Éditeur(s) : Public Library Science
Résumé : Estimating diversity and abundance of fish species is fundamental for understanding community structure and dynamics of coral reefs. When designing a sampling protocol, one crucial step is the choice of the most suitable sampling technique which is a compromise between the questions addressed, the available means and the precision required. The objective of this study is to compare the ability to sample reef fish communities at the same locations using two techniques based on the same stationary point count method: one using Underwater Visual Census (UVC) and the other rotating video (STAVIRO). UVC and STAVIRO observations were carried out on the exact same 26 points on the reef slope of an intermediate reef and the associated inner barrier reefs. STAVIRO systems were always deployed 30 min to 1 hour after UVC and set exactly at the same place. Our study shows that; (i) fish community observations by UVC and STAVIRO differed significantly; (ii) species richness and density of large species were not significantly different between techniques; (iii) species richness and density of small species were higher for UVC; (iv) density of fished species was higher for STAVIRO and (v) only UVC detected significant differences in fish assemblage structure across reef type at the spatial scale studied. We recommend that the two techniques should be used in a complementary way to survey a large area within a short period of time. UVC may census reef fish within complex habitats or in very shallow areas such as reef flat whereas STAVIRO would enable carrying out a large number of stations focused on large and diver-averse species, particularly in the areas not covered by UVC due to time and depth constraints. This methodology would considerably increase the spatial coverage and replication level of fish monitoring surveys.
Plos One (1932-6203) (Public Library Science), 2014-01 , Vol. 9 , N. 1 , P. -

Droits : 2014 Mallet 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.
http://archimer.ifremer.fr/doc/00170/28132/26352.pdf
DOI:10.1371/journal.pone.0084344
http://archimer.ifremer.fr/doc/00170/28132/

Éditeur(s) : Université de la Nouvelle-Calédonie
Résumé : Estimating diversity and abundance of fish is fundamental for the understanding of community structure and dynamics of coral reefs. Observations are generally gathered using Underwater Visual Census (UVC). These informations can also be collected by underwater video techniques involving no diver and allowing a high spatial and temporal coverage. The first part of this PhD thesis is a review of publications using underwater video techniques between 1952 and 2012. The second part present two rotating video systems used to study the diversity of ichthyofauna and habitats in the lagoon of New Caledonia: the STAVIRO (for "STAtion VIdeo ROtative") and the MICADO (for "Module d’Imagerie Côtier, Autonome pour le Développement de l’Observation sous-marine"). The third part of this work is a comparison of these techniques with UVCs and an analysis of the “observer effect” for the rotating video techniques. The comparison between rotating video systems and UVC showed that: (i) fish community data collected by UVC and by STAVIRO differed significantly; (ii) species richness and density of large species were not significantly different between techniques; (iii) species richness and density of small species were higher for UVC; (iv) density of fished species was higher for STAVIRO; and (v) only UVC detected significant differences in fish assemblages structure across reef type. The comparison of fish counts obtained from the same videos by different observers showed that for a defined list of species, estimates of species richness and total abundance can be considered as similar between observers with sufficient experiences (> 6 months). The last part of this PhD is an application of rotating video techniques to the study of daily temporal variations of the ichthyofauna. Daily variations were observed depending on the time of day and the tidal state and typical patterns of variations have been described for some species groups. The outcomes of this work bring original insights of new techniques complementary to traditional techniques in order to enhance our understanding of the functioning and dynamic of coral reef.
L’estimation de la diversité et de l’abondance des espèces de poissons est fondamentale pour comprendre la structure des communautés et la dynamique des récifs coralliens. Les observations sont généralement obtenues par des recensements visuels en scaphandre autonome (UVC). Ces informations peuvent également être obtenues de manière originale grâce aux observations issues des techniques vidéo sous-marines modernes sans plongeur qui permettent des couvertures spatiales et temporelles accrues. La première phase de ce travail de thèse synthétise l’ensemble des travaux ayant été effectués avec des techniques vidéo entre 1952 et 2012. La seconde phase, présente deux systèmes vidéo rotatifs complémentaires, utilisés pour étudier la diversité de l’ichtyofaune et des habitats marins dans le lagon de Nouvelle-Calédonie : le STAVIRO (pour « STAtion VIdéo ROtative ») et le MICADO (pour « Module d’Imagerie Côtier, Autonome pour le Développement de l’Observation sous-marine »). La troisième phase de ce travail consiste à comparer ces systèmes vidéo aux UVC puis à examiner l’effet « observateur » inhérent aux techniques vidéo rotatives. Il résulte de cette étude que : (i) les observations des communautés de poissons par UVC et STAVIRO différaient significativement, (ii) la richesse spécifique et la densité des espèces de grande taille n'étaient pas significativement différentes entre les techniques, (iii) la diversité et la densité des espèces de petite taille étaient plus élevés avec les UVC; (iv) la densité des espèces pêchées était plus élevée avec les STAVIRO et (v) seuls les UVC ont détecté des différences de structure des assemblages en fonction du type de récif. L’étude de l’effet « observateur » a montré que sur une liste d’espèces définie, les dénombrements et les identifications des individus peuvent être considérées comme similaires entre observateurs ayant une expérience suffisante (> 6 mois). La dernière phase de ce travail a permis d’appliquer la technique MICADO à l’étude des variations temporelles de l’ichtyofaune d’un site corallien à l’échelle de la journée. Elle a permis de mettre en évidence des variations cycliques journalières en fonction de l’heure et de la marée et des « profils type » de variations ont pu être identifiés pour certains groupes d’espèces. Ce travail de thèse permet ainsi de participer au développement de nouvelles techniques d’observations complémentaires des techniques traditionnelles afin d’enrichir les connaissances du fonctionnement et de la dynamique des écosystèmes coralliens.

Droits : Université de la Nouvelle-Calédonie
http://archimer.ifremer.fr/doc/00189/30050/28536.pdf
http://archimer.ifremer.fr/doc/00189/30050/

Éditeur(s) : Public Library Science
Résumé : Observing spatial and temporal variations of marine biodiversity from non-destructive techniques is central for understanding ecosystem resilience, and for monitoring and assessing conservation strategies, e.g. Marine Protected Areas. Observations are generally obtained through Underwater Visual Censuses (UVC) conducted by divers. The problems inherent to the presence of divers have been discussed in several papers. Video techniques are increasingly used for observing underwater macrofauna and habitat. Most video techniques that do not need the presence of a diver use baited remote systems. In this paper, we present an original video technique which relies on a remote unbaited rotating remote system including a high definition camera. The system is set on the sea floor to record images. These are then analysed at the office to quantify biotic and abiotic sea bottom cover, and to identify and count fish species and other species like marine turtles. The technique was extensively tested in a highly diversified coral reef ecosystem in the South Lagoon of New Caledonia, based on a protocol covering both protected and unprotected areas in major lagoon habitats. The technique enabled to detect and identify a large number of species, and in particular fished species, which were not disturbed by the system. Habitat could easily be investigated through the images. A large number of observations could be carried out per day at sea. This study showed the strong potential of this non obtrusive technique for observing both macrofauna and habitat. It offers a unique spatial coverage and can be implemented at sea at a reasonable cost by non-expert staff. As such, this technique is particularly interesting for investigating and monitoring coastal biodiversity in the light of current conservation challenges and increasing monitoring needs.
Plos One (1932-6203) (Public Library Science), 2012-02 , Vol. 7 , N. 2 , P. -

Droits : 2012 Pelletier et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License
http://archimer.ifremer.fr/doc/00078/18879/16453.pdf
DOI:10.1371/journal.pone.0030536
http://archimer.ifremer.fr/doc/00078/18879/

Éditeur(s) : Elsevier Science Bv
Résumé : Underwater video techniques are increasingly used in marine ecology studies. Technological progress regarding video cameras, sensors (such as sounders), battery life and information storage make these techniques now accessible to a majority of users. However, diver-based underwater visual censuses, and catch and effort data, remain the most commonly used for observing coastal biodiversity and species. In this paper, we review the underwater video techniques that have been developed since the 1950s to investigate and/or monitor coastal biodiversity. Techniques such as remote underwater video, whether baited or not, diver-operated video and towed video are described, along with corresponding applications in the field. We then analyse the complementary of techniques, first from studies comparing video techniques with other observation techniques, whether video-based or not, and second by documenting their respective cost efficiencies. These findings are discussed with respect to current challenges in monitoring and investigating coastal biodiversity. Video should be more often considered and used, either in addition to or as an alternative to diver-based, fishing and acoustic techniques, as it may be particularly suited for monitoring coastal biodiversity in a variety of areas and on larger scales than hitherto and within an ecosystem-based approach to management and conservation.
Fisheries Research (0165-7836) (Elsevier Science Bv), 2014-06 , Vol. 154 , P. 44-62

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00181/29274/27901.pdf
DOI:10.1016/j.fishres.2014.01.019
http://archimer.ifremer.fr/doc/00181/29274/

Éditeur(s) : Neidine Editeurs
Résumé : This article first draws up a balance sheet of all various implemented techniques to observe and monitor the shallow marine biodiversity. Then the article focuses on the techniques of the rotating high resolution submarine video and their implementation in New Caledonia on various sites and habitats under various management / protection policies such as Marines Protected Areas, strict marine reserves, registered sites on UNESCO world heritage or free access zones. An evaluation of these techniques and of their contributions is proposed in terms of transfer to other geographical zones, of practical feasibility in the technical, logistic and cost point of view as also are analyzed the perspectives offered by those technologies in terms of innovation, of support for the management or as communication tool on the health of the observed biodiversity.
Cet article dresse tout d’abord un bilan des différentes techniques mises en oeuvre pour observer et suivre la biodiversité marine peu profonde. Ensuite l’article se focalise sur les techniques de la vidéo sous marine rotative de haute définition et leur mise en œuvre en Nouvelle-Calédonie sur différents sites et habitats soumis ou non à des règles de gestion/protection tels que des Aires Marines Protégées, des réserves intégrales ou des sites inscrits au patrimoine mondial. Une évaluation de ces techniques et de leur apports est proposée en termes de transfert à d’autres zones géographiques, de faisabilité pratique aux plans techniques, logistiques et de coût comme également sont analysées les perspectives en termes d’innovation, d’appui à la gestion ou encore d’outil de communication sur les états de la biodiversité observée.
Tai Kona (2269-7535) (Neidine Editeurs), 2014-01 , N. 6 , P. 12-26

Droits : Tai Kona
http://archimer.ifremer.fr/doc/00174/28506/26855.pdf
http://archimer.ifremer.fr/doc/00174/28506/