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Turban snails are targeted for their high‐quality meat and, consequently, are often subjected to heavy harvesting pressure. Managing recreational and small‐scale fisheries is challenging, partly due to a lack of biological data underpinning certain regulatory measures. This study aimed to fill current knowledge gaps on the reproductive cycle of the recreationally and culturally harvested Australian turbinid, Turbo militaris. The objectives were to investigate the reproductive timing of T. militaris in New South Wales (NSW) and identify likely environmental drivers of reproductive periodicity. Oocytes and gonads were sampled from wild animals monthly over 15 months at two sites separated by ~500 km. Analysis of oocyte size frequency and gonadosomatic index revealed that T. militaris has a pattern of extended reproduction, which is synchronous between sexes. Turbo militaris was ripest during summer, and spawning appears to have occurred over multiple events, although primarily during winter. Reproductive timing was associated with environmental explanatory variables, including sea surface temperature, wave height, salinity, phytoplankton and nitrate concentration, together accounting for 81% of the variation in oocyte size frequency and 67% in the gonadosomatic index. Reproductive periodicity was correlated with wave conditions and phytoplankton concentrations inconsistently between sites, indicating that the effect of some environmental conditions may be unpredictable or site‐specific. Reproductive timing was asynchronous between two sites in the NSW fishery, posing challenges for designing seasonal fishing closures and community‐based harvesting rules. Spatial closures for species with spawning over extended timeframes, or spatially asynchronous reproductive cycles, are potentially more suitable for achieving fisheries management objectives. [ABSTRACT FROM AUTHOR]

During 20152016, record temperatures triggered a pan-tropical episode of coral bleaching, the third global-scale event since mass bleaching was first documented in the 1980s. Here we examine how and why the severity of recurrent major bleaching events has varied at multiple scales, using aerial and underwater surveys of Australian reefs combined with satellite-derived sea surface temperatures. The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat. Similarly, past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs., Author(s): Terry P. Hughes (corresponding author) [1]; James T. Kerry [1]; Mariana lvarez-Noriega [1, 2]; Jorge G. lvarez-Romero [1]; Kristen D. Anderson [1]; Andrew H. Baird [1]; Russell C. Babcock [...]

Subtropical coral assemblages are threatened by similar extreme thermal stress events to their tropical counterparts. Yet, the mid‐ and long‐term thermal stress responses of corals in subtropical environments remain largely unquantified, limiting our capacity to predict their future viability.The annual survival, growth and recruitment of 311 individual corals within the Solitary Islands Marine Park (Australia) was recorded over a 3‐year period (2016–2018), including the 2015/2016 thermal stress event. These data were used to parameterise integral projection models quantifying the effect of thermal stress within a subtropical coral assemblage. Stochastic simulations were also applied to evaluate the implications of recurrent thermal stress scenarios predicted by four different Representative Concentration Pathways.We report differential shifts in population growth rates (λ) among coral populations during both stress and non‐stress periods, confirming contrasting bleaching responses among taxa. However, even during non‐stress periods, the observed dynamics for all taxa were unable to maintain current community composition, highlighting the need for external recruitment sources to support the community structure.Across all coral taxa, projected stochastic growth rates (λs) were found to be lowest under higher emissions scenarios. Correspondingly, predicted increases in recurrent thermal stress regimes may accelerate the loss of coral coverage, species diversity and structural complexity within subtropical regions.We suggest that these trends are primarily due to the susceptibility of subtropical specialists and endemic species, such as Pocillopora aliciae, to thermal stress. Similarly, the viability of many tropical coral populations at higher latitudes is highly dependent on the persistence of up‐current tropical systems. As such, the inherent dynamics of subtropical coral populations appear unable to support their future persistence under unprecedented thermal disturbance scenarios. [ABSTRACT FROM AUTHOR]

Habitat structural complexity influences biotic diversity and abundance, but its influence on marine ecosystems has not been widely addressed. Recent advances in computer vision and robotics allow quantification of structural complexity at higher‐resolutions than previously achieved. This provides an important opportunity to determine the ecological role of habitat structural complexity in marine ecosystems. We used high‐resolution three‐dimensional (3D) maps to test multiple structural complexity metrics, depth and benthic biota as surrogates of fish assemblages across hundreds of meters on subtropical reefs. Non‐parametric multivariate statistics were used to determine the relationship between these surrogates and the entire fish assemblage. Fish were divided into functional groups, which were used to further investigate the relationship between surrogates and fish abundance using generalized linear models. Fish community composition and abundance were strongly related to habitat complexity metrics, benthic biota and depth. Surface rugosity and its variance had a significant positive influence on the abundance of piscivores and sediment infauna predators, and a negative effect on the abundance of predators, herbivores, planktivores and cleaners. Final models for fish functional groups explained up to 68% of the variance. The best metrics to explain the variance in fish abundance were benthic biota (25 ±7.5% of variance explained, mean ± SE) and complexity metrics (16 ±6.6%, mean ± SE). Our results show that high‐resolution 3D maps and derived metrics can predict a large percentage of variance in fish abundance and potentially serve as useful surrogates of fish abundance across all functional groups in spatially dynamic reefs. [ABSTRACT FROM AUTHOR]

Meta-analyses of disparate studies suggest that size and age of a 'no-take' area (marine sanctuary) can influence its ecological response to protection. Few studies, however, have been designed explicitly to test how these factors influence the abundance trajectories of key species within sanctuaries., Diver surveys on reef habitat were conducted within a subtropical marine park in eastern Australia, to test for differences in abundances of targeted fishes between sanctuaries differing in size and age and compared with fished zones. Four management zones were sampled: (i) small sanctuaries established 1991 (<15 ha of reef and <200 m wide); (ii) large sanctuaries established 2002 (>100 ha of reef and > 500 m wide); (iii) zones which allowed recreational fishing but not commercial fish trapping (>200 ha of reef); and (iv) zones which allowed both recreational fishing and commercial fish trapping (>200 ha of reef). Multiple sites in each management zone were sampled for selected taxa eight times during the austral winter from 2002 to 2012., Many of the targeted taxa examined were more abundant in large sanctuary sites within a few years of the establishment of protection compared with the small sanctuary sites and the fished sites. Red morwong Cheilodactylus fuscus increased in large sanctuaries but were more abundant in the older smaller sanctuaries throughout the study. Similar increases were not observed in fished zones. There was considerable variability among years not associated with management type, including a peak in abundance for several species in 2005 and reduced abundance of many taxa following a destructive storm in 2009., This study provides strong empirical evidence that size and age of 'no take' areas are important for fish, and indicates that larger sanctuaries can rapidly reach levels of fish abundance similar to smaller older sanctuaries., © 2015 Commonwealth of Australia. [ABSTRACT FROM AUTHOR]

Some of the most profound effects of climate change on ecological communities are due to alterations in species interactions rather than direct physiological effects of changing environmental conditions. Empirical evidence of historical changes in species interactions within climate-impacted communities is, however, rare and difficult to obtain. Here, we demonstrate the recent disappearance of key habitat-forming kelp forests from a warming tropical--temperate transition zone in eastern Australia. Using a 10-y video dataset encompassing a 0.6 °C warming period, we show how herbivory increased as kelp gradually declined and then disappeared. Concurrently, fish communities from sites where kelp was originally abundant but subsequently disappeared became increasingly dominated by tropical herbivores. Feeding assays identified two key tropical/ subtropical herbivores that consumed transplanted kelp within hours at these sites. There was also a distinct increase in the abundance of fishes that consume epilithic algae, and much higher bite rates by this group at sites without kelp, suggesting a key role for these fishes in maintaining reefs in kelp-free states by removing kelp recruits. Changes in kelp abundance showed no direct relationship to seawater temperatures over the decade and were also unrelated to other measured abiotic factors (nutrients and storms). Our results show that warming-mediated increases in fish herbivory pose a significant threat to kelp-dominated ecosystems in Australia and, potentially, globally. [ABSTRACT FROM AUTHOR]