Marcus Sheaves

• Doctor of Philosophy
• Professor (Full) at James Cook University

Coastal managers continue to be confronted with making management decisions with few data available and insight of the outcomes. Practical tools that can be used to inform on the effects of different scenarios of changes are particularly important to assist decision-making. This study has applied a Bayesian Belief Network (BBN) to investigate the c...

Mangroves are a critical habitat that provide a suite of ecosystem services and support livelihoods. Here we undertook a global analysis to model the density and abundance of 37 commercially important juvenile fish and juvenile and resident invertebrates that are known to extensively use mangroves, by fitting expert-identified drivers of density to...

Traditionally, lethal stomach dissection has been used to study the diets of sharks and rays, but conservation and animal welfare concerns necessitate non‐lethal alternatives, such as gastric lavage (stomach or gut flushing). In this study, we summarised gastric lavage studies on elasmobranchs to identify which species/groups it has been effective...

Despite the recent global increase in mangrove restoration efforts, our understanding of the outcomes and recovery of biodiversity and re-establishing functionality, such as productive fish habitat, is limited due to the lack of long-term monitoring. Here, we used a space-for-time approach to investigate whether restored mangroves attain similar fi...

Accurate fish segmentation in underwater videos is challenging due to low visibility, variable lighting, and dynamic backgrounds, making fully-supervised methods that require manual annotation impractical for many applications. This paper introduces a novel self-supervised learning approach for fish segmentation using Deep Learning. Our model, trai...

Mangrove restoration projects have become increasingly widespread to compensate for mangrove loss. Despite considerable investment in this restoration activity, post-restoration monitoring is often limited to vegetation recovery with no inclusion of faunal groups, such as macrobenthos communities, even though these groups are excellent bioindicator...

Climate change is shifting animal distributions. However, the extent to which future global habitats of threatened marine megafauna will overlap existing human threats remains unresolved. Here we use global climate models and habitat suitability estimated from long-term satellite-tracking data of the world’s largest fish, the whale shark, to show t...

The global urgency to halt and reverse mangrove loss has led to the implementation of numerous initiatives to protect and restore mangroves and recover critical ecological functions and services. Restoration success is assessed by estimating mangrove survival, while diversity, vegetation structure, and soil characteristics are often overlooked with...

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 locat...

The impacts on marine species from secular warming and heatwaves are well demonstrated; however, the impacts of extreme cold events are poorly understood. Here we link the death of organisms from 81 species to an intense cold upwelling event in the Agulhas Current, and show trends of increasing frequency and intensification of upwelling in the Agul...

Tropical mangroves are known to support fish production, but natural variability in the link between mangrove habitats and fish populations undermines our ability to manage, conserve and restore this ecological relationship. This is largely due to undefined context‐dependence in the use of mangroves by fish. We collected a spatially extensive datas...

2024) Predicting the impacts of clearing on vegetation communities: a model-based approach for identifying conservation priorities in ABSTRACT Predicting outcomes is critical for conservation prioritisation. We predicted the areas that are likely to be impacted using a generalised estimating equation from a logistic regression and intersected our m...

The Great Barrier Reef (GBR) region comprises a diversity of ecosystems including the reefs themselves, inter-reefal habitats, and a mosaic of coastal systems. Here, land and sea are strongly interconnected at multiple spatial and temporal scales by diverse patterns of fish movement. This functional interlinking enables a range of vital ecological...

Information on how the trophic ecology of predators shapes their movement patterns and space-use is fundamental to understanding ecological processes across organisational levels. Despite this, studies combining spatial and trophic ecology to determine how prey preference and/or resource availability shape space use are lacking in marine predators...

Tidal wetlands continue to be threatened by changes in seascape hydrological regime and connectivity resulting from human activities (e.g. urbanisation, engineered barriers) and climate change. Reliable and parsimonious models that can be used by managers and practitioners to simulation tidal wetland hydroperiod dynamics (duration, depth, and frequ...

The Golden Trevally, Gnathanodon speciosus, is a large predatory fish with an extremely broad tropical Indo-Pacific distribution that crosses many biogeographical boundaries. Both published information and freely available imagery suggest that small juvenile G. speciosus are often associated with whale sharks, Rhincodon typus; an association that c...

Oceanic islands play a central role in the study of evolution and island biogeography. The Galapagos Islands are one of the most studied oceanic archipelagos but research has almost exclusively focused on terrestrial organisms compared to marine species. Here we used the Galapagos bullhead shark ( Heterodontus quoyi ) and single nucleotide polymorp...

Intra-specific variability in movement behaviour occurs in all major taxonomic groups. Despite its common occurrence and ecological consequences, individual variability is often overlooked. As a result, there is a persistent gap in knowledge about drivers of intra-specific variability in movement and its role in fulfilling life history requirements...

Urban-industrial seascapes are prevalent around the world, yet we lack a basic understanding of how the mosaic of different habitats in these areas are used by mobile marine fauna, including features such as industrial ports and marinas. Urbanised areas have been alternately characterised in scientific literature as degraded, depauperate, or in som...

Identifying migration routes and key habitats is critical for the management and conservation of migratory species. Tracking and stable isotope analysis (SIA), particularly of carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N), are often used to study animal movements, with SIA particularly useful when animals move through isotopic gradients. Marine turtles are...

One of the main challenges in deep learning-based underwater image enhancement is the limited availability of high-quality training data. Underwater images are difficult to capture and are often of poor quality due to the distortion and loss of colour and contrast in water. This makes it difficult to train supervised deep learning models on large a...

The ability to adopt novel tools continues to become more important for governments and environmental managers tasked with balancing economic development, social needs and environmental protection. An example of an emerging technology that can enable flexible, cost-effective data collection for conservation and environmental management is Unmanned...

DNN for fish tracking and segmentation based on high-quality labels is expensive. Alternative unsupervised approaches rely on spatial and temporal variations that naturally occur in video data to generate noisy pseudo-ground-truth labels. These pseudo-labels are used to train a multi-task deep neural network. In this paper, we propose a three-stage...

Studying where, when, and why specific behaviours occur is critical for identifying meaningful habitat use patterns of marine organisms. However, for some groups including stingrays, information on behavioural ecology is sorely lacking, despite its relevance for understanding their ecological roles/impacts and supporting conservation strategies for...

Despite its consequences for ecological processes and population dynamics, intra-specific variability is frequently overlooked in animal movement studies. Consequently, the necessary resolution to reveal drivers of individual movement decisions is often lost as animal movement data are aggregated to infer average or population patterns. Thus, an em...

Marine ecosystems and their fish habitats are becoming increasingly important due to their integral role in providing a valuable food source and conservation outcomes. Due to their remote and difficult to access nature, marine environments and fish habitats are often monitored using underwater cameras. These cameras generate a massive volume of dig...

Underwater fish segmentation to estimate fish body measurements is still largely unsolved due to the complex underwater environment. Relying on fully-supervised segmentation models requires collecting per-pixel labels, which is time-consuming and prone to overfitting. Self-supervised learning methods can help avoid the requirement of large annotate...

Significance Global vessel traffic is increasing alongside world economic growth. The potential for rising lethal ship strikes on endangered species of marine megafauna, such as the plankton-feeding whale shark, remains poorly understood since areas of highest overlap are seldom determined across an entire species range. Here we show how satellite...

Tidal wetlands are expected to respond dynamically to global environmental change, but the extent to which wetland losses have been offset by gains remains poorly understood. We developed a global analysis of satellite data to simultaneously monitor change in three highly interconnected intertidal ecosystem types—tidal flats, tidal marshes, and man...

Shark bites are of high public concern globally. Information on shark occurrence and behaviour, and of the effects of human behaviours, can help understand the drivers of shark‐human interactions. In Australia, a number of shark bite clusters occurred over the last decade. One of these took place in Cid Harbour the Whitsundays, Queensland, a region...

Mangroves and seagrasses are important nurseries for many marine species, and this function is linked to the complexity and context of these habitats in coastal seascapes. It is also connected to bathymetric features that influence habitat availability, and the accessibility of refuge habitats, but the significance of terrain variation for nursery...

Context Landscape modification alters the condition of ecosystems and the structure of terrain, with widespread impacts on biodiversity and ecosystem functioning. Seafloor dredging impacts a diversity of flora and fauna in many coastal landscapes, and these processes also transform three-dimensional terrain features. The potential ecological signif...

Marine scientists use remote underwater image and video recording to survey fish species in their natural habitats. This helps them get a step closer towards understanding and predicting how fish respond to climate change, habitat degradation and fishing pressure. This information is essential for developing sustainable fisheries for human consumpt...

Marine scientists use remote underwater video recording to survey fish species in their natural habitats. This helps them understand and predict how fish respond to climate change, habitat degradation, and fishing pressure. This information is essential for developing sustainable fisheries for human consumption, and for preserving the environment....

Many complex factors determine the role of estuarine habitats and landscapes in fish growth and survival that ultimately contribute individuals to adult populations. In this chapter, we recognise the diversity of habitats, both those frequently (e.g. submerged aquatic vegetation, mangroves) and infrequently (e.g. shellfish beds, woody debris) evalu...

The mechanisms that govern fauna-habitat associations across multiple spatial scales remain largely undefined. Can environmental factors structure fauna-habitat associations over both local and global spatial scales, alongside biogeographical processes and patterns? We compare the extent to which the use of mangroves by fishes is consistent within...

Landscape modification alters the condition of ecosystems and the complexity of terrain, with consequences for animal assemblages and ecosystem functioning. In coastal seascapes, dredging is routine practice for extracting sediments and maintaining navigation channels worldwide. Dredging modifies processes and assemblages by favouring species with...

High quality nursery grounds are important for species success and the long-term sustainability of fish stocks. However, even for important fisheries species, what constitutes nursery habitats is only coarsely defined, and details of specific requirements are often lacking. In this study we investigated upstream estuarine areas in central Queenslan...

Animals that disrupt sediments through burrowing or foraging contribute to ecosystem function through bioturbation and ecosystem engineering processes linked to their excavation behavior. Empirical evidence linking behavior with function is rare; yet this information is critical for assessing species‐specific functional roles. Using two stingray sp...

Estuaries host unique biodiversity and deliver a range of ecosystem services at the interface between catchment and the ocean. They are also among the most degraded ecosystems on Earth. Freshwater flow regimes drive ecological processes contributing to their biodiversity and economic value, but have been modified extensively in many systems by upst...

Background The interplay of animal dispersal and environmental heterogeneity is fundamental for the distribution of biodiversity on earth. In the ocean, the interaction of physical barriers and dispersal has primarily been examined for organisms with planktonic larvae. Animals that lack a planktonic life stage and depend on active dispersal are how...

Despite genuine attempts, the history of marine and coastal ecosystem management is littered with examples of poor environmental, social and financial outcomes. Marine ecosystems are largely populated by species with open populations, and feature ecological processes that are driven by multiple, interwoven, dynamic causes and effects. This complexi...

Temporal environmental variability causes behavioural and physiological responses in organisms that can affect their spatial location in time, and ultimately drive changes in population and community dynamics. Linking ecological changes with underlying environmental drivers is a complex task that can however be facilitated through the integration o...

Protected areas are a fundamental mechanism for ensuring the persistence of biodiversity. The strategic policy objectives set by governments for protected area land acquisition are strong determinants of biodiversity outcomes. An examination of these objectives is necessary to determine those most influential in designing protected area networks an...

106,107 ✉ replying to A. V. Harry & J. M. Braccini Nature https://doi.org/10.1038/s41586-021-03463-w (2021) Our global analysis 1 estimated the overlap and fishing exposure risk (FEI) using the space use of satellite-tracked sharks and longline fishing effort monitored by the automatic identification system (AIS). In the accompanying Comment, Harry...

Accelerating declines in the extent, quality and functioning of the world's marine ecosystems have generated an upsurge in focus on practical solutions, with ecosystem restoration becoming an increasingly attractive mitigation strategy for systems as diverse as coral reefs, mangroves and tidal flats. While restoration is popular because it promises...

Shallow littoral waters in estuaries provide important nurseries for a diversity of fish species. The recent review of Whitfield (2020; Mar Ecol Prog Ser 649:219-234) reinforced the long-held paradigm that the value of shallow nurseries is due, in part, to these habitats containing few predators and having low predation pressure. We argue that the...

The structure of seafloor terrain affects the distribution and diversity of animals in all seascapes. Effects of terrain on fish assemblages have been reported from most ecosystems, but it is unclear whether bathymetric effects vary among seascapes or change in response to seafloor modification by humans. We reviewed the global literature linking s...

Significance Body shape is a strong predictor of habitat occupation in fishes, which changes rapidly at microevolutionary scales in well-studied freshwater systems such as sticklebacks and cichlids. Deep-bodied forms tend to occur in benthic habitats, while pelagic species typically have streamlined body plans. The recurrent evolution of this patte...

Stakeholder engagement is essential to conserve ecosystems and associated biodiversity. Outdoor recreation specialists represent stakeholder groups that often rely on specific healthy ecosystems and have unique incentives to contribute to conservation and stewardship. We introduce the concept of habitat-dependent outdoor recreation conservation org...

Coastal habitats, such as seagrasses, mangroves, rocky and coral reefs, salt marshes, and kelp forests, sustain many key fish and invertebrate populations around the globe. Our understanding of how animals use these broadly defined habitat types is typically derived from a few well-studied regions and is often extrapolated to similar habitats elsew...

Across many Pacific Island Countries, food insecurity and malnutrition are on the rise. In response, governments, development agencies, and non-governmental organisations are promoting small-scale aquaculture as a complement to fish supplied through coastal fisheries. While small-scale aquaculture has been widely adopted in parts of Asia and Africa...

The limitations imposed by traditional sampling methods have restricted the acquisition of data on key fisheries parameters. This is particularly the case for juveniles because most traditional gear explicitly avoids the capture of juveniles, and the juveniles of many species use habitats in which traditional gear is ineffective. The increasing ava...

Visual analysis of complex fish habitats is an important step towards sustainable fisheries for human consumption and environmental protection. Deep Learning methods have shown great promise for scene analysis when trained on large-scale datasets. However, current datasets for fish analysis tend to focus on the classification task within constraine...

Visual analysis of complex fish habitats is an important step towards sustainable fisheries for human consumption and environmental protection. Deep Learning methods have shown great promise for scene analysis when trained on large-scale datasets. However, current datasets for fish analysis tend to focus on the classification task within constraine...

Seagrass meadows are an important habitat for a variety of animals, including ecologically and socioeconomically important species. Seagrass meadows are recognised as providing species with nursery grounds, and as a migratory pathway to adjacent habitats. Despite their recognised importance, little is known about the species assemblages that occupy...

To test the model that eco-engineering plant boxes on seawalls sustain water temperatures within thermal tolerance to maximize tropical marine biodiversity, we conducted acute thermal effects (AET) experiments using intertidal gastropods (Nerita albicilla and Littoraria articulata). The AET50 (50th percentile) for N. albicilla (39.6 °C) was higher...

Accuracy in representing, communicating and reporting science is critical to the translation of science into knowledge. Any lack of accuracy degrades the quality and reliability of consequent decisions. One common cause of inaccuracy is the use of superseded paradigmatic concepts with a lack of careful validation. This leads to evidentiary dissonan...

Increasing pressure on coastal fisheries poses serious threats to local livelihoods and the food security of Pacific Islanders. In response, governments and development agencies have explored tilapia pond aquaculture as an alternative fish production source. Yet, evidence to date on the impact of tilapia aquaculture on rural livelihoods has been in...

Despite the increasing need to catalogue and describe biodiversity and the ecosystem processes it underpins, these tasks remain inherently challenging. This is particularly true for species that are difficult to observe in their natural environment, such as fossorial and cryptic crabs that inhabit intertidal sediments. Traditional sampling techniqu...

A predictable aggregation of dwarf minke whales (Balaenoptera acutorostrata subspecies) occurs annually in the Australian waters of the northern Great Barrier Reef in June–July, which has been the subject of a long-term photo-identification study. Researchers from the Minke Whale Project (MWP) at James Cook University collect large volumes of under...

All fishery food webs are ultimately underpinned by organic matter produced by algae and plants, some of it supplied by primary producers at the fringes of fish habitats. This is no different in tropical and subtropical estuaries where secondary production by crustaceans and finfish may depend on coastal wetlands (e.g. mangroves, seagrass, saltmars...

On 1 March 2019, the United Nations (UN) General Assembly (New York) declared 2021–2030 the “UN Decade on Ecosystem Restoration.” This call to action has the purpose of recognizing the need to massively accelerate global restoration of degraded ecosystems, to fight the climate heating crisis, enhance food security, provide clean water and protect b...

Managing small-scale fisheries (SSF) is complicated because fishers rarely selectively target valued species but try to maximise their catch by keeping everything regardless of species or size. About 50% of the fish captured for human consumption globally, is produced by SSF, however, there has been repeated failures of fisheries management to effe...

Ecosystem functioning is positively linked to biodiversity on land and in the sea. In high‐diversity systems (e.g. coral reefs), species coexist by sharing resources and providing similar functions at different temporal or spatial scales. How species combine to deliver the ecological function they provide is pivotal for maintaining the structure, f...

Structural habitat complexity is a fundamental attribute influencing ecological food webs. Simplification of complex habitats occurs due to both natural and anthropogenic pressures that can alter productivity of food webs. Relationships between food web structure and habitat complexity may be influenced by multiple mechanisms, and untangling these...

The ecological impacts of landscape modification and urbanisation have transformed the composition of plant and animal assemblages, and altered the condition of ecosystems globally. Landscape transformation influences the spatial distribution of species and ecological functions by selecting for generalist species with wide ecological niches, which...