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Human-induced habitat modifications can severely impact the biology and behavior of wild species. Drifting Fish Aggregating Devices (DFADs), used by industrial purse seine tropical tuna fisheries, significantly increased the number of floating objects found in the open ocean, to which tropical tuna associate. This habitat change raised concerns over the risk of modifying the behavior and altering the biology of tuna and other associated species (the so-called ecological trap hypothesis). Relying on a time-series from 1987 to 2019 of more than 25,000 length-weight samples collected in the western Indian Ocean, we reject the hypothesis that the body condition (Le Cren’s relative condition factor Kn) of yellowfin tuna (Thunnus albacares) decreased concurrently with the increased number of DFADs. This result suggests the absence of negative long-term impacts of DFADs on the condition of tuna. As other factors may have counteracted possible negative effects of DFADs, we recommend a long-term monitoring of habitat, biological and behavioral parameters of tunas to detect any critical change.

Human-induced habitat modifications can severely impact the biology and behavior of wild species. Drifting Fish Aggregating Devices (DFADs), used by industrial purse seine tropical tuna fisheries, significantly increased the number of floating objects found in the open ocean, with which tropical tuna associate. This habitat change raised concerns over the risk of modifying the behavior and altering the biology of tuna and other associated species (the so-called ecological trap hypothesis). Relying on a time-series of more than 25,000 length-weight samples collected in the western Indian Ocean (1987-2019), we reject the hypothesis that the body condition (Le Cren’s relative condition factor Kn) of yellowfin tuna (Thunnus albacares) decreased concurrently with the increased number of DFADs. This result suggests the absence of negative long-term impacts of DFADs on the biology of tuna. As other factors may have counteracted possible negative effects of DFADs, we recommend a long-term monitoring of habitat, biological and behavioral parameters of tunas to detect any critical change.

Ecological traps occurs when animals choose low-quality habitats, leading to a reduction in their reproduction and survival. In the marine environment, this phenomenon has received little attention so far. Habitat modifications are one of the major human-induced rapid environmental change which could provoke such traps. Floating objects are a component of the habitat of pelagic fish species, including tropical tunas, which are known to associate with them. The deployment of thousands of man-made floating objects (called drifting Fish Aggregating Devices-DFADs) by industrial tuna fisheries worldwide over the past three decades has raised concerns over the risk of DFADs forming ecological traps. Relying on a three-decade time series of more than 25,000 length-weight samples collected in the western Indian Ocean (from 1987 to 2019), we reject the hypothesis that the body condition of yellowfin tuna Thunnus albacares decreased concurrently with the increased number of DFADs. While body condition is not the only variable that may indicate a decline in individual fitness, this result ruled out one of the potential negative impacts of DFADs on tuna postulated by a twenty-years-old hypothesis. We recommend that long-term monitoring of biological and behavioral parameters of tunas be conducted to detect any critical change.

This short note presents the details of the methodology used to assess crude estimates of the faux poisson catch of the EU PS fleet over the period 2015-2020 for the major and small tuna species: yellowfin (YFT), bigeye (BET), skipjack (SKJ), frigate tuna (FRI) and little tuna (LTA)., Cette courte note présente les détails de la méthodologie utilisée pour obtenir les estimations brutes des captures de " faux poisson " de la flottille de senneurs de l’UE sur la période 2015-2020 pour les espèces de thonidés grands et mineurs : albacore (YFT), thon obèse (BET), listao (SKJ), auxide (FRI) et thonine (LTA)., Esta breve nota presenta los detalles de la metodología utilizada para evaluar las estimaciones brutas de las capturas de faux poisson de la flota de cerco de la UE durante el período 2015-2020 para especies de grandes y pequeños túnidos: rabil (YFT), patudo (BET), listado (SKJ), melva (FRI) y bacoreta (LTA).

This paper presents an associative behavior-based abundance index (ABBI) providing direct estimates of the abundance of yellowfin tuna (Thunnus albacares) based on their associative behavior around floating objects (FOBs). Considering the associative dynamics of small yellowfin tuna individuals (

This document presents an updated summary of the French purse seine fleet targeting tropical tunas in the Indian Ocean. The statistics cover the period 1981-2020 and specifically focus on the activity of the last year of the fishery. In 2020, a total of 13 French vessels operated in the western Indian Ocean including 10 purse seiners and 3 support vessels. The total capacity weighted by the months of activity for each vessel is 10626t. The total nominal effort in 2020 was of 1805 fishing days and 2414 sets with 1898 sets on floating objects and 516 on free schools. The total catch of the French component of the EU purse seine fleet of the Indian Ocean was 58149t, being composed of 42.2%, 52.6%, 4.5% and 0.8% of yellowfin tuna, skipjack tuna, bigeye tuna and other species respectively. The most noticeable change in 2020 was the decrease of 17.7% for the total of catches in comparison to 2019, respectively 58149t and 70622t. Remarkably, yellowfin tuna and skipjack tuna proportion of catches in 2020 for free swimming school returned to the proportion prevailing before 2018, after 2 years of a different fishing strategy targeting skipjack tuna on free swimming school.

International audience; This paper is an information note on the progress of the development of the new version of T3 following the development of a new statistical model.

Part of the tuna catch of purse seiners, not sold to the canneries, is landed with other bycatch species towards another commercial flow. This local flow better known as “Faux poisson” is an important socio-cultural and economic market for Ivory Coast and neighboring countries. Yet, Faux poisson catches landed to this local market increased this last decade since the development of FAD fishing in the mid-nineties. Regarding major tuna species, the catch landed in the local market is mainly composed of small individuals which are not accounted for in the species composition and in catch at size estimates from conventional sampling. Because of the difficulties of the data collection this portion of tropical tuna landing is ignored in the stock assessment models. The need of improve knowledge is so of prime importance to better assess the sustainability of the fishery and the ecosystem. The document presents the main results of recent research on local market flow landed in Abidjan by purse seiners French fleet in the eastern Atlantic. Data collection improvement and perspective for species composition assessment and catch at size are further discussed

The Tropical Tuna Treatment is a process created at the end of the 90s by EU scientists to estimate catch of the tropical tuna purse seine fishery, for which logbook declarations were known biased. His main purpose is to provide the best estimations for nominal catch and catch effort spatially represented, to the RFMOs. However, the evolution of fishing practices and the extension of the fishing grounds have challenged the T3 methodology in some parts of it processing. Thus, the used of too large spatio-temporal sampling strata was specifically pointed out as the major cause of biases in the catch estimated. This paper presents the new methodology developed to fix this issue and implications on the output estimations compared to the previous version and logbook declarations. Finally, future improvements were discussed.

The knowledge of the juvenile distribution in fisheries is essential to better manage the fishing effort on a stock. The exploration of a large dataset which covers 30 years of the purse seine fishery sampling enabled to study the spatio-temporal dynamic of the juvenile catches of the yellowfin and bigeye tunas. Results showed the existence of several areas of prime importance in terms of catch and concentration in juveniles with seasonal variations. Thus, the south of the fishing ground (Cape Lopez) was fished during winter month and the north during summer months (Cape Verde, Senegal y Mauritania). Offshore coastal zone and Gulf of Guinea were fished almost all along the year. This seasonal pattern is quite stable since the 90s but the proportion of juveniles in schools associated with floating objects tended to increase in both species. This preliminary study opened the way for further research on this important component of the fish stocks. La connaissance de la répartition des juvéniles dans les pêcheries est essentielle pour mieux gérer l'effort de pêche sur un stock. L'exploration d'un vaste jeu de données couvrant 30 ans d'échantillonnage de la pêcherie à la senne a permis d'étudier la dynamique spatio-temporelle des captures de juvéniles d'albacore et de thon obèse. Les résultats ont montré l'existence de plusieurs zones de première importance en termes de capture et de concentration des juvéniles avec des variations saisonnières. Ainsi, le sud de la zone de pêche (Cap Lopez) était pêché pendant les mois d'hiver et le nord pendant les mois d'été (Cabo Verde, Sénégal et Mauritanie). La zone côtière offshore et le golfe de Guinée ont été pêchés presque toute l'année. Bien que ce schéma saisonnier soit stable depuis les années 1990, la proportion de juvéniles dans les bancs associés à des objets flottants avait tendance à augmenter pour ces deux espèces. Cette étude préliminaire a ouvert la voie à d'autres recherches sur cette composante importante des stocks de poissons. El conocimiento de la distribución de los juveniles en las pesquerías es esencial para gestionar mejor el esfuerzo pesquero en un stock. La exploración de un gran conjunto de datos que abarca 30 años de muestreo de la pesquería de cerco permitió estudiar la dinámica espacio-temporal de las capturas de juveniles de rabil y patudo. Los resultados mostraron la existencia de varias zonas de importancia primordial en cuanto a la captura y concentración de juveniles con variaciones estacionales. Así, el sur del caladero (Cabo López) se pescaba durante el mes de invierno y el norte durante los meses de verano (Cabo Verde, Senegal y Mauritania). En la zona costera y en el golfo de Guinea se pescaba casi todo el año. Esta pauta estacional es bastante estable desde los años 90, pero la proporción de juveniles en los cardúmenes asociados a objetos flotantes tendió a aumentar en ambas especies. Este estudio preliminar abrió el camino a nuevas investigaciones sobre este importante componente de los stocks de peces.

In 2018, a total of 14 French vessels operated in the eastern Indian Ocean including 12 purse seiners and 2 supplies. The total capacity weighted by the months of activity for each vessel is 11686t. The total nominal effort in 2018 was of 2885 fishing days and 2723 sets with 2463 sets on floating objects and 260 on free schools. In 2018, the percentage of sets on FOB was 90% and the catches reached 91%. The total catch of the French component of the EU purse seine fleet of the Indian Ocean was 84,729 t, being composed of 36%, 58%, and 6% of yellowfin tuna, skipjack tuna, and bigeye tuna respectively. Thus, the most noticeable change in 2018 is the shift of catches from the free school sets, dominated by yellowfin, to the associated school sets, dominated by skipjack. As a consequence, the increase in total catches mainly concerned the skipjack catches.

These last decades, large herbivores population and outdoor human activities increased tremendously leading to the emergence of new challenges for the management of wild species and recreational activities, which need to reconcile conservation goals and tourist development. In order to face these challenges, wildlife managers need to better understand behavioral choice of animal that lead to their spatial distribution and how these behaviors are influenced by human activities. Based on chamois (Rupicapra rupicapra) as a study case, the aim of this PhD is to enhance our knowledge of spatial behavioral of large herbivores, on one hand by understanding individual selection for food resources according to resource spatial heterogeneity and their temporal dynamics, and on the other hand, by assessing the impact of human outdoor recreational activities on spatial behavior. We first modeled the foodscape of chamois and its seasonal variation by combining field data on vegetation and animal diet with remote sensing data. Then, based on a 10 years dataset of monitoring of >100 animals marked with GPS collars in the Game and Wildlife Reserve of the “massif des Bauges”, we demonstrated chamois adjusted their criteria for spatial selection through time according to the temporal evolution of their forage traits (quality and quantity), accounting notably whether these traits were variable or limiting. This led us to reevaluate the framework of two classical hypotheses in studies of herbivore spatial ecology, the “Forage Maturation Hypothesis” and the emergence of a functional response in habitat selection. One newness in our work is to have accounted for the gregariousness of this species, which allowed us to unveil that socio-spatial structure of the population induced local variation in the habitat selection process, with marked consequences on individual demographic performances. This challenges the idea that individuals should redistribute in space within a population according to available resources, probably because of the importance of social relationships and costs and risks associated with dispersal. Second, we investigated the response of chamois to disturbances resulting from 3 outdoor activities. We assessed the spatial use of recreationists by ditributing GPS-tracker from which we defined landscape of disturbance to animal. Ski touring and hiking both impacted animal movements, resulting in supplementary energetic expenditures. On the other hand, hunting induced complex spatial responses in chamois that need further investigation, as the response to hunters could not be differentiated from responses to hikers who continue to be on site even during the hunting period. We conclude this work with proposals for a better long-term management of wildlife compatible with the practice of outdoor recreational activities., Ces dernières décennies, l'augmentation conjointe des populations de grands herbivores et des activités humaines de nature a donné lieu à de nouveaux enjeux de gestion du territoire conciliant objectifs de conservation et développement touristique. Afin de faire face à ce défi, les gestionnaires ont besoin de mieux comprendre les choix comportementaux qui sont à l’origine de la répartition spatiale des animaux et l’impact des activités humaines sur ces comportements. En prenant l'exemple du chamois (Rupicapra rupicapra), l'objectif de cette thèse est de répondre à ce besoin de connaissances sur le comportement spatial des grands herbivores, en prenant en compte d'une part la sélection des ressources alimentaires en fonction de l'hétérogénéité spatiale et de la dynamique de leur environnement, et d'autre part la réponse comportementale à l'influence de différents types d'activités récréatives de plein air. Nous avons tout d’abord modélisé le paysage alimentaire du chamois et ses variations saisonnières en combinant des données sur la végétation et sur le régime alimentaire à des données de télédétection. Puis à partir de 10 années de suivi de près de 100 animaux par collier GPS dans la Réserve de Chasse et de Faune Sauvage du massif des Bauges, nous avons démontré que les chamois ajustent leurs critères de sélection spatiale au cours du temps en fonction de l’évolution temporelle des caractéristiques de leur fourrage (qualité et quantité), notamment en fonction de leur variabilité ou caractère limitant. Ceci nous a amené à réévaluer le cadre d’application de deux hypothèses classiques en écologie spatiale des herbivores, l’hypothèse de la maturation du fourrage (Forage Maturation Hypothesis) et l’existence d’une réponse fonctionnelle dans la sélection d’habitat. Une des originalités de cette thèse est d’avoir pris en compte le caractère grégaire de cette espèce et de montrer comment la structure socio-spatiale de la population entraîne des variations locales du processus de sélection d’habitat, avec des implications démographiques fortes pour les individus. Nos résultats remettent en cause l’idée que les animaux se redistribuent au sein des populations en fonction des ressources disponibles, ce qui découle probablement de l’importance des relations sociales et du cout et des risques associés à la dispersion. Dans un second temps, nous avons abordé la thématique du dérangement du chamois face à trois activités humaines saisonnières, dont l’étude de la distribution dans notre site d’étude, à l’aide de GPS distribués aux pratiquants, a permis d’établir le paysage du dérangement pour les animaux. Le ski de randonnée et la marche à pied impactent clairement les déplacements des animaux, induisant une dépense énergétique supplémentaire. En revanche pour la chasse, la complexité de la réponse des chamois ne permet pas à l'heure actuelle de différentier l’impact des chasseurs de simples randonneurs, qui sont également présent sur le site en période de chasse. Ce travail se conclut par des propositions de gestion durable des populations sauvages compatibles avec la pratique des activités de loisirs de plein air.

This article deals with the construction of an interdisciplinary research program aboutinterrelationship between outdoor activities and wildlife in the Bauges mountains (Alpes). This research program is build on a twofold partnership : a partnership between researchers and local stakeholders, and a partnership between researchers coming from different disciplines, social sciences and ecology. The article emphasizes pros and cons of the research project coconstruction. It presents the exchange views between the different collaborators on three main subjects : i) the research protocol which coordinates research on the field and included elements useful for stakeholders decision making ; ii) methodologies which crossed different qualitative, quantitative and spatial datas (GPS) ; iii) concepts used in the research such as the “landscape” concept. The reflective analysis allows identifying some elements favorable for an interdisciplinary research proceeding bringing together different collaborators.; Cet article analyse le développement d’un programme de recherche interdisciplinaire visant à mieux connaître les interrelations entre les pratiquants de sports de nature et la faune sauvage sur le massif des Bauges (Alpes). Ce programme de recherche est construit sur un doublepartenariat qui est ici analysé : il s’agit d’un partenariat entre chercheurs et praticiens de terrain et entre chercheurs venant de différentes disciplines, les sciences humaines et sociales et l’écologie. L’article revient sur les avantages et limites de la co-construction de ce travail derecherche. Il présente une analyse réflexive des échanges qui ont eu lieu entre les différents partenaires en ce qui concerne : i) la définition du protocole de recherche afin que le travail de recherche soit coordonné sur le terrain et apporte des éléments utiles à la prise de décision des gestionnaires du territoire ; ii) les méthodes mobilisées qui ont permis de croiser différentes données qualitatives, quantitatives et spatialisées (utilisation de l’outil GPS) ; iii) les concepts discutés au sein de la recherche telle que la notion de paysage. Ce retour d’expérience permetd’identifier des éléments favorables au bon déroulement d’une recherche interdisciplinaire et multi-partenariale.

This article deals with the construction of an interdisciplinary research program aboutinterrelationship between outdoor activities and wildlife in the Bauges mountains (Alpes). This research program is build on a twofold partnership : a partnership between researchers and local stakeholders, and a partnership between researchers coming from different disciplines, social sciences and ecology. The article emphasizes pros and cons of the research project coconstruction. It presents the exchange views between the different collaborators on three main subjects : i) the research protocol which coordinates research on the field and included elements useful for stakeholders decision making ; ii) methodologies which crossed different qualitative, quantitative and spatial datas (GPS) ; iii) concepts used in the research such as the “landscape” concept. The reflective analysis allows identifying some elements favorable for an interdisciplinary research proceeding bringing together different collaborators.; Cet article analyse le développement d’un programme de recherche interdisciplinaire visant à mieux connaître les interrelations entre les pratiquants de sports de nature et la faune sauvage sur le massif des Bauges (Alpes). Ce programme de recherche est construit sur un doublepartenariat qui est ici analysé : il s’agit d’un partenariat entre chercheurs et praticiens de terrain et entre chercheurs venant de différentes disciplines, les sciences humaines et sociales et l’écologie. L’article revient sur les avantages et limites de la co-construction de ce travail derecherche. Il présente une analyse réflexive des échanges qui ont eu lieu entre les différents partenaires en ce qui concerne : i) la définition du protocole de recherche afin que le travail de recherche soit coordonné sur le terrain et apporte des éléments utiles à la prise de décision des gestionnaires du territoire ; ii) les méthodes mobilisées qui ont permis de croiser différentes données qualitatives, quantitatives et spatialisées (utilisation de l’outil GPS) ; iii) les concepts discutés au sein de la recherche telle que la notion de paysage. Ce retour d’expérience permetd’identifier des éléments favorables au bon déroulement d’une recherche interdisciplinaire et multi-partenariale.