ArticlePDF Available

Whale Sharks, Rhincodon typus, Aggregate around Offshore Platforms in Qatari Waters of the Arabian Gulf to Feed on Fish Spawn

Authors:
  • Elasmo Project

Abstract and Figures

Whale sharks, Rhincodon typus, are known to aggregate to feed in a small number of locations in tropical and subtropical waters. Here we document a newly discovered major aggregation site for whale sharks within the Al Shaheen oil field, 90 km off the coast of Qatar in the Arabian Gulf. Whale sharks were observed between April and September, with peak numbers observed between May and August. Density estimates of up to 100 sharks within an area of 1 km(2) were recorded. Sharks ranged between four and eight metres' estimated total length (mean 6.92±1.53 m). Most animals observed were actively feeding on surface zooplankton, consisting primarily of mackerel tuna, Euthynnus affinis, eggs.
Content may be subject to copyright.
Whale Sharks,
Rhincodon typus
, Aggregate around
Offshore Platforms in Qatari Waters of the Arabian Gulf
to Feed on Fish Spawn
David P. Robinson
1
*, Mohammed Y. Jaidah
2
, Rima W. Jabado
3
, Katie Lee-Brooks
4
, Nehad M. Nour El-
Din
2
, Ameena A. Al Malki
2
, Khaled Elmeer
2
, Paul A. McCormick
2
, Aaron C. Henderson
5
, Simon J. Pierce
6
,
Rupert F. G. Ormond
1,7
1Herriot-Watt University, Edinburgh, United Kingdom, 2Qatar Ministry of Environment, Doha, Qatar, 3UAE University, Abu Dhabi, United Arab Emirates, 4Environment
Department, University of York, Heslington, York, United Kingdom, 5The School for Field Studies, Center for Marine Resource Studies, Turks & Caicos Islands, 6Marine
Megafauna Foundation/ECOCEAN USA, Tofo Beach, Mozambique, 7Marine Conservation International, Edinburgh, United Kingdom
Abstract
Whale sharks, Rhincodon typus, are known to aggregate to feed in a small number of locations in tropical and subtropical
waters. Here we document a newly discovered major aggregation site for whale sharks within the Al Shaheen oil field,
90 km off the coast of Qatar in the Arabian Gulf. Whale sharks were observed between April and September, with peak
numbers observed between May and August. Density estimates of up to 100 sharks within an area of 1 km
2
were recorded.
Sharks ranged between four and eight metres’ estimated total length (mean 6.9261.53 m). Most animals observed were
actively feeding on surface zooplankton, consisting primarily of mackerel tuna, Euthynnus affinis, eggs.
Citation: Robinson DP, Jaidah MY, Jabado RW, Lee-Brooks K, Nour El-Din NM, et al. (2013) Whale Sharks, Rhincodon typus, Aggregate around Offshore Platforms
in Qatari Waters of the Arabian Gulf to Feed on Fish Spawn. PLoS ONE 8(3): e58255. doi:10.1371/journal.pone.0058255
Editor: Maura Geraldine Chapman, University of Sydney, Australia
Received December 14, 2012; Accepted February 5, 2013; Published March 13, 2013
Copyright: ß2013 Robinson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The research project was funded through the Qatar Ministry of Environment. Direct collaborators within the Qatar Ministry of Environment also
provided advice, support in study design, data collection and analysis. DPR’s work on this manuscript was supported by funding from the Save Our Seas
Foundation. SJP’s work on this manuscript was supported by the Shark Foundation and private donors. The journal publication fees for this manuscript were
provided by Maersk Oil. All other funders, apart from collaborators from the Qatar Ministry of Environment, had no role in the preparation or decision to publish
the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: sharkwatcharabia@gmail.com
Introduction
The whale shark, Rhincodon typus, has a circumglobal distribution
in tropical and subtropical oceans [1]. It is the world’s largest
extant fish, yet there are still significant gaps in our understanding
of its behaviour and ecology [2]. Furthermore, while of great
popular interest and value to marine wildlife tourism [3,4],
populations have been impacted by fisheries throughout the Indo-
Pacific [5–10] Whale sharks have therefore been classified as
Vulnerable on the IUCN Red List of Threatened Species [11] and
listed on Appendix II of the Convention on International Trade of
Endangered Species (CITES) in 2002.
Whale sharks are known to feed on a variety of planktonic and
nektonic organisms [1] by flexibly employing surface ram feeding,
sub-surface filter feeding or stationary suction feeding [12,13].
Whale sharks are known to aggregate seasonally in a number of
areas, including Western Australia [14], Belize [15], Northern
Mexico [16], Philippines [17], Djibouti [18], Mozambique [19],
the Maldives [20,21] and Seychelles [22,23], usually in response to
a regular or seasonally driven planktonic food source [24,25].
These aggregations all occur close to coasts or reefs and are usually
dominated by juvenile and sub-adult males [21,26–29]. In most
locations, research is based on the mark-recapture of photo-
identified sharks. Each individual can be distinguished by their
distinctive, persistent natural spot patterns [30,31], and many have
been shown to return in subsequent years to the same location
[21,28,29,32]. Satellite-linked pop-up archival and other satellite
tags have been deployed to show that sharks are capable of
significant long-distance movements, often through a series of
political jurisdictions [16,23,33–39]. Given that coastal aggrega-
tion sites are characterised by size-and sexual-segregation,
increased study of offshore sites is a key requirement to further
conservation and management of the species [2]. Currently, little
is known about the offshore occurrence of whale sharks, although
Sequeira et al. [40] used data from oceanic purse-seine fleets to
document their pelagic occurrence within the Indian Ocean.
There have been few previous records of whale sharks in the
Arabian Gulf and adjacent seas. Data from inside the Arabian
Gulf include encounters from Iraq [41] and Kuwait [42], while
Brown [43] reported sightings from the UAE between 1987 and
1992, including five encounters inside the Arabian Gulf and one
on the UAE east coast, with sharks of up to 10 m in length. In a
1981 demersal fisheries report relating to the Arabian Gulf and
Gulf of Oman, Sivasubramaniam & Yesaki [44] listed the whale
shark as an unmarketable species for the region. Beech [45]
recorded a further encounter on the Arabian Gulf side of the UAE
in 2002. Immediately outside the Arabian Gulf, White & Barwani
[46,47] reported several encounters from the Straits of Hormuz
and Gulf of Oman, and Blegvad [48] had two encounters in
Iranian waters in the Strait of Hormuz.
PLOS ONE | www.plosone.org 1 March 2013 | Volume 8 | Issue 3 | e58255
More recently however, with the large increase in populations of
Gulf States and the associated growth in the SCUBA diving and
boating community, there has been a marked increase in whale
shark encounters, particularly by divers in the Musandam region
of Oman. To access these data, the senior author established a
regional public sightings initiative, ‘‘Sharkwatch Arabia’’, in June
2010 to begin collating reports of whale shark sightings from the
Arabian Gulf and adjacent waters. When anecdotal reports
suggested that a previously unknown aggregation of up to 100
or more whale sharks was occurring during the boreal summer
months in the Al Shaheen Oil field (S. Stig, pers. comm. 2010),
approximately 90 km off the coast of Qatar in the Gulf, the
opportunity was taken to investigate the occurrence of such a large
aggregation in offshore waters. Here we provide details on the
biological phenomena driving this aggregation, along with the
numbers, temporal occurrence and population structure of sharks
sighted at Al Shaheen.
Materials and Methods
No specific permits were required for any part of this research.
The project was carried out in conjunction with the Qatar
Ministry of Environment. All research activities took place within
Qatari waters and the sampling did not involve endangered or
protected species.
Study Area
The Al Shaheen gas field lies approximately 145 km north of
Doha, the Qatari capital, and 90 km offshore in the Arabian Gulf,
which is a shallow, almost enclosed body of water with an average
depth of 30 m (Figure 1). The Gulf is exposed to extreme
environmental conditions, with sea surface temperatures regularly
exceeding 35
˚C during summer and dropping below 15
˚C during
the winter, while a lack of precipitation and high evaporation rates
result in salinity in excess of 39 ppt [49]. Project surveys were
undertaken in an area covering approximately 300 km
2
of the gas
field, bounded by eight fixed gas platforms.
Platform Based Observations
Volunteer Maersk Oil staff, stationed on the platforms, provided
reports of opportunistic observations of whale sharks. These
sightings, often supported by video and photography, were logged
throughout the May to December 2011 study period. The
platforms are elevated, with 360uviews to the water from most
areas. All workers were briefed to report sightings and to record
the time of the sighting along with the estimated number of
individual sharks to their designated sightings collator. Only sharks
reported during daylight hours were used in the final figures. One
person stationed on each of the eight platforms was asked to collate
sightings on a daily basis from their platform workers and log every
time a shark or group of sharks was observed. Only the maximum
number of sharks observed per day in one group was used in
analysis so as to eliminate repeat observations. The website www.
whaleshark.org was used to provide archived reports of whale
shark occurrence in the region that occurred prior to the start of
this study.
Boat Based Observations
Eight boat-based surveys were conducted between 23
rd
April
2011 and 8
th
October, 2011. The surveys were carried out from a
10 m vessel powered by twin 250 cc engines, which took an
average of two hours to reach the study area. Survey start times
varied between 5 and 9 a.m. During each survey, a set route was
followed from one to the next of the eight fixed gas platforms.
Whale sharks were detected from sightings of the first dorsal and
or caudal fin breaking the surface of the water. For logistical
reasons no surveys could be conducted during August and
September or during periods when wind speed exceeded 12 knots.
Upon sighting an individual or an aggregation of sharks, a GPS
location and time were recorded and a team of between four and
six researchers entered the water, using snorkelling gear and
equipped with digital cameras. Researchers took photographs of
the flank area on each shark behind the fifth gill slit and above the
pectoral fin for the purposes of individual identification [30].
Photographs were also taken of any notable scars. Where possible,
the size of each animal was estimated, usually by comparison with
the boat or another snorkeler, and the sex of each animal was
determined by the presence (males) or absence (females) of
claspers. After completion of in-water observations, the numbers of
whale sharks were estimated based on observations both in water
and from the boat. Subsequently, images collected in the field were
catalogued and then processed using I
3
S software [50].
Plankton Sampling and Analysis
On each trip, one sample was taken at each fixed sample station
using a 200 mm mesh net with 50 cm mouth diameter and
attached flow meter, towed for three minutes at a speed of 1 to 2
knots. Wherever possible Conductivity-Temperature-Depth
(CTD) casts were made and water temperature and salinity were
recorded approximately 10 cm below the surface of the water
(Table 1).
Plankton were preserved in 4% buffered formalin. In addition,
further surface plankton tows were conducted and replicate
environmental data recorded whenever a shark or group of sharks
was encountered. These ‘‘during feeding’’ plankton samples were
taken at the most central location of the feeding group, and where
possible the net towed in the same direction as the feeding sharks
were swimming. In one instance, a ‘‘post-feeding’’ plankton
sample was subsequently taken at the same GPS location after the
sharks had moved away to determine whether plankton was still
present in the area.
Three replicate sub-samples of 2 ml were transferred into petri
dishes and the zooplanktonic organisms present identified and
enumerated to species level under a compound microscope at
1006magnification using standard keys [51–54]. The mean of the
three counts was used to estimate the numerical abundance of
each zooplankton species. The volume of water filtered was
calculated from the flow meter reading, and the approximate
abundance and density of each species determined per cubic
meter. The bio-volume of the zooplankton sample was determined
using an adapted settlement method [55]; the volume of the
original sample was increased to 1 litre and the plankton allowed
to settle for 24 hours before the settlement value (ml/l) was
recorded. Mann-Whitney Utest was used to compare zooplankton
bio-volume (ml/l) and organisms per m
3
for samples taken within
the study area and outside the study area at the comparison
station.
Genetic Identification of Fish Eggs
The ‘‘during feeding’’ plankton sampling methodology was
modified following sampling on 14
th
May, when high concentra-
tions of fish eggs were found in the sample. This modified method
involved immediate completion of a second plankton tow for one
minute, with this second sample preserved in ethanol for COI
(Cytochrome oxidase subunit 1) DNA barcoding to determine the
fish species present.
Approximately 25 mg of each sample collected was sub-
sampled and DNA was extracted (Qiagen kit: www.qiagen.com).
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 2 March 2013 | Volume 8 | Issue 3 | e58255
The 650 bp COI barcode region was then amplified by
Polymerase Chain Reaction (PCR) using a reaction mix (20 ml)
containing Ampli Taq Gold 360 master Mix (Applied Biosystems;
www.appliedbiosystems.com), 2 mL DNA template (concentration
of 20 ng/ml) and 1 ml of each of two primers: BLCO11490 F (59-
GGT CAA CAA ATC ATA AAG ATA TTG G-39) and
BHCO2198R (59-TAA ACT TCA GGG TGA CCA AAA AAT
CA-39). The cycling parameters were 35 cycles of 95uC/1 min,
40uC/1 min and 72uC/1 min 30 sec, with a final extension step at
72uC for 7 min, followed by cooling to 4uC (Folmer et al., 1994).
PCR products were then visualized on 1.5% agarose gels.
Five ml of these PCR products were then purified using
ExoSAp-iT Enzyme (USB; www.usbweb.com) according to the
manufacturer procedure, following which they were labelled using
a BigDyeHTerminator v.3.1 Cycle Sequencing Kit (Applied
Biosystem). The Big Dye PCR Products were then purified using a
standard ethanol precipitation method (following Applied Biosys-
tem standard protocol). The purified product from all samples was
then sequenced bi-directionally using an ABI 3130 DNA
sequencer (Applied Biosystem) and sequence trace files assembled
using Sequencing Analysis v.5.1. The resulting sequences were
then matched against individual specimens in the Barcode of Life
(BOLD) database (www.bold.org).
Results
Archival Data
Seven previous encounters of whale sharks in Qatari waters had
been reported to the global whale shark database (www.
whaleshark.org) from individuals and oil platform workers in the
region since 2004. Included in these seven reports are Soren Stig’s
August 2007 report of a large whale shark aggregation in Al
Shaheen (Figure 2) and a second report in May 2010 of an
encounter with approximately 30 whale sharks off the coast of
Qatar.
Platform Based Observations
Maersk platform workers frequently reported large numbers
of whale sharks around the platforms between May and August
(Figure 3), and three sharks in early September. No sharks were
reported between October and December even though the
number of platform workers remained the same. The maximum
estimated number observed over a single month was 178,
recorded during June. The maximum number of sharks
observed by platform workers at any one time was estimated
to be 40 animals.
Figure 1. Map showing the respective locations of Qatar, the United Arab Emirates and the Al Shaheen oil and gas field within the
Arabian Gulf, and (inset) of the Arabian Gulf itself in relation the Arabian Peninsula.
doi:10.1371/journal.pone.0058255.g001
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 3 March 2013 | Volume 8 | Issue 3 | e58255
Boat Based Observations
Two individual whale sharks were encountered on 23
rd
April
2011, both of which were swimming slowly at the surface with no
feeding behaviour apparent. On subsequent dates when sharks
were observed they were present in large groups, moving at speed
with their mouths wide open, skimming the surface layer, actively
ram feeding.
On 14
th
May 2011, an estimated 30 sharks were encoun-
tered. Surface water temperatures were 27.3uC with a salinity of
39.1 ppt (Table 1). Due to the fast swimming speed of the
feeding sharks it was difficult to obtain photographs of both left
and right sides for photo-identification purposes. Up to 14
sharks were identified, with nine animals being photographed
on the left and five on the right. Sex was determined for six of
these individuals, two females and four males. Size estimates of
the sharks varied between 6 m and 10 m. Significant scarring
was noted on three (23%) of the identified individuals, with two
bearing evidence of severe boat impact trauma distinguished by
defined propeller marks on the body. No fresh wounds or
scarring were observed, suggesting that the injuries were not
recent. Ramı
´rez-Macı
´as et al [56] found 13–33% of whale
sharks photographed near Holbox Island, Mexico, had signif-
icant scarring attributable to boat strikes. Although the
percentage of scarring we observed fell within the range
reported in the Holbox Island study, the number of whale
sharks assessed for scarring from the 2011 season was low (14)
and so further investigation into scarring is warranted. The
sharks were observed feeding at a plankton bio-volume density
of 90 ml/l (Table 1). The number of organisms (per m
3
) from
fixed sampling within the study area varied throughout the
sampling period between 766 and 56, 414 (mean
18844.48613248.37). The ‘‘during feeding’’ sample taken on
this occasion contained 12, 447 organisms (per m
3
), notably
lower than the mean for the 2011 sampling season. This sample
contained a high density of fish eggs.
On 9
th
July 2011, an estimated 100 whale sharks were
encountered under similar conditions. Surface water temperatures
were 29.58uC with a salinity of 39.5 ppt (Table 1). One hundred
and four identities were captured, 53 of left sides and 51 of right
sides; only one shark was re-encountered from the 14
th
May 2011
aggregation. Twenty-one male and four female sharks were sexed.
Size was estimated for nine individuals and ranged between four
and eight metres in length. High concentrations of fish eggs were
present in the water column on both occasions. These sharks were
observed feeding at a plankton bio-volume density of 95 ml/l. The
number of organisms (per m
3
) from fixed sampling within the
study area varied throughout the sampling period between 766
and 56, 414 (mean 18844.48613248.37). The ‘‘during feeding’’
samples taken on this date contained 19, 484 organisms (per m
3
),
not notably different from the mean; this sample also contained
large quantities of fish eggs. The ‘‘post-feeding’’ sample contained
52.6% of the bio-volume (ml/l) and 71.8% of the number of
organisms (per m
3
) than the ‘‘during feeding’’ sample taken four
hours previously in the same location (Table 1). Samples of fish
eggs from this day were subjected to COI barcoding and
sequences compared to the Barcode of Life (BOLD) database
(www.bold.org). Two separate sequences generated from inde-
Table 1. Bio-volume, in-water surface temperature, salinity and numbers of organisms in plankton samples taken at fixed
sampling stations and at sites where feeding whale sharks were encountered.
Date Sampling Location Bio-volume ml/l Organisms per m
3
#sharks Surface Temp Salinity
23-April-11 N/A 2 N/A N/A
7-May-11 1 26.0 16421 0 24.5 39.4
7-May-11 Comparison 18.0 9976
14-May-11 1 10.0 766 30 27.3 39.1
14-May-11 2 60.0 4725
14-May-11 During Feeding 90.0 12447
14-May-11 Comparison 12.0 1511
29-May-11 1 40.0 8803 0 26.4 38.79
29-May-11 2 76.0 32214
29-May-11 Comparison 8.0 7634
7-Jun-11 1 28.0 18305 0 N/A N/A
7-Jun-11 2 4.0 22160
7-Jun-11 Comparison 8.0 22173
25-Jun-11 1 50.0 13036 0 N/A N/A
25-Jun-11 2 40.0 30019
25-Jun-11 Comparison 60.0 23190
9-Jul-11 1 24.0 40702 100 29.58 39.5
9-Jul-11 During feeding 95.0 19484
9-Jul-11 Post feeding 50.0 13988
8-Oct-11 1 64.0 56414 0 28.7 41.03
8-Oct-11 2 620.0 16904
8-Oct-11 Comparison 7.5 24862
doi:10.1371/journal.pone.0058255.t001
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 4 March 2013 | Volume 8 | Issue 3 | e58255
pendent egg samples matched mackerel tuna (Euthynnus affinis) with
100.0% similarity.
Fish eggs were the dominant plankton in the two samples taken
‘‘during feeding’’ by whale sharks (14
th
May and 9
th
July),
accounting for 66.1% and 76.55% of the organisms present
(Table 2). In no other samples did fish eggs account for more than
10.25%, except in the sample taken at station 2 on 8
th
October.
Samples of fish eggs from 8
th
October were also subjected to COI
barcoding and sequences compared to the Barcode of Life
(BOLD) database (www.bold.org). Two separate sequences
generated from independent egg samples matched Indian oil
sardine (Sardinella longiceps) with 100.0% similarity.
Bio-volume (ml/l) and number of organisms (per m
3
) from the
comparison station taken outside the study area (n = 5) were found
to be statistically different from samples taken at fixed sample
station 1 (n = 7) and fixed sample station 2 (n = 5) located within
the study area (Bio-volume: Mann-Whitney Utest, p = 0.05;
Organisms per m
3
: Mann-Whitney Utest, p = 0.05).
Other species of marine megafauna were recorded during field
surveys and by the platform workers. These included large pods of
spinner dolphins (Stenella longirostris), Indo Pacific bottlenose
dolphin (Tursiops aduncus), hawksbill sea turtle (Eretmochelys
imbricata), green sea turtle (Chelonia mydas) and loggerhead sea
turtle (Caretta caretta), the Arabian sea snake (Hydrophis lapemoides),
yellow bellied sea snake (Pelamis platurus), Cobia (Rachycentrum
canadum), schools of scalloped hammerhead sharks (Sphyrna lewini)
and other species of unidentified requiem sharks (Carcharhinidae).
Discussion
A large number of whale sharks frequented the Al Shaheen Oil
field from May through to September 2011. Concurrent plankton
sampling suggested that this aggregation is related to mackerel
tuna spawning events, although the results should not be
considered conclusive due to the low sample size. The results of
the statistical tests also suggest that the study area may have a
higher overall productivity than open water outside of the study
area, although the plankton sampling was not performed to
specifically test this hypothesis. Observations from the boat
surveys, platform workers combined with the plankton analysis
results suggest that the platforms in the Al Shaheen area are also
acting as offshore reefs and support an increased biodiversity
compared to areas further from oil or gas platforms. Fish and
crustacean spawning events have also been cited as a factor in the
occurrence of whale sharks at a number of other sites, including
Gladden Spit in Belize, Christmas Island in the Indian Ocean and
Yucatan Peninsula in Mexico [15,24,25]. The Qatar aggregation
Figure 2. An image taken by Maersk Oil platform worker Soren Stig on 15
th
August 2007, showing an aggregation of whale sharks
feeding at the surface in the Al Shaheen Oil Field.
doi:10.1371/journal.pone.0058255.g002
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 5 March 2013 | Volume 8 | Issue 3 | e58255
Figure 3. Estimated number of whale sharks seen during platform and boat observations and moon phase for May through
September 2011.
doi:10.1371/journal.pone.0058255.g003
Table 2. Results of taxonomic inspection of plankton samples showing for each sample the taxa of plankton which accounted for
the largest, second largest and third largest portion of the plankton in terms of numbers of individuals, and for each taxa and for
fish eggs, the percentage of the zooplankton by numbers for which they accounted.
Date
Sampling
Location Dominant Family (%) Second most dominant (%) Third most dominant (%)
Fish eggs
(%)
7-May-11 1 Radiolaria 68.33 Copepoda stages 17.33 Sagita spp. 2.66 0.33
7-May-11 Comparison Copepoda stages 56.23 Appendicularia 13.14 Fish eggs 7.3 7.3
14-May-11 1 Radiolaria 38.6 Appendicularia 29.93 Sagita spp. 3.95 0
14-May-11 2 Appendicularia 21.8 Echinodermata larvae 21.8 Copepoda stages 26.11 0
14-May-11 Comparison Protohabdonella spp. 23.69 Echinodermata larvae 23.69 Labidocera spp. 13.17 0
14-May-11 During Feeding Fish eggs 66.1 Radiolaria 18.49 Copepoda stages 3.42 66.1
29-May-11 1 Radiolaria 85.96 Echinodermata larvae 12.08 Copepoda stages 0.83 0
29-May-11 2 Radiolaria 59 Appendicularia 16.66 Copepoda stages 4 3.6
29-May-11 Comparison Radiolaria 42.4 Copepoda stages 28.48 Bivalve veligers 11.4 0
7-Jun-11 1 Radiolaria 78.8 Appendicularia 7.97 Cyclopoidae 4.41 1.7
7-Jun-11 2 Radiolaria 58.48 Appendicularia 17.49 Fish eggs 10.25 10.25
7-Jun-11 Comparison Noctiluca 18.27 Copepoda stages 21.89 Appendicularia 16.87 1.61
9-Jul-11 1 Copepoda stages 33.86 Chaetognatha spp. 16.93 Calanoidae spp. 13.96 3.43
9-Jul-11 During feeding Fish eggs 76.54 Copepoda stages 10.46 Calanoidae spp. 2.97 76.54
9-Jul-11 Post Feeding Copepoda stages 30.82 Bivalve veligers 15.53 Appendicularia 10.82 3.06
8-Oct-11 1 Radiolaria 74.40 Appendicularia 5.03 Copepoda stages 2.95 2.79
8-Oct-11 2 Fish eggs 85.13 Radiolaria 10.77 Echinodermata Larvae 1.02 85.13
8-Oct-11 Comparison Bivalve veligers 59.21 Copepoda stages 14.26 Calanoidae spp. 4.8 2.32
doi:10.1371/journal.pone.0058255.t002
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 6 March 2013 | Volume 8 | Issue 3 | e58255
seems to be similar in terms of density and behaviour of sharks to
the ‘‘Afuera’’ aggregation (Figure S1) described to occur off the
Yucatan Peninsula of Mexico. Whale sharks also aggregate to feed
on tuna (little tunny Euthynnus alletteratus) spawn, in that location.
Little tunny have also been linked to whale shark occurrence
elsewhere [25,40,57].
Observations by both the platform workers and the authors
suggest that the tuna are aggregating under or close to the
platforms, and may be spawning in these locations which appear
to be acting as fish aggregating devices (FADs). The tendency for
tropical tuna to aggregate under floating structures is well-known,
with half of the world’s tuna catch now obtained around FADs
[58,59]. The species to which the eggs belonged from 9
th
July
‘‘during feeding’’ sample, as determined by the barcoding process,
was the mackerel tuna. This species is a principal target of one
FAD fishery in the Philippines [60]. It is thus possible that the
large number of platforms in the field may in part be responsible
for the large numbers of tuna spawning. Hoffmayer et al [61],
similarly observed that the offshore platform areas in the Gulf of
Mexico were acting as offshore reefs that were then frequented by
whale sharks [62].
Mackerel tuna are migratory and widely distributed throughout
the Indian Ocean [63]. Fisheries records confirm that this species
occurs in Qatari waters [64], where it is believed to aggregate to
spawn from May through to the end of August (M. Al-Jaidah, pers.
obs.). Sivasubramaniam & Ibrahim [64] found that the largest
specimens appeared in catches off Qatar between April and
October, but they failed to record any females with ripe ovaries.
Nevertheless the fact that the period when adults of this species are
present in Qatari waters coincides with the apparent whale shark
season supports the identity of the eggs of which the sharks are
feeding. The last recorded whale shark by the platform workers in
2011 was in early September, and no whale sharks were observed
feeding on high concentrations of Indian oil sardine S. longiceps eggs
taken from the October 8
th
sample. Sivasubramaniam. & Ibrahim
[64] highlight that Al Shaheen is within a highly productive area
for sardines, and it remains possible that the sharks also feed on the
eggs of this or other fish species. It is not yet known why the sharks
were not observed in the area beyond early September, even
though there was still a potential source of food. Further plankton
sampling taken at ‘‘during feeding’’ events is needed to build on
the information collected here.
The specific temporal drivers of tuna spawning and resulting
whale shark feeding aggregations, within the broader spring-
summer season, remain unclear. Aggregations were encountered
during boat surveys in May and July, but few surveys were possible
during June and August. These were the peak months for whale
shark sightings by platform-based observers with 178 and 166
sharks recorded, respectively. While at least some sharks were
present throughout the May to September period, it appears likely
that dense feeding aggregations occur as a specific response to tuna
spawning. The lunar phase is known to have an effect on some fish
spawning events and the subsequent occurrence of whale shark
aggregations [34]. However, in this case, observations of whale
sharks from the platforms occurred throughout the month, and
sometimes over consecutive days, with no clear correlation with
the phase of the moon. Mckinney et al [62] also noted numerous
reports of whale shark observations from platform workers over
consecutive days in the Gulf of Mexico.
Mean bio-volume (ml/l) was above average for the ‘‘during
feeding’’ samples when large aggregations were encountered on
14
th
May and 9
th
July. Both of these samples were dominated by
fish eggs, which, excluding the sample taken at station two on 8
th
October, made up no more than 10.25% in any other sample. On
9
th
July the ‘‘post feeding’’ plankton sample, taken at the same
location four hours after intense feeding was observed but when
the sharks were no longer feeding, showed a decline in the
proportion of the sample made up of fish eggs from 76.54 to
3.06%. Soon after the ‘‘post feeding’’ sample was taken, the
feeding sharks were observed 3 km south of where they had been
observed four hours previously. The currents at the time were
moving south so it is presumed the sharks were moving with
drifting fish eggs in the water column.
Temperature and salinity were recorded within the Al Shaheen
field of 27.3uC and 39.1 ppt on 14
th
May, and 29.58uC and
39.5 ppt on 9
th
July (Table 1). On both these dates, whale sharks
were encountered within the area feeding at the surface. No
temperature or salinity data was recorded in the field during the
months of August or September when water temperatures in the
Arabian Gulf are at their peak [49]. Platform workers frequently
observed whale sharks throughout August (Figure 3) demonstrat-
ing that the sharks are able to tolerate the high temperature and
salinity experienced in the Al Shaheen field during the summer
months. Sequeira et al [40] used 17 years of archived whale shark
sightings data from tuna purse-seine fisheries fleets around the
Indian Ocean in an attempt to predict whale shark occurrence
using variables including temperature. It was found that the whale
sharks preferred a narrow band of temperature with 90% of
sightings occurring between 26.5uC and 30uC and hypothesised
that whale sharks may avoid higher temperatures as this may
elevate metabolic rates and subsequently increase food require-
ments. The two aggregations that occurred in Al Shaheen on 14
th
May and 9
th
July fell within the range of temperature that
Sequeira et al [40] found whale sharks to prefer. However, whale
sharks were still occurring and feeding at the surface within the Al
Shaheen area through August, the warmest month. A Maersk
supply vessel recording water temperature within the field
recorded that the temperature in the upper 10 m of the water
column constantly exceeded 33uC throughout the entire month of
August, reaching a maximum of 33.8uC on 12th August 2011 (S.
Bach, pers. comm.). This shows that whale sharks are able to not
only tolerate, but actively feed in temperatures of 33uC. As few
marine habitats in the world experience the same extremes of
environmental conditions as the Arabian Gulf, it may be here that
the upper tolerance levels for whale sharks in terms of both
temperature and salinity are to be found. The ability for whale
sharks to tolerate these natural extremes of temperature and
salinity, and how it may influence their ecology, is important to
note in a changing global climate.
Strict standardisation of observer effort was not possible as a
result of the fixed nature of platform-based surveys and the
difficulty of access for boat-based surveys. While platform workers
observed large numbers of whale sharks in months when they were
undetected during the boat surveys, the ability of platform workers
to estimate the number of sharks in the area is limited due to the
static location of the platforms. Thus on 9
th
July the boat survey
estimated over 100 sharks present in one location, yet the platform
workers reported only 40 sharks that week. Images submitted to
the project’s website-based public sightings scheme ‘‘Sharkwatch
Arabia’’ by an oil rig worker in Saudi Arabia document the
occurrence on 6
th
July of an aggregation of some 50 sharks
approximately 130 km west of Al Shaheen. The whale sharks had
been observed repeatedly at this site over the previous week,
suggesting this may also be a regular aggregation site. Greater
recruitment and training of platform workers to assist with the
project, along with a more regular boat-based surveys and
expansion to encompass aerial observations [25,65], would help
to provide a more accurate assessment of shark distribution and
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 7 March 2013 | Volume 8 | Issue 3 | e58255
numbers. Given that the peak timing of whale shark observations
in the Straits of Hormuz and Gulf of Oman is in April and
November [47,48], slightly before/after the Qatari aggregation, it
is also plausible that sharks may leave the Gulf and travel more
broadly within the Arabian Sea.
The large numbers of whale sharks observed at Al Shaheen and
comparisons with numbers from other known aggregations [14–
23] indicate that this area is a major aggregation site for the
species. Mckinney et al [62] highlight that the association between
whale sharks and offshore platforms warrants further investigation.
Here we suggest that the whale sharks aggregating in the Al
Shaheen area are indirectly associated with the platforms through
the presence of spawning tuna (Figure S2). The small number of
boat-based surveys possible over the course of this study, coupled
with the fast swimming speed and erratic movements of feeding
sharks, made efforts to photo-identify individual sharks difficult.
Nevertheless, 63 left side identities and 56 right side identities were
collected overall, with only one individual encountered on more
than one occasion (14
th
May and 9
th
July). Vessel access is
restricted in the area and, for operational and security reasons,
there is a 500 m restricted zone around all platforms (S. Bach,
pers. comm.). Thus, as well as favouring spawning of tuna, the oil
field may be effectively serving as a sanctuary for the whale sharks,
as they are less prone to disturbance. It is hoped that further
consultation with the Qatar Ministry of Environment and Maersk
Oil will lead to proposals for sustaining the marine life of this
unintended protected area.
A recent review of whale shark biology and ecology [2]
highlighted the need to determine whether aggregations of
individuals occur at offshore sites, as well as in the coastal
locations where in recent years they have become well studied
[14,15,23–25,27]. In particular the future identification of hitherto
unknown offshore aggregation locations might help provide a
rationale for the species’ trans-oceanic foraging. The observations
presented here clearly demonstrate that aggregations of these
animals can occur at a site as far as 90 km offshore (but still
shallow: 60 m deep); however it remains to be considered whether
the aggregation is essentially similar in character from those
described for more coastal locations where the sharks also
aggregate in response to a seasonally available high-value food
source [14,15,23–25,27].
Supporting Information
Figure S1 An aerial image of a whale shark aggregation
in the Al Shaheen area showing typical density of feeding
sharks and variation in size (image taken by Mo-
hammed Y. Jaidah).
(TIF)
Figure S2 A split level image showing a whale shark in
close proximity to an offshore platform in the Al
Shaheen area (image captured by Warren Baverstock).
(TIF)
Acknowledgments
We thank staff at the Qatar Ministry of Environment for their assistance, in
particular Masoud Almarri, Ameera M. AL-Emady and Salma H. AL-
Hajri. We thank Maersk Oil and the platform workers, in particular Steffen
Bach for his support and Soren Stig for reporting the aggregating sharks
and, the Qatar Coast Guard for logistical support. We also thank Jennifer
Schmidt for helpful comments on the manuscript. The authors wish to
acknowledge use of the Maptool program for analysis and graphics in this
paper. Maptool is a product of SEATURTLE.ORG. (Information is
available at www.seaturtle.org). The ECOCEAN Global Whale Shark
Database (www.whaleshark.org) was also used as a resource for this study.
Author Contributions
Conceived and designed the experiments: DPR MYJ RWJ KLB PAM.
Performed the experiments: DPR MYJ RWJ KLB NMN AAA KE PAM.
Analyzed the data: DPR MYJ RWJ KLB NMN AAA KE ACH SJP
RFGO. Contributed reagents/materials/analysis tools: DPR MYJ NMN
AAA KE PAM. Wrote the paper: DPR MYJ RWJ KLB NMN AAA KE
PAM ACH SJP RFGO.
References
1. Compango LJV (2001) Sharks of the world. An annotated and illustrated
catalogue of shark species known to date, Vol. 2. Bullhead, carpet and mackrel
sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO species
catalogue for fisheries purposes.
2. Rowat D, Brooks KS (2012) A review of the biology, fisheries and conservation
of the whale shark Rhincodon typus. Journal of Fish Biology 80: 1019–1056.
Available: http://doi.wiley.com/10.1111/j.1095-8649.2012.03252.x. Accessed
13 April 2012.
3. Newman HE, Medcraft AJ, Colman JG (2002) Whale Shark Tagging and
Ecotourism. Elasmobranch Biodiversity, Conservation and Management:
Proceedings of the International Seminar and Workshop, Sabah, Malaysia,
July 1997. by: IUCN, Gland, Switzerland and Cambridge, UK. p. 230.
4. Norman B (1999) Aspects of the biology and ecotourism industry of the whale
shark Rhincodon typus in north-western Australia Murdoch University, Western
Australia. Available: http://researchrepository.murdoch.edu.au/231/. Accessed
15 November 2012.
5. Ramachandran A, Sankar T (1990) Fins and Fin Rays from Whale Shark
(Rhincodon typus Smith). Fishery Technology 27: 138. Available: http://
ezproxy1.hw.ac.uk:2183/scholar?q = Ramachandran,+A.+and+Sankar,+TV+
1990.+Fins+and+Fin+Rays+from+Whale+Shark+(Rhincodon+typus+Smith).
+Fishery+Technology+27:+138&btnG = &hl = en&as_sdt = 0,5. Accessed 15
November 2012.
6. Che-Tsimg C, Kwang-Ming L, Shoon-Jeng J (1997) Preliminary report on
Taiwan’s whale shark fishery.
7. Joung S-J, Chen C-T, Clark E, Uchida S, Huang WYP (1996) The whale shark,
Rhincodon typus, is a livebearer: 300 embryos found in one ‘‘megamamma’’
supreme. Biology of Fishes 46: 219–223. Available: http://www.springerlink.
com/index/M21R2608U3PV5451.pdf. Accessed 5 January 2012.
8. Trono R (1996) Philippine whale shark and manta ray fisheries. Shark News 7:
13.
9. Hanfee F (2001) Gentle Giants of the Sea: India’s Whale Shark Fishery: a
Report on Trade in Whale Shark Off the Gujarat Coast. TRAFFIC-India,
WWF-India. Available: http://scholar.google.com/scholar?hl= en&btnG =
Search&q = intitl e:Gentle+Giants+of+the+Sea:+India’s+Whale+Shark+Fishery
#0. Accessed 5 January 2012.
10. Alava MNR, Yaptinchay AA, Dolumbal ERZ, Trono RB (2002) Fishery and
trade of whale sharks and manta rays in the Bohol Sea, Philippines.
Elasmobranch Biodiversity, Conservation and Management: Proceedings of
the International Seminar and Workshop, Sabah, Malaysia, July 1997. by:
IUCN, Gland, Switzerland and Cambridge, UK. 132–148.
11. Norma n B (2005) Rhincodon typus. In: IUCN 2012 IUCN Red List of
Threatened Species Version 20.
12. Motta PJ, Maslanka M, Hueter RE, Davis RL, De la Parra R, et al. (2010)
Feeding anatomy, filter-feeding rate, and diet of whale sharks Rhincodon typus
during surface ram filter feeding off the Yucatan Peninsula, Mexico. Zoology
(Jena, Germany) 113 : 199–212. Available: http://www.ncbi.nlm.ni h.gov/
pubmed/20817493. Accessed 1 August 2011.
13. Nelson JD, Eckert SA (2007) Foraging ecology of whale sharks (Rhincodon
typus) within BahI
`a de Los Angeles, Baja California Norte, ME
`xico. Fisheries
Research 84: 47–64. Available: http://www.sciencedirect.com/science/article/
B6T6N-4MC12HB-6/2/643eaf0d61ac5c3473681b9b3c9db7d2.
14. Colman JGJ (1997) A review of the biology and ecology of the whale shark.
Journal of Fish Biology 51: 1219–1234. Available: http://onlinelibrary.wiley.
com/doi/10.1111/j.1095-8649.1997.tb01138.x/abstract. Accessed 5 January
2012.
15. Heyman W, Graham R, Kjerfve B, Johannes R (2001) Whale sharks Rhincodon
typus aggregate to feed on fish spawn in Belize. Marine Ecology Progress Series
215: 275–282. Available: http://www.int-res.com/abstracts/meps/v215/p275-
282/.
16. Eckert SA, Stewart BS (2001) Telemetry and satellite tracking of whale sharks,
Rhincodon typus, in the Sea of Cortez, Mexico, and the north Pacific Ocean.
Environmental Biology of Fishes 60: 299–308. Available: http://www.
springerlink.com/index/M50W140707T54613.pdf. Accessed 5 January 2012.
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 8 March 2013 | Volume 8 | Issue 3 | e58255
17. Alava M, Yaptinchay A, Acogido G (1997) Fishery and trade of whale shark
(Rhincodon typus) in the Philippines. … Elasmobranch Society (AES ….
Available: http://scholar.google.com/scholar?as_q= fishery+and+trade+of+
whale+in+the+philippines+#4. Accessed 15 November 2012.
18. Rowat D, Meekan MG, Engelhardt U, Pardigon B, Vely M (2006) Aggregations
of juvenile whale sharks (Rhincodon typus) in the Gulf of Tadjoura, Djibouti.
Environmental Biology of Fishes 80: 465–472. Available: http://www.
springerlink.com/index/10.1007/s10641-006-9148-7. Accessed 13 June 2011.
19. Pierce SJ, Me´ndez-Jime´nez A, Collins K, Rosero-Caicedo M, Monadjem A
(2010) Developi ng a Code of Conduc t for whale shark interactions i n
Mozambique. Aquatic Conservation: Marine and Freshwater Ecosystems 20:
782–788. Available: http://doi.wiley.com/10.1002/aqc.1149. Accessed 5 No-
vember 2011.
20. Anderson R, Ahmed H (1993) The shark fisheries of the Maldives. MOFA, Male´
and FAO, Rome 73pp. Available: ftp://ftp.fao.org/fi./CDrom/bobp/cd1/
Bobp/Publns/MIS/0007.pdf. Accessed 15 November 2012.
21. Riley MJ, Hale MS, Harman A, Rees RG (2010) Analysis of whale shark
Rhincodon typus aggregations near South Ari Atoll, Maldives Archipelago.
Aquatic Biology 8: 145–150. Available: ,Go to ISI.://000276012500005.
Accessed 22 July 2011.
22. Rowat D (1997) Seychelles whale shark tagging project - pilot project report.
Phelsuma Nature Protection Trust of Seychelles 5: 77–80. Available: http://
islandbiodiversity.com/Phelsuma 5–11.pdf. Accessed 15 November 2012.
23. Rowat D, Gore M (2007) Regional scale horizontal and local scale vertical
movements of whale sharks in the Indian Ocean off Seychelles. Fisheries
Research 84: 32–40. Available: http://linkinghub.elsevier.com/retrieve/pii/
S0165783606003985. Accessed 22 August 2011.
24. Meekan M, Jarman S, McLean C, Schultz M (2009) DNA evidence of whale
sharks (Rhincodon typus) feeding on red crab (Gecarcoidea natalis) larvae at
Christmas Island, Australia. Marine and Freshwater Research 60: 607–609.
Available: http://www.publish.csiro.au/?paper = MF08254. Accessed 5 January
2012.
25. De la Parra Venegas R, Hueter R, Gonza´lez Cano J, Tyminski J, Grego rio
Remolina JJ, et al. (2011) An unprecedented aggregation of whale sharks,
Rhincodon typus, in Mexican coastal waters of the Caribbean Sea. PloS one 6:
e18994. Available: http://www.pubmedcentral.nih.gov/articlerender.fcgi?
artid = 3084747&tool = pmcentrez&rendertype = abstract. Accessed 25 July
2011.
26. Meekan MG, Bradshaw CJA, Press M, Mclean C, Richard s A, et al. (2006)
Population size and structure of whale sharks Rhincodon typus at Ningaloo
Reef, Western Australia. Marine Ecology Progress Series 319: 275–285.
27. Graham RT, Roberts CM (2007) Assessing the size, growth rate and structure of
a seasonal population of whale sharks (Rhincodon typus Smith 1828) using
conventional tagging and photo identification. Fisheries Research 84: 71–80.
Available: http://linkinghub.elsevier.com/retrieve/pii/S0165783606004024.
Accessed 22 July 2011.
28. Brooks K, Rowat D, Pierce SJSJ, Jouannet D, Vely M, et al. (2011) Seeing Spots:
Photo-identificat ion as a Regional Tool for Whale Shark Identification.
WIOMSA 9: 185–194. Available: http://www.iotc.org/files/proceedings/
2011/wpeb/IOTC-2011-WPEB07-INF18.pdf. Accessed 5 January 2012.
29. Rowat D, Brooks K, March A, McCarten C, Jouannet D, et al. (2011) Long-
term membership of whale sharks (Rhincodon typus) in coastal aggregations in
Seychelles and Djibouti. Marine and Freshwater Research 62: 621. Available:
http://www.publish.csiro.au/?paper = MF10135.
30. Arzoumanian Z, Holmberg J, Norman B (2005) An astronomical pattern-
matching algorithm for computer-aided identification of whale sharks Rhinco-
don typus. Journal of Applied Ecology 42: 999–1011. Available: http://doi.
wiley.com/10.1111/j.1365-2664.2005.01117.x. Accessed 25 July 2011.
31. Marshall AD, Pierce SJ (2012) The use and abuse of photographic identification
in sharks and rays. Journal of fish biology 80: 1361–1379. Available: http://
www.ncbi.nlm.nih.gov/pubmed/22497388. Accessed 13 November 2012.
32. Speed CW, Meekan MG, Bradshaw CJA (2007) Spot the match - wildlife photo-
identification using information theory. Frontiers in zoology 4: 2. Available:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid = 1781941&
tool = pmcentrez&rendertype = abstract. Accessed 17 July 2011.
33. Eckert SA, Dolar LL, Kooyman GL, Perrin W, Rahman RA (2002) Movements
of whale sharks (Rhincodon typus) in South-east Asian waters as determined by
satellite telemetry. Journal of Zoology 257: 111–115. Available: http://doi.wil ey.
com/10.1017/S0952836902000705. Accessed 12 July 2011.
34. Graham RT, Roberts CM, Smart JCR (2006) Diving behaviour of whale sharks
in relation to a predictable food pulse. Journal of the Royal Society, Interface/
the Royal Society 3: 109–116. Available: http://www.pubmedcentral.nih.gov/
articlerender.fcgi?artid = 1618489&tool = pmcentrez&rendertype = abstract. Ac-
cessed 16 July 2011.
35. Wilson SG, Polovina JJ, Stewart BS, Meekan MG (2005) Movements of whale
sharks (Rhincodon typus) tagged at Ningaloo Reef, Western Australia. Marine
Biology 148: 1157–1166. Available: http://www.springerlink.com/index/10.
1007/s00227-005-0153-8. Accessed 27 July 2011.
36. Wilson SG, Stewart BS, Polovina JJ, Meekan MG, Stevens JD, et al. (2007)
Accuracy and precision of archival tag data: a multiple-tagging study conducted
on a whale shark (Rhincodon typus) in the Indian Ocean. Fisheries
Oceanography 16: 547–554. Available: http://doi.wiley.com/10.1111/j.1365-
2419.2007.00450.x. Accessed 10 September 2011.
37. Hsu H-H, Joung S-J, Liao Y-Y, Liu K-M (2007) Satellite tracking of juvenile
whale sharks, Rhincodon typus, in the Northwestern Pacific. Fisheries Research
84: 25–31. Available: http://linkinghub.elsevier.com/retrieve/pii/S016578360
6003973. Accessed 26 June 2011.
38. Gifford A, Compagno LJV, Levine M, Antoniou A (2007) Satellite tracking of
whale sharks using tethered tags. Fisheries Research 84: 17–24. Available:
http://linkinghub.elsevier.com/retrieve/pii/S0165783606003961. Accessed 30
October 2011.
39. Brunnschweiler JM, Baensch H, Pierce SJ, Sims DW (2009) Deep-diving
behaviour of a whale shark Rhincodon typus during long-distance movement in
the western Indian Ocean. Journal of fish biology 74: 706–714. Available:
http://www.ncbi.nlm.nih.gov/pubmed/20735591. Accessed 23 June 2011.
40. Sequeira A, Mellin C, Rowat D, Meekan MG, Bradshaw CJA (2011) Ocean-
scale prediction of whale shark distribution. Diversity and Distributions: no–no.
Available: http://doi.wiley.com/10.1111/j.1472-4642.2011.00853.x. Accessed
3 November 2011.
41. Mahdi (1971) Additions to the marine fish fauna of Iraq (n.d.). Available: http://
www.getcited.org/pub/101380230. Accessed 15 November 2012.
42. Bishop JM, Abdul-Ghaffar AR (1993) Whale Shark Observations off Kuwai t’s
Coast in 1992. Journal of Fish Biology 43: 939–940. Available: http://dx.doi.
org/10.1111/j.1095-8649.1993.tb01168.x.
43. Brown J (1992) Whale shark Rhincodon typus (Smith 1929). Tribulus 2.1: 22.
Available: http:// scholar.google.com/schol ar?q = whale+shark+-+rhincodon+
typus+tribulus&btnG = &hl = en&as_sdt = 0,5#1. Accessed 15 November 2012.
44. Sivasubramaniam K, Yesaki M (1981) Demersal resources of the Gulf and Gulf of
Oman. Regional Fishery Survey and Development Project …. Available: http://
scholar.google.com/scholar?hl = en&btnG = Search&q = intitle:Demersal+
Resources+of+the+Gulf+and+Gulf+of+Oman#2. Accessed 21 November
2012.
45. Beech MJ (2005) Whale Sharks. In: The Emirates: a natural history. Hallyer P,
Aspinall S, editors Abu Dhabi. Available: http://scholar.google.com/
scholar?hl = en&btnG = Search&q = intitle:The+Emirates:+A+Natural+History
#0. Accessed 15 November 2012.
46. White AE, Barwani MA (1971) A Survey of the Trucial States Fisheries
Resource with Reference to the Sultanate of Oman. Volume 1. Dubai: Trucial
States Council.
47. White AW, Barwani MA (1971) Common sea fishes of the Arabian Gulf and
Gulf of Oman. Dubai: Trucial States Council.
48. Blegvad H (1944) Danish Scientific Investigations in Iran, Part III. Fishes of the
Iranian Gulf. Available: http://scholar.google.com/scholar?q = danish+
scientific+investigations+in+iran.+Part+iii&btnG = &hl = en&as_sdt = 0,5#0.
Accessed 15 November 2012.
49. Sheppard C, Al-Husiani M, Al-Jamali F, Al-Yamani F, Baldwin R, et al. (2010)
The Gulf: A young sea in decline. Marine Pollution Bulletin 60: 13–38.
Available: http://dx.doi.org/10.1016/j.marpolbul.2009.10.017.
50. Van Tienhoven AM, Den Hartog JE, Reijns RA, Peddemors VM (2007) A
computer-aided program for pattern-matching of natural marks on the spotted
raggedtooth shark Carcharias taurus. Journal of Applied Ecology 44: 273–280.
Available: http://doi.wiley.com/10.1111/j.1365-2664.2006.01273.x. Accessed
31 July 2011.
51. Rose M (1933) Copepods Pelagiques. In Faune de France. Paris: Le Chevalier.
52. Newell GE, Newell RC (1979) Marine plankton: a practical guide. Ltd HE,
editor London: Hutchinson Educational Ltd.
53. Yamaji I (1986) Illustrations of the marine plankton of Japan. Japan: Hoikusha
Publishing Co. Ltd.
54. Todd CD, Laverack MS (1991) Coastal marine zooplankton: a practical manual
for students viii. Cambridge: Cambridge University Press.
55. Struthers I, Rissik D (2009) Plankton: A guide to their ecology and monitoring
for water quality. Struthers IM, Rissik D, editors Collingwood, Australia:
CSIRO Publishing.
56. Ramı
´rez-Macı
´as D, Meekan M, De La Parra-Venegas R, Remolina-Sua´rez F,
Trigo-Mendoza M, et al. (2012) Patterns in composition, abundance and
scarring of whale sharks Rhincodon typus near Holbox Island, Mexico. Journal
of fish biology 80: 1401–1416. Available: http://www.ncbi.nlm.nih.gov/
pubmed/22497390. Accessed 17 November 2012.
57. Compagno LJV (1984) FAO species catalogue. v. 4: Sharks of the world. An
annotated and illustrated catalogue of shark species known to date. FAO
fisheries synopsis: 209–211.
58. Girard C (2004) FAD: Fish Aggregating Device or Fish Attracting Device? A
new analysis of yellowfin tuna movements around floating objects. Animal
Behaviour 67: 319–326. Available: http://linkinghub.elsevier.com/retrieve/pii/
S000334720300438X. Accessed 5 March 2012.
59. Fonteneau A, Pallares P, Pianet R (2000) A worldwide review of purse seine
fisheries on FADs. Peˆche thonie`re et dispositifs …. Available: http://archimer.
ifremer.fr/doc/00042/15278/. Accessed 16 November 2012.
60. Itano D, Fukofuka S, Brogan D (2004) The development, design and recent
status of anchored and drifting FADs in the WCPO. … on Tuna and Billfish,
Majuro, Republic of the …. Available: http://www.spc.int/DigitalLibrary/
Doc/FAME/Meetings/SCTB/17/INF_FTWG_3.pdf. Accessed 16 November
2012.
61. Hoffmayer ER, Franks JS, Driggers WB, Oswald KJ, Quattro JM (2007)
Observations of a feeding aggregation of whale sharks, Rhincodon typus, in the
north central Gulf of Mexico. Gulf and Caribbean Research 19: 69.
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 9 March 2013 | Volume 8 | Issue 3 | e58255
62. McKinney J, Hoffmayer E, Wu W, Fulford R, Hendon J (2012) Feeding habitat
of the whale shark Rhincodon typus in the northern Gulf of Mexico determined
using species distribution modelling. Marine Ecology Progress Series 458: 199–
211. Available: http://www.int-res.com/abstracts/meps/v458/p199-211/. Ac-
cessed 4 July 2012.
63. Motlagh ST, Hashemi S, Kochanian P (2010) Po pulation biolo gy and
assessment of Kawakawa (Euthynnus affinis) in Coastal Waters of the Persian
Gulf and Sea of Oman (Hormozgan Province). Iranian Journal of Fisheries …
9: 315–326. Available: http://www.jifro.ir/browse.php?a_id = 11&slc_lang =
en&sid = 1&printcase = 1&hbnr = 1&hmb = 1. Accessed 15 November 2012.
64. Sivasubramaniam K, Ibrahim M (1983) Pelagic fish resources and their fishery
around Qatar. Qatar University Science Bulletin 3: 297–327.
65. Rowat D, Gore M, Meekan MG, Lawler IR, Bradshaw CJA (2009) Aerial
survey as a tool to estimate whale shark abundance trends. Journal of
Experimental Marine Biol ogy and Ecology 368: 1–8. Available: http://
linkinghub.elsevier.com/retrieve/pii/S0022098108004371. Accessed 27 July
2011.
Whale Sharks Aggregate in Qatari Waters
PLOS ONE | www.plosone.org 10 March 2013 | Volume 8 | Issue 3 | e58255
... Many of these constellations occur seasonally and are driven by localized high prey availability (e.g. Nelson and Eckert 2007;Robinson et al. 2013;. New sites continue to be discovered, with significant constellations also described from Robinson et al. 2013), and off Gujarat in India (Hanfee 2001 Some other hotspots rarely have multiple sharks present at the same time, but are rather distinct locations where individual whale sharks are reliably sighted throughout a season. ...
... Nelson and Eckert 2007;Robinson et al. 2013;. New sites continue to be discovered, with significant constellations also described from Robinson et al. 2013), and off Gujarat in India (Hanfee 2001 Some other hotspots rarely have multiple sharks present at the same time, but are rather distinct locations where individual whale sharks are reliably sighted throughout a season. ...
... Whale sharks are more resident in feeding areas than in transit areas ), as they can obviously take advantage of a reliable and persistent food source for up to several months (Robinson et al. 2013). They also generally have a higher site fidelity to feeding areas than to transit areas (Norman and Morgan 2016). ...
... 10 How will climate change affect environmental variables that shape habitat conditions, species movement and dispersal, residency and larval success, and hence seascape connectivity between O&G structures? trophic cascades and the movement of resources through trophic connectivity (Reeves et al., 2019;Topolski & Szedlmayer, 2004), altering grazing and predator populations (Friedlander et al., 2014;Robinson et al., 2013) and enriching sediments through bio-deposition from upper layers (Love et al., 1999). diameter pipelines might present a physical barrier to mobile invertebrate species such as crabs and lobsters (Glaholt, 2008) or even seastars, urchins and sea cucumbers, yet some research suggests this is not the case for many invertebrate species (Todd et al., 2020c). ...
... O&G structures appear to provide feeding opportunities (Arnould et al., 2015;Robinson et al., 2013;Russell et al., 2014) and facilitate dispersal of protected species (Henry et al., 2018). ...
... Acoustic telemetry revealed that whale sharks (Rhincodon typus) were drawn to O&G platforms off north-west Australia from natural habitat off Ningaloo Reef 340 km away . Attraction included infrequent visits over a 6-week period, to high residency, potentially for feeding , with feeding observed at offshore platforms in the Arabian Gulf (Robinson et al., 2013 (Russell et al., 2014). Seals have also been observed attempting to forage on fish underwater around O&G pipelines . ...
Article
Full-text available
Offshore platforms, subsea pipelines, wells and related fixed structures supporting the oil and gas (O&G) industry are prevalent in oceans across the globe, with many approaching the end of their operational life and requiring decommissioning. Although structures can possess high ecological diversity and productivity, information on how they interact with broader ecological processes remains unclear. Here, we review the current state of knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological connectivity with natural marine habitats. There is a paucity of studies on the subject with only 33 papers specifically targeting connectivity and O&G structures, although other studies provide important related information. Evidence for O&G structures facilitating vertical and horizontal seascape connectivity exists for larvae and mobile adult invertebrates, fish and megafauna; including threatened and commercially important species. The degree to which these structures represent a beneficial or detrimental net impact remains unclear, is complex and ultimately needs more research to determine the extent to which natural connectivity networks are conserved, enhanced or disrupted. We discuss the potential impacts of different decommissioning approaches on seascape connectivity and identify, through expert elicitation, critical knowledge gaps that, if addressed, may further inform decision making for the life cycle of O&G infrastructure, with relevance for other industries (e.g. renewables). The most highly ranked critical knowledge gap was a need to understand how O&G structures modify and influence the movement patterns of mobile species and dispersal stages of sessile marine species. Understanding how different decommissioning options affect species survival and movement was also highly ranked, as was understanding the extent to which O&G structures contribute to extending species distributions by providing rest stops, foraging habitat, and stepping stones. These questions could be addressed with further dedicated studies of animal movement in relation to structures using telemetry, molecular techniques and movement models. Our review and these priority questions provide a roadmap for advancing research needed to support evidence‐based decision making for decommissioning O&G infrastructure. Offshore platforms and related fixed structures supporting the oil and gas (O&G) industry are prevalent in all oceans. We review current knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological seascape connectivity. There is a paucity of studies assessing connectivity and O&G structures. We discuss existing knowledge and identify critical knowledge gaps for decision‐making, such as the need to understand how O&G structures modify and influence movement patterns of mobile species and dispersal. Our review and priority questions provide a roadmap for advancing research needed to support evidence‐based decision‐making for decommissioning O&G infrastructure.
... According to the IUCN, the dugong is vulnerable with decreasing status (Marsh and Sobtzick, 2019). • The whale shark (Rhincodon typus), the world's largest fish, appears between April and September about 90 km off Qatar's coastline to feed on plankton and tuna eggs (Robinson et al., 2013). Observations indicate that the Arabian Gulf is home to one of the world's largest gatherings of whale sharks (Bach and Al-Jaidah, 2012;Robinson et al., 2013) as it offers an abundance of food due to the unique marine characteristics of the region (Bach et al., 2014;Robinson et al., 2017). ...
... • The whale shark (Rhincodon typus), the world's largest fish, appears between April and September about 90 km off Qatar's coastline to feed on plankton and tuna eggs (Robinson et al., 2013). Observations indicate that the Arabian Gulf is home to one of the world's largest gatherings of whale sharks (Bach and Al-Jaidah, 2012;Robinson et al., 2013) as it offers an abundance of food due to the unique marine characteristics of the region (Bach et al., 2014;Robinson et al., 2017). The whale shark's life cycle and migration habits are poorly understood; therefore, its conservation requires global efforts. ...
Article
Full-text available
The preservation of our planet’s decreasing biodiversity is a global challenge. Human attitudes and preferences toward animals have profound impacts on conservation policies and decisions. To date, the vast majority of studies about human attitudes and concern toward animals have focused largely on western, educated, industrialized, rich and democratic (i.e., WEIRD) populations. In order to mitigate biodiversity loss globally, an understanding of how humans make decisions about animals from multicultural perspectives is needed. The present study examines familiarity, liking and endorsement of government protection amongst six broad cultural groups living in Qatar for five threatened animal species indigenous to the Arabian Gulf. Our findings highlight similarities and differences across cultures toward animals. Overall, familiarity did not predict endorsement for government protection after liking was accounted for. Liking, however, emerged as an important predictor of endorsement for government protection across cultures, although the degree of animal liking varied culturally. WEIRD and South East Asian participants showed similar and more positive attitudes toward animals compared to the other groups. Participants from the Arabian Gulf, Sub-Saharan Africa, Middle East and North Africa, and South Asia responded similarly toward the animals. Interestingly, the Arabian Gulf group demonstrated significantly less liking and protection endorsement for animals, including those animals which play an important role in their culture. This research highlights intriguing avenues for future research and points to liking as a possible universal human attitude toward animals that influences decision making about conservation across all cultures while suggesting applications for improving education.
... As well as staying further from shore, sharks in the Arabian Gulf also travelled the shortest distances per day (Fig. 2a). This may be related to local prey availability with the offshore platforms of the Al Shaheen oil field (where all sharks from this aggregation were tagged) acting as fish aggregating devices and attracting large numbers of whale sharks to feed (Robinson et al., 2013). Whale sharks have also been observed feeding around oil and gas platforms off north-western Australia , north-eastern Brazil (Sampaio et al., 2018) and in the northern Gulf of Mexico (McKinney et al., 2012). ...
... Has this aggregation adapted to local thermal conditions or could whale sharks be phenotypically plastic? Are they able to tolerate much broader temperature ranges than previously thought (Nakamura et al., 2020) or is this the upper thermal tolerance limit of the species (Robinson et al., 2013)? As SSTs warm, will whale shark distributions shift poleward as predicted (Sequeira et al., 2014) or will their gigantothermy and behavioural thermoregulation allow whale sharks to cope with warming? ...
Article
Full-text available
Conservation and management of mobile marine species requires an understanding of how movement behaviour and space-use varies among individuals and populations, and how intraspecific differences influence exposure to anthropogenic threats. Because of their long-distance movements, broad distribution and long lifespan, whale sharks (Rhincodon typus) can encounter multiple, cumulative threats. However, we lack knowledge on how sharks at different aggregations use their habitats, and how geographic variation in anthropogenic threats influences their vulnerability to population decline. Using movement data from 111 deployments of satellite-linked tags, we examined how whale sharks at five aggregations in the Indian Ocean varied in their exposure to six anthropogenic impacts known to threaten this endangered species. Tagged sharks were detected in territorial waters of 24 countries, and international waters, with individuals travelling up to 11,401 km. Despite long-distance movements, tagged sharks from each aggregation occupied mutually exclusive areas of the Indian Ocean, where they encountered different levels of anthropogenic impacts. Sharks in the Arabian Gulf had the greatest proximity to oil and gas platforms, and encountered the warmest sea surface temperatures and highest levels of shipping, pollution and ocean acidification, while those from the Maldives and Mozambique aggregations had the highest exposure to fishing and human population impacts respectively. Our findings highlight the need for aggregation-specific conservation efforts to mitigate regional threats to whale sharks. Multinational coordination is essential for implementing these efforts beyond national jurisdictions and tackling issues of global conservation concern, including the consequences of climate change and an expanding human population.
... Other sites with modelled n of more than 100 include offshore Qatar in the Arabian Gulf and St. Helena in the South Atlantic. The former site is associated with the sharks feeding on mackerel tuna Euthynnus affinis eggs (Robinson et al., 2013;Robinson et al., 2016), similar to the Yucatan site (de la Parra Venegas et al., 2011). The drivers for the latter are not yet fully understood, but St Helena is unique in hosting a mostly adult 1:1 male to female aggregation where courtship and attempted mating behaviours have been reported (Perry et al., 2020). ...
Article
Full-text available
The world’s largest extant fish, the whale shark Rhincodon typus, is one of the most-studied species of sharks globally. The discovery of predictable aggregation sites where these animals gather seasonally or are sighted year-round – most of which are coastal and juvenile-dominated – has allowed for a rapid expansion of research on this species. The most common method for studying whale sharks at these sites is photographic identification (photo-ID). This technique allows for long-term individual-based data to be collected which can, in turn, be used to evaluate population structure, build population models, identify long-distance movements, and assess philopatry and other population dynamics. Lagged identification rate (LIR) models have fewer underlying assumptions than more traditional capture mark recapture approaches, making them more broadly applicable to marine taxa, especially far-ranging megafauna species like whale sharks. However, the increased flexibility comes at a cost. Parameter estimations based on LIR can be difficult to interpret and may not be comparable between areas with different sampling regimes. Using a unique data-set from the Philippines with ~8 years of nearly continuous survey effort, we were able to derive a metric for converting LIR residency estimates into more intuitive days-per-year units. We applied this metric to 25 different sites allowing for the first quantitatively-meaningful comparison of sightings-derived residence among the world’s whale shark aggregations. We validated these results against the only three published acoustic residence metrics (falling within the ranges established by these earlier works in all cases). The results were then used to understand residency behaviours exhibited by the sharks at each site. The adjusted residency metric is an improvement to LIR-based population modelling, already one of the most widely used tools for describing whale shark aggregations. The standardised methods presented here can serve as a valuable tool for assessing residency patterns of whale sharks, which is crucial for tailored conservation action, and can cautiously be tested in other taxa.
... Offshore platforms play various ecological roles, including acting as aggregation sites for marine megafauna (Haugen & Papastamatiou, 2019;Robinson et al., 2013), nurseries for juvenile fishes Nishimoto et al., 2019), and providing habitat for economically important and overfished species Love et al., 2006). The presence of these offshore platforms creates new habitat, which can have a significant impact on fish production; platforms in California are some of the most productive fish habitats in the world, and platforms in Gabon have higher fish biomass than pristine reefs in the Pacific (Claisse et al., 2014;Friedlander et al., 2014). ...
Article
Full-text available
The decommissioning of offshore oil and gas platforms typically involves removing some or all of the associated infrastructure and the consequent destruction of the associated marine ecosystem that has developed over decades. There is increasing evidence of the important ecological role played by offshore platforms. Concepts such as novel ecosystems allow stakeholders to consider the ecological role played by each platform in the decommissioning process. This study focused on the Wandoo field in Northwest Australia as a case study for the application of the novel ecosystem concept to the decommissioning of offshore platforms. Stereo-baited remote underwater video systems were used to assess the habitat composition and fish communities at Wandoo, as well as two control sites: a sandy one that resembled the Wandoo site pre-installation, and one characterized by a natural reef as a control for natural hard substrate and vertical relief. We found denser macrobenthos habitat at the Wandoo site than at either of the control sites, which we attributed to the exclusion of seabed trawling around the Wandoo infrastructure. We also found that the demersal and pelagic taxonomic assemblages at Wandoo more closely resemble those at a natural reef than those which would likely have been present pre-installation, but these assemblages are still unique in a regional context. The demersal assemblage is characterized by reef-associated species with higher diversity than those at the sand control and natural reef control sites, with the pelagic community characterized by species associated with oil platforms in other regions. These findings suggest that a novel ecosystem has emerged in the Wandoo field. It is likely that many of the novel qualities of this ecosystem would be lost under decommissioning scenarios that involve partial or complete removal. This study provides an example for classifying offshore platforms as novel ecosystems.
... We saw up to 49 different whale sharks in a day, demonstrating that large aggregations do occur, but these were rare. Fewer individuals in an aggregation make it easier to identify all individuals present, which is less the case where large aggregations of >100 individuals occur such as off Isla Mujeres in Mexico, and off Qatar (de la Parra Venegas et al. 2011, Robinson et al. 2013. It is an advantage for CMR studies when fewer sharks are missed. ...
Article
Full-text available
Many large marine species are vulnerable to anthropogenic pressures, and substantial declines have been documented across a range of taxa. Many of these species are also long-lived, have low individual resighting rates and high levels of individual heterogeneity in capture probability, which complicates assessments of their conservation status with capture-�mark-�recapture (CMR) models. Few studies have been able to apply CMR models to whale sharks Rhincodon typus, the world’s largest fish. One of their aggregation sites off Mafia Island in Tanzania is characterised by unusually high residency of this Endangered species, making it an ideal target for CMR methods. Three different CMR models were fitted to an 8 yr photo-identification data set to estimate abundance, population trend and demographic parameters. As anticipated, resighting rates were unusually high compared to other aggregations. Different CMR models produced broadly similar parameter estimates, showing a stable population trend with high survivorship and limited recruitment. Tagging and biopsy sampling for concurrent research did not negatively affect those sharks’ apparent survival or capture probabilities. Scenario-based power analyses showed that only pronounced abundance trends (±30%) would be detectable over our study period, at a 90% level of probability, even with the relatively high precision in yearly abundance estimates achieved here. Other, more transient whale shark aggregations, with reduced precision in abundance estimates, may only be able to confidently detect a similar trend with CMR models after 15-20 yr of observations. Precautionary management and long-term monitoring will be required to assist and document the recovery of this iconic species.
... The species is distributed across tropical and warm temperate marine waters worldwide (Rowat & Brooks, 2012). Although individual whale sharks are highly mobile, and capable of swimming thousands of kilometres each year (Ramírez-Macías et al., 2017;Diamant et al., 2018;Rohner et al., 2018), they often display site fidelity to areas with a predictably high density of their prey (Graham & Roberts, 2007;Rohner et al., 2020), which include a variety of zooplankton and small bait fish (Heyman et al., 2001;Robinson et al., 2013;Rohner et al., 2013a;Rohner et al., 2015a). ...
Article
• Between September and December, whale sharks (Rhincodon typus) aggregate in the coastal waters off Nosy Be, an island in north-western Madagascar. Swimming with these sharks has become an important tourism activity, but no formal protection is in place in Madagascar to protect this endangered species from the potential negative effects of tourism or other human impacts. • Boat-based surveys (n = 405) were conducted from tourism vessels from September to December, 2015–2019. For most sightings (98%), whale sharks were sighted while foraging for bait fish at the surface, in association with mackerel tuna (Euthynnus affinis) and seabirds (Sternidae). A total of 408 individual whale sharks were individually photo-identified over this period. All individuals were immature, and 82% of sexed sharks were male. Sharks ranged from 3.0 to 8.0 m in total length (TL), with a mean TL of 5.65 ± 0.94 m (n = 66) for females and 5.46 ± 1.09 m for males (n = 295). • Most sharks (72% of the identified individuals) were only identified once within the study period. Movement modelling showed an open population with a short mean residence time of 7.2 days. Resightings were recorded from up to 12 years apart (2007–2019). Ten sharks were seen in all five seasons during 2015–2019. A basic POPAN mark–recapture model estimated a total population size of 681 (608–763) sharks over the 2015–2019 period. • Nosy Be waters are an important foraging ground for juvenile whale sharks. Sighting data demonstrate that a high proportion of the sharks’ preferred habitat lies outside existing protected areas, but within an identified Key Biodiversity Area. National species-level protection and increased spatial management is warranted to secure the continued presence of whale sharks in this region.
... While the species' high mobility and extensive use of oceanic habitats means that even the largest contemporary MPAs are unlikely to enclose the full life cycle of individual whale sharks, focusing on threat mitigation at specific locations could provide substantial benefits at a population level.Whale shark mortalities from ship strikes can likely be reduced by implementing specific management measures at high-risk locations(Pirotta et al. 2019;Schoeman et al. 2020). Major shipping activity occurs near areas where large numbers of whale sharks routinely feed on the surface, such as the Al Shaheen area off Qatar(Robinson et al. 2013(Robinson et al. , 2017 and off the Yucatan coast of Mexico (de la ParraVenegas et al. 2011;Hueter et al. 2013). Real-time mitigation measures, such as temporary re-routing or speed reduction, could be implemented to reduce the danger to these whale sharks (see Chapter 11), as has been done successfully for some marine mammals(Pirotta et al. 2019;Schoeman et al. 2020). ...
Article
Full-text available
An individual whale shark (Rhincodon typus) was recorded on January 15, 2020, during the marine megafauna drone-monitoring. The animal was filmed for approximately 400 m of swimming at an average speed of 4.8 km/h, 650 m southwest of the mouth of a river impacted by the rupture of a mining tailing dam 5 years ago. The whale shark is a filter-feeding and highly migratory species. This is a rare record of this threatened species, representing the importance of recovering and protecting biodiversity in the Rio Doce river mouth region.
Article
Full-text available
In coastal waters of several locations globally, whale sharks (Rhincodon typus) form seasonal aggregations, most of which largely comprise juvenile males of 4-8 m length. Evaluation of the period that individuals stay within these size-and age-specific groupings will clarify our understanding of the transition between life-stages in this species and how this might affect their long-term conservation. Long-term photo-identification studies in Seychelles and Djibouti provided data to evaluate this. The Seychelles aggregation had 443 individuals averaging 5.8 m identified between 2001 and 2009; however, the Djibouti aggregation comprised smaller individuals of 3.7 m mean length with 297 individuals identified between 2003 and 2010. In Seychelles, 27% of individuals identified in 2001 were seen again in 2009, while in Djibouti none of the whale sharks identified in 2003 were seen in 2010, although 13% from 2004 were. This suggests that membership periods in the Djibouti aggregation are shorter than in the other juvenile aggregations, such as in Seychelles. Continued photo-identification monitoring of other Indian Ocean aggregations might in time show the next location of these young sharks' life-cycle and thereby allow development of informed national and regional management plans.
Article
Full-text available
On 26 June 2006 an aggregation of 16 whale sharks was observed for a period of 4 hr in the north central Gulf of Mexico (GOM). The sharks remained within an area about 1.0 km 2 in size and continuously ram filter fed at the surface. Visual analysis of a plankton sample collected from the study site revealed the presence of copious amounts of fish eggs in mid-embryonic development and a minor amount of other zooplankton. A second plankton sample (control) collected about 3.5 km from the study site in an area where no whale sharks were pres-ent contained few eggs, however other zooplankton were similar to the study site sample in species composition and abundance. Two egg morphs were identified, and samples of one of the morphs, which represented 98% of the eggs at the study site, were verified by genetic analysis as little tunny, Euthynnus alleteratus. The observed feed-ing behavior and the abundance of fish eggs at the study site indicated the whale sharks were feeding on recently spawned little tunny eggs. This represents the first confirmed observation of a feeding aggregation of whale sharks in the GOM. RESUMEN El 26 de Junio del 2006 un agrupamiento de 16 tiburones ballena fue observado por un periodo de 4 horas en el centro norte del Golfo de Méjico (GOM). Los tiburones permanecieron dentro de un área alrededor de 1.0 km 2 y continuamente se desplazaron filtrando alimento en la superficie. Un análisis visual de una muestra de plankton colectada en el sitio de estudio revela la presencia de grandes cantidades de huevos de peces en un desar-rollo intermedio del embrión y una pequeña cantidad de otro zooplancton. En un área donde no habían tiburones ballena, una segunda muestra de plancton (control) colectada (alrededor de 3.5 km. del sitio de estudio) presento pocos huevos de peces, sin embargo el otro zooplancton fue similar en composición de especies y abundancia con la muestra colectada en el sitio de estudio. Dos formas de huevos fueron identificadas, la forma que represento el 98% de los huevos en el sitio de estudio fue identificada mediante un análisis genético como bacoreta, Euthynnus alletteratus. El comportamiento de alimentación observado y la abundancia de huevos de peces en el área de estudio indicaron que los tiburones ballena se alimentaron de un desove de huevos reciente de bacoreta. Esto representa la primera observación confirmada de una agregación de tiburones ballena en el GOM.
Article
Full-text available
Whale shark Rhincodon typus is a globally distributed species, but there is a lack of knowledge pertaining to their biology, seasonal occurrence, and distribution in the northern Gulf of Mexico (NGOM). Understanding critical habitat for whale sharks is essential on both a regional and global basis for proper management because of their large migratory range. The goal of the present study was to describe the regional distribution of whale shark feeding aggregations in the NGOM by exploiting a presence-only dataset collected as a part of a volunteer sighting survey. Whale shark aggregations have been documented in large numbers in the NGOM since 2003, and species distribution models provide a unique approach to analyzing these presence data. We used maximum entropy and ecological niche factor analysis, 2 algorithms designed for predicting species distribution based only on presence data, to analyze data for the summer period in 2008 and 2009. Cohen’s kappa (kappa) and the ‘area under the receiver operating characteristic curve’ (AUC) were used to evaluate model performance with an external testing dataset. Kappa values ranged from 0.28 to 0.69, and AUC values ranged from 0.73 to 0.80, indicating that the predicted distribution had a fair to substantial agreement with the testing data. Distance to continental shelf edge, distance to adjacent petroleum platforms, and chlorophyll a were the variables most strongly related to whale shark sightings, likely due to an association of these variables with high food availability. Suitable habitat was predicted along the continental shelf edge, with the most suitable habitat predicted south of the Mississippi River Delta. The spatial distribution of suitable habitat is dynamic; therefore, a multi-year study is underway to better delineate temporal trends in regional whale shark distribution and to identify consistent areas of high suitability. Presenceonly habitat models are a powerful tool for delineating important regional habitat for a vulnerable, highly migratory species.
Book
Plankton is an invaluable reference for environment managers, water authority ecologists, estuary and catchment management committees, coastal engineers, and students of invertebrate biology, environmental impact assessment and marine biology. This practical book provides a comprehensive introduction to the biology and ecology of plankton and describes its use as a tool for monitoring water quality. All the major freshwater and coastal phytoplankton and zooplankton groups are covered and their associated environmental issues are discussed. A chapter on best practice in sampling and monitoring explains how to design, implement and conduct meaningful phytoplankton and zooplankton monitoring programs in marine and freshwater habitats, as well as how to analyse and interpret the results for effective management decision-making. Real-life case studies demonstrate the use of plankton for identifying and monitoring water quality issues.
Article
Three well-documented accounts of whale sharks, Rhiniodon typus, in Kuwait's coastal waters represent the first report of this species in the area since 1968.