Éditeur(s) : HAL CCSD PeerJ
Résumé : International audience
Acoustic recording has been recognized as a valuable tool for non-intrusive monitoring of the marine environment, complementing traditional visual surveys. Acoustic surveys conducted on coral ecosystems have so far been restricted to barrier reefs and to shallow depths (10–30 m). Since they may provide refuge for coral reef organisms, the monitoring of outer reef slopes and describing of the soundscapes of deeper environment could provide insights into the characteristics of different biotopes of coral ecosystems. In this study, the acoustic features of four different habitats, with different topographies and substrates, located at different depths from 10 to 100 m, were recorded during daytime on the outer reef slope of the north Coast of Moorea Island (French Polynesia). Barrier reefs appeared to be the noisiest habitats whereas the average sound levels at other habitats decreased with their distance from the reef and with increasing depth. However, sound levels were higher than expected by propagation models, supporting that these habitats possess their own sound sources. While reef sounds are known to attract marine larvae, sounds from deeper habitats may then also have a non-negligible attractive potential, coming into play before the reef itself.
ISSN: 2167-8359

Droits : http://creativecommons.org/licenses/by/
hal-01654685
http://hal.upmc.fr/hal-01654685
http://hal.upmc.fr/hal-01654685/document
http://hal.upmc.fr/hal-01654685/file/peerj-4019.pdf
DOI : 10.7717/peerj.4019

Éditeur(s) : HAL CCSD Oldendorf/Luhe
Résumé : International audience
Unmanned aerial vehicles (UAVs) are being increasingly used in studies of marinefauna. Here, we tested the use of a UAV (DJI Phantom II®) to assess fine-scale variation in densitiesof 2 elasmobranchs (blacktip reef sharks Carcharhinus melanopterus and pink whiprays Himanturafai) on reef systems off Moorea (French Polynesia). We flew parallel transects designed to samplereef habitats (fringing, channel and sandflat habitats) across 2 survey blocks. Block 1 included ashark and ray provisioning site with potentially higher elasmobranch densities, whereas Block 2most likely had lower densities with no provisioning activities. Across 10 survey days in July 2014,we flew 3 transects (400 m) within each survey block (n = 60 total transect passes). As expected,densities (animals ha−1) were significantly higher in Block 1 than in Block 2, particularly where provisioningactivities occur. Differences between habitats surveyed were also found. Our study providesthe first direct estimates of shark and ray densities in coral-reef ecosystems and demonstratesthat UAVs can produce important fishery-independent data for elasmobranchs, particularly inshallow-water habitats.
ISSN: 0171-8630

hal-01416757
https://hal-univ-perp.archives-ouvertes.fr/hal-01416757
DOI : 10.3354/meps11945

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Coral reefs are increasingly being altered by a myriad of anthropogenic activities and natural disturbances. Long-term studies offer unique opportunities to understand how multiple and recurrent disturbances can influence coral reef resilience and long-term dynamics. While the long-term dynamics of coral assemblages have been extensively documented, the long-term dynamics of coral reef fish assemblages have received less attention. Here, we describe the changes in fish assemblages on Tiahura reef, Moorea, from 1979 to 2011. During this 33-yr period, Tiahura was exposed to multiple disturbances (crown-of-thorns seastar outbreaks and cyclones) that caused recurrent declines and recoveries of coral cover and changes in the dominant coral genera. These shifts in coral composition were associated with long-term cascading effects on fish assemblages. The composition and trophic structure of fish assemblages continuously shifted without returning to their initial composition, whereas fish species richness remained stable, albeit with a small increase over time. We detected nonlinear responses of fish density when corals were most degraded. When coral cover dropped below 10 % following a severe crown-of-thorns sea star outbreak, the density of most fish trophic groups sharply decreased. Our study shows that historical contingency may potentially be an important but largely underestimated factor explaining the contemporary structure of reef fish assemblages and suggests that temporal stability in their structure and function should not necessarily be the target of management strategies that aim at increasing or maintaining coral reef resilience.
ISSN: 0722-4028

hal-01282725
https://hal-univ-perp.archives-ouvertes.fr/hal-01282725
DOI : 10.1007/s00338-015-1371-2

Éditeur(s) : HAL CCSD CRIOBE
Résumé : International audience
https://hal-univ-perp.archives-ouvertes.fr/hal-01302967

ISBN : 978-2-9547466-0-9
hal-01302967
https://hal-univ-perp.archives-ouvertes.fr/hal-01302967

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1-10 cm, i.e. among branches of the same colony) to the reef scale (1-10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral-Symbiodinium symbiosis is a key process in scleractinian coral physiology, and Symbiodinium density provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link with Symbiodinium density. Density of Symbiodinium did not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events.
ISSN: 0025-3154

hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942/document
https://hal.archives-ouvertes.fr/hal-00905942/file/Ladriereetal2014.pdf
DOI : 10.1017/S0025315413001252

Éditeur(s) : HAL CCSD Cambridge University Press
Résumé : International audience
The reproduction of Rhinecanthus aculeatus (Linnaeus,1758), a tropical Indo-Pacific reef fish, occurs aroundthe full and new moon (Kuwamura 1997). Spawningbegins 16 to 45 min before the sunrise. The courtshipsbegin 7 to 27 min before the spawning. A specific behaviourof the courtships is when the male places itsrostrum against the caudal peduncle of the female(Kuwamura 1997).Observations have been recorded in the lagoon ofTiahura [shallow sandy area (0.5 - 2 m deep) withalgae Hypnea spinella (C.Agardh) Kützing, 1847 -Moorea, French Polynesia; 17°29′27′ S, 149°53′32″O]in March and April 2015. Fifteen R. aculeatus (fivemales and ten females) lived in this area where themales have territories, which included the subterritoriesof the females. During video-recorded courtships,in addition to the behaviour described byKuwamura (the nuzzling), two new behaviours havebeen observed: circling and touching. During the circling,the male and the female swim to the surface inprogressively larger circles (Fig. 1). The circling behaviourhas been observed in other Balistidae such asPseudobalistes flavimarginatus (Rüppell, 1829) andBalistapus undulatus (Park, 1797) (Lobel andJohannes 1980). During the touching, the abdomensof the male and the female’s touch each other withoutgametes emission (Fig. 2). The touching has been reportedfor Xanthichthys mento (Jordan and Gilbert1882) (Kawase 2003).Although Balistidae present different reproductivestrategies, they have common reproduction features,such as the time and the day of hatching andspawning (Kawase 2003). Our observations are innovativebecause the courtship of R. aculeatus is morecomplicated than previously described. This resultsuggests, thus, that Balistidae have also some commoncourtship behaviour features. These behaviours mayfacilitate the release of gametes, as with the nuzzling(Kuwamura 1997) or can convince the partner to mate.We do not know if these patterns are phylogeneticallyrelated. But as the egg care strategy of Balistidae (biparentalvs maternal) appears to be related to the distributionof food and breeding sites, more than by thephylogeny (Kuwamura 1997), more studies on thistopic will be useful to better understand the establishement of these behaviours.
EISSN: 1755-2672

hal-01562097
https://hal-univ-perp.archives-ouvertes.fr/hal-01562097
DOI : 10.1007/s12526-016-0464-7

Éditeur(s) : HAL CCSD Elsevier Science
Résumé : International audience
Some anthropogenic noise is now considered pollution, with evidence building that noise from human activities such as transportation, construction and exploration can impact behaviour and physiology in a broad range of taxa. However, relatively little research has considered the effects of repeated or chronic noise; extended exposures may result in habituation or sensitisation, and thus changes in response. We conducted a field-based experiment at Moorea Island to investigate how repeated exposure to playback of motorboat noise affected a coral reef fish (Dascyllus trimaculatus). We found that juvenile D. trimaculatus increased hiding behaviour during motorboat noise after two days of repeated exposure, but no longer did so after one and two weeks of exposure. We also found that naïve individuals responded to playback of motorboat noise with elevated ventilation rates, but that this response was diminished after one and two weeks of repeated exposure. We found no strong evidence that baseline blood cortisol levels, growth or body condition were affected by three weeks of repeated motorboat-noise playback. Our study reveals the importance of considering how tolerance levels may change over time, rather than simply extrapolating from results of short-term studies, if we are to make decisions about regulation and mitigation.
ISSN: 0013-9327

Droits : http://creativecommons.org/licenses/by/
hal-01357915
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915/file/1-s2.0-S0269749116304468-main.pdf
DOI : 10.1016/j.envpol.2016.05.058

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Color polymorphism is widespread in animals and can be associated with temporary adjustments to environmental variables (phenotypic plasticity). In teleost fishes, one of the most remarkable examples of color plasticity is background adaptation in flatfishes. However, such rapid and complete changes in body color and pattern remain relatively unreported in other species. The convict surgeonfish Acanthurus triostegus is a gregarious species whose body color pattern consists of black vertical bars on a whitish body. Here, we describe an entirely reverse body color pattern (white vertical bars on a blackish body) that we observed in some A. triostegus juveniles in a nursery area at Moorea Island, French Polynesia. In aquaria, we determined that change from one color pattern to the other is rapid, reversible, and corresponds to phenotypic plasticity associated with aggressive behavior.
ISSN: 0722-4028

hal-01628304
http://hal.upmc.fr/hal-01628304
http://hal.upmc.fr/hal-01628304/document
http://hal.upmc.fr/hal-01628304/file/Besson_2017_Complete_and_rapid.pdf
DOI : 10.1007/s00338-017-1631-4