DIODON VOL 35 No 2

Décembre 2014
Vol 35 No.2
editorial
Sommaire
EDITORIAL
VOYAGE PLONGEE : Requins marteaux à gogo…
ACTUALITE : Tian Xiang : 18e récif artificiel à
Maurice
Chers amis lecteurs,
D’après la NOAA, ce mois de septembre 2014, la planète a
connu un coup de chaud sans précédent depuis le début des
relevés de températures en 1880. En effet, La température
moyenne mesurée sur les terres émergées a été de 15,7°C, soit
0,72 °C au-dessus de la moyenne du XXe siècle (15 °C). Sans
pouvant pour autant faire un lien direct avec le réchauffement
climatique, le climat global, n’étant analysable que sur des
échelles de temps très longues (par-delà les fluctuations locales
et momentanées), cette chaleur exceptionnelle s’inscrit dans la
tendance à la hausse du XXe siècle : chacune des décennies
étant plus chaude que la précédente, sauf pour les années 1940.
Parallèlement, les dirigeants européens siégeant à Bruxelles
sont parvenus le 24 octobre à un accord sur l’ampleur de la
réduction des émissions de gaz à effet de serre : réduction de
40% d’ici 2030 par rapport aux niveaux de 1990. Mais quid des
pays comme les Etats-Unis et la Chine ? Cet accord sera-t-il
suffisant pour limiter la hausse de 2 degrés de la température
mondiale qui se profile à l’horizon 2050? Rien n’est moins
sûr. Depuis le dernier rapport du Giec en 2009 la situation
s’est aggravée. En effet les émissions de gaz à effet de serre
ne cessent de s’accélérer malgré les efforts engagés. Elles
ont augmenté de plus de 30% entre 1990 et 2010. En cause:
le retour en force du charbon, redevenu plus compétitif. Ce
réchauffement affecte aussi les océans bien sûr, causant des
bouleversements incessants de nos écosystèmes. Ainsi :
- les espèces tropicales envahissent de plus en plus les mers
tempérées comme en Méditerranée par exemple par le
biais du Canal de Suez. En effet dans le sud de la France
ont été péchés en 2010 des poissons qui jusqu’à lors ne
se rencontraient que dans les eaux de la Mer Rouge ou
même dans les eaux mauriciennes comme le barracuda ou
le poisson flûte Fistularia commersonii !
- le blanchiment des coraux s’étend de plus en plus vers les
zones hors tropicales, comme celui de grande amplitude
survenu en juillet/août de cette année à Miami et en Floride
en général, pourtant situé au dessus du tropique du cancer.
- le corail se détériore de plus en plus. En effet les derniers
relevés de 2014 indiquent que la Grande Barrière de Corail
en Australie est dans le pire état jamais connu et qu’elle est
en train de perdre sa capacité à se régénérer. Sa couverture
corallienne a diminué de moitié depuis les années 1980
lorsque le récif a été répertorié comme un site du patrimoine
mondial.
- l’acidification des océans se poursuit : leur pH moyen étant
passé de 8,16 au début du 19e siècle à 8,05 aujourd’hui.
Or l’échelle de pH est « logarithmique » : une baisse de 1
unité reflète une concentration en ions H+ multipliée par
10 !
- etc…. les exemples sont trop nombreux pour tous les citer
ici.
Nous, avec nos partenaires (MSDA en particulier) si petit
que nous soyons à l’échelle de la planète, nous poursuivons
nos actions afin de lutter contre ce fléau. Les dernières
ACTUALITE : Stranding of Dwarf Sperm Whale
(Kogia Sima)
ENVIRONNEMENT : Progress of the REMMOA
aerial surveys conducted in the French EEZ and
adjacent waters: contrasted cetacean habitats in the
southwest Indian Ocean. (End)
ENVIRONNEMENT : Coral reefs are the most
diverse Earth ecosystem
BIOLOGIE : MOLLUSQUES ENDÉMIQUES DE
L’OCÉAN INDIEN
Le Cône textile vaulbert, Conus (Cylinder) textile
vaulberti
ACTUALITE : Expedition to Agalega
MONDE : Culler whales keep a balance
2
3
7
9
11
15
19
21
23
actions en date sont, entre autres, le coulage du Tiang Siang
137 comme 18e récif artificiel à Maurice ou encore l’exposition
« Un point de vue sur les requins ». Vous pourrez avoir tous les
détails de ce sabordage, ainsi qu’un livret présentant l’exposition
dans ce Diodon.
Vous pourrez aussi vous tenir au courant de certaines autres actions
du MMCS comme l’expédition à Agaléga ou encore l’étude du
cachalot nain échoué à Bambous Virieux en mars. De nombreux
autres articles à ne mas manquer non plus dont un sur la plongée
avec les requins marteaux et les raies mantas en Mer Rouge…
Ainsi, sans plus tarder, je vous laisse découvrir ce nouveau Diodon.
Bonne lecture!
N. von Arnim
DIODON
Photo page de garde
Corail mou : Dendronephthya klunzingeri
Photo : Yann von Arnim
Elphinstone, Mer Rouge.
2
voyage plongÉe
Requins marteaux
Paris, 21h, aérogare Charles de
Gaule.
Un brouhaha nous entoure.
Attablés face à face, je sirote
un thé aux agrumes pendant que
mon mari, titille son sandwich
aseptisé déballé il y a quelque
minutes du cellophane. Notre vol
pour Dubaï embarque dans 50
minutes. Cette ville où les hôtels
de luxe et les plages chaudes sont
la destination de nos nombreux
voisins, n’est pourtant pas ce qui
nous attire. Pour nous ce ne sera
qu’une escale vers une destination
beaucoup plus exotique : une
croisière plongée en Mer Rouge
au départ de Port-Soudan.
Après avoir somnolé tant bien que
mal pendant notre escale de 7h à
Dubaï, puis avoir été tour à tour
frigorifiés et ébouillantés dans
l’avion qui nous menait à notre
destination finale, il est déjà 17
heures quand nous nous préparons
à embarquer sur l’Océanos qui
sera notre bateau de croisière. La
foule qui nous entoure s’affaire,
dans un embouteillage de zodiacs,
à diriger tous les plongeurs
débarqués, du seul vol de la
semaine, sur le bon bateau, ce qui
n’est pas une mince affaire chacun
s’interpellant avec animation
dans une langue étrangère, qui
en arabe, qui en italien, qui en
français, qui en russe, qui en
anglais, qui en espagnol, et j’en
passe !!
En attendant le sauf conduit des
autorités pour quitter le port, nous
déballons le matériel de plongée,
tandis que le soleil, tel un artificier
contrôlant à merveille sa pyrotechnie,
déverse ses derniers rayons dans
un flamboiement de couleurs,
changeant progressivement de
l’orange au violet ….
Et c’est parti. Notre excursion sousmarine nous mènera au Nord de Port
Soudan, dans les eaux limpides des
atolls de Sanganeb et Shab Rumi
avant de terminer sur l’incroyable
épave de l’Umbria.
Que ce soit à Sanganeb ou à Shab
Rumi, nous plongeons sur des
tombants descendant en escalier
de 5 à plus de 200 mètres où
patrouillent requins marteaux,
requins gris de récif, barracudas en
bancs serrés, caranges qui copinent
avec les licornes pour former de
vastes bancs bicolores, bécunes,
thons, napoléons…
A raison de 3 à 4 plongées par jour,
débutons toujours dans le bleu où
de nombreux requins marteaux
(Sphyrna lewini), timides, viennent
faire une brève apparition, avant de
déguerpir, effarouchés par le banc
de plongeurs que nous formons,
surmonté de sa large colonne de
bulles, mais curieux tout de même,
ils pointent à nouveau leur nez,
s’éloignent à nouveau, reviennent
vérifier si nous sommes toujours
là etc…. Après une dizaine de
minutes à contempler leur ballet,
DIODON
3
à gogo…
nous nous arrachons avec peine
aux -40 mètres du bleu et la
plongée se poursuit le long du
tombant que nous remontons
progressivement pour éviter
les paliers de décompression,
et là, c’est l’explosion de
couleurs : les gorgones
d’espèces variées (Melithaea
sp., Supergorgia hicksoni) allant
du rouge au violet, disputent la
place aux coraux durs de toutes
formes et teintes comme le corail
de feu (Millepora dichotoma)
étalant ses éventails de dentelle
brune bordée du rouge intense
des éponges encroûtantes, ou le
corail peau d’éléphant (Mycedium
elephantotus) formant de
véritables tables prêtes à recevoir
la vaisselle fine, ou encore ces
coraux imitant des fils de fer
tordus (Cirripathes anguina),
sans compter les patates de toutes
sortes, comme des mamelles
multiples, et j’en passe, ainsi
qu’aux coraux mous du genre
Dendronephthya, flamboyants
dans leurs couleurs chatoyantes
allant du rose au rouge vif et
passant par tous les tons d’orangé
et de violet. Entre les dédales de
cette vie fixée, une kyrielle de
poissons de récifs colorés s’agite
en tous sens à notre approche.
Une nuée de barbiers orange
(Pseudoanthias squamipinnis),
typiques de la Mer Rouge,
virevoltent au gré du courant et
des mouvements des plongeurs,
les poissons ange géographes
attirent notre regard de leur robe
magnifique imitant une ile d’or au
milieu d’une mer d’azur, quelques
pseudochromis de Fridman
(Pseudochromis fridmani),
endémiques de la Mer Rouge,
dansent un ballet en tutu violet.
Mais mon préféré reste le poisson
voyage plongÉe
DIODON
4
voyage plongÉe
DIODON
5
voyage plongÉe
en transport de troupes pendant la 2e guerre mondiale,
transportait bombes, obus, détonateurs, véhicules etc… quand
le 9 juin 1940, arrivant en vue de Port Soudan il mouille sur
le Wingate Reef. Malheureusement, le lendemain, l’entrée en
guerre de l’Italie amène le capitaine à organiser le sabordage
du navire : les différentes plaques d’obturation des prises
d’eau étant brisées et l’équipage évacué sous couvert d’un
hypothétique exercice d’évacuation. Ainsi, sur un fond de 38
mètres, remontant jusqu’à 3 mètres de la surface où affleurent
les bossoirs tribord, l’Umbria git sur le côté babord tel un
mastodonte, intact, sans traces d’explosion ni brèche, avec
sa cargaison complète. Les mats, grues de chargements et la
cheminée, tels de grands tentacules tordus, rejoignent le fond.
Les parois du château, peu abimées, donnent une bonne idée
de cette partie de l’épave, avec les quatre paires de bossoirs
des chaloupes de chaque côté, et le large trou cylindrique
d’où sortait la cheminée. Suivant prudemment notre guide,
nous nous faufilons à travers couloirs et coursives : des cales
avec ses murs de bombes, de munitions, et de voitures aux
toilettes du capitaine, en passant par la cuisine et son four
à pizza jusqu’aux montagnes de bouteilles de chianti, sans
oublier la salle des machines ! Exceptionnel, même pour les
non-amateurs d’épaves comme moi !!!
papillon jaune (Chaetodon semilarvatus),
toujours en couple et qui arbore une robe
jaune fluo avec un œil maquillé de bleu.
Nous ne voulons plus sortir la tête de
l’eau ! Et pourtant la magie continue une
fois remontés : dans les lagons de Sanganeb
et Shab Rumi s’ébattent des familles de
dauphins qui, curieux, sont attirés par notre
zodiac sur le chemin du retour, et partagent
avec nous des moments magiques en apnée.
Le clou de la croisière restera l’épave de
l’Umbria : nos trois dernières plongées
du séjour. Ce cargo italien, transformé
Nathalie von Arnim
Bibliographie :
•
Amar et Isabelle Guillen ; L’épave de l’Umbria en Mer
Rouge au large du Soudan
•
http://greec.free.fr; l’Umbria
•
Helmut DEBELIUS : Guide du récif corallien, Mer
Rouge
•
Helmut Gothel : Guide de la faune sous-marine poissons, Mer Rouge – Océan Indien ; Editions Ulmer
DIODON
6
ACTUALITES
L’Épave du Tian Xiang, 18ème Récif
Artificiel à Maurice
Le 16 Juin 2014 le bateau de pêche
chinois, le Tian Xiang No137, a
été sabordé au large de Flic en
Flac par 43 mètres de fond par la
Mauritius Marine Conservation
Society (MMCS) et la Mauritian
Scuba Diving Association (MSDA).
Avec le Water Lili en 1980, le Tug
No2 en 1981, les Pneus en 1986,
le St Gabriel en 1987, le Kei Sei
No113 en 1987, le Stella Maru en
1989, le Carp en 1989, le Silver
Star en 1991, l’Orient en 1992, le
Hassen Mian en 1996, le Jabeda en
1996, le Star Hope en 1998, le Hoi
Siong No6 en 2003, le Long Teh en
2010, la Baignoire en 2011 et en
incluant les récifs crées par d’autres
organismes tel le patrouilleur Amar
sabordé en 1998 et le Pasifoo sombré
accidentellement en 2013, Maurice
compte maintenant 18 récif artificiels
dont deux sont situés au Nord de
l’ile, douze dans l’Ouest, trois dans
l’Est et un au Sud.
Le Tian Xiang 137 a longtemps
navigué dans le Pacifique et
l’Océan Indien comme palangrier.
Enregistré sous pavillon chinois à
la «Inter-American Tropical Tuna
Commission» sous le No8451 et à la
Commission des Thons de l’Océan
Indien sous le NoIOTC00839 son
indicatif d’appel radio fut BZYI.
Construit en 1980, il mesurait 45.3
mètres de long par 8.5 mètres de
large et sa jauge brute était de
496 tonneaux. Les propriétaires
successifs furent la Seven Seas
Marine S.A. basé à Belize ainsi que
la Tianjin Deepsea Fishing Co., la
Tixiang Fishing Co. et la Tianjin
Tianxiang Fishing Co. basés en
Chine avec comme agent à Maurice
IBL Fishing Co. Ltd..
Pour le Tian Xiang, le remorquage
depuis le port et le positionnement
sur le site se sont déroulés sans
problèmes. Avant de quitter le port
le bateau avait été nettoyé de tout
débris flottant, des ouvertures avaient
été pratiquées dans les caissons
étanches des cales, et les réservoirs
de fuel avaient été vidés pour être de
nouveau rempli avec de l’eau de mer.
Par ailleurs pour faciliter le sabordage,
quatre trous rectangulaires de 25cm
par 35cm avaient été pratiqués de part
et autre de la coque et ceci à l’avant
et à l’arrière. Ces trous avaient été
prédécoupés au port puis ouverts une
fois sur le site.
D’un point de vu « timing » le bateau
a quitté le Port à 8h30 remorqué par
le Sir Seewoosagur, il est arrivé sur
le site à 11h00, le câble acier de la
remorque fut lâché à 11h34, le premier
trou dans la coque fut ouvert à 12h26,
le deuxième à 12h43, le troisième
à 12h50 et le dernier à 12h56. On
s’apprêtait alors à ouvrir les vannes et
à évacuer le bateau quand tout à coup
le Tian Xiang prend l’eau par l’un des
trous et commence à s’enfoncer. Ce
fut alors avec célérité que l’évacuation
fut terminée, Yann quittant en dernier
le futur récif artificiel à 13h07 tandis
que celui-ci s’inclinait sur tribord
pour s’enfoncer par l’arrière pour
toucher le fond à 13h18. Finalement
au son des corps de brumes, celui-ci
disparait complètement à 13h20. Ainsi,
le sabordage, à partir du moment où le
dernier trou fut ouvert dans la coque,
n’a duré 24 minutes, ce qui fut un
record!
Plusieurs plongées d’inspection en
juin et en juillet 2014 ont montré que
l’épave du Tian Xiang s’est stabilisée
sur un fond de sable à 44 mètres de
profondeur et à environ 60 mètres à
l’ouest du site choisi ce qui peut être
considéré comme étant parfait pour un
navire de 44m de long.
Dans la plupart des cas, les récifs
artificiels sont colonisés en quelques
mois, en attirant de nombreuses espèces
de poissons et d’invertébrés. Ils sont
d’abord colonisés par des espèces
pionnières, puis ils offrent un milieu
de substitution à une biodiversité plus
importante. C’est aussi le cas du Tian
Xiang étant donné que des plongées
effectués 4 à 6 semaines après le
sabordage ont montré que l’ensemble
du navire est recouvert d’un duvet
algal et qu’il a été colonisé par de
nombreux jeunes poissons récifaux
dont principalement : des demoiselles
DIODON
7
à 3 taches (Dascyllus trimaculatus),
des chromis à 2 couleurs (Chromis
dimidiata), des rougets roses
(Parupenaus rubescens), des
poissons de verre (Parapriacanthus
ransonneti), des poissons papillons
de Klein (Chaetodon kleinii), des
poissons papillon de Blackburn
(Chaetodon blackburnii), des labres
nettoyeurs (Labroides dimidiatus),
des poissons chirurgien à marque
orange (Acanthurus auranticavus),
des balistes bleus (Odonus niger)
et quelques poissons lion (Pterois
volitans).
Dorénavant le Tian Xiang prendra
une retraite bien méritée et, telle
une perle se formant lentement
autour d’un nucleus, servira de
support au développement d’un riche
écosystème.
Un grand merci à tous ceux qui nous
ont aidés à faire de ce sabordage une
belle réussite en particulier à l’équipe
du MMCS et de la MSDA, à Nico Kux
et à l’équipe des mécaniciens de la
MPA ainsi que le Bureau du Premier
Ministre, le Ministère de la Pêche,
le Ministère de l’Environnement, le
Commissaire de Police, les National
Coast Guards, le Mauritus Ports
Authority, IBL Fishing Ltd, le
Mauritius Underwater Group, les
Moulins de la Concorde sans oublier
les centres de plongée de la côte
ouest, Abyss, Ticabo, Exploration
Sous-Marine, JP Appadu, Nemo,
Euro Divers, Ocean Divers, Sea
Urchin et Sun Divers.
Yann von Arnim
Bibliographie
von Arnim Y., La Hausse de Lalouvière
P., 2000, Artificial reefs in Mauritius.
Diodon Vol. 21. Special Issue.
von Arnim N., 2003, Un nouveau récif
artificiel, le Hoi Siong No6. Diodon
Vol.24 :1 p.20.
Lieske E., Myers R.F., 1995, Guide
des poissons des récifs coralliens.
Delachaux et Niestlé.
ACTUALITES
Le Tian Xiang
Les derniers instants du Tian Xiang
Un nouveau terrain pour la vie marine
DIODON
Un recif artificiel est né
8
ACTUALITES
Stranding of Dwarf Sperm Whale
(Kogia Sima)
T
he Mauritius Marine Conservation society
received phone calls from Albion Fisheries
Research Centre and the Ferme Marine de
Mahebourg alerting us to a stranded cetacean farm
near the village of Bambous Virieux, on the 24th
of March 2014. The identity of the cetacean caused
confusion as it was reported as both a dolphin and
a whale. The animal died that afternoon only 10
minutes after our arrival on site. It was identified
easily on sight as a member of the Kogiidae family
and Kogia genus. Determining which species, either
a Pygmy Sperm Whale (Kogia breviceps) or a Dwarf
Sperm Whale (Kogia Sima) was more difficult as
they weren’t even considered as different species
until the mid-1960’s. (1)
of the total length. (Plön, 2004). The animal had a
total length of 221cm and was male. As males of
this species are known to reach 260cm it is believed
this was a sub-adult between the ages of 2.9 and 15
years (3).
Dwarf and Pygmy Sperm Whales share many
characteristics. Several of these, such as the
presence of a single blow-hole slightly left of center
and the appearance of a false gill and an under
slung jaw, can also cause them to be mistaken for
sharks. (Plön, 2004). The whale that was stranded
in Mahebourg Lagoon was identified as a Dwarf
Sperm Whale because the length between its nose
and dorsal fin, 100c m, was less than 50% of the
total length, 221 cm, and because of the dolphinlike appearance of its dorsal fin located further to
the posterior, at a distance back greater than 50%
The whale underwent a necropsy to determine the
cause for its stranding. The major organs (liver,
kidneys and lungs) did not show obvious signs of
parasites or cysts; however the fore stomach and
main stomach had large numbers of endo-parasites.
Plön (2004) reports that parasitism is prevalent in
the Kogiidae family, and in particular there can be
large amounts of nematodes in the stomach.
DIODON
This whale is rarely encountered and is extremely
difficult to identify at sea. The Dwarf Sperm Whale
seems to live mainly over the continental shelf and
slope, off tropical and warm temperate coasts of all
oceans (4). Mauritius matches this description with
its tropical waters and location on the Mascarene
Plateau, a continental shelf which stretches from the
island of Reunion in the south to Saya de Malha in
the north (5).
Photos of these parasites were sent to Dr. Nahiid
Stephens, a wildlife vet pathologist at Murdoch
University, who suggested that the parasites
9
ACTUALITES
were likely nematode worms known as Anisakids
(from the family Aniskidae, a member of genus
Contracaecum or Anisakis). These parasites were
causing ulceration and swelling in the stomach
wall. However, the level of infestation is unlikely
to have contributed to the death of the animal. The
heart was photographed as this species is known
to be susceptible to heart failure (Bossart et al.
1985; Credle, 1988). However, the photos proved
inconclusive.
Other reasons for the live stranding could include
possibilities that changes in the Earth’s magnetic
field caused the whale to lose its sense of direction;
earthquakes or storms caused the animal to panic;
loud underwater sound from activities such as sonar
or seismic activity caused its sonar system to fail;
or the animal was simply lost or sick. (Carwadine,
2002). However, all of these are theoretical and very
difficult to prove.
Should you see a sick or stranded marine mammal
(whale, dolphin, seal) or turtle please contact Albion
Fisheries Research Centre 238 4100 and MMCS
483 7781. There are some basic things you can do
to assist the animal. Determine whether the animal
is alive by looking for breathing and eye movement.
If the animal is on the shore, reef or shallow water
you should:
ƒƒ
Try to keep it in the upright position, keep
quiet and do not make sudden movements to
avoid additional stress.
ƒƒ
Provide shade/ shelter if possible and cover
the animal in a wet towel or sheet but DO
NOT cover the blow hole.
DIODON
ƒƒ
Dig shallow trenches under the flippers.
ƒƒ
If possible take a photograph of the animal or
draw it.
Do not try to apply sunscreen, go too close to the tail
or attempt to move the animal until information has
been collected and authorities informed. It is illegal
to remove or kill any marine mammal in Mauritius.
Alec Reade MMCS Volunteer (2014)
Imogen Webster Scientific Coordinator
References
(1)http://www.iucnredlist.org/details/11048/0
(2) http://eprints.ru.ac.za/2799/1/Pl%C3%B6n-PHDTR05-154.pdf
(3) http://www.environment.gov.au/cgi-bin/sprat/public/
publicspecies.pl?taxon_id=58
(4) http://www.cms.int/reports/small_cetaceans/data/K_
sima/K_sima.htm
(5)http://www.vliz.be/projects/marineworldheritage/
sites/2_Masc%20Plateau_S%20Malha.php?item=The%20
Indian%20Ocean
Bossart, G. D., Odell, D. K. and Altman, N. H. 1985.
Cardiomyopathy in stranded pygmy and dwarf sperm
whales. Journal of the American Veterinary Medical
Association 187(11): 1137-1140.
Carwardine, M. 2002. Whales, Dolphins and Porpoises.
Credle, V. R. 1988. Magnetite and magnetoreception in
stranded dwarf and pygmy sperm
whales, Kogia simus and Kogia breviceps. M.Sc. Thesis.
Division of Biology and Living Resources, Rosenstiel
School of Marine and Atmospheric Science, University
of Miami, Miami, Florida, USA. 86 pp.
Plön, S. 2004. The status and natural history of pygmy
(Kogia breviceps) and dwarf (K. sima) sperm whales off
Southern Africa. PhD Thesis, Rhodes University, South
Africa.
10
ENVIRONNEMENt
SC/64/E14
Progress of the REMMOA aerial surveys conducted in the
French EEZ and adjacent waters: contrasted cetacean
habitats in the southwest Indian Ocean. (End)
SOPHIE LARAN, GHISLAIN DORÉMUS, LAURA MANNOCCI, OLIVIER VAN CANNEYT, PIERRE
WATREMEZ, ADÈLE CADINOUCHE, VIOLAINE DULAU-DROUOT, FRANÇOIS-XAVIER MAYER, DEVIS
MONTHY, NORBERT ANDRIANARIVELO, YVETTE RAZAFINDRAKOTO, ANLI TOILIBOU & VINCENT
RIDOUX
Habitat modeling
Models of density surface were
obtained for seven groups of
cetaceans: small delphininae
(29% of the deviance explained),
large delphininae (19%),
small globicephalinae (25%),
Risso’s dolphin (49%), large
globicephalinae (29%), beaked
whales (20%) and Physteroidea
(Kogidae and Physeteridae;
33%). As examples, only the
small delphininae and the Risso’s
dolphin models are described
below.
The best model for density of small
delphininae selected longitude,
latitude, depth, distance to the 200
m contour, gradient of chlorophyll,
sea surface temperature (p=0.000),
then slope and primary production
(p=0.001) as significant covariates.
It explained 29% of the deviance.
Prediction was produced for the
whole region with the environmental
conditions as of December 2009
(figure 7 left). For the Risso’s
dolphin the best model selected
longitude, latitude, depth, slope,
distance to the 2 000 m contour,
gradient of chlorophyll, primary
production and sea surface
temperature (p=0.000), then
chlorophyll with a time lag of 2
months (p=0.01) as significant
covariates. This model explained
49% of the deviance (figure 7
right).
Predictions for the seven cetacean
taxa were then made for the whole
region and pooled together. This
prediction clearly highlighted the
importance of the Mozambique
Channel and the Seychelles
Plateau for cetaceans (Figure 8).
Figure 7. Predicted density distributions and sightings for small delphininae (left) and Risso’s dolphin (right) with
environmental conditions as of December 2009.
DIODON
11
ENVIRONNEMENt
SC/64/E14
air are well known and include the
heavier logistic constraints placed
on survey design (aircrafts are
‘central-place’ survey platforms);
higher number of sightings that
cannot be identified to species;
difficulty to implement the double
platform methodology and hence
to estimate detection probability
on survey track. In the case of
the REMMOA survey series, cost
related issues were key elements
of the decision because of the
vast geographical span of the
project, which made a series of
ship surveys too expensive. Some
of the aircraft-specific limitations
can be mitigated.
Figure 8: Pooled predicted density distribution pooled for seven cetacean
taxa: small delphininae, large delphininae, small globicephalinae, Risso’s
dolphin, large globicephalinae, beaked whales and Physteroidea (Kogidae and
Physeteridae) with environmental conditions as of December 2009.
DISCUSSION AND
PERSPECTIVES
General
Regarding the choice of the
survey platform, aircrafts versus
ships, the advantages and
limitations of both types are well
known. Vessels allow a higher
proportion of sightings to be
identified at species level; thanks
to their higher passenger capacity,
they also allow double platform
methodology to be implemented
and therefore the detection
probability on track line to be
estimated; finally, because of their
much longer autonomy, logistic
constraints on survey design are
lower. Their drawbacks include
the limited flexibility of vessel
utilization during survey period
which generally precludes quick
reaction to changing weather and
sea conditions, hence resulting
in a lower rate of platform usage
in optimal detection conditions;
ships generate positive and negative
interaction biases with the survey
target species (either cetaceans
or birds) which imply speciesspecific analyses; because of limited
steaming speed, several ships are
needed to cover extended survey
areas if sufficient spatial resolution
is needed for modelling; finally
cost and carbon print per unit
effort (km surveyed in effort) are
higher. For aircrafts, the higher
flexibility of utilization allows
an optimal rate of platform usage
under good detection conditions;
there is no evidence of survey
target species reaction to survey
platform (this may be different with
a helicopter); extended areas can
be surveyed in a limited amount
of time; costs and carbon print
are lower per unit effort flown
(km surveyed in effort). Several
limitations to surveying from the
DIODON
12
Distribution patterns in the SW
Indian Ocean
The southwest Indian Ocean is
an oceanographically contrasted
region where three broad systems
can be recognized: the Seychelles,
the Mascarene Islands and the
Mozambique Channel, that belong
to three distinct Large Marine
Ecosystems (the Indian monsoon
gyre, the East African coastal and
the Indian south subtropical gyre
provinces respectively) as defined
by Longhurst (1998) largely
on the basis on oceanographic
processes. Marine Ecoregions Of
the World (MEOW) is another
system of bioregionalization that
incorporates more biological
element and focus on shelf
habitats (Spalding et al., 2007).
In this latter context, the whole
study region of the present paper
belongs to one single province
called the Western Indian Ocean
and our surveyed areas belong to
several of its marine ecoregions:
Seychelles, Cargados CarajosTromelin, Mascarene Islands and
Western to Northern Madagascar.
ENVIRONNEMENt
The preliminary analyses
conducted on the REMMOA
data set tend to fit well within
these bioregionalization systems.
In particular encounter rates,
relative densities and prediction
of preferred habitats all concur to
oppose areas of the Mozambique
Channel and the Seychelles
characterized by generally higher
values with areas of the Mascarenes
characterized by much lower
values in general. A closer look
at the data would suggest that not
all cetaceans, and by extension
pelagic megafauna, would
respond similarly to differences
in oceanographic processes
between areas. In particular, it
appears that deep divers may
be more equally distributed
between areas suggesting that
they would be less sensitive to
the oceanographic parameters
classically used to describe
surface marine productivity. To
develop further these analyses
and better interpret the causal
relationship underlying the
variety top predator distribution
patterns, data on the distribution
of their prey would be essential.
However, direct measurements
of prey field or prey densities
in the different water layers of
interest to cetaceans are unlikely
to be available in the southwest
Indian Ocean in a near future.
SEAPODYM is a model initially
developed for investigating
spatial population dynamics
of tuna under the influence of
both fishing and environmental
effects (Lehodey, 2004 a, b;
Lehodey and Senina, 2009). This
model allows prediction of both
temporal and spatial distribution
of secondary consumers in
oceanic ecosystems at various
water depths and therefore has
the potential to provide additional
covariates of direct interest to top
predator ecology.
Perspectives
In the near future the immediate
priority is to complete the first
series of REMMOA surveys. The
next REMMOA aerial survey is
planned in the southwest Pacific
Ocean between November 2012
and March 2013, and the eastern
Caribbean/Guiana plateau region is
planned to be surveyed regionally
later on (Table 1). Lessons drawn
from the first steps are extremely
useful for the continuation of the
project. In the southwest Pacific, the
French EEZ (2,040,000 km²) is split
into two sub-units: the large New
Caledonia and the smaller Wallis
and Futuna area that are located
some 15° longitude apart.
The long term objectives of the
REMMOA surveys is to establish
an initial situation of cetacean and
other pelagic megafauna diversity
and relative abundance and to
build up a monitoring strategy
to be implemented from this
point onwards. In 2013-2014 a
workshop is planned to be hold
in order to examine the statistical
properties of the complete data
set and infer recommendations for
monitoring strategies in the future.
In this exercise, expertise from the
marine mammal, seabird and fish
scientific communities would be
most welcome and the outcomes
of this work extremely useful for
all stakeholders and managers in
charge of monitoring cetaceans
across the tropics.
DIODON
13
SC/64/E14
ACKNOWLEDGMENTS
The French Ministry in charge
of the environment (Ministère de
l’Ecologie, du Développement
Durable, du Logement et du
Transport, MEDDLT) and the
Agency for marine protected
a r e a s ( A g e n c e d e s a i re s
marines protégées, AAMP)
funded the project. The Indian
Ocean Commission (IOC), the
Governments of all Member
States (Comoros, FranceRéunion Island, Madagascar,
Mauritius, Seychelles) and the
prefecture of the Terres Australes
et Antarctiques Françaises
considerably facilitated the
regional approach conducted
in the SW Indian Ocean. The
French Ministry of Foreign
Affairs (Ministères des Affaires
Etrangères et Européennes), the
French Embassies in Madagascar,
Mauritius and the Seychelles
offered their help in contacting
the appropriate authorities and
the French ONCFS in Mayotte.
Civil Aviation authorities in
Madagascar, Mauritius, the
Seychelles and French Polynesia
were extremely helpful with all
aspects related with the flights.
Non-governmental organisations
C e t a M a d a i n M a d a g a s c a r,
Globice in Réunion, Mauritius
Marine Conservation Society
in Mauritius, Megaptera in
Réunion, Naturalistes de Mayotte
in Mayotte. All other observers:
Rebecca Guezel, Aurélie Hermans,
Morgane Perri, Claire Pusineri,
who were very professional in the
air and friendly project mates on
land. Finally, we are particularly
indebted to all aircraft crew
members of Aerosotravia, France
and Madagascar Trans Air, for
their continuous high level of
professionalism and enthusiasm
despite hundreds of hours flying
in strait lines over the ocean.
environnement
SC/64/E14
REFERENCES
Buckland, S.T., Anderson, D.R.,
B u r n h a m , K . P. , L a a k e , J . L . ,
Borchers, D.L. and Thomas L. 2001.
Introduction to distance sampling:
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populations. Oxford University Press,
Oxford UK.vi+xv+432pp.
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Marques, F. F. C.; Buckland, S. T.
In Advanced Distance Sampling;
Buckland, S. T., Anderson, D.
R., Burnham, H. P., Laake, J. L.,
Borchers, D. L., Thomas, L., Eds.;
Oxford: New York, 2004.
Laran, S., Van Canneyt, O., Dorémus,
G., Mannocci, L., Ridoux, V. and
Watremez, P. 2012. Distribution et
abondance de la mégafaune marine
dans le sud-ouest de l’océan Indien
tropical. REMMOA- Océan Indien.
Final report for the French Marines
Protected Area Agency [unpublish,
in french]. 168p.
Lehodey, P. 2004a. A Spatial
Ecosystem And Populations
Dynamics Model (SEAPODYM)
for tuna and associated oceanic toppredator species: Part I Lower and
intermediate trophic components.
17th meeting of the Standing
Committee on Tuna and Bill fish,
Majuro, Republic of Marshall Islands,
9-18 Aug. 2004, Oceanic Fisheries
Programme, Secretariat of the
Pacific Community, Noumea, New
Caledonia, Working Paper: ECO-1:
26 pp. http://www.spc.int/OceanFish/
Html/SCTB/SCTB17/ECO-1.pdf
Lehodey, P. 2004b. A Spatial Ecosystem
And Populations Dynamics Model
(SEAPODYM) for tuna and associated
oceanic top-predator species: Part II
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Tuna and Bill fish, Majuro, Republic
of Marshall Islands, 9-18 Aug. 2004,
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Noumea, New Caledonia, Working
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int/OceanFish/Html/SCTB/SCTB17/
ECO-2.pdf
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A user manual for SEAPODYM
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wcpfc.int/system/files/documents/
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Geography of the Sea. San Diego:
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Laran, S., Rinaldi, R., Van Canneyt, O.
and Ridoux, V. (in review). Top predator
communities from two contrasting
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Atlantic. Submitted to Journal of Marine
Systems.
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Laran, S., Van Canneyt, O., Watremez,
P. 2010. Mapping diversity and
relative density of cetaceans and other
pelagic megafauna across the tropics:
general design and progress of the
REMMOA aerial surveys conducted in
the French EEZ and adjacent waters.
DIODON
14
Paper SC/62/E14 presented at the
Scientific Committee meeting of the
International Whaling Commission,
May 31st –June 11th, 2010, Agadir,
Maroc.
Spalding, M.D., H.E. Fox, G.R.
Allen, N. Davidson, Z.A. Ferdaña,
M. Finlayson, B.S. Halpern, M.A.
Jorge, A. Lombana, S.A. Lourie, K.D.
Martin, E. McManus, J. Molnar, C.A.
Recchia and J. Robertson. 2007. A
bioregionalization of coastal and shelf
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E., Laake, J. L., Strindberg, S.,
Hedley, S. L., Bishop, J. R. B.,
Marques, F. F. C. & Burnham, H.
P. 2010. Distance software: design
and analysis of distance sampling
surveys for estimating population
size. Journal of Applied Ecology,
47, 5-14.
Van Canneyt, O., Dorémus, G.,
Certain, G., Ridoux, V., Jérémie,
S., Rinaldi, R. and Watremez, P.
2009. Distribution et abondance des
Cetaces dans la Zone Economique
Exclusive des Antilles françaises par
observation aerienne. Final report for
the French Marines Protected Area
Agency [unpublish, in french]. 44p.
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Dorémus, G., Laran, S., G., Ridoux,
V., Bolaños, J., Jéremie, S., and
Watremez, P. 2010. Distribution et
abondance de la mégafaune marine
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environnement
Coral reefs are the most diverse Earth ecosystem
Martin Pêcheux; Institut des
Foraminifères Symbiotiques
- 16, rue de la Fontaine de
l’Espérance - 92160 Antony
- France; martin.pecheux@
free.fr
Key-words: reef, coral,
biodiversity, tropic, forest,
symbiosis.
Abstract: Comparisons are
made of biodiversity between
coral reefs and tropical rain
forests. It is clear that coral
reefs are the most diverse
ecosystem of the Earth with
its spectrum of variability and
when ecological processes are
considered, not just species
numbers.
Reefs are often quoted as one
of the most diverse marine
ecosystems (Reaka-Kudla,
1997). No. Reefs are the most
diverse of all Earth ecosystems.
We do not have to count
biodiversity just in term of
number of species, but in
term of processes/patterns, of
original enzymatic pathways
till innate comportments,
of fit to and evolving in a
particular ecological niche,
with both abiotic (“Court
Jester”, Barnosky, 2001) and
biotic (“Red Queen”) factors,
at different time and spatial
scales, i.e. of life invention. Of
course this is not quantifiable,
but a good measure is given
by DNA divergence (although,
with my Y chromosome – 1.61%
length -, I am nearer to male
bonobos– 1.23% difference - than
to woman). An approximation of
this divergence is the number of
phyla. For animals, reefs are the
richest Earth ecosystem with 30
represented phyla whereas there
is only 19 terrestrial ones (Paulay,
1997).
The only animal phylum found
on land and not in reefs is the
anecdotal Onychophora (cousins
of arthropods and tardigrades,
marine at first in the Precambrian,
actually 11 genera). Three other
animal phyla are marine but not
found in reefs; Orthonectida,
24 species of parasitic worms
of marine invertebrates,
Cycliophora, 3 microscopic
species, one undescribed, cousin
of rotifers, living on Atlantic
and Mediterranean crustacean
buccal pieces, and the famous
Pogonophores, the big red
annelids living from H2S near
rift events (of which half of
taxonomists make it a class
or put it in an other family)
(for all, source: Wikipedia).
DIODON
15
Of course, the oldest, the more
time for radiation and DNA
divergence. Reefs are the oldest
biotope on the Earth since 3.4
billion years ago with reef
stromatoliths (Allwood et al.,
2007), and the prominent place
of life till planktonic appraisal
(500 My at least, from isotope,
Saltzman, 2011) and land
conquest (in Silurian, 425-475
My by Rhynia, Cooksonia from
green algae).
I will not consider the case of
the bentic deep sea ecosystem,
said to be surprisingly rich,
with so wide an areal surface
extent. It is often quoted that
reefs are the rain forests of the
sea. No: rain forests are the
reefs of the land. Tropical rain
forests are the most diverse
land ecosystem, said to be the
one with 40%-70% of all biotic
species, etc…
In fact, tropical rain forests are
said to be especially diverse
primarily by the number of
arthropods species. Erwin
(1982, in Strain, 2011) and
his colleagues gassed 19 trees
in Panama, collecting about
1000 unique beetle species.
So, they extrapolate this
number to 30 million species.
Hamilton et al. (2010) estimate
more reasonably that there
are 2.5-3.7 million tropical
environnement
arthropod species. It is very
difficult to know exactly,
but insects would represent
about 80% of all forest species
(T. Bourgoin, specialist of
tropical insects, Collection
Director at National Museum
of Natural History, Paris, com.
pers.). Why a so great number
of species? They don’t seem
to play exceptional ecological
roles: predation on plants, and
between them, decomposition,
recently pollinisation, even if
each one is at its own place. It
appears that there are so man
beetles in part because they are
more or less specialized feeders
on few tree species (cf. May,
2010).
perfect. Curiously, the number
of hermatypic coral species is
similar to the number of genera
of tropical trees: Hubbell et al.
(2008) report that 514 tree genera
have been found in the Amazon in
over 300,00 samples. Symbioses
of corals with zooxanthellae,
though, is less evolved by less
intricated than endosymbioses of
trees with chloroplasts. Diversity
of zooxanthellae clades appears
usual for dinoflagellates, but a
priori greater than chloroplasts
with their own short DNA. The
accessory groups of the primary
trophic level in forests (small
plants, grasses, epiphytes, lichens,
bryophytes and particularly
vines) are somewhat like trees,
whereas in reefs there is a huge
diversity: green, brown, red fleshy
and crustose algae, angiosperm
sea-grasses, Tridacna molluscs
with zooxanthellae, seven order
of sponges associated with
zooxanthellae or cyanobacteria,
large foraminifers symbiotic
with zooxanthellae, diatoms,
chlorophytes, rhodophytes or
free undigested chloroplasts,
and the chordate ascidians with
the particular pro-eu-karyotic
Prochloron sp. (synthesis in
Pecheux, 1998). Rare species
contribute surely over all equally
to complex ecosystem stability
(cf. Isbell et al., 2011), the best
measure of fit biodiversity.
For the main primary trophic
level and equivalently
morphological shaping groups
of the ecosystem, in reefs,
there are about 108 genera
and 800 species of hermatypic
corals. Hubbell et al. (2008)
estimate the number of Amazon
tree species to be 12 500, and
Hamilton et al. (2010), for
whole tropics, to be 50 000.
But introgression by common
pollinisators, the presence of
interspecific hybrids allowing
a flux of genetic pools between
related species, might be more
important than currently
evaluated (Danthu, 2011). Such
phenomenon is also current in
corals (Vollmer and Palumbi, Main groups of the upper trophic
2002), where the morphological level seem roughly at equality,
definition of species is not echinoderms, crustaceans, big
DIODON
16
molluscs and above, numerous
fishes and few marine upper
vertebrates (sea serpents,
seven marine turtles of two
separated lineages, few
iguana and crocodiles, sea
birds, cetaceans), compared to
freshwater fishes, amphibians,
reptiles, birds, and above,
mammals.
Groups of the intermediate
levels seem of small size, which
could hypothetically explain
their species number, as for
example of micro-molluscs,
micro-arthropods, foraminifers,
worms, compared to insects,
arachnids, worms. Molluscs and
arthropods are protostomians
which may influence size.
Nematods and plathyhelminths
too, but the annelids (“true
worms”, rough 15 000 species)
appeared to me, aside the
evolved deuterostomiana, as
a third superphyllum, with
mouth and anus derived from
blastopore (“schizostomian”).
And for micro-organisms,
most remains to be known.
Reefs have the “help” of been
bathed by the whole planktonic
ecosystem, of course, important
in their economy.
Regionalism is similar, with
two main provinces in reefs,
Caribbean and Indo-Pacific,
and three in tropical forests,
Amazon, Congo basin and
South-East Asia, and many
ACTUALITES
Dive
with the best
Mauritian Scuba
Diving Association
Tel./Fax: (230) 454 0011
Email: [email protected]
www.msda.mu
50 centres
de plongées à Maurice
Affiliated to CMAS
DIODON
DIODON
17
17
environnement
minor ones. There is a great
difference between coral
reefs and tropical forests:
Tropical forests occupied in
the past about 10%-15%,
and now 5%-7% of Earth
surface (convergent sources),
whereas reefs, with 284 803
km2 (Spalding et al., 2001, but
deeper water not evaluated) on
Earth (mean radius 6 371 km),
occupy only 0.558%. How
can an ecosystem with twenty
times less spatial distribution
have more variability? It is
quite amazing. Moreover,
many reefs like those scattered
across the Pacific Ocean are
isolated (Volkov et al., 2007).
Why are tropics more diverse?
An old question. Because they
are old stable ecosystems (Jetz
et al. 2012)? But there are
migrations. Perhaps because
with temperature, energy
activation of enzymes is lower,
allowing a greater facility to
create new pathways. Why are
tropical animals so coloured?
That, I really don’t know.
So, to conclude, it appears to
me clearly that reefs are the
most diverse Earth ecosystem.
This is a supplementary reason
to worry of strong reef decay
for a global cause, CO2,
whereas we “know” how to
stop rapidly deforestation.
Acknowledgments I am
grateful to Charles Birkeland,
who helped me with data and
correction of the English. This
work was supported by French
AAH n°2504010.
References
Allwood AC, Walter MR, Burch IW,
Kamber BS (2007) 3.43 billionsyear-old stromatolite reef from the
Pilbara Craton of Western Australia:
Ecosystem scale insights to early life on
Earth. Precambrian Res 158:198-227.
Note: that calcification is evaporitic,
who will believe them?
Barnosky AD (2001) Distinguishing
the effects of the Red Queen and Court
Jester on Miocene mammals evolution
in the Northern Rocky Mountains.
J Vertebr Paleontol 21:172-185
Danthu P (2011) Pour une gestion
durable des baobabs et des écosytèmes
à baobabs des Îles de l’Océan Indien:
approche de la diversité biologique,
des usages et des représentations
des espèces du genre Adansonia
à Madagascar, aux Comores et à
Mayotte. In: FRB (ed). La biodiversité
des îles de l’océan Indien, Colloque
14-15 December, Paris. pp 39-41
Hamilton AJ (2010) Quantifying
uncertainity in estimation of tropical
Arthropod Species richness. Am Nat
176:90-95
Hubbell SP, He F, Condit R, Bordade-Agua R, Kellner J, ter Steege H
(2008) How many species are there in
Amazon and how many of them will
go extinct ? Proc Nat Acad Sciences
US, 105:11498-11504
Isbell F and 14 authors (2011) High
plant diversity is needed to maintain
ecosystem services. Nature 477:199202
DIODON
18
Jetz W, Thomas GH, Joy JB,
Hartmann K, Mooers O (2012) The
global diversity of birds in space and
time. Nature 491:444-448
May RM (2010) Tropical Arthropod
Species, More or Less? Science 329:
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Paulay G (1997) Diversity and
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Birkeland C (ed) Life and Death
of Coral Reefs. Chapman & Hall,
London, pp 298-353
Pecheux M (1998) Review on coral
reef bleaching. Atoll Res Bull,
Edilivre, Paris, France, printed in
2013, 255 pp. Available at www.
reefbase.org or martin-pecheux.fr
Reaka-Kudla ML (1997) The
global biodiversity of coral reefs:
a comparison with rain forests.
In: Reaka-Kudla ML, Wilson PE,
Wilson EO (eds) Biodiversity II:
understanding and protecting our
biological ressources. Joseph Henry
Press, Washington DC, pp 83-108
Saltzman M (2011) Plankton key
to origin of Earth’s first breathable
atmosphere. Proc Nat Acad Sciences
US, 140:8456-8460. Note: I am not
sure of that. And there was nobody
to breath.
Spalding M, Ravilious C, Green
E (2001) World Atlas of Coral
Reefs. UNEP World Conservation
Monitoring Center, University of
California Press, 424 pp. Available
from.http://www.reefbase.org
Strain D (2011) 8.7 million: a new
estimate for all the complex species
on Earth. Science 333:1083
Volkov I, Banavar JR, Hubell SP,
Maritan A (2007) Pattern of relative
species abundance in rain forests and
coral reefs. Nature 450:45-49
Vollmer SV, Palumbi SR (2002)
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296:2023-2025
biologie
MOLLUSQUES ENDÉMIQUES DE L’OCÉAN INDIEN
1 4. Le cône textile vaulbert, Conus (Cylinder) textile
vaulberti Lorenz 2012
Le célèbre cône textile,
Conus textile Linnaeus 1758,
connu pour sa beauté et sa
dangerosité, se rencontre
dans tout l’ouest de l’Océan
Indien et la Mer Rouge dont
l’Ile Maurice. Lors d’une
récente visite dans la région
en 2012, dont à St Brandon
(Cargados Carajos), le Dr. F.
Lorenz a isolé la population
de cônes textiles de St.
Brandon en une sous-espèce
: le cône textile vaulbert,
Conus textile vaulberti
Lorenz 2012. Certains autres
Figure 1 : Le célèbre cône malacologistes en feraient
textile
même une espèce à part :
Conus vaulberti. D’autres
tentatives en ce sens avaient déjà étaient faites dans le
passé. En effet un spécimen hypothétiquement originaire
de St Brandon avait été nommée Conus textile f. scriptus
par Sowerby en 1858. Cependant le nom scriptus ayant
déjà été utilisé par Deshayes par deux fois pour nommer
des cônes (en 1823 et en 1831), et Sowerby n’ayant décris
scriptus que brièvement sans citer la localité d’origine,
le Dr. Lorenz décida de décrire à nouveau l’espèce sur
de nouvelles bases et avec une origine certaine.
Ce cône textile vaulbert
diffère des autres cônes
textiles par plusieurs
caractères : sa coquille est
plutôt petite, ne dépassant
pas 50 mm, alors que celle
du cône textile peut aller
jusqu’à plus de 100 mm.
Elle est par ailleurs plus
légère, moins épaisse,
avec une forme plus
cylindrique. De plus le
graphisme, plus finement
dessiné, ne présente que
deux couleurs : un fond
blanc avec un motif tireté
en forme de tente, mais
plus triangulaire, de
couleur marron foncé sans
aucune ombre bleutée, jaune
orangée ou rouge orangée,
ni condensé en taches plus
sombres. L’apex est aussi
blanc au lieu d’être rose pâle
à rouge orangé. L’ouverture
est plus large, en particulier
dans sa partie antérieure, la
partie postérieure étant plus
resserrée.
L’habitat du Conus textile
vaulberti est représenté par
des zones peu profondes
du lagon de St Brandon,
sous des rochers et à moitié
enterré dans un sable fin
et propre. On ne le trouve
aucune part ailleurs.
Dans la communauté
Figure 3 : Conus textile
des malacologistes, on a
vaulberti
l’habitude d’utiliser le nom
scriptus pour les spécimens
de cônes textiles qui présentent une variante plus pâle
de leurs motifs, et que l’on peut trouver dans le sud de
Madagascar ou ailleurs dans l’Océan Indien, mais en
aucun cas ces cônes n’ont la forme plus étroite et plus
cylindrique du cône textile vaulbert, ni leur coquille
plus légère et moins épaisse, ni l’apex blanc, ce qui fait
bien de cette sous-espèce, une sous-espèce endémique
de St Brandon.
Nathalie von Arnim
Références :
ƒƒ
Lorenz F. (2012) A new subspecies of Conidae
from Mauritius (Gastropoda). Schriften zur
Malakozoologie 27: 21-24. [30 December 2012]
ƒƒ
WoRMS taxon details (http://www.marinespecies.
org/); Conus (Cylinder) textile vaulberti Lorenz,
2012
ƒƒ
Eric Le Court de Billot & David Touitou, Conidae
from Mauritius. Seashell collector.com [november
2013
Last Update : January 2014]
Figure 2 : Conus textile
vaulberti
DIODON
19
biologie
Figure 4 : Conus textile
Figure 5 : Conus textile vaulberti
DIODON
20
ACTUALITES
Expedition to Agalega
observations from shore, of cetaceans inhabiting the
surrounding waters was recorded.
The goal of this expedition was to obtain baseline
information on marine mega-fauna to be used as a
reference for future expeditions and to enable longterm monitoring. These data will also be useful when
making decisions regarding the future of the island
and its management in terms of marine resources. In
addition, it is hoped that data will be used to develop
a more sustainable balance between fishing activities,
development, economic growth and the conservation of
the marine environment and resources.
10°25’S, 56’40’E and about 560 km south of Mahe (Seychelles).
The trip north was rough with constant wind and
occasional showers. We arrived at the islands midmorning on June 26th. Our stay was scheduled to be 3 or
4 days however, due to rough sea conditions which made
unloading the cargo difficult, we did not depart the island
until the afternoon of the 2nd July. The return trip was a
lot smoother and we were able to record more sightings.
While some basic rapid assessments of birds, turtles
and other marine resources have been conducted,
they are limited in number, and no previous cetacean
surveys have been conducted. The Mauritius Marine
Conservation Society (MMCS) is currently running a
project concerning the diversity of marine mega-fauna
around Mauritius – this trip was an opportunity to include
a larger area in this study.
Overall 10 observations of cetaceans were recorded
along with 232 bird and 12 marine debris sightings
during 35h35 and 988.5km of observation effort.
No turtles were observed while at sea. Eleven
species of bird and five species of cetacean were
recorded in addition to some unidentified (Table 1).
Data collection began the day of departure, June 24th
2013. The research focused primarily on occurrence and
distribution of cetaceans (whales and dolphins), marine
turtles and seabirds during the voyage. On the island,
any evidence, such as bones, accounts from locals or
Table 1: List of seabird and cetacean species encountered during the voyage.
Bird Species Sightings
Cetacean Species Sightings
Common Noddy, Anous stolidus
16
Spinner dolphin, Stenella longirostris 1
Lesser Noddy, Anous tenuirostris
1
Humpback Whale, Megaptera novaeangliae 1
Sooty tern, Sterna fuscata 132
Unidentified whale 1
Tropicbird, Phaethon sp.
7
Unidentified dolphin 2
Red-tailed Tropicbird,
Phaethon rubricauda
14
Unidentified Beaked whale 1
White-tailed Tropicbird,
Phaethon lepturus
2
Pilot whale, Globicephala macrorhynchus 3
Fairy tern, Gygis alba
39
Sperm Whale, Physeter macrocephalus 1
Masked Booby, Sula dactylatra 6
Sub-antarctic Skua, Catharacta Antarctica1
Frigate, Fregata sp
1
Petrel/Shearwater Pterodroma spp.
/ Puffinus spp. 4
Unidentified 8
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21
ACTUALITES
Locals informed us that whales would
occasionally strand on the south west
of both the north and south islands.
One local was wearing a necklace
made with the tooth of a whale, likely
a beaked whale, and also showed us
a skull.
Turtles were seen in the lagoon on
both sides of North Island and an adult
green turtle (Chelonia mydas) was
observed surfacing to breath in the
vicinity of the anchored ship (outside
the lagoon) as loading was occurring
for departure. Unfortunately, we
also found the remains of nine adult
individuals while we walked around
the islands including some egg shells.
Seabirds were observed nesting on both
islands but seemed to be concentrated
on South Island. The most common
species included Fairy terns, and
common and lesser Noddys. Sooty
terns and Frigate birds were only seen
in flight and in very small numbers.
While we focused on the cetaceans,
turtles and seabirds, with the additional
time we also took the opportunity
to collect information on invasive
species, conducted marine debris
transects, and also distribution data
on the Agalegan Day Gecko. We were
lucky to observe the Sacred Ibis (there
are only about 20-25 individuals on the
islands) but did not manage to find the
coconut crabs.
The information collected during this
expedition will be included in the
final report for the Diversity Project
due to be completed in October this
year. The additional data will be
shared and hopefully published to
On the island, we found evidence that cetaceans certainly inhabit the increase awareness of environmental
surrounding waters. The head of a dolphin was found on the beach on the issues such as marine debris and turtle
north east coast, North Island. Head shape, colouration and teeth count indicate poaching.
a spinner dolphin (Stenella longirostris). This one appeared to have been
partially eaten by a shark.
Imogen Webster
Scientific Coordinator
Only larger cetacean species were encountered on the return trip including
humpback whales (Megaptera novaeangliae), pilot whales (Globicephala
macrorhynchus), beaked whales and sperm whales (Physeter macrocephalus).
There was an additional sighting of an unidentified whale.
DIODON
22
monde
Culler whales keep a balance
Victoria Laurie
MIRG researchers watch killer whales off Ningaloo Reef.
THE triumphant return of humpback whales along
the West Australian coast is a rare recovery story in
conservation that lifts the spirits.
After several decades of commercial slaughter, humpback
sightings are now commonplace as they migrate along
the coast.
“It’s probably just a matter of time before we see a
decrease to a more sustainable level,” he said.
The WA researchers, working with scientists from the US
Nat­ional Oceanic and Atmospheric Administration, have
been tracking the seasonal appearance of killer whales
in the region since 2008, using satellite tagging and the
collection of tissue samples.
Pods of a few hundred remaining animals in the 1960s
have grown by about 10 per cent each year; an estimated
30,000 now move between their feeding grounds in
Antarctica and calving grounds as far north as Camden
Sound in the Kimberley.
They have observed the killer whales targeting newborn
humpback calves off the Cape Range Peninsula and
Ningaloo coast. “A huge food source of 3000 vulnerable
calves per year simply can’t be ignored for too long,”
says Mr Totterdell.
Yet there is another recovery story that may ensure
that humpbacks are kept in healthy but not excessive
numbers.
“From only very sporadic reports in previous decades,
killer whales are now seen consistently throughout
winter.”
A team of Australian and US researchers has observed
a small increase in killer whales, or orcas. The result is
more predators hunting down and killing the humpbacks’
calves.
The joint team has submitted its first scientific paper on
Ningaloo’s killer whales for publication. But the real
thrill lies in witnessing survival behaviour at play in the
natural world, says Mr Totterdell.
The cycle of survival and sacrifice in the wild constitutes
a natural check on exploding species numbers, says
researcher John Totterdell, from the WA-based Marine
Information & R
­ esearch Group.
“Being there to document the return of the apex predator
in this ecosystem is pretty special.”
Reprint from : « The Australian » September 3rd 2014
The estimated stable population before commercial
whaling was about 18,000 so the population of 30,000
is unlikely to last, Mr ­Totterdell said.
DIODON
23
DIODON
Bulletin de l’Association
pour la Protection
et la Sauvegarde de la Mer.
Le MMCS est également la commission scientifique
de la Mauritian Scuba Diving Association.
The Mauritius Marine Conservation Society
c/o The Mauritius Underwater Group
Railway road
Phoenix
REPUBLIQUE DE MAURICE
Tel : (230) 696.53.68
E-mail : [email protected]
Site web : www.mmcs-ngo.org
Rédacteur en chef
Nathalie von Arnim
Equipe de rédaction
Nathalie von Arnim, Sophie Laran, Ghislain Dorémus, Laura Mannocci, Olivier van Canneyt, Pierre Watremez,
Adèle Cadinouche, Violaine Dulau-Drouot, François-Xavier Mayer, Devis Monthy, Norbert Andrianarivelo, Yvette
Razafindrakoto, Anli Toilibou, Vincent Ridoux, Alec Reade, Imogen Webster, Martin Pecheux, Yann von Arnim.
Photo : Kelsey Roberts
Blanchiment du corail de feu en plaque (Blade Fire Coral) Millepora Complanata, en Floride (juillet 2014)