Mahmood S. Shivji

Nova Southeastern University | NSU · Halmos College of Arts & Science

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...

Aim Shoaling of large oxygen minimum zones (OMZs) that form along eastern margins of the world's oceans can reduce habitat availability for some pelagic fishes. Our aim was to test the hypothesis that habitat compression caused by shoaling of the Pacific OMZ in tropical regions creates a boundary to the southern distribution of shortfin mako sharks...

Hammerhead sharks are among the most iconic and threatened shark species. Research has focused on the large hammerhead species, with relatively little work conducted on their smaller-bodied relatives, which face many of the same threats. One such species, the scalloped bonnethead Sphyrna corona , is assessed as Critically Endangered by the IUCN Red...

Context Satellite telemetry has revolutionised the study of animal movement, particularly for mobile marine animals, whose movements and habitat make consistent, long-term observation difficult. Aims Summarise the movements of Rio Lady, a mature female whale shark (Rhincodon typus), to characterise these movements, and to predict expected behaviour...

Despite being a heavily fished species, little is known about the movements of silky sharks (Carcharhinus falciformis). In this study, we report the longest (in duration and distance traveled) and most spatially extensive recorded migration for a silky shark. This shark, tagged with a fin‐mount satellite transmitter at the Galapagos Islands, travel...

Resources in the pelagic environment tend to be patchily distributed, often resulting in animals engaging in adaptive behaviors to maximize foraging success. While these behaviors have been examined in horizontal and vertical dimensions separately, there has been limited work integrating these functionally related movements in sharks. We investigat...

The oceanic whitetip shark, Carcharhinus longimanus, is a Critically Endangered, circumtropical, and highly migratory, pelagic shark. Yet, little information exists on its population genetic dynamics to guide conservation management practice. We present a first worldwide, mitochondrial and nuclear DNA assessment of the population genetic status of...

Niche partitioning among closely related, sympatric species is a fundamental concept in ecology, and its mechanisms are of broad interest for understanding ecosystem functioning and predicting the impacts of human-driven environmental change. However, identifying mechanisms by which top marine predators partition available resources has been especi...

Information about the composition of pelagic communities generally lags far behind that of coastal communities, and largely derives from fisheries data that do not reflect small and non-target species. Spatiotemporal vertebrate diversity and variability associated with environmental drivers across a 3,486 km2 area of a highly productive pelagic mar...

Blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) are ecologically important predators and valuable species throughout the world’s recreational, commercial, and subsistence fisheries. Comparing multi-species vertical habitat use can inform ecological uncertainties such as inter-species competition, as well as relative vulnerabi...

Pelagic predators must contend with low prey densities that are irregularly distributed and dynamic in space and time. Based on satellite imagery and telemetry data, many pelagic predators will concentrate horizontal movements on ephemeral surface fronts—gradients between water masses—because of enhanced local productivity and increased forage fish...

Nassau grouper (Epinephelus striatus, Serranidae) were one of the most important fishery species in the Caribbean, but are now listed as critically endangered. Population collapse in most places occurred primarily by fishers targeting their spawning aggregation sites, where thousands of fish gathered during full moon periods from December to April....

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...

Foraging behavior and interaction with prey is an integral component of the ecological niche of predators but is inherently difficult to observe for highly mobile animals in the marine environment. Billfishes have been described as energy speculators, expending a large amount of energy foraging, expecting to offset high costs with periodic high ene...

The scalloped hammerhead shark, Sphyrna lewini, is a Critically Endangered, migratory species known for its tendency to form iconic and visually spectacular large aggregations. Herein, we investigated the population genetic dynamics of the scalloped hammerhead across much of its distribution in the Eastern Tropical Pacific (ETP), ranging from Costa...

Despite increasing threats of extinction to Elasmobranchii (sharks and rays), whole genome-based conservation insights are lacking. Here we present chromosome-level genome assemblies for the Critically Endangered great hammerhead (Sphyrna mokarran) and the Endangered shortfin mako (Isurus oxyrinchus) sharks, with genetic diversity and historical de...

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first globa...

High recreational catch rates of istiophorid billfishes in the eastern tropical Pacific (ETP) have led to substantial eco-tourism derived economic benefits for the countries in the region, prompting many countries to mandate catch-and-release practices for recreational anglers. Previous estimates of billfish post-release behaviours and recovery per...

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...

We present complete mitogenome sequences of three shortfin mako sharks (Isurus oxyrinchus) sampled from the western Pacific, and eastern and western Atlantic oceans. Mitogenome sequence lengths ranged between 16,699 bp and 16,702 bp, and all three mitogenomes contained one non-coding control region, two rRNA genes, 22 tRNA genes, and 13 protein-cod...

Assessing the impacts of the Deepwater Horizon oil spill (DWHOS) on deep-sea fish assemblages of the Gulf of Mexico (GOM) has been hindered by an absence of baseline (pre-spill) data concerning the population genetic dynamics of these fishes. The lanternfishes (Myctophidae) are a speciose, yet understudied, taxonomic group, that comprise a signific...

The roosterfish (Nematistius pectoralis) is a piscivorous predator targeted extensively in recreational fisheries throughout the eastern tropical Pacific; however, its biology is poorly understood. To address these shortcomings, we investigated vertical habitat use and behaviour of roosterfish in coastal Panama using pop-up satellite archival tags....

Understanding the population dynamics of highly mobile, widely distributed, oceanic sharks, many of which are overexploited, is necessary to aid their conservation management. We investigated the global population genomics of tiger sharks (Galeocerdo cuvier), a circumglobally distributed, apex predator displaying remarkable behavioral versatility i...

Understanding reproductive behaviours and the environmental conditions that facilitate reproduction is important for successful reproduction in managed care. Complex reproductive behaviours have been observed in both aquarium and free-ranging elasmobranchs. Sexual conflicts, including pre-copulatory behaviours in sand tiger sharks Carcharias taurus...

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).

This study provides the first standardized global microsatellite database for a shark species, the tiger shark (Galeocerdo cuvier). Genotyping of reference individuals was used to develop and apply a calibration key for data from eight microsatellite loci data produced by three different laboratories, thereby allowing merging of genotypes into a si...

Cosmopolitan marine pelagic species display variable patterns of population connectivity among the world’s major oceans. While this information is crucial for informing management, information is lacking for many ecologically important species, including apex predators. In this study we examine patterns of genetic structure in the broadnose sevengi...

Profiles of symbiotic microbial communities ("microbiomes") can provide insight into the natural history and ecology of their hosts. Using high throughput DNA sequencing of the 16S rRNA V4 region, microbiomes of five shark species in South Florida (nurse, lemon, sandbar, Caribbean reef, and tiger) have been characterized for the first time. The mic...

The pelagic Gulf of Mexico (GoM) is a complex system of dynamic physical oceanography (western boundary current, mesoscale eddies), high biological diversity, and community integration via diel vertical migration and lateral advection. Humans also heavily utilize this system, including its deep-sea components, for resource extraction, shipping, tou...

The bull shark (Carcharhinus leucas) is a large, mobile, circumglobally distributed high trophic level predator that inhabits a variety of remote islands and continental coastal habitats, including freshwater environments. Here, we hypothesize that the barriers to dispersal created by large oceanic expanses and deep-water trenches result in a heter...

Ecotourism opportunities in the marine environment often rely heavily on provisioning to ensure the viewing of cryptic species by the public. However, intentional feeding of wildlife can impact numerous aspects of an animals' behavior and ecology. Southern stingrays (Hypanus americana) provisioned at Stingray City Sandbar (SCS) in Grand Cayman have...

Abstract Ecotourism opportunities in the marine environment often rely heavily on provisioning to ensure the viewing of cryptic species by the public. However, intentional feeding of wildlife can impact numerous aspects of an animals’ behavior and ecology. Southern stingrays (Hypanus americana) provisioned at Stingray City Sandbar (SCS) in Grand Ca...

The whitespotted eagle ray Aetobatus narinari is a tropical to warm‐temperate benthopelagic batoid that ranges widely throughout the western Atlantic Ocean. Despite conservation concerns for the species, its vertical habitat use and diving behaviour remain unknown. Patterns and drivers in the depth distribution of A. narinari were investigated at t...

Vagile, large-bodied marine organisms frequently have wide range dispersion but also dependence on coastal habitats for part of their life history. These characteristics may induce complex population genetic structure patterns, with resulting implications for the management of exploited populations. The scalloped hammerhead, Sphyrna lewini, is a co...

Upper trophic level predators dramatically impacted by fisheries include the large-bodied hammerhead sharks, which have become species of conservation concern worldwide. Implementing spatial management for conservation of hammerhead populations requires knowledge of temporal distribution patterns and habitat use, identification of essential habitat...

We present the mitochondrial genome sequence of a gray reef shark, Carcharhinus amblyrhynchos (Bleeker 1856), a coral reef associated species. This is the first mitogenome for this species from the western Indian Ocean. The mitogenome is 16,705 bp in length, has 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a non-coding control region, a...

The sea surface microlayer (SML) is the upper 1 mm of the ocean, where Earth’s biogeochemical processes occur between the ocean and atmosphere. It is physicochemically distinct from the water below and highly variable in space and time due to changing physical conditions. Some microorganisms influence the composition of the SML by producing surfact...

Migratory movements in response to seasonal resources often influence population structure and dynamics. Yet in mobile marine predators, population genetic consequences of such repetitious behaviour remain inaccessible without comprehensive sampling strategies. Temporal genetic sampling of seasonally recurring aggregations of planktivorous basking...

Understanding the connectivity of reef organisms is important to assist in the conservation of biological diversity and to facilitate sustainable fisheries in these ecosystems. Common methods to assess reef connectivity include both population genetics and biophysical modelling. Individually, these techniques can offer insight into population struc...

We report the first complete mitochondrial genome of a shortfin mako shark from the Atlantic Ocean. The genome had 16,700 base pairs and contained 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a non-coding D-loop. There were 81 individual differences compared to the published mitochondrial genome of a shortfin mako from the Pacific Ocea...

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...

Animal movement and habitat selection are in part a response to landscape heterogeneity. Many studies of movement and habitat selection necessarily use environmental covariates that are readily available over large‐scales, which are assumed representative of functional habitat features such as resource availability. For widely distributed species,...

The white shark ( Carcharodon carcharias ; Chondrichthyes, Elasmobranchii) is one of the most publicly recognized marine animals. Here we report the genome sequence of the white shark and comparative evolutionary genomic analyses to the chondrichthyans, whale shark (Elasmobranchii) and elephant shark (Holocephali), as well as various vertebrates. T...

Although over half of all known elasmobranchs are batoids, with many species exploited and several of conservation concern, little is known of their population genetic structure and micro-evolutionary history. Here, we used sequence variation in 648 bp of the mitochondrial control region to study the phylogeography of the southern stingray (Hypanus...

Pelagic sharks are vulnerable to overfishing because of their low reproductive rates, generally low growth rates, and high catch rates in tuna and billfish fisheries worldwide. Pelagic sharks often migrate long distances, but they may also occur close to shore, making it difficult to classify their behaviour on the continuum from oceanic nomad to c...

The deep waters of the open ocean represent a major frontier in exploration and scientific understanding. However, modern technological and computational tools are making the deep ocean more accessible than ever before by facilitating increasingly sophisticated studies of deep ocean ecosystems. Here, we describe some of the cutting-edge technologie...

Recent advances in genome-scale sequencing technology have allowed the development of high resolution genetic markers for the study of non-model taxa. In particular, transcriptome sequencing has proven to be highly useful in generating genomic markers for use in population genetic studies, allowing for insight into species connectivity, as well as...

• The night shark, Carcharhinus signatus, is a mesopelagic, semi‐oceanic shark species found only in the Atlantic Ocean. It is one of the most frequently caught sharks in pelagic longline fisheries and is classified as Vulnerable by the International Union for the Conservation of Nature (IUCN). Despite their prevalence in commercial fisheries, the...

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...

Grouper spawning aggregations along deep reefs of the US Virgin Islands represent a large potential prey source for predators including sharks. To examine the relationship between grouper spawning aggregations and sharks, we tagged three species of groupers and three species of sharks with acoustic transmitters and monitored their movements over se...

The silky shark, Carcharhinus falciformis, is a large-bodied, oceanic-coastal, epipelagic species found worldwide in tropical and subtropical waters. Despite its commercial importance, concerns about overexploitation, and likely ecological significance of this shark as an upper trophic-level predator, understanding of its population dynamics remain...