Marc Leopold | Institut de Recherche pour le Développement (IRD - France) (original) (raw)

Papers by Marc Leopold

Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the riv... more Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the river Amazon, which constitute a major structuring factor for the estuarine, coastal, and shelf marine ecosystems. Moreover, the marked seasonal and interannual variabilities play important roles in the stability or fluctuations in the environmental parameters that influence biodiversity at the ecological, population, and genetic levels. Previous and ongoing studies of the marine and littoral biota relate mostly to commercial marine species, protected species in danger of extinction and, specially, to the biodiversity and functioning of local coastal and littoral ecosystems such as estuaries, mudflats, sandy beaches and, particularly, littoral mangroves. A more integrated approach involving local, regional, and international scientific collaboration is needed for a better assessment and understanding of marine biodiversity. Such studies would benefit from international cooperation that woul...

PloS one, 2017

In the Pacific, the protection of coral reef resources is often achieved through the implementati... more In the Pacific, the protection of coral reef resources is often achieved through the implementation of village-based marine reserves (VBMRs). While substantial fisheries benefits are often reported, results of quantitative approaches are controversial for benthic macroinvertebrates, whose life history traits may cause low congruence with protective measures implemented at non-ecologically relevant scales. This study investigated the structural and behavioral responses of the exploited topshell Tectus niloticus within a very small (0.2 km2) VBMR in Vanuatu, south Pacific. The results of underwater surveys and a nine-month tagging experiment emphasized contrasted, scale-dependent responses. At the reserve scale, our results failed to demonstrate any positive effect of protection after three years of closure. In contrast, abundance, density and biomass increased more than ten-fold in the southern part of the reserve, along with significantly larger (25%) individual sizes. The dispersal...

Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the riv... more Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the river Amazon, which constitute a major structuring factor for the estuarine, coastal, and shelf marine ecosystems. Moreover, the marked seasonal and interannual variabilities play important roles in the stability or fluctuations in the environmental parameters that influence biodiversity at the ecological, population, and genetic levels. Previous and ongoing studies of the marine and littoral biota relate mostly to commercial marine species, protected species in danger of extinction and, specially, to the biodiversity and functioning of local coastal and littoral ecosystems such as estuaries, mudflats, sandy beaches and, particularly, littoral mangroves. A more integrated approach involving local, regional, and international scientific collaboration is needed for a better assessment and understanding of marine biodiversity. Such studies would benefit from international cooperation that would allow the gathering of new information and the comparison of previous data, the organization of common oceanographic surveys, the homogenisation of analytical protocols, and also favour the exchange of scientists and postgraduate students for a real transfer of ideas, techniques, and know-how. Moreover, research on the comparative biodiversity of analogous littoral and marine ecosystems in different parts of South America would allow a more accurate estimate of marine biodiversity on a continental scale.

ABSTRACT Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une ... more ABSTRACT Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité en plein essor en Nouvelle-Calédonie, dont les effets sur les habitats coralliens et les espèces associées sont très mal connus. L’ancrage de navires de croisière, qui a commencé à Lifou en 1995, et dans le lagon d’Ouvéa en 2006, est à l’origine de dégradations ponctuelles des récifs. Le comité de cogestion d’Ouvéa et de Beautemps-Beaupré, créé en 2007 dans le cadre de l’inscription au Patrimoine mondial de l’UNESCO, se montre vigilant sur cette question. Son rôle est d’élaborer le plan de gestion participatif des lagons, récifs et écosystèmes associés ainsi que d’assurer sa mise en oeuvre effective. Composé de 19 représentants permanents des co-gestionnaires (autorités coutumières, Province et commune), il a constitué 5 groupes de travail thématiques dont l’un s’intéresse à l’aménagement du territoire (ancrage des paquebots et autres navires, pêche, protection du littoral). Relayant les questionnements des populations locales et des collectivités quant à la préservation du milieu et des ressources sur les sites fréquentés, cette étude visait à évaluer l’impact des perturbations occasionnées par les paquebots de croisière sur les paysages benthiques et les communautés de poissons associées. Les observations sous-marines sur le site de mouillage ont été effectuées par vidéo à l’aide d’un prototype développé par l’Ifremer, et ont permis de cartographier différentes catégories de substrat. Le présent rapport détaille les opérations réalisées dans la province des îles Loyauté (PIL) sur les sites d’Ouvéa (IRD/Ifremer, financement IFRECOR) et de Lifou (Ifremer/prestataire privé, financement PIL).

Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité ... more Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité en plein essor en Nouvelle-Calédonie, dont les effets sur les habitats coralliens et les espèces associées sont très mal connus. L’ancrage de navires de croisière, qui a commencé à Lifou en 1995, et dans le lagon d’Ouvéa en 2006, est à l’origine de dégradations ponctuelles des récifs. Le comité de cogestion d’Ouvéa et de Beautemps-Beaupré, créé en 2007 dans le cadre de l’inscription au Patrimoine mondial de l’UNESCO, se montre vigilant sur cette question. Son rôle est d’élaborer le plan de gestion participatif des lagons, récifs et écosystèmes associés ainsi que d’assurer sa mise en oeuvre effective. Composé de 19 représentants permanents des co-gestionnaires (autorités coutumières, Province et commune), il a constitué 5 groupes de travail thématiques dont l’un s’intéresse à l’aménagement du territoire (ancrage des paquebots et autres navires, pêche, protection du littoral). Relayant les...

In Vanuatu, fishing for sale and/or subsistence has severely affected the live stocks of reef mac... more In Vanuatu, fishing for sale and/or subsistence has severely affected the live stocks of reef macroinverterbrates, with populations now considered close to collapse in many locations despite the presence of suitable habitats for juveniles and adults. In this context, Vanuatu has been experiencing since the early 1990s a striking upsurge in small-scale initiatives to protect marine invertebrate resources, in particular trochus (Tectus niloticus), giant clams (Tridacna spp.), green snail (Turbo marmoratus) and sea cucumbers. Based on the existence of an extensive network of tabu areas managed by the local communities, the main objective of the EFITAV project ("Efficiency of tabu areas in Vanuatu") is to assess the capacity of tabu areas to restore and/or to maintain the level of reef resources, in order to provide objective criteria to optimize their effectiveness. The first phase of this project was implemented in Vanuatu from September 2011 to August 2012.

ABSTRACT This final report presents the results of the participative survey conducted in August 2... more ABSTRACT This final report presents the results of the participative survey conducted in August 2008 in Emau Island (North Efate, Vanuatu) to enforce the local capacity in underwater biological monitoring techniques (coral reef fish & invertebrates).

VertigO, 2013

Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit. Érudit est un consortium interuniversitaire sans but lucratif composé de l'

PLoS ONE, 2013

Parts of coral reefs from New Caledonia (South Pacific) were registered at the UNESCO World Herit... more Parts of coral reefs from New Caledonia (South Pacific) were registered at the UNESCO World Heritage list in 2008. Management strategies aiming at preserving the exceptional ecological value of these reefs in the context of climate change are currently being considered. This study evaluates the appropriateness of an exclusive fishing ban of herbivorous fish as a strategy to enhance coral reef resilience to hurricanes and bleaching in the UNESCO-registered areas of New Caledonia. A two-phase approach was developed: 1) coral, macroalgal, and herbivorous fish communities were examined in four biotopes from 14 reefs submitted to different fishing pressures in New Caledonia, and 2) results from these analyses were challenged in the context of a global synthesis of the relationship between herbivorous fish protection, coral recovery and relative macroalgal development after hurricanes and bleaching. Analyses of New Caledonia data indicated that 1) current fishing pressure only slightly affected herbivorous fish communities in the country, and 2) coral and macroalgal covers remained unrelated, and macroalgal cover was not related to the biomass, density or diversity of macroalgae feeders, whatever the biotope or level of fishing pressure considered. At a global scale, we found no relationship between reef protection status, coral recovery and relative macroalgal development after major climatic events. These results suggest that an exclusive protection of herbivorous fish in New Caledonia is unlikely to improve coral reef resilience to large-scale climatic disturbances, especially in the lightly fished UNESCO-registered areas. More efforts towards the survey and regulation of major chronic stress factors such as mining are rather recommended. In the most heavily fished areas of the country, carnivorous fish and large targeted herbivores may however be monitored as part of a precautionary approach.

Journal of Sea Research, 2012

Little is known about the effects of mud crabs population patterns on their exploitation. We used... more Little is known about the effects of mud crabs population patterns on their exploitation. We used complementary approaches (experimental, fisher-based) to investigate how small-scale variations in density, size and sex-ratio related to the ecology of S. serrata may impact fishing practices in New Caledonia. Crabs were measured/sexed across 9 stations in contrasted mangrove systems between 2007 and 2009. Stations were described and classified in different kinds of mangrove forests (coastal, riverine, and estuarine); vegetation cover was qualitatively described at station scale. Annual catch was used as an indicator of fishing pressure. Middle-scale environmental factors (oceanic influence, vegetation cover) had significant contributions to crab density (GLM, 84.8% of variance), crab size and sex-ratio (b 30%). While small-scale natural factors contributed significantly to population structure, current fishing levels had no impacts on mud crabs. The observed, ecologically-driven heterogeneity of crab resource has strong social implications in the Pacific area, where land tenure system and traditional access rights prevent most fishers from freely selecting their harvest zones. This offers a great opportunity to encourage site-specific management of mud crab fisheries.

Journal of Experimental Marine Biology and Ecology, 2009

The use of scuba-based photo/video methods for characterizing coral reef habitats has gained incr... more The use of scuba-based photo/video methods for characterizing coral reef habitats has gained increased popularity within the last decade, but few work examined the potentiality of surface photography to provide accurate, reliable habitat profiles in contrasted habitats. Photo transects were thus conducted by snorkeling in contrasted reef biotopes (reef flat, reef crest, sandy bottom) from the southwest lagoon of New Caledonia, to develop and test a "quick and clean" approach suitable for addressing monitoring as well as researchoriented programs. Pictures were taken by a snorkeler from the surface over twelve (20 × 1 m) reef crest/reef flat/soft bottoms transects using a standard 8 Mpixel digital-camera with underwater housing. Habitats were characterized from percent covers for 15 categories of local habitat variables related to sediment type and substrate coverage. Exhaustive area analyses using computer-assisted manual digitalizing were used to provide reliable habitat profiles from the digital pictures. Results were subsequently compared with surface estimates derived from random stratified point count techniques, for numbers of points comprised between 1 and 99 per m 2. Sampling-based randomization techniques allowed us to provide robust, reliable statistical estimates of accuracy and precision over 1000 randomized bootstrap replicates per transect. Results emphasized high accuracy and precision at transect scale whatever the reef biotopes considered, with maximum deviations from reference values of ∼ 1 percent cover in almost all cases and associated variances b 0.001. From a practical point of view, using a 9 points/m 2 ratio clearly provided reliable, quantitative descriptions of our reef transects (maximal errors b 1.5 percent cover with 95% confidence level). Costeffectiveness is high, with 15-30 minutes/transect from field data collection (b 10 min) to computation of final percent covers (10-20 min). The method outlined in this paper thus combines high statistical efficiency and logistical ease, and could be used to address more functional perspectives.

ICES Journal of Marine Science, 2014

Collecting spatial information on fisheries catch and effort is essential to understanding the sp... more Collecting spatial information on fisheries catch and effort is essential to understanding the spatial processes of exploited population dynamics and to manage heterogeneously distributed resources and uses. The use of fishers' knowledge through geographical information systems (GISs) is increasingly considered as a promising source of local information on small-scale coastal fisheries. In this paper we describe the first framework for mapping entire small-scale coastal fisheries using fishers' knowledge on catch size and fishing effort. Four mangrove and coral reef fisheries targeting invertebrates or finfish in New Caledonia (southwest Pacific) were mapped following a five-step framework: (i) stratified random sampling of regular fishers; (ii) collection of fishers' knowledge of fishing areas, fishing effort, and catch size through map-based interviews; (iii) data integration into a spatial geodatabase; (iv) statistical extrapolation of fisher data to the fishery scale...

Environmental Conservation, 2013

SUMMARYMany sea cucumber fisheries have dramatically declined worldwide due to rapid overexploita... more SUMMARYMany sea cucumber fisheries have dramatically declined worldwide due to rapid overexploitation and ineffective management. This study designed an innovative management strategy for small-scale, data-limited sea cucumber fisheries in Pacific Island countries. Firstly, a local quota-based comanagement system was implemented in New Caledonia to manage a small-scale sandfish Holothuria scabra fishery. A habitat map derived from high-resolution satellite imagery was used to stratify survey sampling and assess the harvestable stock biomass. The latter has been monitored as the reference biomass (RB) since 2008 and repeatedly used by the local fishers’ organization and Fisheries Department officers to set adaptive total allowable catches and regulations of fishing effort. Results showed the excellent performance of this fishery between 2008 and 2012, both biologically (167% increase in total stock biomass) and economically (146% increase in annual returns from catches). Secondly, th...

Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the riv... more Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the river Amazon, which constitute a major structuring factor for the estuarine, coastal, and shelf marine ecosystems. Moreover, the marked seasonal and interannual variabilities play important roles in the stability or fluctuations in the environmental parameters that influence biodiversity at the ecological, population, and genetic levels. Previous and ongoing studies of the marine and littoral biota relate mostly to commercial marine species, protected species in danger of extinction and, specially, to the biodiversity and functioning of local coastal and littoral ecosystems such as estuaries, mudflats, sandy beaches and, particularly, littoral mangroves. A more integrated approach involving local, regional, and international scientific collaboration is needed for a better assessment and understanding of marine biodiversity. Such studies would benefit from international cooperation that woul...

PloS one, 2017

In the Pacific, the protection of coral reef resources is often achieved through the implementati... more In the Pacific, the protection of coral reef resources is often achieved through the implementation of village-based marine reserves (VBMRs). While substantial fisheries benefits are often reported, results of quantitative approaches are controversial for benthic macroinvertebrates, whose life history traits may cause low congruence with protective measures implemented at non-ecologically relevant scales. This study investigated the structural and behavioral responses of the exploited topshell Tectus niloticus within a very small (0.2 km2) VBMR in Vanuatu, south Pacific. The results of underwater surveys and a nine-month tagging experiment emphasized contrasted, scale-dependent responses. At the reserve scale, our results failed to demonstrate any positive effect of protection after three years of closure. In contrast, abundance, density and biomass increased more than ten-fold in the southern part of the reserve, along with significantly larger (25%) individual sizes. The dispersal...

Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the riv... more Marine biodiversity in French Guiana is strongly influenced by the amagon River waters of the river Amazon, which constitute a major structuring factor for the estuarine, coastal, and shelf marine ecosystems. Moreover, the marked seasonal and interannual variabilities play important roles in the stability or fluctuations in the environmental parameters that influence biodiversity at the ecological, population, and genetic levels. Previous and ongoing studies of the marine and littoral biota relate mostly to commercial marine species, protected species in danger of extinction and, specially, to the biodiversity and functioning of local coastal and littoral ecosystems such as estuaries, mudflats, sandy beaches and, particularly, littoral mangroves. A more integrated approach involving local, regional, and international scientific collaboration is needed for a better assessment and understanding of marine biodiversity. Such studies would benefit from international cooperation that would allow the gathering of new information and the comparison of previous data, the organization of common oceanographic surveys, the homogenisation of analytical protocols, and also favour the exchange of scientists and postgraduate students for a real transfer of ideas, techniques, and know-how. Moreover, research on the comparative biodiversity of analogous littoral and marine ecosystems in different parts of South America would allow a more accurate estimate of marine biodiversity on a continental scale.

ABSTRACT Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une ... more ABSTRACT Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité en plein essor en Nouvelle-Calédonie, dont les effets sur les habitats coralliens et les espèces associées sont très mal connus. L’ancrage de navires de croisière, qui a commencé à Lifou en 1995, et dans le lagon d’Ouvéa en 2006, est à l’origine de dégradations ponctuelles des récifs. Le comité de cogestion d’Ouvéa et de Beautemps-Beaupré, créé en 2007 dans le cadre de l’inscription au Patrimoine mondial de l’UNESCO, se montre vigilant sur cette question. Son rôle est d’élaborer le plan de gestion participatif des lagons, récifs et écosystèmes associés ainsi que d’assurer sa mise en oeuvre effective. Composé de 19 représentants permanents des co-gestionnaires (autorités coutumières, Province et commune), il a constitué 5 groupes de travail thématiques dont l’un s’intéresse à l’aménagement du territoire (ancrage des paquebots et autres navires, pêche, protection du littoral). Relayant les questionnements des populations locales et des collectivités quant à la préservation du milieu et des ressources sur les sites fréquentés, cette étude visait à évaluer l’impact des perturbations occasionnées par les paquebots de croisière sur les paysages benthiques et les communautés de poissons associées. Les observations sous-marines sur le site de mouillage ont été effectuées par vidéo à l’aide d’un prototype développé par l’Ifremer, et ont permis de cartographier différentes catégories de substrat. Le présent rapport détaille les opérations réalisées dans la province des îles Loyauté (PIL) sur les sites d’Ouvéa (IRD/Ifremer, financement IFRECOR) et de Lifou (Ifremer/prestataire privé, financement PIL).

Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité ... more Avec plus de 80 paquebots ayant accosté en 2006, le tourisme de croisière constitue une activité en plein essor en Nouvelle-Calédonie, dont les effets sur les habitats coralliens et les espèces associées sont très mal connus. L’ancrage de navires de croisière, qui a commencé à Lifou en 1995, et dans le lagon d’Ouvéa en 2006, est à l’origine de dégradations ponctuelles des récifs. Le comité de cogestion d’Ouvéa et de Beautemps-Beaupré, créé en 2007 dans le cadre de l’inscription au Patrimoine mondial de l’UNESCO, se montre vigilant sur cette question. Son rôle est d’élaborer le plan de gestion participatif des lagons, récifs et écosystèmes associés ainsi que d’assurer sa mise en oeuvre effective. Composé de 19 représentants permanents des co-gestionnaires (autorités coutumières, Province et commune), il a constitué 5 groupes de travail thématiques dont l’un s’intéresse à l’aménagement du territoire (ancrage des paquebots et autres navires, pêche, protection du littoral). Relayant les...

In Vanuatu, fishing for sale and/or subsistence has severely affected the live stocks of reef mac... more In Vanuatu, fishing for sale and/or subsistence has severely affected the live stocks of reef macroinverterbrates, with populations now considered close to collapse in many locations despite the presence of suitable habitats for juveniles and adults. In this context, Vanuatu has been experiencing since the early 1990s a striking upsurge in small-scale initiatives to protect marine invertebrate resources, in particular trochus (Tectus niloticus), giant clams (Tridacna spp.), green snail (Turbo marmoratus) and sea cucumbers. Based on the existence of an extensive network of tabu areas managed by the local communities, the main objective of the EFITAV project ("Efficiency of tabu areas in Vanuatu") is to assess the capacity of tabu areas to restore and/or to maintain the level of reef resources, in order to provide objective criteria to optimize their effectiveness. The first phase of this project was implemented in Vanuatu from September 2011 to August 2012.

ABSTRACT This final report presents the results of the participative survey conducted in August 2... more ABSTRACT This final report presents the results of the participative survey conducted in August 2008 in Emau Island (North Efate, Vanuatu) to enforce the local capacity in underwater biological monitoring techniques (coral reef fish & invertebrates).

VertigO, 2013

Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit. Érudit est un consortium interuniversitaire sans but lucratif composé de l'

PLoS ONE, 2013

Parts of coral reefs from New Caledonia (South Pacific) were registered at the UNESCO World Herit... more Parts of coral reefs from New Caledonia (South Pacific) were registered at the UNESCO World Heritage list in 2008. Management strategies aiming at preserving the exceptional ecological value of these reefs in the context of climate change are currently being considered. This study evaluates the appropriateness of an exclusive fishing ban of herbivorous fish as a strategy to enhance coral reef resilience to hurricanes and bleaching in the UNESCO-registered areas of New Caledonia. A two-phase approach was developed: 1) coral, macroalgal, and herbivorous fish communities were examined in four biotopes from 14 reefs submitted to different fishing pressures in New Caledonia, and 2) results from these analyses were challenged in the context of a global synthesis of the relationship between herbivorous fish protection, coral recovery and relative macroalgal development after hurricanes and bleaching. Analyses of New Caledonia data indicated that 1) current fishing pressure only slightly affected herbivorous fish communities in the country, and 2) coral and macroalgal covers remained unrelated, and macroalgal cover was not related to the biomass, density or diversity of macroalgae feeders, whatever the biotope or level of fishing pressure considered. At a global scale, we found no relationship between reef protection status, coral recovery and relative macroalgal development after major climatic events. These results suggest that an exclusive protection of herbivorous fish in New Caledonia is unlikely to improve coral reef resilience to large-scale climatic disturbances, especially in the lightly fished UNESCO-registered areas. More efforts towards the survey and regulation of major chronic stress factors such as mining are rather recommended. In the most heavily fished areas of the country, carnivorous fish and large targeted herbivores may however be monitored as part of a precautionary approach.

Journal of Sea Research, 2012

Little is known about the effects of mud crabs population patterns on their exploitation. We used... more Little is known about the effects of mud crabs population patterns on their exploitation. We used complementary approaches (experimental, fisher-based) to investigate how small-scale variations in density, size and sex-ratio related to the ecology of S. serrata may impact fishing practices in New Caledonia. Crabs were measured/sexed across 9 stations in contrasted mangrove systems between 2007 and 2009. Stations were described and classified in different kinds of mangrove forests (coastal, riverine, and estuarine); vegetation cover was qualitatively described at station scale. Annual catch was used as an indicator of fishing pressure. Middle-scale environmental factors (oceanic influence, vegetation cover) had significant contributions to crab density (GLM, 84.8% of variance), crab size and sex-ratio (b 30%). While small-scale natural factors contributed significantly to population structure, current fishing levels had no impacts on mud crabs. The observed, ecologically-driven heterogeneity of crab resource has strong social implications in the Pacific area, where land tenure system and traditional access rights prevent most fishers from freely selecting their harvest zones. This offers a great opportunity to encourage site-specific management of mud crab fisheries.

Journal of Experimental Marine Biology and Ecology, 2009

The use of scuba-based photo/video methods for characterizing coral reef habitats has gained incr... more The use of scuba-based photo/video methods for characterizing coral reef habitats has gained increased popularity within the last decade, but few work examined the potentiality of surface photography to provide accurate, reliable habitat profiles in contrasted habitats. Photo transects were thus conducted by snorkeling in contrasted reef biotopes (reef flat, reef crest, sandy bottom) from the southwest lagoon of New Caledonia, to develop and test a "quick and clean" approach suitable for addressing monitoring as well as researchoriented programs. Pictures were taken by a snorkeler from the surface over twelve (20 × 1 m) reef crest/reef flat/soft bottoms transects using a standard 8 Mpixel digital-camera with underwater housing. Habitats were characterized from percent covers for 15 categories of local habitat variables related to sediment type and substrate coverage. Exhaustive area analyses using computer-assisted manual digitalizing were used to provide reliable habitat profiles from the digital pictures. Results were subsequently compared with surface estimates derived from random stratified point count techniques, for numbers of points comprised between 1 and 99 per m 2. Sampling-based randomization techniques allowed us to provide robust, reliable statistical estimates of accuracy and precision over 1000 randomized bootstrap replicates per transect. Results emphasized high accuracy and precision at transect scale whatever the reef biotopes considered, with maximum deviations from reference values of ∼ 1 percent cover in almost all cases and associated variances b 0.001. From a practical point of view, using a 9 points/m 2 ratio clearly provided reliable, quantitative descriptions of our reef transects (maximal errors b 1.5 percent cover with 95% confidence level). Costeffectiveness is high, with 15-30 minutes/transect from field data collection (b 10 min) to computation of final percent covers (10-20 min). The method outlined in this paper thus combines high statistical efficiency and logistical ease, and could be used to address more functional perspectives.

ICES Journal of Marine Science, 2014

Collecting spatial information on fisheries catch and effort is essential to understanding the sp... more Collecting spatial information on fisheries catch and effort is essential to understanding the spatial processes of exploited population dynamics and to manage heterogeneously distributed resources and uses. The use of fishers' knowledge through geographical information systems (GISs) is increasingly considered as a promising source of local information on small-scale coastal fisheries. In this paper we describe the first framework for mapping entire small-scale coastal fisheries using fishers' knowledge on catch size and fishing effort. Four mangrove and coral reef fisheries targeting invertebrates or finfish in New Caledonia (southwest Pacific) were mapped following a five-step framework: (i) stratified random sampling of regular fishers; (ii) collection of fishers' knowledge of fishing areas, fishing effort, and catch size through map-based interviews; (iii) data integration into a spatial geodatabase; (iv) statistical extrapolation of fisher data to the fishery scale...

Environmental Conservation, 2013

SUMMARYMany sea cucumber fisheries have dramatically declined worldwide due to rapid overexploita... more SUMMARYMany sea cucumber fisheries have dramatically declined worldwide due to rapid overexploitation and ineffective management. This study designed an innovative management strategy for small-scale, data-limited sea cucumber fisheries in Pacific Island countries. Firstly, a local quota-based comanagement system was implemented in New Caledonia to manage a small-scale sandfish Holothuria scabra fishery. A habitat map derived from high-resolution satellite imagery was used to stratify survey sampling and assess the harvestable stock biomass. The latter has been monitored as the reference biomass (RB) since 2008 and repeatedly used by the local fishers’ organization and Fisheries Department officers to set adaptive total allowable catches and regulations of fishing effort. Results showed the excellent performance of this fishery between 2008 and 2012, both biologically (167% increase in total stock biomass) and economically (146% increase in annual returns from catches). Secondly, th...