Context Shark depredation is a human–wildlife conflict occurring in many fisheries around the world. At Cocos (Keeling) Islands in the Indian Ocean, high shark (known as cucut in the local Cocos–Malay language) depredation rates are causing costly loss of target catch and fishing gear for artisanal fishers, increased mortality for target species and negative attitudes towards sharks. Aims This study tested the effectiveness of an electrical shark deterrent device (RPELX) for reducing shark depredation during line fishing for demersal fish species. Methods A randomised experimental design was used to test the RPELX against a control treatment, during 11 days of deepwater fishing for demersal fish. Key results Across 51 fishing sessions, 262 fish were caught. Results of a generalised linear model indicated that treatment and skipper had a significant effect on the number of fish depredated, with the RPELX reducing the probability of a depredation event occurring by 63%. The RPELX device also reduced shark bycatch and loss of fishing gear. Conclusions Overall, the RPELX device can provide substantial environmental and socio-economic benefits to the marine ecosystem and community at Cocos (Keeling) Islands. Implications Further testing of the RPELX in other demersal line fisheries, where depredation is occurring around the world, is strongly recommended.

Context Block-and-chain moorings are widely used in urban estuaries and are known to damage habitat-forming species. Environmentally Friendly Moorings (EFMs) are emerging as an alternative mooring design to promote habitat conservation. The effects of either type of mooring on demersal fish remains poorly understood. Aims We compared fish abundance and community composition between block and chain moorings, EFMs and nearby reference sites within unvegetated soft sediment habitats. Methods We deployed baited and unbaited remote underwater cameras in south-eastern Tasmania, Australia, to compare the composition and abundance of fish at sites with block- and chain-moorings with those with EFMs and natural reference sites. Fish data were extracted from videos using human observations, alongside novel Artificial Intelligence object detection, allowing a detailed assessment of temporal responses within each video. Key results We found lower variation in the composition of fish communities among baited chain-mooring sites than at EFM or reference sites. The flathead Platycephalus bassensis was more abundant at chain-mooring sites than at EFMs or reference sites, but only under baited conditions. Conclusions Mooring types affect demersal fish communities, but effects vary across taxa and are strongly influenced by baiting. Implications These findings suggest that mooring impacts extend beyond disturbance of benthic habitats, showing shifts in fish community composition and notable effects on the flathead Platycephalus bassensis.

Context Aylacostoma species (Gastropoda, Hemisinidae) are sensitive to environmental changes and low dissolved oxygen concentrations, making them particularly vulnerable to disturbances such as dam construction. The ‘Aylacostoma Project’ aims to conserve some species of the genus, maintaining populations in captivity. Phylogeographic studies play a key role in this context, because they provide insights into the genetic diversity of populations, an essential aspect for conservation. Aims The main objective of this study was to investigate the phylogeographic structure and genetic diversity of the following three Aylacostoma species from the Paraná River Basin: A. brunneum, Aylacostoma sp. and A. chloroticum. Methods The analyses were based on 81 partial sequences of the mitochondrial COI region from different localities, obtained from GenBank and the present study. Key results Eight haplotypes were identified across the analysed populations, with A. chloroticum comprising six haplotypes. Some haplotypes were exclusive to specific localities. Conclusion This study has highlighted new information about the phylogeographic pattern of the group, showing a phylogeographic structure among Aylacostoma species from the Paraná River Basin. Implications This is the first phylogeographic study of Aylacostoma to include molecular data from natural populations of A. chloroticum and Aylacostoma sp. from the upper Paraná River Basin, Brazil.

Restoration programs are increasingly essential for supporting the recovery of threatened species, yet their success depends on identifying and mitigating key threats. This study presents the first direct video evidence of fish predation on transplants of the Endangered soft coral Dendronephthya australis by yellowfin leatherjackets (Meuschenia trachylepis) in the Port Stephens estuary, New South Wales, Australia. Fish predation, previously undocumented for D. australis, now joins a growing list of stressors, including physical damage, sedimentation and freshwater influx, that are collectively impeding the coral recovery. It was observed that M. trachylepis fed on both stalks and polyps of outplanted coral fragments, although polyps appeared less vulnerable once retracted, potentially owing to the defensive role of sclerites. Experiments in the wild demonstrated that transplant survival was significantly improved when soft corals were placed under predator exclusion cages. Predation events such as these represent a substantial bottleneck to restoration success, particularly in the early post-transplant phase of corals. These findings highlighted the complex, multi-stressor environment facing D. australis and emphasised the need for restoration strategies that include protective measures, such as caging, to reduce fish predation until transplants mature. A more holistic understanding of these threats is critical for improving conservation outcomes for this threatened species.

Context River regulation has altered the timing and magnitude of hydrological connectivity between rivers and their floodplains, with potential consequences for zooplankton that persist by diapausing eggs in sediment ‘egg banks’. Aims We examined how water temperature and recent inundation history of riverbank v. floodplain sediments influence emergence, diversity and community composition of zooplankton. Methods Dry riverbank and floodplain sediments from the lower Lachlan River (New South Wales, Australia) were rewetted and incubated in temperature-controlled cabinets at 10°C (winter) and 21°C (spring). Emerging zooplankton were sampled repeatedly over 6 weeks and identified to the lowest feasible taxonomic level. Key results Greater abundance of zooplankton emerged at warmer temperatures, and floodplain sediments supported a greater abundance and diversity of emerging zooplankton, whereas differences in community composition between habitats were minor, perhaps because all collected sediments had been recently inundated by large-scale flooding. Conclusions Seasonal timing and the extent of floodplain inundation jointly govern activation of sediment egg banks and zooplankton emergence dynamics in this regulated lowland river–floodplain system. Implications Management that maintains lateral river–floodplain connectivity, particularly during warmer periods, is likely to support high zooplankton abundance with potential flow-on effects for the riverine food webs.

Context. Highly migratory species (HMS), such as tunas, billfishes and sharks are a major component of the top predator guild in oceanic ecosystems, but the trophic relationships of many populations remain poorly understood. Aims. This study aimed to characterise the trophic ecology and habitat use of ten HMS collected from two Subtropical oceanic regions around New Zealand. Methods. We examined δ13C and δ15N in muscle tissue of HMS considering differences in capture locations and body size. Key results. Three trophic groups were distinguished: (1) swordfish, (2) tunas and Lamna nasus (porbeagle) in northern New Zealand, and (3) marlins and other pelagic sharks. Despite stable isotope overlap among taxonomically similar species, subtle differences in foraging strategies likely contribute to variation in ecological roles. Trophic position estimates revealed that HMS occupy high trophic levels, though these estimates may be influenced by variations in δ15N baseline. Stable isotope analysis indicated consistent trophic relationships across the two investigated oceanic regions, with evidence of ontogenetic shifts in resources use in some species. Conclusions. Stable isotope ratios varied widely among HMS, suggesting exploitation of diverse foraging habitats and extensive migration Implications. These data highlight the diverse trophic roles of HMS and emphasise their significance in structuring marine food webs and ecosystem functioning.

Context: Fine-grained classification of cephalopod beaks faces significant challenges due to small inter-class variations and large intra-class variations, limiting the accuracy of existing methods for morphologically similar species. Aims: To develop a fine-grained classification method that can automatically identify discriminative anatomical regions and improve species identification accuracy. Methods: We constructed a dataset of 14,000 images from 700 beak pairs of seven cephalopod species. Building upon ResNet101, we combined region grouping with Beta prior constraints to achieve adaptive segmentation of key anatomical regions and attention-weighted feature learning. Key results: Our method achieved classification accuracies of 97.00% and 97.36% for upper and lower beaks respectively, improving upon the best existing model by 2.79-3.79%. The model automatically focused on discriminative features including lateral wall posterior margin curvature, hood development patterns, and wing structures. Conclusions: The proposed weakly-supervised regional segmentation approach significantly improves both classification performance and interpretability, with results highly consistent with biological knowledge. Implications: This method provides an efficient solution for cephalopod species identification, with broad application prospects in ecological research and fisheries management.

Context Spatial targeting involves relocating fishing effort to reduce unwanted catch (e.g. bycatch) while maintaining target catch. However, it is challenging to measure target–bycatch separation, develop viable scenarios for fishing effort relocation, and measure impacts on fishers. Aims We demonstrate a simple but data-driven spatial prioritisation analysis, to evaluate whether local changes to fishing location can reduce bycatch with minimal reduction in target catch in an ocean prawn trawl. Methods Using observed and predicted catch compositions, we extend a published spatial prioritisation method to evaluate the impact of spatial targeting on target catch and bycatch, and measure fisher impact on the basis of the percentage of historical effort relocated. Key results Spatial targeting effectiveness varied by species priority. Although shark and ray bycatch showed reduction potential (up to a 30–60% decrease in bycatch for a 0–15% decrease in target catch), differences among data sources created uncertainty about priority fishing locations. Limited spatial separation between main target and bycatch species also meant unlikely total bycatch reduction. Fisher impacts varied, with effort redistribution often exceeding bycatch reduction gains. Conclusions Spatial targeting has the potential for avoiding specific species, but is unlikely to reduce total bycatch in this fishery. Implications This prioritisation framework offers a simple but robust method to explore spatial targeting by using observed or predicted catch compositions.

Context Aquaculture, a vital protein-rich food source, faces numerous challenges, including disease outbreaks triggered by industrial effluents. Aims The discharge of toxic effluents from paint industry significantly threatens aquatic life, particularly fish. These effluents contain various hazardous substances such as heavy metals, organic and inorganic pollutants, which cause detrimental effects on aquatic ecosystems. Methods Traditionally, antibiotics have been used to mitigate harmful effects of pollutants; however, their overuse has led to concerns about antibiotic resistance, environmental pollution and adverse health effects. Key results To solve this problem, herbal supplements, particularly those derived from plants, offer a sustainable solution by boosting the immune system of aquatic organisms and promoting a healthier ecosystem. Conclusions Herbal supplements such as ginger, turmeric, garlic and many others, offer promising alternatives because they exhibit antioxidant, anti-inflammatory and immune modulatory effects, which help protect fish against the toxic effects of paint-industry effluents. By contrast, antibiotics have demonstrated limited efficacy and cause potential adverse effects on both fish health and the environment. Implications Overall, herbal supplements offer a safer and more effective approach to mitigate the toxic effects of effluents on fish, highlighting their potential as a sustainable solution for aquatic environmental protection.