Context Settlement and metamorphosis are key processes influencing the natural recruitment and aquaculture production of aquatic organisms. Recruitment requirements in limpets (Patellogastropoda) are mostly unknown, because of the lack of reliable settlement inducers. Aims This study tested the reliability of different cues as settlement inducers for competent larvae of the economically valuable Patella aspera. Methods Natural crustose coralline algae (CCA) and biofilms of the benthic diatom Navicula salinicola were tested as positive controls. The following four pharmacological agents were tested as chemical inducers in a wide range of concentrations: gamma-aminobutyric acid (GABA), acetylcholine (ACH), 3-isobutyl-1-methylxanthine (IBMX) and potassium chloride (KCl). Settlers were identified by the velum loss and teleoconch development. Key results CCA were strong settlement cues in all the assays. Contrary to previous hypotheses, GABA was a weak inducer with a peak effect at 10−5 M. Neither the diatom biofilms nor the other pharmacological agents (ACH, IBMX and KCl) promoted the settlement response. All pharmacological agents at high concentrations influenced larval behaviour. Conclusions CCA were reliable positive controls and settlement inducers for the production of post-larvae. With regard to pharmacological agents, P. aspera showed restrictive settlement requirements that should be considered for ecological and aquaculture studies in other limpet species. Implications This method allows the study of the settlement biology of limpets. It provides a positive control and integrates animal monitoring and comparative response to other cues.

Context In total, 43 shallow waterbodies were sampled in 1983 in the vicinity of Casey Station and nearby islands in Antarctica. The following physico-chemical parameters were obtained: water and air temperature, pH, conductivity, dissolved oxygen, plus major and minor elements. Aims To identify the physico-chemical characteristics of these waters and determine their origin, and calculate their mineral saturation indices. Methods Waters were analysed using standard methods, including for some elements, flame-atomic absorption spectrometry, spectrophotometry, ion chromatography and gravimetric determination. Mineral saturation indices were calculated using the PHREEQ program. Key results Water salinities were generally low and in the range of 120–1200 mg L−1 (total dissolved solids, TDS), except for one site connected to the sea, and four slightly saline sites. The Na/Cl, Cl/Br and Ca/SO4 ratios of several waters were in the vicinity of seawater ratios, implying a contribution of marine aerosols. However, the Mg/Ca ratio of most waters departed from the seawater ratio, plus there was concordance between the molar ratios of (Na + K)/(Ca + Mg) of many of the waters sampled and those calculated from rock geochemical analyses from diverse lithologies. Such chemical ‘provincialism’ appears to be dictated by rock composition. Nitrate and phosphate concentrations were high in the vicinity of penguin rookeries. Conclusions Two sources of ions are identified, one as marine aerosols as shown by three sets of ratios (Na/Cl, Cl/Br and Ca/SO4) with known marine values, and the other from the weathering of local rocks as shown by (Na + K)/(Ca + Mg) of the lake waters compared to the same ratios for the surrounding rocks. Only a few waterbodies have saturation levels for several carbonate minerals (calcite, aragonite, dolomite and rhodochrosite). Implications Future work is recommended for monitoring the waterbodies surrounding Casey Station as a result of the increased atmospheric CO2 concentration that has occurred over the past 40 years, and likely also with the cessation of building activities around Casey Station.

Context Swimming crab is a vital fishery resource and a valuable source of income in the southern East China Sea, but it lacks management strategies, especially when using different fishing gear. Aims This study aimed to determine the effects of spatial–temporal conditions and vessel capacity on swimming crabs by using different fishing-gear types in the Taiwan Strait (TS). Methods We used generalised linear mixed models (GLMMs) to investigate data from Taiwanese vessels (2011–2019) on how spatial–temporal conditions and vessel capacity affected the catch of swimming crabs when using trawls, gill-nets and traps. Key results The results showed that the traps (>80.0%) caught more swimming crabs in the TS than did the gill-nets (6.6%) and trawls (8.0%). Additionally, the GLMM analysis showed that Charybdis feriatus, Portunus pelagicus and Portunus sanguinolentus catches by traps and trawls were significantly affected by different fishing locations, climate events, work hours and vessel sizes. However, for gill-nets, spatial–temporal conditions and vessel capacity did not affect the catch of C. feriatus. Conclusions Monitoring fishing efforts and environmental factors is vital to understanding their impacts on marine ecosystems. Implications These findings enable future sustainable crab fishing through harvesting strategy planning, ecosystem management and spatial–temporal governance.

Context Streams on subantarctic Macquarie Island were first sampled for freshwater invertebrates in 1992 when rabbit numbers were low. Then an average 11.6 taxa per site were recorded. Between 2000 and 2011, vegetation was overgrazed as rabbit numbers increased. In 2008 and 2010, 7.4–8.4 taxa per site were recorded, abundance of most taxa had decreased and greatest compositional changes occurred at sites exposed to moderate or severe vegetation damage. Rabbits were eradicated in 2011 and substantial regrowth of vegetation was evident by 2016. Aims Sites were resampled in 2016 to determine the extent to which the invertebrate communities had changed after rabbit removal. Methods In all, 13 of the original 15 sites sampled in 1992 were resampled. Five kick samples were taken at each site. Key results Mean taxon richness (8.2 taxa per site) and community composition at individual sites remained, in 2016, very similar to that recorded in 2008 and 2010 when the island was heavily grazed. Conclusions Recovery of stream invertebrate communities appeared to be slow, possibly because few refuges were available. Minor changes in climate and water quality did not influence recovery. Implications Stream invertebrate communities could take a decade or more to recover.

This special issue of Marine and Freshwater Research, ‘Sustainable Development on Water Resources Management, Policy and Governance’, highlights the recent advancements in these areas that were presented at the 4th International Symposium on Water Resource and Environmental Management (WREM 2021). Featuring 12 articles of significant scientific value, this collection primarily focuses on the sustainable development of water resources management, policy and governance.

Context To inform the economic value of Loktak Lake, a Ramsar Site located in north-eastern India, and to suggest sustainable management and wise use of the Lake. Aim To find out the stakeholder preferences and the marginal willingness to pay over improved conservation and management of Loktak Lake. Method Choice Experiment Method, a stated preference method used for environmental valuation is employed in the study. Result The majority of the stakeholders have indicated their strong preference for effective conservation of the Lake with improvement in the fish catch and recreational sites as part of the improved conservation and management of the Lake. Conclusion The stakeholders’ preferences vary significantly in terms of the levels of improvement for different attributes. The high preference for increased fish catch and recreational sites indicated the importance of fish in the social and economic life of the households and scope of alternative employment opportunities respectively. But reduction of phumdi is not preferred as it is linked with the traditional fishing practices. Further, the local stakeholders do not prefer increased alternative employment opportunities, which may be attributed to the trust issues between the local stakeholders and wetland managers. Implication The livelihood options of the dependent communities should be integrated as part of the conservation and management policy of the Loktak Lake. It necessitates more inclusive wetland management or governance structure, and a framework needs to be developed with more local stakeholder participation and to develop site-specific employment generation or income generation schemes to reduce the dependence on the wetland. The participatory approach and continuous involvement of local communities in managing resources will help sustain the environment in the long run.

Context Transboundary sharing of river water is not just an international problem, it also cascades down to regional, state and local levels. Water cooperation in the Brahmaputra River basin among China, India, Bhutan and Bangladesh has long been contested. However, it is unclear how the four countries can cooperate and what the cornerstones for their cooperation might be. Aims Better transboundary management of Brahmaputra requires a new direction from the current situation of fragmented cooperation, conflicts and disputes in the region and increasing threats of climate change. Methods To explore possible consensus, we conducted an advocacy coalition assessment of the four countries on the basis of the heterogeneous ecosystem services valued by each nation. Key results Whereas China and India are focused on politics, Bangladesh and Bhutan are primarily concerned about the basin in physical terms. Although each nation values the Brahmaputra in different ways, it is possible to initiate strong collaboration on the basis of shared beliefs. We found that hydropower-supported energy transitions for clean and affordable energy supply meet the needs and expectations of all nations, especially under the threats of climate change. Conclusions A sustainable energy change coalition can help reduce carbon emissions, acquire green energy, irrigate land in dry seasons, and manage disasters and increasing runoffs from melting glaciers. We conclude our paper with insights for each nation and hydropower development as a whole that might help the nations manage the Brahmaputra River more sustainably by overcoming their unmatched or mismatched values and interest. Implications Water in shared rivers can raise regional conflicts, but it does not have to if mismatched deep core beliefs among nations can be avoided through cooperation.

Context Where water is used to support ecosystem processes under a changing climate, it is vital that it is done efficiently. The Australian bass (Percalates novemaculeata) is a freshwater fish endemic to south-eastern Australia that has been adversely affected by anthropogenic disturbances. This has prompted investigations as to the use of environmental water in support of the species in addition to widespread stocking. Aims We investigate whether environmental flows and stocking in isolation support a population of Australian bass more effectively than they do in combination, under various climate-change scenarios. We also determine the cost efficiency of each strategy. Methods We used an age-based stochastic population model to determine outcomes of strategies. Key results Our model suggested that the application of two or three large environmental flows per year was highly effective in all but the most-extreme climate-change scenarios. Alternatively, the value of stocking increased with an increasing severity of climate change. The cost of delivery of environmental flows far exceeds that of stocking. However, stocking directly benefits only a single species (in this case Australian bass), whereas the provision of environmental water has multi-species benefits, in addition to being vital to maintaining the river ecosystem itself. Conclusions Under severe climate-change scenarios, stocking, and the use of environmental water in support of populations, may be successful only to a point. Implications Extreme climate change may therefore negate any attempts to halt the decline of populations of some species.

Context The influence of anthropogenic pressures on plankton communities in well-flushed estuaries has been overlooked. Owing to this ecosystem’s short water-residence time, they are foreseen to be mainly composed of microorganisms from neritic–oceanic sources, more resilient to anthropogenic impacts. Aims This study characterises the bacterioplankton of Urdaibai, a small-drainage estuary located at a UNESCO biosphere reserve, to unravel its annual dynamic and ecological status. Methods Amplicon sequencing was used to assess the euhaline bacterioplankton shifts and microgAMBI index depicted the ecological status of the estuary. Key results A differentiated community was identified in upstream waters throughout the year. In addition, organisms commonly associated with faecal waste were detected. The ecological status of the estuary was poor or moderate along the annual cycle, but surprisingly worsened during winter. Conclusions The above suggests that the bacterial community dynamic in this well-fluxed small-drainage estuary is more complex than anticipated. Importantly, the analysis of pollution-indicative bacteria proved that the water policy of this estuary needs to be further evaluated. Implications The completion of an efficient sewage treatment system for this protected and touristic estuary is strongly recommended. Incorporating bacterial information to its current monitoring system will constitute a useful and valuable tool.

Context Seabirds are important bio-indicators that play an important role in nutrient cycling within coastal communities. Yet, the impact of anthropogenic noises produced from coastal developments across seabird species has received little attention. To create more refined and effective mitigation strategies, a better understanding of how different seabird species and individuals respond to anthropogenic noise is required. Aims This study aimed to assess how individual seabirds respond to noises resulting from coastal development (construction noises). Methods We investigated the behavioural (vigilance, distress) and physiological (heart rate) responses of little penguins (Eudyptula minor) to experimental playback of construction noises and the potential impacts of construction noises on breeding success. Key results Little penguins spent significantly more time in vigilance (but showed no increase in heart rate) during the construction noise playback than they did during the control. Nests exposed to the noise experiment were more likely to produce at least one fledgling compared with those that were not. Conclusions and implications Our results support the distracted prey hypothesis, which over long periods may reduce the time individuals spend performing biologically important behaviours and increase predation risk.