Darren Andrew Whitehead

Founder - Shark Research Mexico

The bluntnose sixgill shark (Hexanchus griseus) is a wide‐ranged deep‐water shark species found off continental and insular shelves. Despite its global distribution, little is known about the reproductive ecology of the species, particularly with regard to the location and timing of important phenological events such as mating and pupping. In this...

Sharks are particularly susceptible to bioaccumulation due to their life history characteristics and trophic position within marine ecosystems. Despite this, studies of bioaccumulation cover only a small proportion of extant species. In this study we report concentrations of trace elements and heavy metals in blood samples of Sphyrna lewini for the...

Elasmobranchs (sharks and rays) exhibit a wide range of body forms adapted to various ecological niches. Body form differs not only between species, but between life stages of individual species as a result of ontogenetic allometry. In sharks, it has been proposed that these ontogenetic shifts in body form result from shifts in trophic and/or spati...

Recent studies have uncovered mosaic patterns of allometric and isometric growth underlying ontogenetic shifts in the body form of elasmobranch species (shark and rays). It is thought that shifts in trophic and spatial ecology through ontogeny drive these morphological changes; however, additional hypotheses relating to developmental constraints ha...

Amidst global declines in elasmobranch populations resulting predominantly from overfishing, the need to gather data regarding shark ecology is greater than ever. Many species remain data deficient or at risk of going extinct before sufficient conservation measures can be applied. In this review, we summarise existing knowledge regarding the biolog...

Shark populations globally are facing catastrophic declines. Ecotourism has been posited as a potential solution to many of the issues facing shark conservation, yet increasingly studies suggest that such activity may negatively influence aspects of shark ecology and so further pressure declining populations. Here we combine UAV videography with de...

The central tenet of ecomorphology links ecological and morphological variation through the process of selection. Traditionally used to rationalise morphological differences between taxa, an ecomorphological approach is increasingly being utilised to study morphological differences expressed through ontogeny. Elasmo-branchii (sharks, rays and skate...

Despite being the world's largest fish, many questions remain regarding the ecology and behaviour of the whale shark (Rhincodon typus). We present the first direct evidence of whale sharks engaging in bottom‐feeding behaviour and provide potential explanations for this foraging strategy. We suggest that whale sharks actively feed on benthic prey, e...

Shark populations globally are facing catastrophic declines. Ecotourism has been posited as a potential solution to many of the issues facing shark conservation, yet increasingly studies suggest that such activity may negatively in uence aspects of shark ecology and so further pressure declining populations. Here we combine UAV videography with dee...

In addition to the selective importance of interspecific morphological variation, ontogenetic morphological variation may reflect different selective regimes to which successive developmental stages are subjected. The typical body form of carcharhiniform sharks is considered relatively conserved, yet sharks exhibit a wide range of body sizes and sh...

Sharks are particularly susceptible to bioaccumulation due to their life history characteristics and trophic position within marine ecosystems. Despite this, studies of bioaccumulation cover only a small proportion of extant species. In this study we report concentrations of trace elements and heavy metals in blood samples of S. lewini for the firs...

Measurements obtained from aerial imagery can be used to calculate body shape, condition and growth rates of large surface-associated marine megafauna. In this study, an unoccupied aerial vehicle (UAV) was used to obtain aerial images of an elasmobranch species, the whale shark (Rhincodon typus). Pre-caudal length (PCL) and multiple body width meas...

The silky shark (Carcharhinus falciformis) is a pelagic carcharhiniform shark species distributed globally in tropical and subtropical oceans. In this study, we report a seasonal sex segregated aggregation off the southern tip of the Baja California Peninsula and record the distribution and frequency of mating wounds, to determine if males targeted...

Concentrations of Ag, Cr, Mn and Ni were measured in tissues of two whale sharks (Rhincodon typus) stranded in La Paz Bay (LAP) and Punta Bufeo (PB), Gulf of California, during 2017 and 2018. The concentration range of Ni (0.012–1.12 µg/g ww) and Cr (0.16–5.21) in the epidermis of both specimens was lower compared to the concentrations found in the...

The aim of this study is to provide preliminary observations on the microanatomy of Rhincodon typus skin using histology and electron microscopy analyses. Skin biopsies were obtained from a deceased juvenile male shark (548 cm total length) stranded in La Paz, Mexico, during February 2018. The results of this study evidenced the basic structure of...

The Gulf of California represents an important hotspot for whale shark (Rhincodon typus) aggregation. Anthropogenic activities and natural sources could expose sharks to high levels of trace elements (TEs). To determinate these levels in this endangered species, concentrations of As, Cd, Cu, Pb and Zn (in ng/g ww) were measured in 130 whale shark s...

This study constitutes the first descriptions of morphological abnormalities in the silky shark Carcharhinus falciformis from a near term embryo obtained in the Gulf of California, Mexico. External exploration and X-ray images were taken to describe the specimen, which revealed that the embryos deformities were located in the cephalic region sugges...

Abundance and typology of microplastics (MPs) were measured in 12 water samples collected from two whale sharks feeding areas of the Gulf of California (Bahía de los Angeles (BLA) and Bahia de La Paz (LAP)). The concentration of MPs was 0.47 MPs/ m ³ in BLA and 0.63 MPs/ m ³ in LAP. Overall, films were the most abundant type of MPs (41%; n = 74) fo...

Trace elements were determined in three areas of the right (RL) and left (LL) lobe of the liver obtained from a whale shark (Rhincodon typus) stranded in Mexico. Mean ± standard error concentrations in µg g-1 wet weight were for zinc (Zn) RL: 22.5 ± 2.1; LL: 26.5 ± 7.1, arsenic (As) RL: 33.0 ± 1.6; LL: 20.0 ± 9.9 and cadmium (Cd) RL: 15.5 ± 0.9; LL...

In this study we present the first attempt at modelling the feeding behaviour of whale sharks using a machine learning analytical method. A total of eight sharks were monitored with tri‐axial accelerometers and their foraging behaviours were visually observed. Our results highlight that the random forest model is a valid and robust approach to pred...

The whale shark is an endangered species that usually feeds in coastal areas of highly productive seas such as the Gulf of California, Mexico. This study aims to describe the effect of sea surface temperature, chlorophyll a, bathymetry and slope on the habitat suitability of whale sharks in three important aggregation sites of the Gulf of Californi...

The use of stable isotope analysis has proven to be a reliable approach to investigate the diet of whale sharks in their natural habitat. A total of 63 whale sharks (50♂, 13♀) were sampled from the two localities (La Paz Bay n = 32, Yucatan Peninsula n = 31) in Mexico. Isotopic signatures differed greatly between both localities with mean values fo...

Marine animal tracking has become one of the major tools used to understand the behavior and ecology of a multitude of species in the ocean, thus there is an increasing body of knowledge about this subject worldwide, particularly for sharks. Nevertheless, little was known of the movement patterns of shark in the Mexican Pacific (MXP) and Gulf of Ca...

Background: Bahía de la Paz, Mexico have seasonal blooms of planktonic prey that support a range of marine species including whale sharks (Rhincodon typus). Goals: This study includes the first sampling cycle that covers all climatic seasons, to know changes in the abundance and composition of zooplankton in the coastal waters off the El Mogote Sa...

The whale shark is the world’s largest filter feeding shark and holds international protection as an endangered species. It is known to form seasonal aggregations linked to blooms of zooplanktonic organisms. The aim of this study was to investigate whether whale shark foraging behaviors are related to the density and/or concentration of available p...

Background. Bahía de la Paz, Mexico have seasonal blooms of planktonic prey that support a range of marine species including whale sharks (Rhincodon typus). Goals. This study includes the first sampling cycle that covers all climatic seasons, to know changes in the abundance and composition of zooplankton in the coastal waters off the El Mogote San...

Mercury and selenium were measured for first time in the endangered species whale shark (Rhyncodon typus) from two areas of the Gulf of California, Bahía Los Angeles (BLA) and Bahía La Paz (LAP) using dermal biopsies of seventy specimens. Additionally, nineteen zooplankton samples from LAP were analysed. Concentrations (ng/g, wet weight (ww)) in bi...

The number of individual whale shark Rhincodon typus sightings registered October 2015–March 2018 in Bahia de La Paz, Mexico, ranged from 73 to 129 animals per season (total 1662), with the majority of them identified as males. Density plot maps showed high correlations in sightings between sample seasons and revealed potential hotspot areas. Our s...

This paper is the first report with morphometric measurements in the Eastern Tropical Pacific of a deceased 5.48 m juvenile whale shark Rhincodon typus, from a rare stranding in La Paz Bay in the Gulf of California, Mexico. Biological measurements and age estimation are provided by the analysis of photographs and growth in rings from vertebrae.

Background: By minimizing energetic costs and maximizing food intake animals are able to increase the amount of energy available to them for growth and reproduction, ultimately increasing their fitness. We aimed to identify and characterize behaviors of whale shark by applying machine learning algorithms on accelerometry data, which has never been...

The present study analyses whale shark Rhincodon typus stranding in the Gulf of California, Mexico, reported by the public, scientists, authorities and artisanal fishermen. A total of 14 strandings were documented during the period 2001–2018. The total length of R. typus ranged from 350–1,102 cm, with a sex ratio of 3.5:1 (males: females). This stu...

The whale shark Rhincodon typus (Smith 1829) is an internationally protected species highly susceptible to the fisheries that could exist in coastal aggregation areas. In the Gulf of California, the seasonal presence of whale sharks is predictable and well studied. However, there is no published information regarding strandings, anatomical observat...

The Bay of La Paz plays host to annual blooms of planktonic prey items that support large marine species such as whale sharks (R.typus). This study aimed to analyze the seasonal zooplankton abundance in a known aggregation site for whale sharks in order to understand the importance of different taxonomic groups to these plankton feeders. A total of...

The Gulf of California represents an important hotspot for whale shark (Rhincodon typus) aggregation. Anthropogenic activities and natural sources could expose sharks to high levels of trace elements (TEs). To deter-minate these levels in this endangered species, concentrations of As, Cd, Cu, Pb and Zn (in ng/g ww) were measured in 130 whale shark...