Shark depredation is a growing challenge for fisheries globally, yet the specific species involved remain poorly understood. This research aimed to identify depredating shark species in Queensland rod and reel fisheries through genetic analysis of depredated samples collected through citizen science by commercial, charter and recreational fishers. In total, 195 depredated fish samples, from 48 different teleost species, and 78 fishing line-clippings were analysed. Mitochondrial DNA analysis successfully identified 79% of samples analysed (215) to species level, equating to 14 depredating shark species with 98% from the genus Carcharhinus. The top five depredating species in descending order included bull sharks (C. leucas), grey reef sharks (C. amblyrhynchos), pigeye sharks (C. amboinensis), sandbar sharks (C. plumbeus), and the blacktip shark complex (C. limbatus/tilstoni). Bull sharks were dominant depredators in all regions and in all seasons, while other species were found to vary seasonally and spatially across Queensland waters. The emerging use of line-clippings proved to be a reliable and efficient method for identifying depredating sharks, particularly when depredated fish remains were unavailable. Genetic sequencing provides a valuable tool for identifying the species responsible for depredation, enabling fisheries managers to refine monitoring efforts and implement more effective, species-specific management strategies that address both conservation and fishery sustainability goals.

Citizen science facilitates cost-effective ecological data collection at much larger scales than would otherwise be feasible. This is particularly useful for the study of highly migratory species with broad distributions, such as billfishes. Participants in citizen science benefit from an increase in scientific literacy, a sense of satisfaction and enhanced understanding. However, there are common challenges involved in citizen science projects, including the recruitment and long-term retention of participants. Applying knowledge about participant motivations and concerns is needed to overcome these barriers. We conducted an anonymous online survey of 153 game fishers from across Australia, who were largely recruited through game fishing clubs. The survey investigated their perspectives on participating in citizen science on billfish, including their motivations and concerns. Overall, those surveyed were highly motivated to participate in billfish citizen science programmes and reported few barriers to their engagement in research. Alongside wanting to contribute to billfish research and management, game fishers were motivated to participate to counteractive potential negative perceptions of the sport. However, approximately one third of respondents had not participated in research. Therefore, opportunities for further recruitment exist as potential participants almost certainly exceed current participants. Impediments to participation included a lack of communication about opportunities and outcomes of citizen science research. The survey highlighted a need to strengthen citizen science programmes to ensure participant retention and recruitment through targeted engagement and collaboration across organisations, which includes harnessing technology. Improved communication about the purpose and outcomes of research is key. We anticipate that our findings and recommendations are applicable to broader citizen science programmes, particularly those involving recreational fishers or a specialised pool of highly motivated participants. Great opportunity exists for researchers, fisheries managers and fishing organisations to work together to expand citizen science programmes that strategically improve our knowledge of the biology and stocks of billfish and other recreationally important fish species.Read the free for this article on the Journal blog.

Understanding the movements of marine species is essential for predicting and addressing ecological responses to climate change and other human-driven impacts. This knowledge enhances our understanding of species ecology, informing discussions on fisheries interactions and management, and promoting sustainability measures for aquatic resources. Pelagic fish, like dolphinfish Coryphaena hippurus, are attracted to fish aggregation devices (FADs), intended to enhance fishing opportunities for fishers. However, factors influencing presence at FADs are complex due to various environmental and ecological influences, along with the high mobility of the focal species. We tracked the movements of 60 C. hippurus along a continent-wide array of acoustic receivers spanning 3000 km along the east coast of Australia. We aimed to quantify fish residency at FADs, determine the connectivity between FADs, and identify key oceanographic factors influencing C. hippurus movements. C. hippurus exhibited high mobility, travelling up to 1697 km from their release site, occupying regions between 25 degrees S and 34 degrees S. The average residency at FADs was 2.18 d (SD = 6.12 d). Strong connectivity was observed between FADs in Queensland and New South Wales, with fish moving north as temperatures cooled (similar to 19 degrees C) and south as temperatures warmed (similar to 27 degrees C). Movements predominantly occurred southward during southerly current velocities and when mixed layer depth increased (similar to 50 m). Strategically placing FADs in areas with preferred oceanographic features and designing spatially connected networks can enhance the aggregation and connectivity of C. hippurus amid a changing climate.

The capture of a 1000-pound black marlin off the northern Great Barrier Reef (GBR), Australia, in September 1966 initiated the rapid development of a recreational charter fishery that has operated every year since. The fishery has a distinct 2.5-month-long season, covers the same area off the outer edge of the GBR, specifically targets black marlin and has used essentially similar fishing methods through its history. For the first three decades of the fishery, there was no mandatory logbook requirement. Fortuitously, a study conducted in the late 1990s found that some charter captains and crew had kept detailed personal diaries or logs of daily catch and effort, including zero-catch days since the beginning of the fishery. The earlier study analysed CPUE data extracted from such records for the period 1970 through 1997. Here, we present an extension of this analysis with the addition of new daily records spanning 1998-2023. Nominal CPUE for the early period showed high but highly variable values at the beginning of the series, then a declining trend towards the late 1990s. Standardized CPUE since the early 2000s then showed a gradual increase to match that recorded in the early 1970s. Factors having a significant effect on CPUE were Southern Oscillation index, moon phase, meridional current velocity and direction, month, latitude, and captain. The results demonstrate that long-term personal, unbiased daily fishing records may be used to demonstrate fluctuations in stocks, in this case recording a decline and recovery of black marlin CPUE that may not have been possible from other data sources.

The sailfish (Istiophorus platypterus) is a mobile epipelagic billfish whose range extends across the world's tropical and subtropical oceans. Once thought to be two allopatric species, respectively inhabiting the Indo-Pacific and Atlantic oceans, molecular analyses support a single species with global distribution. Adequate sampling of widespread pelagic species presents considerable challenges, and most previous studies on sailfish used small numbers of molecular markers. As such, our understanding of their global population structure was limited. In this study, we collaborated with fisheries researchers and fishers to build a comprehensive genomic dataset of single-nucleotide polymorphisms for sailfish spanning most of its range. Here, we examined genetic variation using three filtering approaches: (i) the full-loci dataset, (ii) putatively neutral loci, and (iii) large-FST loci for 590 sailfish from 20 locations to explore contemporary population structure and connectivity in a global context. Cluster analyses of all datasets indicated three discrete populations: the Atlantic, eastern Pacific, and Indo-West Pacific oceans. For the first time, sailfish sampled from locations across the Indo-West Pacific revealed genetic connectivity throughout this region. Analyses of a subset of large-FST loci suggested a small reduction in gene flow between the western and eastern Atlantic Ocean and between the western Indian Ocean and the rest of the Indo-West Pacific. These insights into contemporary population structure can inform future stock assessments and cross-jurisdictional management of this migratory marine species.

Context Offshore spawning and larval distribution of the wide ranging Scylla serrata (giant mud crab) provides genetic connectivity potential across large spatial scales.Aims We examined the genetic connectivity of S. serrata between and within two large continental shelves of northern and eastern Australia, to inform fisheries assessment and management.Methods Over 300 individuals were sampled from 14 locations, within 6 oceanographic regions, across the 2 continental shelves, providing 40,364 single nucleotide polymorphisms (SNPs) for analysis.Key results Results indicated a single genetic stock along the eastern continental shelf of Australia with no evidence of north to south structuring. A separate genetic stock on the northern continental shelf of Australia was indicated, with evidence supporting a degree of east-west structuring of S. serrata populations within the Gulf of Carpentaria.Conclusions The spatial extent of genetically connected S. serrata metapopulations is likely dependent on the oceanographic features of a region. The spatial scale of S. serrata stocks should be assessed on a case-by-case basis, confirmed by empirical evidence (e.g. SNP analysis) given connectivity is likely dependent on regional oceanographic conditions.Implications The outcomes of this study have implications for management of fished S. serrata stocks, especially where fishing mortality may (or may not) have effects beyond the jurisdiction of interest.

Aggregations are key events, supporting critical ecological and biological functions in many species. For highly mobile and elusive species, aggregations often provide the only feasible opportunities for research. Whale sharks (Rhincodon typus) form at least 30 consistent seasonal aggregation sites globally, yet none have been documented in the Coral Sea, despite sporadic sightings of solitary individuals and groups. This study aimed to identify and characterise the first whale shark aggregation on Australia's east coast by predicting potential sites through a data layering approach and confirming their presence through targeted field expeditions. A combination of historical sightings data, expert and anecdotal knowledge, and scientific knowledge from other whale shark aggregation sites led to the identification of Wreck Bay, situated at the far northern Great Barrier Reef, as potential aggregation habitat. An initial field expedition in 2019 confirmed the aggregation, and three subsequent voyages in 2021-2024 gathered further demographic and movement data. A total of 59 individuals were identified, with a strong male bias (3.5:1) and all classified as immature sharks ranging from 3.5 to 8.0 m in estimated total length. Satellite tracking revealed a mean residence time of approximately 3 weeks (21.6 days ±10.1 SD; range: 7-43 days), with some individuals revisiting the aggregation in subsequent years. The peak aggregation period occurs from late November to late December, with movements concentrated along the continental shelf before dispersing into the Coral Sea. Tracked sharks (n = 18) exhibited wide-ranging movements, with a mean track duration of 144 days (range: 3-770 days) and a mean total track length of 1463 km (range: 19-11,355 km). This study provides the first evidence of a whale shark aggregation in the Coral Sea and highlights Wreck Bay as key habitat for this iconic and globally endangered species.

Context Currently, little information exists describing the population structure of great hammerhead sharks (Sphyrna mokarran) in Australian waters. Aims This study used single nucleotide polymorphisms to investigate fine-scale population structure in S. mokarran across the Indo-Pacific. Methods DNA was extracted from 235 individuals across six Australian locations and a Red Sea outgroup. Population parameters were calculated and visualised to test structuring across locations. Key results No fine-scale population structuring was observed for S. mokarran across the Indo-Pacific. However, population structuring occurred for all Australian locations when compared to the Red Sea outgroup. Conclusions Findings suggest a single stock is most likely for S. mokarran found in Australian waters. Results provide key information for understanding the broad range movements of S. mokarran and help to define the scale of management required to preserve genetic diversity in this species. The structuring between Australia and the Red Sea indicates limited gene flow and movement. Implications Results indicate that large-scale movements of S. mokarran could be occurring to facilitate genetic mixing. Future research focusing on individual tagging to corroborate movements would be highly beneficial to determine how far (and often) individuals are dispersing, and to note where cross-jurisdictional management, including from neighbouring regions in the Indo-West Pacific–Oceania region, are most critical.

Background Acoustic telemetry has become a fundamental tool to monitor the movement of aquatic species. Advances in technology, in particular the development of batteries with lives of > 10 years, have increased our ability to track the long-term movement patterns of many species. However, logistics and financial constraints often dictate the locations and deployment duration of acoustic receivers. Consequently, there is often a compromise between optimal array design and affordability. Such constraints can hinder the ability to track marine animals over large spatial and temporal scales. Continental-scale receiver networks have increased the ability to study large-scale movements, but significant gaps in coverage often remain. Methods Since 2007, the Integrated Marine Observing System's Animal Tracking Facility (IMOS ATF) has maintained permanent receiver installations on the eastern Australian seaboard. In this study, we present the recent enhancement of the IMOS ATF acoustic tracking infrastructure in Queensland to collect data on large-scale movements of marine species in the northeast extent of the national array. Securing a relatively small initial investment for expanding receiver deployment and tagging activities in Queensland served as a catalyst, bringing together a diverse group of stakeholders (research institutes, universities, government departments, port corporations, industries, Indigenous ranger groups and tourism operators) to create an extensive collaborative network that could sustain the extended receiver coverage into the future. To fill gaps between existing installations and maximise the monitoring footprint, the new initiative has an atypical design, deploying many single receivers spread across 2,100 km of Queensland waters. Results The approach revealed previously unknown broad-scale movements for some species and highlights that clusters of receivers are not always required to enhance data collection. However, array designs using predominantly single receiver deployments are more vulnerable to data gaps when receivers are lost or fail, and therefore "redundancy" is a critical consideration when designing this type of array. Conclusion Initial results suggest that our array enhancement, if sustained over many years, will uncover a range of previously unknown movements that will assist in addressing ecological, fisheries, and conservation questions for multiple species.

Understanding population connectivity helps inform resource and conservation managers about appropriate boundaries for management units. However, for many species facing recent increases in fishing or environmental pressure, accurate information on population structure is lacking. Reef Bugs ( Thenus australiensis ), commonly known as Moreton Bay Bugs, are iconic shovel-nosed lobsters in northern Australia and an increasingly important fisheries resource. Around 80% of landings occur in the Queensland East Coast Otter Trawl Fishery (ECOTF) where the first stock assessment of the species is underway. However, knowledge about population structure to inform stock assessment is lacking. We used genome complexity reduction-based sequencing to characterise high-quality Single Nucleotide Polymorphisms (SNPs) used to evaluate population structure among three management zones of the ECOTF. Post-filtering, a total of 3,031 SNPs were used to infer no genetic differences among locations indicating strong genetic population connectivity. The presence of a single panmictic population was further supported by cluster and kinship analyses. Broad-scale genetic connectivity likely results from pelagic larval dispersal due to limited adult movements. Findings of high gene flow among connected populations indicate a single biological stock of T. australiensis on Australia’s east coast and will inform future fisheries management initiatives.

The black jewfish (Protonibea diacanthus) occurs in tropical coastal waters throughout the central Indo‐Pacific. It has long been valued as an important recreational and artisanal fishery species but has become increasingly targeted by commercial fisheries due to demand for its large swim bladder. To better understand how changes in fishing pressure may impact the sustainable exploitation of P. diacanthus populations throughout Eastern Australia, we evaluated the reproductive biology of the species across two management regions in Central Queensland. Reproductive characteristics studied included the size at maturity, fecundity, spawning mode, and season. Spawning periodicity was evaluated throughout the two major management regions and revealed an increase in the gonadosomatic index during the early austral spring, followed by evidence of spawning occurring from September through March with a peak from September to November. Females were found to produce ∼4.5 million ± 1.4 million oocytes (mean ± SE) per batch. Spawning periodicity did not vary latitudinally but was found to differ from other regions in northern Australia. The present study provides reliable maturity and fecundity information to improve future assessment and sustainable management of P. diacanthus.

Context In Australia, the health of our marine, estuarine and freshwater fishes are of critical importance. The aquatic and marine ecosystems, and the fishes that occupy them each have an important role in our country’s ecological, economic, cultural and social wealth. Climate change, resource over-exploitation, invasive animals and diseases, and habitat degradation are just a few of the burgeoning threats that researchers and managers must address to ensure the prosperity of Australia’s natural fisheries resources. In addition, differences in legislative frameworks among jurisdictions hinder our ability to coherently manage fish resources at scales that are relevant biologically, ecologically and socially. Aims Here, we identify the key research priorities for fish and fisheries research in Australia, across seven thematic fields of study. Methods Research priorities were evaluated using a horizon scanning approach which identified research questions related to the field of fish and fisheries research in Australia. Key results A total of 284 unique research questions were categorised and prioritised, resulting in the formation of the top 10 highest priority research questions across each of the seven themes. Conclusions The outcomes from this work can be used to directly complement ongoing work from research providers working in the field of fish and fisheries as well as the development of new areas of research. Implications The priorities identified will enable researchers and policy makers to identify critical knowledge gaps, develop collaborative research programs, investigate novel approaches, and to improve transparency around decision-making processes.

Permeable phylogeographic barriers characterize the vast open ocean, boosting gene flow and counteracting population differentiation and speciation of widely distributed and migratory species. However, many widely distributed species consists of distinct populations throughout their distribution, evidencing that our understanding of how the marine environment triggers population and species divergence are insufficient. The sailfish is a circumtropical and highly migratory billfish that inhabits warm and productive areas. Despite its ecological and socioeconomic importance as a predator and fishery resource, the species is threatened by overfishing, requiring innovative approaches to improve their management and conservation status. Thus, we presented a novel high-quality reference genome for the species and applied a seascape genomics approach to understand how marine environmental features may promote local adaptation and how it affects gene flow between populations. We delimit two populations between the Atlantic and Indo-Western Pacific oceans and detect outlier loci correlated with sea surface temperature, salinity, oxygen, and chlorophyll concentrations. However, the most significant explanatory factor that explains the differences between populations was isolation by distance. Despite recent population drops, the sailfish populations are not inbred. For billfishes in general, genome-wide heterozygosity was found to be relatively low compared to other marine fishes, evidencing the need to counteract overfishing effects. In addition, in a climate change scenario, management agencies must implement state-of-the-art sequencing methods, consider our findings in their management plans, and monitor genome-wide heterozygosity over time to improve sustainable fisheries and the long-term viability of its populations.

Solutions occurring within complex systems such as recovery of species are urgently needed. One path forward involves action agendas that extend across the full range of stakeholder groups. Approaches that can foster cooperative behavior across a range of vested interests can create environments supporting species recovery. This paper reports the stakeholder identification process used to gather divergent opinions. A total of 923 priorities from 239 stakeholders were identified. Consensus approaches were utilized, resulting in 25 top priorities, selected by 61 stakeholders. This study demonstrates how consensus areas for action can be illuminated and supported by diverse stakeholder groups whose relationships have previously been indicated as antagonistic. Results indicate support for a range of actions that can be implemented to protect iconic fish species such as pearl perch and snapper in Southeast Queensland. Stakeholders supported actions that; change fishing practices for groups (recreational, commercial and charter); extended monitoring and reporting; improved compliance; changes to fishing management practices; extended fishing control measures and the construction of additional artificial reef habitats.

Fish stocking occurs in aquatic systems for conservation purposes, to create or enhance recreational fisheries and to enhance wild-catch commercial fisheries. Identifying and quantifying the contribution of stocking efforts to wild populations is crucial to informing these management objectives. Provenance determination methods trade off accuracy, replicability, and costeffectiveness at fishery-relevant scales. We present and assess multiple methods for provenance determination using a case study of barramundi (Lates calcarifer) in the Dry Tropics region of northern Australia. A novel application of near-infrared spectroscopy (NIRS) is compared to two established methods for fish provenance, otolith microchemistry and genetic parentage analysis using microsatellites. The otolith microchemistry method was able to provide extremely high provenance resolution (>99% accuracy). The microsatellite parentage analysis method had a slightly lower overall accuracy (95%), likely as a result of genetic introgression in this region. Provenance determination using otolith NIRS had the lowest overall accuracy (76%). Once limitations regarding spectral noise, image resolution, and sample size are addressed, NIRS may have potential for costeffectively determining provenance in fish.

Cryptic mortality in fisheries relates to the unobserved or unrecorded mortality in a target ecosystem and is an important aspect of harvest management for fishery managers. Depredation is a key, observable form of cryptic mortality that relates to predators consuming a targeted species being caught within a fishing industry. This is of particular interest to the Queensland spanner crab fishing industry, where additional unobserved or unrecorded mortality through depredation of catch could be restricting current efforts to rebuild the population. High-resolution cameras were deployed on 178 baited tangle-nets (dillies) to investigate cryptic mortality, species interactions, and depredation within the spanner crab Ranina ranina fishery in Queensland, Australia. Physical parameters including current speed, temperature, depth, and time of soak were recorded. Depredation events were observed in the fishery by two species of endangered batoid species, the bowmouth guitarfish Rhina ancylostoma and wedgefish Rhynchobatus spp. However, rates of depredation in the fishery were low, with only 3.82% of crabs depredated. Fishing losses were calculated by comparing the total crabs on retrieval of a dilly, against total crabs observed while still soaking (MaxN) and at the beginning of retrieval. Overall, there was a loss of 37% in potentially harvested crabs through a combination of cryptic mortality and inefficient fishing practices. However, 27% of the losses could be reduced through shorter deployment times. We identified a significant correlation between the rate of depredation and current speed (similar to 0.6-0.8 knots), soak time and depth (<35 m). We also report spanner crab shell damage caused by mantis shrimp interactions, that likely contribute to an increase in spanner crabs discards due to unmarketable product. By identifying the species and drivers involved in spanner crab depredation, this study provides insights into ways that depredation events can be mitigated and managed.

Context Alien freshwater snails pose a substantial risk to Australian native aquatic biota. Aims This study aims to determine the thermal and salinity ranges of two introduced species within Australia, Pomacea sp. and Anentome sp., to facilitate predictions of their potential geographic range should they become widely established. Methods Laboratory tests were conducted to assess behavioural responses of snails to altered temperature or salinity after different acclimation regimes. Key results After acclimation at 25°C, Pomacea sp. had a median activity range of 13.5–38°C and Anentome sp. of 12–38.5°C. Higher acclimation temperatures produced observable effects, whereas lower acclimation temperatures did not. Salinity tolerances differed, with Pomacea sp. remaining active at up to 8 parts per thousand (ppt) (after acclimation at 25°C), with acclimation at 20°C resulting in a lower salinity tolerance. By contrast, Anentome sp. snails were active at up to 5 ppt after low salinity acclimation, demonstrating enhanced salinity tolerance compared with non-salinity acclimations. Conclusions These results showed that both snails are capable of surviving temperatures and salinities that would allow invasion into subtropical and warm-temperate Australian aquatic systems. Implications Free from the constraints of natural predators, competitors, and parasites, these snails should be of great concern to biosecurity agencies in Australia.