Lee J. Baumgartner’s research while affiliated with Charles Sturt University and other places

Context Understanding chemical properties and biogeochemical changes can help us answer difficult ecological questions. Water chemistry is often dynamic in large tropical rivers, particularly in deltas where sea tides and river hydrological regimes are extremely influential. Aims This study assessed the spatial variability of water chemistry by measuring the elemental concentrations of seven trace elements and strontium isotopes (87Sr:86Sr) in the Ayeyarwady River Basin in Myanmar. Methods Inductively Coupled Plasma Optical Emission Spectroscopy and multi-collector inductively coupled plasma mass spectrometry were used to quantify concentrations of trace elements and strontium isotopes at 50 sampling sites, covering 1700 km of the Ayeyarwady River. Data was grouped into regions for statistical analyses. Key results Three elements (Sr, Ca, and Mg) showed distinct longitudinal concentration profiles, which were higher at the coast but consistently lower in freshwater. For example, elemental concentrations at coastal areas were 22-, 63-, and 150-times higher than in freshwater further upstream for Ca, Sr, and Mg, respectively. Although, longitudinal concentration profiles of 87Sr:86Sr ratios varied along the Ayeyarwady River, they were not significantly different among regions. Conclusions Longitudinal profiles of dissolved elements varied significantly. In particular, three elements (Sr, Ca, and Mg) are good indicators to differentiate between marine and freshwater in the Ayeyarwady River. Implications Our findings provide important baseline information on water chemistry for future fish otolith (inner ear of bony fish) chemistry studies to track fish migrations in the basin.

Dam development is fragmenting migratory pathways in the Mekong Basin, yet scientific understanding of Mekong fish migrations is limited. Therefore, the first-ever transboundary acoustic telemetry network was deployed in the Mekong, Sekong, and Sesan rivers in Cambodia and Lao PDR to track movements of 81 individual fish representing 12 different species from June 2022 through March 2024. Upstream movement by Pangasius conchophilus during the transition between dry and wet seasons aligned with local ecological knowledge. Movements of Pangasius larnaudii between the Mekong and Sekong rivers represent a previously undocumented migratory pathway for this species. Long-distance movements by Hemibagrus wyckioides into the 3S basin contradicted the assumption that the species moves only short distances. Together, these findings imply that fragmentation of riverine habitats from planned dams may lead to greater impacts on populations of these species than were formerly assumed.

Perca fluviatilis (the European perch) is one of the most common and well-studied freshwater fishes in the world, largely owing to its widespread distribution and popularity among anglers and aquaculturalists. It has been especially well-studied in its native ranges of Eurasia, but has received far less attention elsewhere. Here we review key aspects of the general biology and ecology of the European perch, by considering learnings from countries where it is native in addition to those where it has been introduced. Our review demonstrates that the European perch is a highly fecund, trophic generalist that can live in a wide range of habitats and withstand a wide range of physico-chemical conditions. The growth rates and sexual development of the European perch vary among geographical regions, largely due to differences in climatic conditions, with populations in warmer Southern Hemisphere regions tending to exhibit faster growth rates and attain sexual maturity at younger ages than populations occurring in most cooler Eurasian regions. Genetic differentiation has also been observed in native populations from different parts of Europe, although it remains unclear as to whether native and non-native populations differ genetically, and what the ecological implications of any such differences are. Future research should prioritise assessing both genetic and phenotypic differences between native and non-native populations, and determining the ecological implications of these differences. Such knowledge is crucial for informing European perch conservation and/or aquaculture management in countries where it is native; and invasive species management in countries where it has been introduced.

Context There is a global problem with ongoing riverine infrastructure projects where, despite knowledge of potential environmental impacts, there is rapid development, often without appropriate environmental safeguards. This results in fragmentation of riverine fish communities, especially diadromous species. Understanding freshwater fish larval ecology is critical to provide insight into the likely impacts of these projects. Aims To assess fish larval biodiversity on the basis of DNA barcoding, abundance and its distribution pattern in the Cibareno River. Methods Fish larvae were collected at six locations in the Cibareno River. The larvae were identified by DNA barcoding. Key results A notable disparity was seen in the distribution of larval abundance in different locations. The non-native species, Poecilia reticulata, was the most abundant larval species, with an intraspecific diversity of 0.003 (99.7% similarity). The upstream area exhibited a lower level of larval species diversity than did the downstream area. Conclusions Genetic identification can reliably identify fish larvae and determine their spatial riverside distribution in the Cibareno River. The conservation of connectivity maintains fish community integrity and diversity between upstream and downstream locations in the weir building plan. Implications This discovery emphasises the relevance of larval identification in fish biodiversity assessment and sustainable fisheries resource monitoring.

The environmental effects of large dams on river connectivity are well recognized and mapped globally. However, datasets describing the distribution and attributes of smaller barriers (such as weirs and culverts) are lacking or incomplete for many regions. This has hindered accurate impact assessments for water resource planning, biased understanding of restoration potential and limited research aiming to understand and mitigate river fragmentation effects. Developing an efficient method to accurately record river barriers, including small ones, has become a priority. We critically examine barrier mapping approaches, from field survey to automated detection, showcasing recent approaches to recording, counting and classifying river barriers. We demonstrate how incomplete barrier databases, particularly those lacking many small barriers, provide a flawed basis for water management and ecological restoration planning. We discuss the efficiency and accuracy of alternative barrier mapping approaches, highlight future priorities and emphasize harmonizing barrier assessment methods to generate reliable, freely available information for effective basin-level management.

Fish biodiversity assessments are vital for understanding threats and aquatic ecosystem health. In the Poso River, Central Sulawesi, changes in biodiversity are influenced by habitat alteration, non-native species, and overfishing. This study evaluates fish and crustacean biodiversity in the Poso River system to address these challenges for improving fisheries management, conservation, and fish passage integration into hydropower development. The present biodiversity study utilized a comprehensive methodology that encompassed both traditional taxonomic approaches and DNA barcoding, specifically targeting the mitochondrial cytochrome c oxidase subunit-1 ( COI ) gene for accurate species identification and spatial boundary validation. The survey was conducted in the upstream, hydropower area and downstream areas of the river. We found 27 species of fish in the Poso River, including both native (e.g., Anguilla celebesensis , Oryzias nebulosus , Rhyacichthys aspro ) and non-native species (e.g., Melanochromis auratus , Amphilophus trimaculatus , Oreochromis niloticus ). Two International Union for Conservation of Nature (IUCN) red listed endangered species were also observed (e.g., Adrianichthys poptae and Mugilogobius sarasinorum ). DNA barcoding was performed to examine species spatial boundaries. The fish population in the Poso River was dominated by non-native species, accounting for 85.70% of the total population. The upstream reaches had the highest fish abundance and diversity, while the downstream reaches had the lowest. There was, however, no significant difference in species richness and diversity across different locations and seasons. The dominance of non-native species in the Poso River necessitates the improvement of existing fishways within the hydropower dams potentially through the development of selective technology that can block the distribution of these non-native species. This research highlights the critical issue of non-native species proliferation and the potential threat they pose to native fish populations, providing valuable insights for conservation and management efforts in Indonesia and similar ecosystems worldwide.

A fishway is an engineered structure designed to help fish navigate past artificial barriers in rivers such as dams, weirs and regulators. An effective fishway design requires an understanding of fish biodiversity and migration requirements of the local community. To support the conceptual design of a fishway at Caringin Weir in the Cibareno River in Indonesia, we conducted a fish biodiversity assessment using experimental fishing and an eDNA metabarcoding survey. In early 2022, experimental fishing was conducted at six sampling sites upstream and downstream of the planned weir, and the sites were surveyed seven times during the wet and dry seasons. Environmental DNA sampling was conducted once during the wet season at each of the six sites. A total of 72 aquatic species were detected, comprising 40 fish species and seven crustacean species captured during experimental fishing and 36 fish species identified through eDNA metabarcoding. Twelve fish species (18.46%) were detected using both methods. The total number of all species caught and species richness in experimental fishing varied significantly between upstream and downstream areas ( p < 0.05), but there were no significant differences between seasons ( p > 0.05). There was also a significant difference in the species richness upstream and downstream using eDNA metabarcoding ( p < 0.05). There were also numerous diadromous species, further highlighting the need for an effective fishway design to enable these species to complete their migrations. Based on the species present, migratory behaviour and economic importance, we prioritised six fish and crustacean species to be considered during fishway design: Anguilla marmorata , Tor tambra , Barbodes binotatus , Sicyopterus sp., Rhyacichthys aspro and Macrobrachium sp.