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Globally, work is being undertaken to preserve biodiversity and prevent further species extinctions. Yet, without adequate data about the presence of species within ecosystems, hidden extinctions can occur without our knowledge. Given that poleward range retractions are projected for bull kelp (Durvillaea amatheiae) in southeastern Australia, there is the potential for hidden extinctions to occur in associated macrofaunal species. However, this risk cannot be assessed due to the limited data on the invertebrate macrofauna associated with D. amatheiae. We documented macrofauna within D. amatheiae holdfasts, with the objective of establishing a first analysis of the holdfast fauna for this kelp and identifying, where possible, any host-specific taxa. Holdfasts were collected at six locations, spanning most of the range of D. amatheiae on the southeastern Australian mainland. Macrofauna were removed from holdfasts and identified to the lowest possible taxonomic level. Modelling was applied to determine factors correlated with patterns of assemblages among locations. Holdfast assemblages were found to vary significantly among locations and exhibited a latitudinal gradient in assemblage structure. The northernmost location (Aragunnu), which has the highest risk of D. amatheiae range retractions, was found to have distinct species assemblages and generally higher diversity and abundance than locations further south. However, no host-specific taxa were identified in samples, indicating that there is a low risk of multiple hidden species extinctions occurring in holdfast macrofauna, due to future range retractions of D. amatheiae. Rather, most of the macrofauna taxa in D. amatheiae holdfasts were found to also occur in association with the sympatric golden kelp Ecklonia radiata, which is not expected to undergo range retractions at the latitudes where losses of D. amatheiae are projected. Overall, there is an urgent need to develop strategies to combat projected future range retractions of D. amatheiae to reduce impacts on the species that rely on D. amatheiae for habitat. [ABSTRACT FROM AUTHOR]

Extreme weather events such as floods are becoming more frequent, and pose a substantial threat to Australia's nearshore marine communities. In March 2021, a 450 km stretch of the eastern NSW coastline experienced a La Niña-related rainfall event over several days, resulting in large volumes of freshwater ingress to marine systems. Port Stephens, an estuary 250 km north of Sydney, recorded its highest week of rainfall on record. This was followed by two more flood events in March 2022 and June 2022. Prior to 2021, the marine-dominant Eastern Port of Port Stephens was home to the world's largest aggregations of Dendronephthya australis, an endangered species of soft coral endemic to the south-east coast of Australia. Using data from a 2019–2022 D. australis monitoring program in Port Stephens, spanning the unprecedented series of flood events in 2021–2022, we detail the impacts of flood events on the population. Prior to the floods, aggregations of colonies were persisting, and individuals were growing at two of the four monitored sites. However, flooding in March 2021 caused a 91% decline in the remaining areal extent of D. australis. Modelling of likely causative factors highlighted water depth as the most significant environmental variable correlated with coral loss. Corals in shallower waters experienced lower salinity and were the most impacted. Continued monitoring during 2021 and 2022 documented the loss of all remaining aggregations in the estuary after further La Niña-related rainfall events, to the point where D. australis is now on the brink of localised extinction. [ABSTRACT FROM AUTHOR]

The urchin Centrostephanus rodgersii is expanding its range southward in eastern Australia, which has been associated with negative ecological impacts, including shifts from kelp forests to barrens. However, limited analyses are available that examine the factors influencing its abundance and distribution across the entirety of this range. Here, we utilise data from 13,085 underwater visual census surveys, from 1992 to 2022, to develop an urchin density model for C. rodgersii across its historical and extending geographical range. We apply this model to examine whether C. rodgersii densities are increasing and to project future urchin densities by 2100 under IPCC climate scenario RCP 8.5. Significant increases in C. rodgersii densities were detected in data for the South-east marine region of Australia, which encompasses Tasmania, Victoria, and the far south coast of New South Wales (NSW) over the last 30 years. In the Temperate East marine region (encompassing Queensland and NSW waters to 36.6° S), however, no significant increases in densities were observed. Future projections indicated that further substantial increases in C. rodgersii densities are likely to occur in the South-east marine region and substantial reductions in most of the Temperate East marine region by 2100. Importantly, results indicate that current and future changes to C. rodgersii densities in Australia vary among marine regions. Therefore, the future ecological impacts of urchins on temperate ecosystems, including the formation of barrens, will also vary among regions. Consequently, management actions will need to differ among these regions, with the South-east marine region requiring mitigation of the impacts of increasing C. rodgersii densities, whereas the Temperate East marine region may need actions to preserve declining C. rodgersii populations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The temperate soft coral Dendronephthya australis has been listed as Endangered in NSW, Australia, owing to its restricted geographic range, rapidly declining populations, and a number of escalating threats. Research to assess practical methods for aquarium cultivation of D. australis for rehabilitation of wild populations is considered a high priority.Previous attempts at restoration by transplanting D. australis fragments have had limited success, but identified key challenges, which included achieving attachment to substrates and identifying appropriate foods to maximize survival.This study presents the results of experiments promoting the attachment of cuttings (nubbins) removed from donor colonies to moveable substrates (small concrete discs). Using a balanced orthogonal experimental design, three feeding regimes were tested: live artemia, live rotifers and dry powdered zooplankton.Donor colony survival and growth were also monitored over a 6 month period in the field.An overall nubbin survival rate of 100% was achieved under all three feeding regimes. Attachment rates were similar across feeding treatments, although nubbin behavioural responses (percentage of open polyps before feeding) suggested some preference for live rotifers.The cutting removal process had no significant effect on donor colonies in the wild, indicating that this is a sustainable approach for restoration.Overall, this study substantially advances the methodology for maintaining an Endangered azooxanthellate soft coral in aquaria and provides valuable input for management programmes aimed at implementing transplantation into the wild to aid species recovery. [ABSTRACT FROM AUTHOR]

Illegal fishing is an acknowledged problem within no‐take areas (NTAs), which are frequently used as a marine conservation management tool. While gathering data on illegal fishing is difficult, it is necessary, as these data enable increased efficiency of compliance patrols, where resources are inherently limited. In particular, information about short‐term temporal variations in illegal fishing in NTAs is needed to guide management and compliance efforts. To address this knowledge gap, daily variations in illegal fishing effort were examined using surveillance cameras at two sites in New South Wales, Australia. Generalised linear modelling (GLM) identified that illegal fishing was significantly greater on non‐working days and during periods with no rain, light winds and slight seas. The GLM developed provided useful predictions of illegal activity in both the NTA used to build the model and in a second nearby NTA. The study demonstrated that illegal fishing was principally concentrated on days with good boating conditions and was greater at the study site closer to boat launching facilities. These insights will assist with future targeting of enforcement, community outreach and management efforts, which should focus on days and sites with an increased likelihood of illegal fishing. [ABSTRACT FROM AUTHOR]

Dendronephthya australis , an Endangered soft coral primarily found in the central coast region of New South Wales (NSW), Australia, is in rapid decline. The largest known aggregations are located within the Port Stephens estuary, where the populations have been mapped in detail via towed video at four-year intervals since 2011. Since the distribution was initially mapped in 2011, the areal extent decreased by 67.5%, and is now 9300 m2 compared to 28,600 m2 in 2011. Forest-based Species Distribution Models (SDMs) determined that the primary variables associated with the presence of D. australis (including depth, current velocity, slope, and the distance from the estuary mouth and the shoreline) remained largely unchanged suggesting an alternative cause of declines. General Linear Models (GLMs) identified that losses were associated with distance from shore, and change in depth and current velocity from 2007 to 2018. As these three variables are linked to sediment mobilisation within the estuary, this process is likely to be a key contributing factor to the decline of D. australis – this is supported by in situ observations over the same time period. As Port Stephens is a hydrodynamically complex environment, and has a wide variety of both commercial and recreational uses, other, as yet unidentified, processes may also be contributing to soft coral loss. The only remaining aggregations are found in depths of 4–11 m, which makes them highly vulnerable to fishing and boating impacts, as well as severe storm events. [Display omitted] • The endangered soft coral Dendronephthya australis declined by 67.5% over 8 years. • Random Forest modelling approach utilised for Species Distribution Models. • General Linear Models show a likely link between sediment mobilisation and decline. [ABSTRACT FROM AUTHOR]