage WCI to incorporate fish and, in so doing, reduce conflicts and optimise the benefits to both people and the ecosystem services upon which they depend. Results from rice–fish culture experimental trials in Myanmar’s Ayeyarwady Delta are providing an evidence base for the importance of integrating fish into WCI, highlighting a range of both environmental and social benefits. By using less than 13% of paddy land area and through best management practices, existing rice productivity is sustained, alongside a 25% increase in economic returns for the same land area from fish. In addition, there are considerably more protein and micronutrients available from the fish produced in the system. Should these farming system innovations be adopted at scale, Myanmar stands to benefit from increased employment, incomes and nutritional value of farm plots (alongside associated reductions in pesticide pollution) and water use benefits

Flow management to control excessive growth of Macrophytes - An assessment based on habitat suitability modeling

Original ResearchMediterranean rivers in intensive agricultural watersheds usually display outgrowths of macrophytes – notably alien species – due to a combination of high concentrations of nutrients in the water runoff and low flows resulting from water abstraction for irrigation. Standard mechanical and chemical control is used to mitigate the problems associated with excessive growth of plant biomass: mainly less drainage capacity and higher flood risk. However, such control measures are cost and labor-intensive and do not present long-term efficiency. Although the high sensitivity of aquatic vegetation to instream hydraulic conditions is well known, management approaches based on flow management remain relatively unexplored. The aim of our study was therefore to apply physical habitat simulation techniques promoted by the Instream Flow Incremental Method (IFIM) to aquatic macrophytes – the first time it has been applied in this context – in order to model shifts in habitat suitability under different flow scenarios in the Sorraia river in central Portugal. We used this approach to test whether the risk of invasion and channel encroachment by nuisance species can be controlled by setting minimum annual flows. We used 960 randomly distributed survey points to analyze the habitat suitability for the most important aquatic species (including the invasive Brazilian milfoil Myriophyllum aquaticum, Sparganium erectum, and Potamogeton crispus) in regard to the physical parameters ‘flow velocity,’ ‘water depth,’ and ‘substrate size’. We chose the lowest discharge period of the year in order to assess the hydraulic conditions while disturbances were at a low-point, thus allowing aquatic vegetation establishment and subsistence. We then used the two-dimensional hydraulic River2D software to model the potential habitat availability for different flow conditions based on the site-specific habitat suitability index for each physical parameter and species. Our results show that the growth and distribution of macrophytes in the hydrologically stable vegetation period is primarily a function of the local physical instream condition. Using site-specific preference curves and a two-dimensional hydraulic model, it was possible to determine minimum annual flows that might prevent the excessive growth and channel encroachment caused by Myriophyllum aquaticuminfo:eu-repo/semantics/publishedVersio

Application of Probabilistic Neural Networks to microhabitat suitability modelling for adult brown trout (Salmo trutta L.) in Iberian rivers

Probabilistic Neural Networks (PNN) have been tested for the first time in microhabitat suitability modelling for adult brown trout (Salmo trutta L.). The impact of data prevalence on PNN was studied. The PNN were evaluated in an independent river and the applicability of PNN to assess the environmental flow was analysed. Prevalence did not affect significantly the results. However PNN presented some limitations regarding the output range. Our results agreed previous studies because trout preferred deep microhabitats with medium-to-coarse substrate whereas velocity showed a wider suitable range. The 0.5 prevalence PNN showed similar classificatory capability than the 0.06 prevalence counterpart and the outputs covered the whole feasible range (from 0 to 1), but the 0.06 prevalence PNN showed higher generalisation because it performed better in the evaluation and it allowed a better modulation of the environmental flow. PNN has demonstrated to be a tool to be into consideration.The authors would like to thank the Spanish Ministry of Economy and Competitiveness for its financial support through the SCARCE project (Consolider-Ingenio 2010 CSD2009-00065). We are grateful to the colleagues who worked in the field and in the preliminary data analyses, especially Marta Bargay, Aina Hernandez and David Argibay. The works were partially funded by the Confederacion Hidrografica del Jucar (Spanish Ministry of Agriculture, Food and Environment), that also provided hydrological and environmental information about the study sites. The authors also thank the Direccion General del Agua and INFRAECO for the cession of the microhabitat data. Finally, we also thank Javier Ferrer, Teodoro Estrela and Onofre Gabaldo (Confederacion Hidrografica del Jucar) for their help and the data provided. Thanks to Grieg Davies for the academic review of English.Muñoz Mas, R.; Martinez-Capel, F.; Garófano-Gómez, V.; Mouton, A. (2014). Application of Probabilistic Neural Networks to microhabitat suitability modelling for adult brown trout (Salmo trutta L.) in Iberian rivers. Environmental Modelling and Software. 59:30-43. https://doi.org/10.1016/j.envsoft.2014.05.003S30435