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Pierce S.J.,Manta Ray and Whale Shark Research Center | Pierce S.J.,All Out Africa Research Unit | Mendez-Jimenez A.,All Out Africa Research Unit | Collins K.,All Out Africa Research Unit | And 2 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2010

The whale shark (Rhincodon typus) is a popular focal species within the global marine tourism industry. Although this has contributed to increased protection being granted to the species in several countries, tourism itself can be detrimental to the sharks in the absence of appropriate management. Potential impacts can be mitigated, at least in the short term, by adherence to well-designed interaction guidelines. A burgeoning marine tourism industry based on swimming with whale sharks has developed at Tofo Beach in Mozambique. However, no formal management is currently in place at this site. The behaviour of whale sharks during interactions with boats and swimmers were recorded during 137 commercial snorkelling trips run from Tofo Beach over a 20 month period. Whale sharks were encountered on 87% of trips, which operated year-round. Boat proximity and shark size were significant predictors of avoidance behaviour. No avoidance responses were recorded at >20 m boat distance. The mean in-water interaction time between sharks and swimmers was 8 min 48 s overall. There was a significant decrease in interaction times during encounters where sharks expressed avoidance behaviours, and also in cases where sharks had expressed boat avoidance behaviour before swimmers entered the water. It is suggested that mean encounter times can be extended through adherence to a basic Code of Conduct for operators and swimmers that enforces minimum distances between the sharks, boats and swimmers. Using encounter time as a measure of the 'success' of interactions holds promise, as longer encounters appear to be indicative of lower impacts on sharks while also providing higher customer satisfaction for swimmers. Copyright © 2010 John Wiley & Sons, Ltd.


Holmes B.J.,University of Queensland | Pepperell J.G.,Pepperell Research and Consulting Pty Ltd | Griffiths S.P.,CSIRO | Jaine F.R.A.,University of Queensland | And 3 more authors.
Marine Biology | Year: 2014

Partial migration is considered ubiquitous among vertebrates, but little is known about the movements of oceanodromous apex predators such as sharks, particularly at their range extents. PAT-Mk10 and SPOT5 electronic tags were used to investigate tiger shark (Galeocerdo cuvier) spatial dynamics, site fidelity and habitat use off eastern Australia between April 2007 and May 2013. Of the 18 tags deployed, 15 recorded information on depth and/or temperature, and horizontal movements. Tracking times ranged between four and 408 days, with two recovered pop-up archival tags allowing 63 days of high-resolution archived data to be analysed. Overall mean proportions of time-at-depth revealed that G. cuvier spent the majority of time-at-depths of <20 m, but undertook dives as deep as 920 m. Tagged sharks occupied ambient water temperatures from 29.5 °C at the surface to 5.9 °C at depth. Deep dives (>500 m) occurred mostly around dawn and dusk, but no definitive daily dive patterns were observed. Horizontal movements were characterised by combinations of resident and transient behaviour that coincided with seasonal changes in water temperature. While the majority of movement activity was focused around continental slope waters, large-scale migration was evident with one individual moving from offshore Sydney, Australia, to New Caledonia (c. 1,800 km) in 48 days. Periods of tiger shark residency outside of Australia’s fisheries management zones highlight the potential vulnerability of the species to unregulated fisheries and the importance of cross-jurisdictional arrangements for species’ management and conservation. © 2014, Springer-Verlag Berlin Heidelberg.


Rohner C.A.,CSIRO | Rohner C.A.,University of Queensland | Rohner C.A.,Manta Ray and Whale Shark Research Center | Couturier L.I.E.,CSIRO | And 7 more authors.
Marine Ecology Progress Series | Year: 2013

Whale sharks Rhincodon typus are large filter-feeders that are frequently observed feeding in surface zooplankton patches at their tropical and subtropical coastal aggregation sites. Using signature fatty acid (FA) analyses from their subdermal connective tissue and stomach content analysis, we tested whether whale sharks in Mozambique and South Africa predominantly feed on these prey and/or what other prey they target. Arachidonic acid (20:4ω6; mean ± SD = 17.8 ± 2.0% of total FA), 18:0 and 18:1ω9c were major FA of whale sharks, while in contrast, coastal epipelagic zooplankton collected near feeding whale sharks had 22:6ω3 (docosahexaenoic acid), 16:0 and 20:5ω3 (eicosapentaenoic acid) as major FA. Stomach contents of 3 stranded sharks were dominated by mysids (61 to 92% of prey items), another one by sergestids (56%), and a fifth stomach was empty. The dominant mysids (82% index of relative importance) were demersal zooplankton that migrate into the water column at night, suggesting night-time feeding by whale sharks. High levels of bacterial FA in whale sharks (5.3 ± 1.4% TFA), indicating a detrital link, potentially via demersal zooplankton, also support night-time foraging activity. High levels of oleic acid (16.0 ± 2.5%) in whale sharks and their similarity with FA profiles of shrimp, mysids, copepods and myctophid fishes from the meso- and bathypelagic zone suggest that whale sharks also forage in deep-water. Our findings suggest that, in the patchy food environment of tropical systems, whale sharks forage in coastal waters during the day and night, and in oceanic waters on deep-water zooplankton and fishes during their long-distance movements. © The authors 2013. Open Access under Creative Commons by Attribution Licence.


Kashiwagi T.,University of Queensland | Kashiwagi T.,Queensland Government | Marshall A.D.,Manta Ray and Whale Shark Research Center | Bennett M.B.,University of Queensland | Ovenden J.R.,Queensland Government
Molecular Phylogenetics and Evolution | Year: 2012

Manta rays have been taxonomically revised as two species, Manta alfredi and M. birostris, on the basis of morphological and meristic data, yet the two species occur in extensive mosaic sympatry. We analysed the genetic signatures of the species boundary using a portion of the nuclear RAG1 (681 base pairs), mitochondrial CO1 (574. bp) and ND5 genes (1188. bp). The assay with CO1 sequences, widely used in DNA barcoding, failed to distinguish the two species. The two species were clearly distinguishable, however, with no shared RAG1 or ND5 haplotypes. The species were reciprocally monophyletic for RAG1, but paraphyletic for ND5 sequences. Qualitative evidence and statistical inferences using the 'Isolation-with-Migration models' indicated that these results were better explained with post-divergence gene flow in the recent past rather than incomplete lineage sorting with zero gene flow since speciation. An estimate of divergence time was less than 0.5. Ma with an upper confidence limit of within 1. Ma. Recent speciation of highly mobile species in the marine environment is of great interest, as it suggests that speciation may have occurred in the absence of long-term physical barriers to gene flow. We propose that the ecologically driven forces such as habitat choice played a significant role in speciation in manta rays. © 2012 Elsevier Inc.


Rohner C.A.,Manta Ray and Whale Shark Research Center | Rohner C.A.,University of Queensland | Rohner C.A.,CSIRO | Pierce S.J.,Manta Ray and Whale Shark Research Center | And 8 more authors.
Marine Ecology Progress Series | Year: 2013

Sightings of planktivorous elasmobranchs at their coastal aggregation sites are often linked to biological, environmental and temporal variables. Many large planktivorous elasmobranchs are also globally threatened species, so it is necessary to try and separate population trends from environmentally driven, short-term fluctuations. We investigated the influence of environmental variables on sightings of 3 species of planktivorous elasmobranchs off Praia do Tofo, Mozambique: the reef manta ray Manta alfredi, giant manta ray M. birostris and whale shark Rhincodon typus. We used 8- (2003 to 2011) and 6-yr (2005 to 2011) logbook data for manta rays and whale sharks, respectively, and constructed a generalised linear model with animal sightings as the response. Predictors included temporal (year, month, time of day), biological (plankton categories), oceanographic (water temperature, time from high tide, current direction and strength and wave height) and celestial (moon illumination) indices. These predictors best fitted reef manta ray sightings, a coastal species with high residency, but less so for the wider-ranging giant manta rays and whale sharks.We found a significant decline in the standardised sightings time series for the reef manta ray (88%) and whale shark (79%), but not for the giant manta ray. © Inter-Research 2013.


Couturier L.I.E.,University of Queensland | Couturier L.I.E.,CSIRO | Rohner C.A.,CSIRO | Rohner C.A.,Manta Ray and Whale Shark Research Center | And 10 more authors.
PLoS ONE | Year: 2013

Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope δ15N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ω6 polyunsaturated fatty acids and slightly enriched δ13C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs. © 2013 Couturier et al.


Town C.,University of Cambridge | Marshall A.,Manta Ray and Whale Shark Research Center | Sethasathien N.,University of Edinburgh
Ecology and Evolution | Year: 2013

For species which bear unique markings, such as natural spot patterning, field work has become increasingly more reliant on visual identification to recognize and catalog particular specimens or to monitor individuals within populations. While many species of interest exhibit characteristic markings that in principle allow individuals to be identified from photographs, scientists are often faced with the task of matching observations against databases of hundreds or thousands of images. We present a novel technique for automated identification of manta rays (Manta alfredi and Manta birostris) by means of a pattern-matching algorithm applied to images of their ventral surface area. Automated visual identification has recently been developed for several species. However, such methods are typically limited to animals that can be photographed above water, or whose markings exhibit high contrast and appear in regular constellations. While manta rays bear natural patterning across their ventral surface, these patterns vary greatly in their size, shape, contrast, and spatial distribution. Our method is the first to have proven successful at achieving high matching accuracies on a large corpus of manta ray images taken under challenging underwater conditions. Our method is based on automated extraction and matching of keypoint features using the Scale-Invariant Feature Transform (SIFT) algorithm. In order to cope with the considerable variation in quality of underwater photographs, we also incorporate preprocessing and image enhancement steps. Furthermore, we use a novel pattern-matching approach that results in better accuracy than the standard SIFT approach and other alternative methods. We present quantitative evaluation results on a data set of 720 images of manta rays taken under widely different conditions. We describe a novel automated pattern representation and matching method that can be used to identify individual manta rays from photographs. The method has been incorporated into a website (mantamatcher.org) which will serve as a global resource for ecological and conservation research. It will allow researchers to manage and track sightings data to establish important life-history parameters as well as determine other ecological data such as abundance, range, movement patterns, and structure of manta ray populations across the world. © 2013 The Authors. Ecology and Evolution.


Marshall A.D.,University of Queensland | Marshall A.D.,Manta Ray and Whale Shark Research Center | Dudgeon C.L.,University of Queensland | Bennett M.B.,University of Queensland
Marine Biology | Year: 2011

The size and structure of a photographically identified population of reef manta ray, Manta alfredi, were examined at aggregation sites over a four-year period in southern Mozambique. The use and standardisation of photo-ID techniques was examined as a minimally-intrusive means to study this species. Using these techniques, we report on the size, structure and seasonality of this population of M. alfredi. In total, 449 individuals were identified during this time period, 40.5% of which were re-sighted on at least one occasion. The longest period between re-sighting events was 1,252 days. During the study period, annual population size estimates for M. alfredi ranged from 149 to 454 individuals. The superpopulation size estimate for the entire study period was 802 individuals, the first reported for M. alfredi at a monitored aggregation site. A highly significant sex bias was evident with a female:male ratio of 3.55:1. The majority of rays (89.9% males; 49.7% females) were considered mature, with most individuals between 3.0 and 4.9 m in disc width. Manta alfredi were observed at the study sites in each month of the calendar year. The maximum number of individual rays seen per dive was 30. Large numbers of rays (20 + per dive) were seen in the months of November, December and January, which coincide with the breeding season. Natural markings were unique to individuals and did not change substantially with time, which provided further support for their use in the identification of individual M. alfredi over multiple years. Multiple re-sightings of individual M. alfredi suggest that many individuals in this population exhibit site fidelity to the examined aggregation sites. As target subsistence fishing for M. alfredi exists along the Mozambican coastline, management efforts to monitor and prevent overexploitation at these critical habitats should be a priority. © 2011 Springer-Verlag.


Marshall A.D.,Manta Ray and Whale Shark Research Center | Marshall A.D.,ECOCEAN United States | Pierce S.J.,Manta Ray and Whale Shark Research Center | Pierce S.J.,ECOCEAN United States
Journal of Fish Biology | Year: 2012

The use of photography to discriminate between individuals in a population using natural markings or aberrations is increasingly being utilized to support field research on elasmobranchs. This non-intrusive method has facilitated investigation of a wide variety of subjects including population composition, abundance estimates, residency and movement, demography and social behaviours. Here the first detailed review of photo-identification as a research technique for sharks and rays is provided, and its assumptions, current applications and potential highlighted. The limitations and practical considerations of photographic studies are also investigated with recommendations on initial survey design and ongoing data collection using current technology. Future directions are also explored with an emphasis on a move towards standardized approaches and automated recognition programmes to facilitate global collaborative work. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.


Marshall A.D.,University of Queensland | Marshall A.D.,Manta Ray and Whale Shark Research Center | Bennett M.B.,University of Queensland
Journal of Fish Biology | Year: 2010

The application of a photographic identification methodology using the unique ventral surface markings (natural spot patterns) of an observed population in southern Mozambique enabled many aspects of the reproductive ecology of reef manta rays Manta alfredi to be examined. The region encompassing the study site was identified as a mating ground for M. alfredi based on observations of mating events and fresh mating scars on females. The distribution of these pectoral fin scars was highly biased and indicated a strong lateralized behavioural trait, with 99% of these scars occurring only on the left pectoral fin. No other elasmobranch has been reported to display behavioural lateralization. The study region also acts as a birthing ground, with individuals typically giving birth in the austral summer period after a gestation of c. 1 year. Reproductive periodicity in M. alfredi was most commonly biennial, but a few individuals were pregnant in consecutive years, confirming an annual ovulatory cycle. The production of a single pup appears to be the normal situation, although observations in the wild as well as during opportunistic dissections of individuals killed by fisheries revealed that two pups are conceived on occasion. Many aspects of the study have contributed to the limited baseline data currently available for this species and have highlighted the potential need for more conservative conservation strategies. © 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.

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