Long-term continuous datasets that record fishery catch are key to predicting and managing changes in fisheries. Unfortunately, long-term datasets are rare for recreational fisheries, which hinders our ability to understand long-term changes within these fisheries. Here we use several unconventional long-term datasets, including tournament and tagging program data, to assess changes in catch composition over time in the Australian east coast marlin fishery. We found significant changes to the species and size composition of species within the fishery over time. In the 1930s, catch was solely comprised of striped (Kajikia audax) and black (Istiompax indica) marlin. Black marlin proportionally dominated the fishery in the 1940s to 1980s, but the proportions of blue (Makaira nigricans) and striped marlin increased significantly from the 1980s until present. Currently, the fishery is comprised of primarily striped and black, and to a lesser extent blue marlin. Declines in the mean weight of black and striped marlin were also evident from the 1930s to 1980s. Technological advances improving offshore access may have driven changes in species composition. Our results demonstrate a potential change in technology and gear reshaping species composition within a fishery. This highlights how recreational fisheries, particularly those offshore, have changed with the technology over time, and the potential for future technological to dramatically alter recreational fisheries globally.

We document a unique dorsal protrusion of a southern eagle ray (Myliobatis tenuicaudatus) by-caught in a trawler off the coast of New South Wales, Australia. Radiological imaging led us to conclude the abnormality is a congenital defect that resulted in a pair of additional pelvic fins growing on the dorsal surface. It is unlikely the abnormality had substantial impact on the growth and survival of the animal since it had grown substantially since birth and there was minimal impact to structures that facilitate the movement required to forage and evade predators.

Marine ecosystems are increasingly threatened by overfishing and human-induced pressures that compromise stock assessments through species misidentification. In this study, we evaluate the efficacy of portable X-ray fluorescence (pXRF) as a rapid, non-destructive tool for species identification in fisheries monitoring, using marlin (Istiophoridae) as a model system. Anal fin spine samples from black, blue, and striped marlin were collected at recreational tournaments and processed for elemental analysis. Multivariate analyses, including permutational multivariate analysis of variance, non-metric multidimensional scaling, and similarity percentage analysis, revealed significant interspecies differences in elemental composition. Notably, blue marlin exhibited distinct elemental profiles—potentially reflecting unique habitat use and trophic interactions—compared to black and striped marlin. Classification using canonical analysis of principal coordinates achieved correct classification rates of 68.0% for concentration data and 81.3% for raw spectral counts, while machine learning achieved classification rates of 51.5% ± 1.73% for concentration data and 62.6% ± 1.44% for raw spectral counts—each substantially exceeding the null hypothesis expectation of 33% accuracy for random guessing among three classes. These results underscore the ability of pXRF to discriminate species based on their elemental signatures and highlight the potential of pXRF as a cost-effective, field-deployable complement to traditional genetic methods in improving fisheries monitoring and conservation strategies.

Quantitatively assessing mortality post coral bleaching at scale is inherently difficult, yet can be achieved with georeferenced imagery from aerial drones. Here, we assess the coral bleaching mortality rate from the 2024 global bleaching event at the iconic Lizard Island, Australia. Using drone-derived orthomosaics of the northern and southern sides of the island collected during and after the bleaching event, we measured the area of bleached coral and the area of live coral remaining after bleaching. Across twenty 10 × 10 m quadrats, mean bleaching mortality was 92.2 ± 6.8

Color vision is widespread in marine vertebrates but is notably lacking in whales, dolphins, seals, and apparently also sharks. All sharks studied to date possess only a single spectral class of cone and are thus potentially totally color blind. The reason why sharks lack color vision is unclear, but as the visual pigments of only a handful of this large and ecologically diverse taxon have been studied, more data are required to address this question. Here, we assembled the retinal transcriptomes of 9 species from 7 families and 3 orders within the superorder Galeomorphii to screen for visual opsin and phototransduction genes. We reveal that cone monochromacy is widespread in galeomorph sharks, but the type of cone opsin expressed varies, with lamniform and orectolobiform sharks expressing a long-wavelength-sensitive (LWS) opsin, and carcharhiniform and heterodontiform sharks expressing a rhodopsin-like 2 (RH2) opsin. Cone monochromacy has evolved from a dichromatic ancestral state at least 4 times, implying strong selection pressure to prioritize achromatic over chromatic vision. While all species express the GRK1A and GRK7 isoforms of G protein-coupled receptor kinase, only sharks with the LWS cone opsin express the GRK1B isoform, which suggests that nonspectral functions of photoreception may have influenced, or result from, the opsin complement in the shark retina. Finally, we show that the shark rod (RH1) opsin gene shows evidence of positive selection at sites known to influence pigment kinetics (i.e. metarhodopsin II stability) and that the rate of retinal release likely differs substantially between species in ways that reflect their physiology and ecology.

Aega serricauda sp. nov., from southeastern Australian waters, belongs to a group of species within Aega that is characterised by a strongly flattened antennula peduncle, a prominent seta opposing the dactylus on pereopods 2 or 2 and 3, and moderately to strongly serrate margins to the pleotelson and uropods. In addition, species in this group have elongate bodies with subparallel margins. Aega serricauda is characterized by the pleotelson being nearly as long (0.97 ratio) as wide, a clearly angled posterior margin (that part that is serrated, with slender and robust setae) that forms an angle of 95° at the apex, lateral margins (the lateral part free of setae) comprising 40% or pleotelson length, and uropodal rami extending to or slightly beyond the pleotelson posterior margin. A. serricauda sp. nov. has been recorded in waters off eastern Tasmania and was collected from the surface of three species of elasmobranch: Galeorhinus galeus (school shark), Squalus acanthias (spiny dogfish) and Dipterus cerva (white spotted skate).

There is an urgent need for improved monitoring approaches to rapidly and accurately assess sea cucumber populations at ecologically relevant scales. Timely surveys are critical for informing effective fisheries management and decision-making. Traditional surveys, undertaken via snorkelling, manta tows, or SCUBA, are limited to shallow and accessible areas; however, sea cucumbers inhabit a broad range of depths, including areas beyond safe diving limits and exposed shallow waters inaccessible by boat. To overcome these limitations and increase the rapidity of field collection, we propose the use of remote sensing technologies to survey sea cucumber populations across a range of depths. Here, we evaluated the effectiveness of aerial drones and in-water remote operated vehicles (ROVs) for assessing sea cucumber species and abundances across various depth ranges (< 50 m) on the Great Barrier Reef, Australia. Aerial drone orthomosaics and ROV video footage were compared to more traditional snorkel and SCUBA-based assessments conducted at similar depths. The vast majority of pairwise comparisons between in-water ROV video counts and snorkel or SCUBA assessments found no significant differences in sea cucumber assemblages. Counts from aerial drone-derived orthomosaics, however, were significantly lower, counting approximately half as many sea cucumbers as snorkel counts. This was largely attributed to poor weather during the drone surveys. Remote methods were significantly faster in the field for surveying a given area than traditional methods. Given that towed ROVs can efficiently cover a broader depth range and aerial drones are effective for survey shallow areas under suitable weather conditions, we recommend using a combination of aerial drones and towed ROVs to survey sea cucumbers, with tool selection guided by prevailing weather conditions. This approach offers the advantages of collecting multiple types of data from a single data source, vastly increasing survey efficiency, and providing a historical record for future assessments. The methods have the potential to be used to survey other benthic–associated species.

Quantifying the trophic role of a species is key to understanding its ecology and ecological role. Their trophic role can influence community composition, ecosystem stability, and nutrient transport and cycling between habitats through ingestion, egestion, and excretion, which requires an understanding of species diet and habitat use. Despite the regular occurrence of sawsharks in Australian temperate fisheries, there remains limited information on their trophic ecology or habitat use, but they are assumed to be benthic consumers. We used fatty acid and stable isotope profiles along with stomach content analysis to investigate the trophic ecology of two sympatric species of sawsharks, the common sawshark (Pristiophorus cirratus) and southern sawshark (Pristiophorus nudipinnis) in south-eastern Australia. Stable isotope analysis of δ13C, δ15N, and δ34S in sawshark muscle revealed that P. nudipinnis fed at a higher trophic level than P. cirratus, and mixing models and stomach contents indicated P. nudipinnis was surprisingly reliant on pelagic and benthopelagic prey sources. In contrast, P. cirratus preyed on more benthic invertebrate species, not found in P. nudipinnis. This bentho-pelagic partitioning between species was supported by P. nudipinnis fatty acid profiles having higher levels of tracers associated with dinoflagellate basal sources (16:1/16:0, 22:6ω3) than P. cirratus, indicating a reliance on pelagic food webs. These data demonstrate that sawsharks are mesopredators that play a substantial role linking pelagic and benthic food webs and highlights the value of incorporating multiple biochemical tracers to provide a comprehensive representation of an animal’s trophic ecology and role in and between ecosystems.

Patterns of mother–embryo fractionation of 13 C and 15 N were assessed for their predictability across three species of batoids caught as by-catch in south-eastern Australia. Stable isotope analysis of 24 mothers and their litters revealed that isotope ratios of embryos were significantly different from their corresponding mothers and that the scale and direction of the difference varied within and across species. The range of variation across species was 3.5‰ for δ 13 C and 4‰ for δ 15 N, equivalent to a difference in trophic level. In one species ( Urolophus paucimaculatus ) litters could be significantly enriched or depleted in 13 C and 15 N relative to their mothers' isotope signatures. These results suggest that patterns of mother–embryo isotope fractionation vary within and between species and that these patterns may not be explained only by developmental mode. Contrasting patterns of fractionation between and within species make it difficult to adjust mother–embryo fractionation with broad-scale correction factors.

Bluelined goatfish (Upeneichthys lineatus) rapidly change their body colour from a white horizontally banded pattern to a seemingly more conspicuous vertically banded red pattern, often when foraging. Given the apparent conspicuousness of the pattern to a range of observers, it seems unlikely that this colour change is used for camouflage and instead may be used for communication/signalling. Goatfish often drive multispecies associations, and it is possible that goatfish use this colour change as a foraging success signal to facilitate cooperation, increase food acquisition, and reduce predation risk through a ‘safety in numbers’ strategy. Using a novel approach, we deployed 3D model goatfish in different colour morphs—white without bands, white with black vertical bands, and white with red vertical bands—to determine whether the red colouration is an important component of the signal or if it is only the vertical banding pattern, regardless of colour, that fish respond to as an indicator of foraging success. Use of remote underwater video allowed us to obtain information without the influence of human observers on the communities and behaviours of other fish in response to these different colours exhibited by goatfish. We found that conspecifics were more abundant around the black- and red-banded model fish when compared with the white models. Conspecifics were also more likely to forage around the models than to pass or show attraction, but this was unaffected by model colour. No difference in the abundance and behaviour of associated heterospecifics around the different models was observed, perhaps due to the static nature of the models. Some species did, however, spend more time around the red- and black-banded fish, which suggests the change in colour may indicate benefits in addition to food resources. Overall, the results suggest that the body colour/pattern of U. lineatus is likely a signalling tool but further work is required to explore the benefits to both conspecifics and heterospecifics and to further determine the behavioural functions of rapid colour change in U. lineatus.

The increase in the use of molecular methodologies in systematics has driven the necessity for a comprehensive understanding of the limitations of different genetic markers. Not every marker is optimal for all species, which has led to multiple approaches in the study of the taxonomy and phylogeny of polyclad flatworms. The present study evaluates base-substitution rates of nuclear ribosomal (18S rDNA and 28S rDNA), mitochondrial ribosomal (16S rDNA), and protein-codifying (cytb, cox1) markers for this taxonomic group, with the main objective of assessing the robustness of these different markers for phylogenetic studies. Mutation rates and Ti/Tv ratios of the other markers were assessed for the first time. We estimated substitution rates and found cytb to be the most variable, while 18S rDNA was the least variable among them. On the other hand, the transition to transversion (Ti/Tv) ratio of the different genes revealed differences between the markers, with a higher number of transitions in the nuclear gene 28S and a higher number of transversions in the mitochondrial genes. Lastly, we identified that the third codon position of the studied protein-codifying genes was highly variable and that this position was saturated in the cox1 marker but not in cytb. We conclude that it is important to assess the markers employed for different phylogenetic levels for future studies, particularly in the order Polycladida. We encourage the use of mitochondrial genes cytb and 16S for phylogenetic studies at suborder, superfamily, and family levels and species delimitation in polyclads, in addition to the well-known 28S and cox1.

ABSTRACTGiant clams (Tridacna and Hippopus) are large marine bivalves occupying tropical and subtropical reefs in the Indo‐Pacific. Giant clam populations have declined in many areas of the Indo‐Pacific and continue to be threatened by harvesting and environmental change. The small giant clam (Tridacna maxima) occurs throughout the Indo‐Pacific and has been subject to several phylogeographic studies across its range. However, given its broad range, there are several areas where the genetic diversity and connectivity of T. maxima populations has not been characterised. Here, we analyse the mitochondrial marker cytochrome oxidase 1 (CO1) to examine the genetic diversity and connectivity of T. maxima in two regions: Australia's Coral Sea Marine Park and the Cook Islands. Samples were collected from 13 reefs within the Coral Sea Marine Park and ten islands within the Cook Islands archipelago. Tridacna maxima across the sampled region of the Coral Sea did not display any population structure, whereas significant population structure was detected for T. maxima within the Cook Islands. For the Cook Islands, most pairwise comparisons involving an island in the northern group (Manihiki) were significant, as were comparisons for Palmerston (a more centrally located island) and the southern islands, Rarotonga and Mangaia. Both regions displayed high haplotype diversities (> 0.90), indicating that they are important repositories of genetic diversity. Additional CO1 data from throughout T. maxima's distribution showed that the Coral Sea clams belonged to the clade occurring in the South‐Western Pacific Ocean, whilst those from the Cook Islands belonged to a unique clade found in the Central Pacific Ocean. This clade extended from Fiji in the west to French Polynesia in the east and the atolls of Palmyra and Tarawa (Kiribati) in the north. Our assessment of genetic diversity and population structure in these regions will assist with management decisions for the species.

The Australian cownose ray ( Rhinoptera neglecta ) is an understudied batoid that occurs along Australia's north and east coasts. Currently classified as Data Deficient on the IUCN Red List of Threatened Species, major knowledge gaps exist regarding the species' geographic range, habitat use and the drivers influencing its presence in coastal Australian waters. Sightings of R. neglecta were collected during systematic aerial surveys conducted along 980 km (~47%) of the New South Wales (NSW) coastline between 2017 and 2019. North-bound surveys were flown 500 m offshore, whilst return surveys were flown along the beach/sea interface (inshore or nearshore). Using generalized additive models and a set of nine predictors, we examined the relationship between the spatio-temporal occurrence of R. neglecta , their group size and the biophysical environment at the southernmost extent of their distribution. Results for the presence/absence (44.20% deviance explained) and group size of R. neglecta observed offshore and inshore (42.58 and 41.94% deviance explained, respectively) highlighted latitude, day of year, sea surface temperature, rainfall, wind speed, and wind direction as common influences to the three models. The models indicated R. neglecta were more likely to be present in the northern half of NSW during spring and summer months. However, larger group sizes were more likely to be observed in more southern regions during the same seasons, regardless of whether they were observed offshore or inshore. Group size is also likely influenced by more localized conditions, such as SST and tidal flows. This study represents the largest attempt to date to decipher the spatial ecology of R. neglecta and provides insights into the spatio-temporal distribution and relative abundance of the species along the full extent of the NSW coastline, extending the species' known distribution by over 70 km southward.

Biological data, such as length–weight relationships, are essential for the management and stewardship of harvested individuals. Sea cucumbers are a lucrative industry globally but many of the associated fisheries lack species-level biological data, which reduces the effectiveness of any management strategy. The Queensland Sea Cucumber Fishery (QSCF) on the Great Barrier Reef is managed through various controls: primarily catch limits, effort limits, zoning, and size restrictions. Over 20 species may be harvested but there is a lack of comprehensive biological data for many of these species, particularly important life history characteristics. This study addresses this knowledge gap by assessing 2621 individual length–weight relationships of key-target sea cucumber species associated with the fishery across the range of the distribution of the species and covering a variety of habitats, depths, sampling times, and management zones. Linear models with log transformations were used to analyse the relationships between length and weight. Results revealed significant positive relationships for all assessed species, with Holothuria atra having the clearest relationship between length and weight (R2 = 0.45). Only negative allometric relationships were observed, as is the case for many species of holothurians. Despite challenges associated with measuring and weighing these soft and elastic animals, results will be useful for understanding length–weight dynamics across species. This research underscores the importance of robust biological data for the effective management of sea cucumber fisheries and ultimately reef health.

The Queensland Shark Control Program (QSCP) started in 1962 to reduce the number of shark-human incidents by deploying nets and drumlines across the most popular beaches. The program targets large shark species (white, tiger and bull sharks) that are potentially hazardous to bathers. However, this strategy is lethal for other sharks and marine wildlife, including threatened and endangered species. Thus, finding non-lethal strategies is a priority. To better manage shark-human interactions, establishing a better understanding of the factors that drive shark movement is key. Here we used sea surface temperature (SST), rainfall and distance to rivers as environmental variables to predict the presence of whaler sharks in southern Queensland based on 26 years of catch data from the QSCP. We found that SST is positively corelated to sharks caught by drumlines, while rainfall was associated with the number of sharks captured in shark nets. In addition, more sharks were captured by nets and drumlines further away from rivers, and nets captured roughly 10 times more sharks than drumlines over the period of study. In contrast to tiger sharks, the catch data indicate the number of whalers has not declined over the past 26 years. Our findings suggest that environmental variables can be used to predict the movement of large sharks and by incorporating this knowledge into management plans and public education programs, may ultimately reduce shark-human incidents.

Sympatric species that share morphological similarities tend to diversify their prey resources to coexist. The striped cowfish (Aracana aurita) and ornate cowfish (A. ornata) live together on the continental shelf from western to southern Australia including Tasmanian waters. The present study analyzed stomach contents and stable isotope ratios (delta C-13 and delta N-15) to investigate the use of food resource between the two species collected in Tasmanian waters, Australia. In total, 139 A. aurita and 46 A. ornata were collected from 2014 to 2018. The small size class of A. aurita (<140 mm SL) mainly consumed polychaetes and amphipods, while its large size class (>= 140 mm SL) preyed more on bivalves and crustacean decapods. The main prey items of the small size class of A. ornata (<140 mm SL) were amphipods and crabs. No differences in diet were observed between the sexes of either species. Stable isotope analyses showed significant differences in delta N-15 and delta C-13 between the two species, but not between the two size classes of A. aurita (ANOVA, P < 0.05). Integrating analyses of stomach contents and stable isotopes indicated that the two species preferred different food resources based on different trophic sources. Consequently, although the habitats of the two species overlap, both species can co-exist through dietary segregation.

Context Knowledge of sawshark reproductive biology is limited to general parameters such as reproductive mode and litter size. The mating system is currently unknown. Aim To test for multiple paternity in the common (Pristiophorus cirratus) and southern (Pristiophorus nudipinnis) sawshark and investigate the occurrence of hybridisation between these two species. Methods Pups from a single litter of each species and an adult P. nudipinnis displaying mismatches in its morphology and mitochondrial DNA were genotyped with nuclear single-nucleotide polymorphisms (SNPs). Multiple paternity was assessed using pairwise relatedness and sibship analysis, and hybridisation was examined using three approaches (principal-component analysis, admixture analysis and clustering with NewHybrids). Key results Multiple paternity was detected in both species, with two males siring the seven-pup litter in P. cirratus and two males siring the two-pup litter in P. nudipinnis. Hybridisation between the two species was also confirmed, with the mismatched adult identified as a first-generation hybrid. Conclusions The mating system of sawsharks involves polyandry, and hybridisation between the two co-occurring Australian species is possible. Implications These results provide new information on sawshark reproductive biology and highlight the need for combined use of mitochondrial and nuclear markers in future genetic studies involving these species.

The genus Smeagol consists of five named species of air-breathing marine slugs (restricted to southern Australia and New Zealand) and three undescribed taxa from southern Japan. Only one species, S. hilaris, is known to be from New South Wales (NSW), and it previously had a known distribution limited to one site, Merry Beach on the south coast. This diminutive invertebrate is classified as critically endangered in NSW due to its extremely restricted distribution and concern about its historically declining numbers. Accordingly, the aims of this study were to survey the known population of S. hilaris at Merry Beach and to explore other potentially suitable sites, using a visual census method, to determine if further populations or species exist in NSW. The resulting quantitative surveys of the known population and a new population at Storm Bay, Kiama, NSW, are reported here. DNA barcoding of a ~650 bp segment of the mitochondrial cytochrome c oxidase I (COI) gene for several individuals from each population confirmed the conspecificity among the two populations. The population at Merry Beach was found to remain viable, while the discovery of the new population of S. hilaris represents a doubling of the known global populations of this species. Details of the highly-specialised niche habitat occupied by Smeagol in New South Wales and recommendations for ongoing management are documented.

Increasing ocean acidification is a concern due to its potential effects on the growth, development, and survival of early life stages of tuna in oceanic habitats and on the spatial extent of their suitable nursery habitat. To investigate the potential effects of increasing CO2 on otolith calcification of 9-day old pre-flexion stage yellowfin tuna (Thunnus albacares), an experiment was conducted at the Inter-American Tropical Tuna Commission's Achotines Laboratory in Panama during 2011. Fertilized eggs and larvae were exposed to mean pCO2 levels that ranged from present day (355 mu atm) to two levels predicted to occur in some areas of the Pacific in the near future (2013 and 3321 mu atm), and to an extreme value equivalent to long-term projections for 300 years in the future (9624 mu atm). The results indicated significantly larger otoliths (in area and perimeter) with significant, and increasing, fluctuating asymmetry at acidification levels similar to those projected for the near future and long-term. Otoliths increased significantly in size despite a significant decrease in somatic length with increasing pCO2. A consistent correlation between otolith and somatic growth of yellowfin tuna larvae among treatments was evident (i.e., larger otoliths were still associated with larger larvae within a treatment). The observed changes in otolith morphology with increasing ocean acidification have the potential to indirectly affect larval survival through dysfunction of the mechanosensory organs, but this remains to be verified in yellowfin tuna larvae.

Giant clams are common across a broad geographic range and contribute important ecological functions within coral reef environments. However, giant clams are subject to considerable harvest pressure and require careful management that is underpinned by accurate data collection. The taxonomy of giant clams has undergone many changes, and recently, Tridacna noae (Röding 1798) has been resurrected as a valid species, distinct from the morphologically similar Tridacna maxima (Röding 1798). Using genetic analysis, this research confirms the presence of T. noae for the first time in the Cook Islands, extending the currently known distribution of the species by 1340 km south-east. This confirmation highlights that T. noae was possibly previously misidentified, causing overestimations of the abundance of other giant clam species. This new record improves the accuracy of identification and stock assessments, and ongoing management in the Cook Islands.