scholarly journals The ecological connectivity of whale shark aggregations in the Indian Ocean: a photo-identification approach

2016 ◽  
Vol 3 (11) ◽  
pp. 160455 ◽  
Author(s):  
Samantha Andrzejaczek ◽  
Jessica Meeuwig ◽  
David Rowat ◽  
Simon Pierce ◽  
Tim Davies ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Time Frame ◽  
Ocean Basin ◽  
Identification System ◽  
Whale Shark ◽  
Monte Carlo Simulation Study ◽  
Photo Identification ◽  
Christmas Island ◽  
Modelling Studies ◽  
Whale Sharks

Genetic and modelling studies suggest that seasonal aggregations of whale sharks ( Rhincodon typus ) at coastal sites in the tropics may be linked by migration. Here, we used photo-identification (photo-ID) data collected by both citizen scientists and researchers to assess the connectedness of five whale shark aggregation sites across the entire Indian Ocean at timescales of up to a decade. We used the semi-automated program I 3 S (Individual Interactive Identification System) to compare photographs of the unique natural marking patterns of individual whale sharks collected from aggregations at Mozambique, the Seychelles, the Maldives, Christmas Island (Australia) and Ningaloo Reef (Australia). From a total of 6519 photos, we found no evidence of connectivity of whale shark aggregations at ocean-basin scales within the time frame of the study and evidence for only limited connectivity at regional (hundreds to thousands of kilometres) scales. A male whale shark photographed in January 2010 at Mozambique was resighted eight months later in the Seychelles and was the only one of 1724 individuals in the database to be photographed at more than one site. On average, 35% of individuals were resighted at the same site in more than one year. A Monte Carlo simulation study showed that the power of this photo-ID approach to document patterns of emigration and immigration was strongly dependent on both the number of individuals identified in aggregations and the size of resident populations.

scholarly journals Sizing and scarring of whale shark (Rhincodon typus Smith, 1828) in the Cenderawasih Bay National Park

2021 ◽  
Vol 21 (3) ◽  
pp. 199-213
Author(s):  
Yusup A Jentewo ◽  
Roni Bawole ◽  
Tresia S Tururaja ◽  
Mudjirahayu Mudjirahayu ◽  
Zeth Parinding ◽  
...  
Keyword(s):  
National Park ◽  
The Body ◽  
Whale Shark ◽  
Gill Slit ◽  
Rhincodon Typus ◽  
Photo Identification ◽  
Dorsal Fin ◽  
Total Length ◽  
Whale Sharks ◽  
Photo Collection

This study aims to determine the total length and scar condition of the body of whale sharks (Rhincodon typus) in Cendrawasih Bay National Park (TNTC), Papua-Indonesia. Photo-identification was used to identify individuals of the whale shark R. typus based on spot patterns behind the last gill slit of each individual. Photo-identification was also used to determine the scar of the whale shark. The total length of whale sharks were estimated based on the length of a snorkeller (assumed to be 1.6 m) swimming alongside the whale shark. We identified 21 individuals of R. typus. Of these 21 individuals, 14 were new sightings and seven were re-sightings that have been recorded in the previous photo collection database. R. typus ranged in size from 2 to 5 m total length (average 3.78 m, ±0,86, N= 21). Based on their size, all individuals of whale shark were categorized as juvenile. 52% of R. typus identified had scars and 38 % were not and 10% were unknown. The majority of whale sharks had amputation (12 individuals) and abrasion (7 individuals) scars. Scars occurred most often on the caudal fin and dorsal fin, five and four individuals respectively. This information is useful for understanding potential threats and designing better management programmes for R. typus conservation in TNTC.

scholarly journals Regional connectivity of whale sharks demonstrated using photo-identification – Western Atlantic, 1999 - 2013

2013 ◽  
Author(s):  
Jennifer McKinney ◽  
Eric R Hoffmayer ◽  
Jason Holmberg ◽  
Rachel Graham ◽  
Rafael de la Parra ◽  
...  
Keyword(s):  
Population Size ◽  
Transition Probabilities ◽  
Regional Cooperation ◽  
Individual Heterogeneity ◽  
Whale Shark ◽  
Western Atlantic ◽  
Entire Study ◽  
Photo Identification ◽  
Initial Identification ◽  
Whale Sharks

Background: Although whale sharks (Rhincodon typus) occur circum-globally, most studies focus on feeding aggregations in small regional areas. Photo identification is a proven tool in assessing population size and structure. While population estimates have been obtained for individual aggregation sites, there has been a lack of broader estimates despite known movement. The aim of this work is to demonstrate connectivity throughout the Gulf of Mexico (GOM) and Caribbean, and provide the first regional population estimate. Methods: Photographs submitted to the ECOCEAN Whale Shark Photo-ID Library Sightings were used to identify individual sharks using techniques described in Holmberg et al. (2009). Sightings data were used to assess the lagged identification rate (LIR) in order to investigate residency, regional mixing, population size, and transition probabilities using modules within SOCPROG 2.4. Results: Identifications from 1998 – 2013, were obtained from Belize (n =132), Mexico (n=3642), Honduras (n = 360), and the USA (n=147). Fifty-four individual sharks were seen in more than one country and used for analysis. For the entire study area, LIR decreased rapidly between one and 64-127 (mean 94.4) days then slightly increased between 256-511 (mean 381.2) days, suggesting a near-annual resighting periodicity. Estimates of mean population size from the best-fitting model were 1897.39 ± 414.30 S.E. (95% C.I. 1191.77 – 2784.03). Evidence suggests individual heterogeneity in movement patterns. Resightings were most likely to occur in the country where initial identification occurred, with the exception of Belize. The highest site fidelity was in Mexico, followed by USA. Conclusions: This study demonstrated individual heterogeneity, fidelity to initial identification site and regional linkages. These data suggest that national and regional cooperation is required for successful whale shark management in the West Atlantic.

scholarly journals Seasonal aggregation of juvenile whale sharks (Rhincodon typus) at Christmas Island, Indian Ocean

Coral Reefs ◽  
2009 ◽  
Vol 28 (3) ◽  
pp. 577-577 ◽  
Author(s):  
J-P. A. Hobbs ◽  
A. J. Frisch ◽  
T. Hamanaka ◽  
C. A. McDonald ◽  
J. J. Gilligan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Rhincodon Typus ◽  
Christmas Island ◽  
Whale Sharks

scholarly journals Demographics and feeding ecology of whale sharks at Mafia Island, Tanzania

2013 ◽  
Author(s):  
Edgar F Cagua ◽  
Jesse Cochran ◽  
Chris Rohner ◽  
Mathias M Igulu ◽  
Jason Rubens ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Site Fidelity ◽  
Western Indian Ocean ◽  
Sampling Effort ◽  
Whale Shark ◽  
Important Region ◽  
Whale Sharks ◽  
Acoustic Array ◽  
And Gender ◽  
Almost All

Background. The Western Indian Ocean is a globally important region for the whale shark Rhincodon typus, with well-studied coastal aggregation sites in southern Mozambique, Seychelles and Djibouti. Here we present an overview of a new study at Mafia Island, Tanzania. Methods. We monitored whale shark abundances on 103 boat trips from October 2012–March 2013. We also used passive acoustic telemetry (VEMCO® V16 tags) and photographic identification to monitor the residency times and local movements of 29 tagged individuals. Shark sizes were estimated using laser photogrammetry. Results. In total we observed 87 individual sharks with a mean of 5.1 ± 5.2 (± SD) per trip and a peak in December of 8.2 ± 6.3. Total length ranged from 4.1 to 9.7 m and almost all sharks were immature. After boat-based visual observations dropped to zero in March 2013 (with the same ongoing sampling effort), the acoustic array still detected 75% of tagged sharks. Tagged individuals were detected by the acoustic array for 73 ± 40 days on average. They showed a strong site fidelity to a 15 km2 area in the inner part of the bay and then progressively moved offshore at the end of the season, matching a decrease in plankton abundance. Sharks were mostly observed feeding on dense patches of the pelagic shrimp Lucifer hanseni, often in association with planktivorous fishes. Photo IDs from 2007-09 and 2012-13 indicate that a large proportion of the juvenile individuals return to Mafia Island each spring-summer. Conclusion. The size range and gender distribution of whale sharks at Mafia Island is similar to other coastal aggregations in the Indian Ocean, but the relatively high site fidelity and residency time stands in contrast.

scholarly journals Demographics and feeding ecology of whale sharks at Mafia Island, Tanzania

2013 ◽  
Author(s):  
Edgar F Cagua ◽  
Jesse Cochran ◽  
Chris Rohner ◽  
Mathias M Igulu ◽  
Jason Rubens ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Site Fidelity ◽  
Western Indian Ocean ◽  
Sampling Effort ◽  
Whale Shark ◽  
Important Region ◽  
Whale Sharks ◽  
Acoustic Array ◽  
And Gender ◽  
Almost All

Background. The Western Indian Ocean is a globally important region for the whale shark Rhincodon typus, with well-studied coastal aggregation sites in southern Mozambique, Seychelles and Djibouti. Here we present an overview of a new study at Mafia Island, Tanzania. Methods. We monitored whale shark abundances on 103 boat trips from October 2012–March 2013. We also used passive acoustic telemetry (VEMCO® V16 tags) and photographic identification to monitor the residency times and local movements of 29 tagged individuals. Shark sizes were estimated using laser photogrammetry. Results. In total we observed 87 individual sharks with a mean of 5.1 ± 5.2 (± SD) per trip and a peak in December of 8.2 ± 6.3. Total length ranged from 4.1 to 9.7 m and almost all sharks were immature. After boat-based visual observations dropped to zero in March 2013 (with the same ongoing sampling effort), the acoustic array still detected 75% of tagged sharks. Tagged individuals were detected by the acoustic array for 73 ± 40 days on average. They showed a strong site fidelity to a 15 km2 area in the inner part of the bay and then progressively moved offshore at the end of the season, matching a decrease in plankton abundance. Sharks were mostly observed feeding on dense patches of the pelagic shrimp Lucifer hansoni, often in association with planktivorous fishes. Photo IDs from 2007-09 and 2012-13 indicate that a large proportion of the juvenile individuals return to Mafia Island each spring-summer. Conclusion. The size range and gender distribution of whale sharks at Mafia Island is similar to other coastal aggregations in the Indian Ocean, but the relatively high site fidelity and residency time stands in contrast.

The arrival of Islam

2017 ◽  
Author(s):  
Carool Kersten
Keyword(s):  
Middle East ◽  
Indian Ocean ◽  
Southeast Asia ◽  
South Asia ◽  
Geographical Area ◽  
Time Frame ◽  
Ocean Basin ◽  
Process Time ◽  
Political Boundaries ◽  
The Republic

The arrival of Islam in Indonesia is bound up with developments in the wider geographical area of Southeast Asia. This chapter presents a broader angle than the current political boundaries of the Republic of Indonesia. The chapter addresses the question of the relatively late local acceptance of Islam, even though Southeast Asia’s contacts with the Middle East and South Asia go back to pre-Islamic times. Based on a critical assessment of the historiography of Southeast Asian Islam, the chapter will identify four key issues that are relevant for a balanced account of the Islamization process: Time frame (13th century); Provenance (theories propose various origins: South Asia, Middle East, and China; Agency (Merchants, religious professionals (missionaries, Sufis), local involvement); Motivations (political, commercial, colonial, religious factors). The emerging picture consists of a variety of starting points, numerous modalities for the diffusion of Islam, positioning the Indian Ocean basin as a vital contact zone. The associated ‘single ocean concept’ turned it into a ‘neutral water’ links the history of the Islamization of Southeast Asia to the newly emerging scholarly field of Indian Ocean studies

scholarly journals Demographics and feeding ecology of whale sharks at Mafia Island, Tanzania

2013 ◽  
Author(s):  
Edgar F Cagua ◽  
Jesse Cochran ◽  
Chris Rohner ◽  
Mathias M Igulu ◽  
Jason Rubens ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Site Fidelity ◽  
Western Indian Ocean ◽  
Sampling Effort ◽  
Whale Shark ◽  
Important Region ◽  
Whale Sharks ◽  
Acoustic Array ◽  
And Gender ◽  
Almost All

Background. The Western Indian Ocean is a globally important region for the whale shark Rhincodon typus, with well-studied coastal aggregation sites in southern Mozambique, Seychelles and Djibouti. Here we present an overview of a new study at Mafia Island, Tanzania. Methods. We monitored whale shark abundances on 103 boat trips from October 2012–March 2013. We also used passive acoustic telemetry (VEMCO® V16 tags) and photographic identification to monitor the residency times and local movements of 29 tagged individuals. Shark sizes were estimated using laser photogrammetry. Results. In total we observed 87 individual sharks with a mean of 5.1 ± 5.2 (± SD) per trip and a peak in December of 8.2 ± 6.3. Total length ranged from 4.1 to 9.7 m and almost all sharks were immature. After boat-based visual observations dropped to zero in March 2013 (with the same ongoing sampling effort), the acoustic array still detected 75% of tagged sharks. Tagged individuals were detected by the acoustic array for 73 ± 40 days on average. They showed a strong site fidelity to a 15 km2 area in the inner part of the bay and then progressively moved offshore at the end of the season, matching a decrease in plankton abundance. Sharks were mostly observed feeding on dense patches of the pelagic shrimp Lucifer hanseni, often in association with planktivorous fishes. Photo IDs from 2007-09 and 2012-13 indicate that a large proportion of the juvenile individuals return to Mafia Island each spring-summer. Conclusion. The size range and gender distribution of whale sharks at Mafia Island is similar to other coastal aggregations in the Indian Ocean, but the relatively high site fidelity and residency time stands in contrast.

DNA evidence of whale sharks (Rhincodon typus) feeding on red crab (Gecarcoidea natalis) larvae at Christmas Island, Australia

2009 ◽  
Vol 60 (6) ◽  
pp. 607 ◽  
Author(s):  
M. G. Meekan ◽  
S. N. Jarman ◽  
C. McLean ◽  
M. B. Schultz
Keyword(s):  
Small Subunit ◽  
Whale Shark ◽  
Faecal Dna ◽  
Rhincodon Typus ◽  
Christmas Island ◽  
Crab Larvae ◽  
Pcr Products ◽  
Whale Sharks ◽  
Primer Sets ◽  
Gecarcoidea Natalis

Whale sharks (Rhincodon typus) are thought to aggregate in nearshore waters around Christmas Island (105°37′E, 10o29′S) to consume the marine larvae of the endemic red land crab (Gecarcoidea natalis). However, there have been no direct observations of sharks feeding on crab larvae. Whale shark faeces were analysed using genetic testing to confirm the presence of crab larvae in their diet. Primers were designed for amplifying two Gecarcoidea natalis mitochondrial small-subunit (mtSSU) rDNA regions. Gel electrophoresis of polymerase chain reaction (PCR) products amplified from whale shark faecal DNA produced bands of the expected size for G. natalis templates. Specificity of both primer sets for G. natalis mtSSU rDNA was expected to be high from comparisons with mtSSU rDNA regions from closely related crabs and we confirmed their specificity empirically. The amplification of fragments from faecal DNA of the same size as those produced from G. natalis DNA indicates that the whale shark had been feeding on G. natalis and that enough of the crab DNA survived digestion to be detected by these PCRs. Our study provides further evidence that aggregations of whale sharks in coastal waters occur in response to ephemeral but predictable increases in planktonic prey.

Can citizen science monitor whale-shark aggregations? Investigating bias in mark–recapture modelling using identification photographs sourced from the public

2012 ◽  
Vol 39 (8) ◽  
pp. 696 ◽  
Author(s):  
Tim K. Davies ◽  
Guy Stevens ◽  
Mark G. Meekan ◽  
Juliane Struve ◽  
J. Marcus Rowcliffe
Keyword(s):  
Conservation Status ◽  
Accurate Estimation ◽  
Encounter Rate ◽  
Whale Shark ◽  
Mark Recapture ◽  
The Public ◽  
Photo Identification ◽  
Online Databases ◽  
Whale Sharks ◽  
Using Data

Context The conservation status of the whale shark, Rhincodon typus, remains uncertain. Throughout their range, whale sharks are a focus for wildlife tourism and many identification photographs taken by tourists have become available online, presenting a potentially valuable source of data for monitoring populations using mark–recapture techniques. However, the suitability of these photographs for mark–recapture models has yet to be investigated. Aims We explore the suitability of identification-photographs available from online databases to produce assessments of life-history parameters and conservation status of whale sharks in the Maldives. Methods To test the validity of using publically sourced images, we used photo-identification images collected from both experienced researchers and tourists between 2003 and 2008 to construct two databases. Images taken by tourists were compiled from online databases. Researcher and public databases were analysed separately and the results of mark–recapture models then compared. Key results The dataset constructed from online public databases did not violate the assumptions of mark–recapture modelling. Estimates of parameters and abundance obtained from models using these data were similar to those produced using data provided by experienced researchers. Conclusions Publically sourced data allowed for the accurate estimation of abundance of whale sharks. These estimates were not confounded by the suitability of photographs, probably because of the high encounter rate in the aggregation, the high residency rate of sharks and the retrospective nature of photo-identification, which limited heterogeneity in capture probability between marked and unmarked sharks. Implications Our findings support the use of publically sourced data for use in mark–recapture studies of whale sharks, at least in situations where sharks are resident to the location. This approach will be useful in regions where data collected by tourists are available online, and research funding is limited.

scholarly journals Whale shark regional research collaboration between Utila, Honduras and Isla Mujeres, México.

2013 ◽  
Author(s):  
Beatriz Eugenia Galvan ◽  
Steve Fox ◽  
Rafael de la Parra
Keyword(s):  
Research Collaboration ◽  
Western Hemisphere ◽  
Individual Identification ◽  
Whale Shark ◽  
Western Atlantic ◽  
Photo Identification ◽  
Large Numbers ◽  
Positive Individual ◽  
Whale Sharks ◽  
Bay Islands

Background. Utila, Bay Islands, Honduras, is one of the few locations in the Western Hemisphere where whale sharks can be spotted year-round, while off the northeastern Yucatan Peninsula, Mexico, they aggregate during summertime in large numbers of up to several hundred. When our research on these sharks began, we hypothesized they migrate south to north from Honduras, then to Belize and finally to Mexico. Methods. From 2007-2013, we documented the presence of whale sharks in both locations using visual tags and photo-identification, to establish the connections between the sites. The international whale shark library ECOCEAN was an important tool for this research. Results. Our research collaboration began on 2007, we have registered and photographed 59 “encounters”, from these, 9 were “Belizeans” and 8 become new Honduran recruits. While 5 more remain as unassigned since positive individual identification has not been possible yet. From our database and ECOCEAN compare, we know that we share several individuals in between the two locations, and some even visit Belize. Conclusion. At least some individuals of the western Atlantic population travel between Honduras and Mexico, and some hang around Belize in between as well.We conclude that whale sharks wander in the Caribbean, the Gulf of México and the open Atlantic Ocean, and aggregate when food blooms are available.

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