James Tweedley

Understanding the behavioral strategies that allow freshwater mussels to persist under environmental stress is essential for their conservation, yet burrowing behavior remains poorly quantified. We tested whether valve movement data could be used to detect and characterize burrowing in the endangered Westralunio carteri; a species endemic to a region undergoing severe climatic drying. Mussels from multiple populations were monitored individually under laboratory conditions using Hall effect sensors, and valve movement patterns were analyzed to distinguish between burrowing and non-burrowing behaviors. Burrowing was associated with rapid, high-amplitude valve movements that lengthened as burial progressed, while non-burrowing behaviors showed distinct, slower patterns. These differences indicate that valvometry can reliably identify burrowing behavior, providing a non-invasive method for monitoring mussel activity. This approach has broad applications for ecological research, conservation assessment, and early-warning biomonitoring of imperiled freshwater mussel populations.

The brown-marbled grouper (Epinephelus fuscoguttatus), a high-value species in international trade, has experienced population declines due to intensive fishing. It is one of 12 grouper and snapper species prioritized for management in Saleh Bay, West Nusa Tenggara, Indonesia. This study analyzed catch data (2017–2022) and biological samples (2020–2021) to update key life history parameters, including natural mortality, von Bertalanffy growth parameters, asymptotic length, and size at maturity. Growth was estimated using an ELEFAN-optimized model applied to catch length–frequency data, while maturity was determined through macroscopic examination of gonads. The updated estimates (L50 = 488 mm for both sex; L95 = 568 mm for females and 616 mm for males) were incorporated into a length-based spawning potential ratio (SPR) assessment. Annual SPR values ranged from 0.13 to 0.28, substantially higher than previous estimates of 0.05–0.07, mainly due to the lower L50 used in this study. Despite this improvement, SPR values remain below the management target of 0.30 for groupers and snappers in Saleh Bay. Limited biological samples, particularly the scarcity of larger individuals and males, introduce uncertainty in the estimates. These findings emphasize the value of locally derived life history information and highlight the need for continued biological sampling to refine growth and reproductive parameters and support sustainable fisheries management.

This review examines possible estuarine fish colonisation processes of the Pacific Ocean that started in the Early Jurassic and gained momentum with the break-up of Pangea. Initial colonisation of the newly-created estuaries by fish is likely to have accelerated during the Devonian, with tropical marine families from the Neotethys Sea region using epicontinental seaways between Asia, Australia, India, Arabia, Europe and the Americas to colonise estuaries on these drifting land masses. Analyses of the presence/absence of fish families and species from selected ecoregions around the Pacific Ocean rim showed that estuary-associated fish families on the eastern and western side of the Pacific Ocean separated out at a Bray-Curtis similarity of 41 % but were only ∼5 % similar at the species level. In terms of past and present geodispersal of fish taxa, tropical species may have used ‘island hopping’ to cover the >19 000 km gap between the tropical western and eastern shores of the Pacific. However, most tropical taxa in the eastern Pacific appear to have originated from the Caribbean area of the Western Atlantic and not from the central Western Pacific fish species ‘hotspot’. In contrast, ichthyofaunal colonisation of Western Pacific regions to the north and south of the ‘hotspot’ was facilitated by ocean currents and the more limited distances between estuaries and coastal ecoregions in this part of the Pacific. The cold temperate waters of the Northern and Southern Pacific Ocean would have acted as a barrier to tropical species attempting to use these routes to cross the Pacific Ocean basin. The prevalence of temperate diadromous fish species in both the temperate northern (e.g. Russia and Alaska) and southern (e.g. New Zealand and Patagonia) estuaries is probably a function of local evolutionary trends that favoured such taxa in those particular regions.

Offshore wind farms (OWF) are rapidly emerging as essential infrastructure for transitioning to renewable energy, and this has been particularly important in the waters of China. To evaluate the impact of OWF construction, Ecopath models were developed for an OWF area and, separately, for a nearby control area, using biological and environmental survey data collected in 2022 and 2023. Functional groups were initially categorized into soft-substrate and hard-substrate (turbine monopiles) communities. The results showed that the colonization of turbine monopiles by sessile organisms significantly increased the productivity of most fish functional groups in the OWF area compared to the control. The OWF ecosystem exhibited higher trophic levels, especially for macroinvertebrates and fish, and a more complex food web with enhanced detritus flow than the control area. Mixed trophic impact analysis indicated a shift from a pelagic to a benthic-dominated system following OWF construction. Notably, detritus accounted for 52 % of total system throughput in the OWF area, compared to 38 % in the control area, highlighting a transition toward detritus-based energy flow. Furthermore, the OWF system showed significantly higher values for total system throughput, omnivory index, connectivity, Finn’s cycling index, and ascendency. Overall, the presence of the OWF resulted in significant changes in the trophic flow and system structure, creating a more complex, mature, and stable benthic-dominated ecosystem. These findings indicate that the establishment of OWF enhances both the structural composition and functional dynamics of surrounding marine ecosystems.

Machine learning has opened the door for the automated sorting (classification) of images, holograms and acoustic backscatters of individual plankton, invertebrates, fish and marine mammals. However, this field is complicated by decades of paradoxically promising reports of classifier performance that do not correlate with real-world uptake of this technology in aquatic sciences. Simple metrics of classifier performance are essential for optimizing, evaluating and comparing machine learning classifiers, but a wide variety of metrics and calculation variants have been proposed. Several characteristics of species count data influence metric behavior: severe imbalance and variance, zero-inflation, high class numbers and contamination with non-target classes. This study explores the hidden complexity of classifier performance metrics for species count data using synthetic datasets and simulated classifier outputs. It demonstrates how these data characteristics can severely distort metric values, with seven of eight variants of the most common metric, Accuracy, returning near-perfect scores (up to 98%) even when no instances are correctly classified. Clear recommendations are made for classifier evaluation pitfalls and metric variants to avoid, ultimately finding one variant of the F1-Score (mF1) to be the most suitable single metric, with several important calculation caveats specific to species count data. Due to ambiguous terminology and inconsistent definitions, it is often impossible to identify which variant of a performance metric has been applied in classifier studies. It is vital that authors are intentional and transparent about their metric use to support the vast potential for machine learning to revolutionize the research and monitoring of aquatic environments.

Estuaries are ephemeral ecosystems on geological timescales, with lifespans dictated by their degree of isolation from the ocean (Hodgkin & Hesp, 1998). The south coast of Western Australia has a Mediterranean climate, with rainfall declining and becoming more variable from west to east. Of the ~50 recognised estuaries in south-western Australia, those within the UNESCO-listed Fitzgerald Biosphere (Picture 1) receive amongst the lowest river flow and are often closed from the ocean by a sand bar at their mouths (Tweedley et al., 2016). Prolonged closure and evaporation lead to hypersalinity. Furthermore, catchment land clearing increases sedimentation, which reduces scouring and the duration of any sand bar breach. Combined with secondary salinsation, these impacts increase the magnitude of future hypersalinity (Hoeksema et al., 2018).

We visited estuaries in the Fitzgerald Biosphere in November 2020, after three years of below-average rainfall. Hypersaline conditions, which are known to reduce fish species richness and faunal complexity (Hoeksema et al., 2023), were recorded in all estuaries (55-240 ppt). The prevalence of hypersalinity has presumably acted as a selection pressure, as most native fish and invertebrate species found were highly salt-tolerant (Krispyn et al., 2021). While few fish species globally can survive prolonged exposure to salinities >50 ppt, in south-western Australia five species have been recorded in salinities ≥100 ppt. The prolonged bar closures required to create these environmental conditions reduce the provision of ecosystem goods and services by these estuaries, as they cannot act as nursery areas for marine species, export nutrients to coastal waters, and the reduced faunal assemblage limits food resources for fish and birds (Cronin-O'Reilly et al., 2024). As water evaporates and salinities increase, fish attempt to move into upstream refuges. However, rock and/or sand bars can prevent this movement, generating mortality events.

Climate predictions suggest reductions in winter rainfall and changes in the frequency of summer storms, which would influence bar breaching (Andrys et al., 2017). Sea levels will rise, but as the sand bars can be 5 m high and hundreds of meters long, the effect of wave overtopping may be limited. The combination of climate change and sedimentation may speed up the transition of some estuaries to salt lakes (Tweedley et al., 2024). Understanding the ecology of estuaries in the Fitzgerald Biosphere may inform the management of estuaries further west, and of low-inflow estuarine systems globally (Tweedley et al., 2019).

Climate change in Mediterranean regions is projected to cause declines in rainfall and higher temperatures and evaporation, which will enhance the formation of barriers at the mouth of low-inflow estuaries and potentially also in the riverine reaches. This review uses data from estuaries in south-western Australia across a rainfall gradient to describe how these barriers form and the effects they have on environmental conditions and biotic communities. The formation of barriers disconnects the estuary from adjacent freshwater and marine environments, prohibiting the movements of fauna and lowering taxonomic and functional diversity. Moreover, the longer periods of bar closure can result in increased frequency and magnitude of hypersalinity, hypoxia and nutrient enrichment. These conditions, in turn, act as stressors, often synergistically, on the floral and faunal communities. In some cases, mass mortality events occur, and some estuaries dry completely. To ensure the functioning of such systems in the future, regular monitoring across a wide range of estuaries is needed to understand how climate change is impacting different types of estuaries. A range of management options are discussed that may help mitigate the effects of increased barrier formation but should be employed as part of a whole-of-catchment approach and regularly evaluated.

The global increase in population and the corresponding demand for sustainable fisheries has intensified the need for innovative fisheries enhancement and protection measures. One measure to be used in this pursuit is the deployment of artificial reefs (ARs). ARs have many definitions and purposes, but can be broadly defined as any man-made structure deployed in an aquatic environment to provide substrate or shelter for biota, particularly fish (Lima et al., 2019). In addition to offering physical shelter, ARs enhance ecological functions by increasing primary production and food availability. Mechanisms include (i) the provision of hard substrate for algal settlement (Choi et al., 2019), which in turn are fed on by invertebrate consumers, and (ii) increased upwelling caused by interactions between local hydrological forces and the physical presence of an AR, making nutrients more available, stimulating phytoplankton growth and increasing nutrient cycling in the immediate and surrounding AR area (Layman & Allgeier, 2020). These processes foster biodiverse and resilient aquatic ecosystems...

Artificial reefs are human-made or altered structures placed in an aquatic environment to mimic certain characteristics of a natural reef. Indigenous cultures have used artificial reefs to harvest aquatic food supplies for thousands of years, including indigenous Australians using artificial reefs as far back as 2,000 BC (Carstairs, 1988; Kerr, 1992). These early reefs were mainly constructed using materials of opportunity such as woody debris including bamboo, rocks and rubble and sunken vessels (such as ancient fishing boats). In more recent history, artificial reefs have advanced significantly, with innovations in design, materials, and purpose (such as coastal protection, tourism and fisheries enhancement). As of 2015, at least 120 artificial reefs had been deployed in Australian waters, with 11 noted in Western Australia (Bateman et al, 2015); however, the number is likely above 7,000 when considering there are more than 1,600 shipwrecks along the coast, jetties, ports and coastal infrastructure, subsea petroleum assets and other artificial reefs...