Ryan Daly

Oceanographic Research Institute

Both the reef manta ray, Mobula alfredi and oceanic manta ray M. birostris, are repeatedly observed in South Africa, yet little is known about the distributions of either species. In this study, we collated citizen science observations since 2003 to reveal six areas in the KwaZulu-Natal (KZN) and Eastern Cape provinces, where manta rays have been s...

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...

Migration is a critical aspect of ocean ecosystems, and understanding this phenomenon answers ecological and management questions. Given the difficulty in tracking ocean animals across large distances, the extent to which different ray species perform long‐distance movements, such as migrations, remains unknown. This study used passive acoustic tel...

Understanding the aggregation and habitat use patterns of a species can aid the formulation and improved design of management strategies aiming to conserve vulnerable populations. We used photo-identification techniques and a novel remote underwater camera system to examine the population sizes, patterns of residency and habitat use of oceanic (Mob...

Giant trevally Caranx ignobilis are iconic, apex marine predators globally distributed in tropical to subtropical regions, where they are of high importance to ecosystems and fisheries. During summer, adults aggregate for spawning, making them vulnerable to overfishing. The world’s largest C. ignobilis aggregation has been recorded in southern Moza...

Acoustic telemetry is a popular approach used to track many different aquatic animal taxa in marine and freshwater systems. However, information derived from focal studies is typically resource‐ and geography‐limited by the extent and placement of acoustic receivers. Even so, animals tagged and tracked in one region or study may be detected unexpec...

Migratory sharks play a key ecological role through movements within and among marine ecosystems, yet many populations are declining. Addressing the decline is especially challenging for wide-ranging species, as they may undertake movements between countries with disparate conservation priorities. To investigate the transboundary migrations of thre...

The International Union for Conservation of Nature (IUCN) estimates that over a third of all chondrichthyan species (sharks, rays and chimaeras) are threatened with extinction, primarily by overfishing (as target or bycatch species). Owing to the wide-ranging distributions of many chondrichthyans, they are often overlooked in marine protected area...

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...

Movements of four adult giant trevally Caranx ignobilis were tracked using passive acoustic telemetry after being released from uShaka Sea World Aquarium in Durban, South Africa, where they had been kept on display for a period of 8 years. All four individuals were detected on a large network of deployed acoustic receivers for a minimum of 3 months...

The coexistence of ecologically and morphologically similar species is often facilitated by the partitioning of ecological niches. While subordinate species can reduce competition with dominant competitors through spatial and/or trophic segregation, empirical support from wild settings, particularly those involving large-bodied taxa in marine ecosy...

A tag-recapture study was undertaken on Polysteganus praeorbitalis in the Pondoland Marine Protected Area (PMPA) on the east coast of South Africa. A total of 1 042 fish were tagged over a period of 16 years and 255 individuals (24.5%) were recaptured, some of them on multiple occasions. Data analysis showed that 84.7% of recaptured fish remained i...

Abstract The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessme...

Scientific output has proven the value of the Oceanographic Research Institute’s Cooperative Fish Tagging Project (ORI-CFTP) to biological and fisheries research, with more than 95 published manuscripts based on data from the ORI-CFTP. This study reviews the project from the perspective of participating anglers. A total of 267 members of the ORI-CF...

Understanding the population structure of a species is important to accurately assess its conservation status and manage the risk of local extinction. The Bull Shark ( Carcharhinus leucas ) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its...

Billfish species (families Istiophoridae and Xiphiidae) are caught in artisanal, recreational, and commercial fisheries throughout the Western Indian Ocean region. However, data and information on the interactions among these fisheries and the ecology of billfish in the WIO are not well understood. Using an in-depth analysis of peer-reviewed articl...

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...

Human activities in the oceans increase the extinction risk of marine megafauna. Interventions require an understanding of movement patterns and the spatiotemporal overlap with threats. We analysed the movement patterns of 33 white sharks (Carcharodon carcharias) satellite-tagged in South Africa between 2012 and 2014 to investigate the influence of...

Movement behaviour of the endemic epinephelid Mycteroperca andersoni (formerly allocated to genus Epinephelus) along the east coast of southern Africa was investigated using both conventional dart tagging and passive acoustic telemetry. Results from both methods showed that this species is likely to be a temporary resident on shallow inshore reefs;...

The diamond ray Gymnura natalensis is endemic to southern Africa where its preference for shallow coastal habitats makes it vulnerable to recreational shore-based angling. Although it makes up approximately 1% of the shore-based tag numbers, little is known about its movements, reproduction or population status in South Africa. This study used thre...

Estuaries provide critical nursery habitat for juvenile bull sharks Carcharhinus leucas, as they have the ability to withstand a wide range of salinities. St Lucia is the largest estuarine lake in Africa and was once a key nursery for bull sharks until a prolonged and near-continuous period of mouth closure and drought between 2002 and 2021. The es...

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...

This article is a response to Murua et al.'s Matters Arising article in Nature, "Shark mortality cannot be assessed by fishery overlap alone," which arose from arising from N. Queiroz et al. Nature https://doi.org/10.1038/s41586-019-1444-4 (2019).

Information on the movement ecology of endangered species is critical for the implementation of effective conservation measures. This study made use of a long-term dart tagging dataset to reveal the movement patterns and growth rates of two size classes of the Critically Endangered whitespotted wedgefish Rhynchobatus djiddensis within its southern...

Defining the home range of vulnerable species is critical for designing effective spatial management strategies. However, animal home ranges often change with ontogeny, and quantifying the associated temporal and spatial changes is particularly challenging for mobile marine species. Here, we investigated how the space use of a top predatory reef-as...

Dinoperca petersi is a relatively common fish species caught in the line-fishery in KwaZulu-Natal (KZN), South Africa. Yet, little is known about the biology and ecology of this species. Movement patterns and growth rate of this species were studied based on data obtained from a long-term tag-recapture study conducted in the iSimangaliso Marine Pro...

Supplementary data for Glass et al. 2020. Marine Ecology Progress Series.

How animals partition activity throughout the day is influenced by processes that affect supply and obtainability of resources. However, as resource supply and usability are often entrained by the same diurnal pattern, it has been difficult to disentangle their relative importance. Given the strong influence that tide has on the distribution and ac...

• The white‐spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark‐like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time‐series data to...

Defining the home range of vulnerable species is critical for designing effective spatial management strategies. However, animal home ranges often change with ontogeny and quantifying the associated temporal and spatial changes is particularly challenging for mobile marine species. Here, we investigate how the space use of a top predatory reef-asso...

Coexistence of ecologically similar species occupying the same geographic location (sympatry) poses questions regarding how their populations persist without leading to competitive exclusion. There is increasing evidence to show that micro-variations in habitat use may promote coexistence through minimizing direct competition for space and resource...

The decline in numbers of reef manta rays (Mobula alfredi) throughout their range has highlighted the need for improved information on their spatial ecology in order to design effective conservation strategies for vulnerable populations. To understand their patterns of movement in Seychelles, we used three techniques—archival pop-up satellite tags,...

The humphead wrasse Cheilinus undulatus is an iconic, ecologically important and Endangered fish species associated with coral reefs in the Indo-Pacific region. Due to its large size and complex life history characteristics, it is vulnerable to overfishing and has undergone substantial population declines in parts of its range. Knowledge of the spe...

Top predators have substantial downstream effects on the structure, function, and resilience of ecosystems. The influence of top predators on an ecosystem can vary if they occur within multiple habitat types and have a wide niche breadth due to spatiotemporal changes in diet. We examined spatial patterns in trophic position and niche width for an e...

Knowledge of population structure, connectivity, and effective population size remains limited for many marine apex predators, including the bull shark Carcharhinus leucas. This large-bodied coastal shark is distributed worldwide in warm temperate and tropical waters, and uses estuaries and rivers as nurseries. As an apex predator, the bull shark l...

Stable isotope analyses provide the means to examine the trophic role of animals in complex food webs. Here, we used stable isotope analyses to characterize the feeding ecology of reef manta rays (Mobula alfredi) at a remote coral reef in the Western Indian Ocean. Muscle samples of M. alfredi were collected from D'Arros Island and St. Joseph Atoll,...

The 2015–2016 global coral reef bleaching event was the most persistent and widespread in history. In its aftermath, efforts are required to understand the extent of the post-bleaching coral mortality and the ability of reefs to recover. This study used benthic photographic data to assess the post bleaching mortality of a coral reef community at D’...

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fle...

This report describes the first record of the piscicolid leech Pontobdella macrothela from Mozambique waters and the first record of P. macrothela parasitizing a Grey Reef Shark (Carcharhinus amblyrhynchos). The leech, P. macrothela, was found attached externally between the third and fourth gill slits of a shark captured off Vamizi Island, Quirimb...

Understanding the behaviours of free-ranging animals over biologically meaningful time scales (e.g., diel, tidal, lunar, seasonal, annual) gives unique insight into their ecology. Bio-logging tools such as accelerometers allow the remote study of elusive or inaccessible animals by recording high resolution movement data. Machine learning (ML) is be...

Two specimens of the marine leech Pontobdella macrothela were found parasitizing the carcharhinid shark, Negaprion acutidens, at St. Joseph Atoll, Amirantes, Republic of Seychelles. This report presents the first record of this piscicolid leech from N. acutidens and is one of the few records of P. macrothela in the West Indian Ocean.

BackgroundA rapid marine fish biodiversity assessment and subsequent surveys were conducted at D’Arros Island and St. Joseph Atoll, Amirantes, Republic of Seychelles. ResultsDive surveys recorded the first national occurrence of 16 reef associated fish species. Ten species had regionally cosmopolitan distributions in the West Indian Ocean and their...

The giant trevally Caranx ignobilis (Forsskål) is an important apex predatory fish typically associated with coral reef communities. It is prized in recreational and commercial fisheries, yet little is known about its aggregation dynamics and susceptibility to fishing pressure. This study reports on a previously undocumented aggregation of mature g...

Aim Concurrently, assessing the effectiveness of marine protected areas and evaluating the degree of risk from humans to key species provide valuable information that can be integrated into conservation management planning. Tiger sharks ( Galeocerdo cuvier ) are a wide‐ranging ecologically important species subject to various threats. The aim of th...

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fi...

A drone was used to study the richness and behaviour of scavengers attracted to the carcass of a sperm whale (Physeter microcephalus) in Seychelles, Western Indian Ocean. Over 30 sharks of 3 species (tiger shark Galeocerdo cuvier, bull shark Carcharhinus leucas and tawny nurse shark Nebrius ferrugineus) were recorded scavenging on the carcass. Tige...

Bull sharks (Carcharhinus leucas) are globally distributed top predators that play an important ecological role within coastal marine communities. However, little is known about the spatial and temporal scales of their habitat use and associated ecological role. In this study, we employed passive acoustic telemetry to investigate the residency patt...

A detailed hydrographic and biological survey was conducted in the region of the Subtropical Convergence in the Indian sector of the Southern Ocean in April 2007. Hydrographic data revealed that the subsurface expression of the Subtropical Convergence (at 200 m), marked by the 10°C isotherm, appeared to meander considerably between 41°S and 42°15’S...

As apex predators, sharks play an important role shaping their respective marine communities through predation and associated risk effects. Understanding the predatory dynamics of sharks within communities is, therefore, necessary to establish effective ecologically based conservation strategies. We employed non-lethal sampling methods to investiga...

This study evaluated the use of a novel underwater biopsy probe designed to collect muscle and dermal tissue samples from large (170–220 cm total length), free-swimming bull sharks Carcharhinus leucas. The biopsy probe tissue retention rate was 87% after 23 trials, and the mean size of retained tissue was 310 mg (SD 78). Biopsy sampling provided a...

A biological survey of the Prince Edward Islands took place in December 2008. The survey repeated an earlier survey of the populations of surface-nesting seabirds on both islands and of fur seals (Arctocephalus spp.) and alien plants on Prince Edward Island in December 2001. Observations on burrowing seabirds, macro-invertebrates and plant communit...

The trophodynamics of the numerically dominant mesozooplankton (200-2000 m) in the vicinity of the Subtropical Convergence (STC) in the Indian sector of the Southern Ocean during austral autumn (April / May) 2007 were investigated as part of the Southern Ocean Ecosystem Variability Study. The survey consisted of six north-south transects each bisec...