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As population-related climate change research increases, so does the need to nuance approaches to this complex phenomenon, including issues related to cultural and linguistic translations. To explore how climate change is understood in understudied societies, a case-study approach is taken to address social representations of climate change by inhabitants of a Maore village in the French island of Mayotte. The study explores how local fishers understand the issue when considering observed environmental changes. Based on analyses of 30 interviews, the study found that social representations and related climate change discourses are not well established, except for individuals in close contact with French institutions. Issues regarding local culture and language reveal the importance of understanding the different components of climate change. Climate change communication and awareness-raising on the island are explored, as well as considerations of culturally and linguistically complex settings with a Global North/Global South interface.

Coastal habitats have long been recognised to be nurseries and growing grounds for many marine organisms. Worldwide, coastal hardening and urbanisation are leading to the removal of natural ecosystems. The tropical island of Bora-Bora in the South Pacific has undergone extensive coastal changes, with the construction of seawalls along more than half of its coastline since the 1950s. The daytime and night-time juvenile and adult fish communities were surveyed with multiple temporal replicates on a range of lagoon and coastal habitats on Bora-Bora. Over 47% of all fish on coastal habitats were juveniles. Mangroves, traditionally viewed as nurseries, had a high daytime and night-time abundance of juveniles, but less than 1% of the coastline of Bora-Bora consists of mangroves. The manmade seawalls, which are the most common type of coastal habitat on the island, were associated with lower juvenile densities during the day and promoted the presence of predators. The comparison of coastal and lagoon sites also highlighted contrasting life history strategies depending on coral reef fish species: although many favour coastal habitats as juveniles, others do not undergo ontogenetic shifts and thus other habitats must be considered when designing management plans to protect juvenile fish. Overall, our surveys show the importance of natural coastal zones in the lifecycle of numerous coral reef fish species in the lagoon of Bora-Bora and highlight the potential long-term impacts of coastal hardening on fish communities.

In the marine environment, fish contribute to key ecological processes such as controlling food-webs through top-down impacts, especially on algae. To date, the assessment of fish grazing activity has mostly been performed using short-term (<1 h) censuses by divers or remote cameras which do not allow estimating the variability of grazing rate within and between days. However, understanding the temporal variation of fish activity and hence contribution of species to ecosystem functioning is of particular interest in the context of biological invasion. Here, using long-duration remote underwater cameras, we recorded fish abundance and grazing events over three consecutive days in October 2019 in a shallow Mediterranean ecosystem from northern Crete. This novel approach allowed us to assess temporal variation of abundance and grazing activity of the two native (Sarpa salpa and Sparisoma cretense) and the two non-indigenous fish species (Siganus rivulatus and Siganus luridus). Non-indigenous Siganus rivulatus was the most common species in the studied coastal habitat, followed by the two native species while the non-indigenous Siganus luridus was scarce. Overall, the non-indigenous S. rivulatus and the native S. salpa are responsible for more than 90% of the recorded grazing activity with similar bite rates between the two species. More than 70% of the grazing activity arose in grazing pulses in the afternoon, supporting the diel feeding hypothesis according to which feeding is greater in the afternoon when nutritive quality of macrophytes is the highest. In addition, some of the highest peaks in grazing activity were driven by a few individuals. Hence, surveys of only abundance could not provide accurate estimates of herbivory. Last, Siganus rivulatus presence did not significantly affect grazing activity of the native Sarpa salpa. Our results demonstrate that long-duration remote underwater videos are a useful tool to accurately assess the contribution of fishes to e

It is widely believed that because of biomechanical trade-offs, fish body shape and the mode of propulsion are strong predictors of swimming performance, with the best cruisers, maneuverers, and accelerators having different body forms and emphasizing different propulsion mechanisms. This paradigm is regularly projected onto routine swimming behavior and dominates the ecomorphological literature, despite the paucity of field measurements. In this study, we measured variation in swimming behavior among 48 species of Indian Ocean coral reef fishes using recordings from a remote stereo video system. We measured average swimming speed, average swimming bout distance, frequency of turns, and percent of time spent station-holding and looked for the predicted trade-offs between them. We find little evidence of the expected relationships between swimming behaviors across species, little evidence that body shape affects swimming, and few differences between species that swim by undulating the body and those that emphasize the use of median and paired fins. Taxa widely thought of as archetypical maneuverers (Chaetodon) and cruisers (Caranx) were not outliers in any behaviors. Our results indicate that swimming behavior is not easily predicted from simple measures of body shape and that alternative swimming modes can produce comparable behavioral profiles.

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities.

In the marine environment, fish contribute to key ecological processes such as controlling food-webs through top-down impacts, especially on algae. To date, the assessment of fish grazing activity has mostly been performed using short-term (<1 h) censuses by divers or remote cameras which do not allow estimating the variability of grazing rate within and between days. However, understanding the temporal variation of fish activity and hence contribution of species to ecosystem functioning is of particular interest in the context of biological invasion. Here, using long-duration remote underwater cameras, we recorded fish abundance and grazing events over three consecutive days in October 2019 in a shallow Mediterranean ecosystem from northern Crete. This novel approach allowed us to assess temporal variation of abundance and grazing activity of the two native (Sarpa salpa and Sparisoma cretense) and the two non-indigenous fish species (Siganus rivulatus and Siganus luridus). Non-indigenous Siganus rivulatus was the most common species in the studied coastal habitat, followed by the two native species while the non-indigenous Siganus luridus was scarce. Overall, the non-indigenous S. rivulatus and the native S. salpa are responsible for more than 90% of the recorded grazing activity with similar bite rates between the two species. More than 70% of the grazing activity arose in grazing pulses in the afternoon, supporting the diel feeding hypothesis according to which feeding is greater in the afternoon when nutritive quality of macrophytes is the highest. In addition, some of the highest peaks in grazing activity were driven by a few individuals. Hence, surveys of only abundance could not provide accurate estimates of herbivory. Last, Siganus rivulatus presence did not significantly affect grazing activity of the native Sarpa salpa. Our results demonstrate that long-duration remote underwater videos are a useful tool to accurately assess the contribution of fishes to e

unctional diversity (FD), the diversity of organism attributes that relates to their interactions with the abiotic and biotic environment, has been increasingly used for the last two decades in ecology, biogeography and conservation. Yet, FD has many facets and their estimations are not standardized nor embedded in a single tool. mFD (multifaceted functional diversity) is an R package that uses matrices of species assemblages and species trait values as building blocks to compute most FD indices. mFD is firstly based on two functions allowing the user to summarize trait and assemblage data. Then it calculates trait-based distances between species pairs, informs the user whether species have to be clustered into functional entities and finally computes multidimensional functional space. To let the user choose the most appropriate functional space for computing multidimensional functional diversity indices, two mFD functions allow assessing and illustrating the quality of each functional space. Next, mFD provides 6 core functions to calculate 16 existing FD indices based on trait-based distances, functional entities or species position in a functional space. The mFD package also provides graphical functions based on the ggplot library to illustrate FD values through customizable and high-resolution plots of species distribution among functional entities or in a multidimensional space. All functions include internal validation processes to check for errors in data formatting which return detailed error messages. To facilitate the use of mFD framework, we built an associated website hosting five tutorials illustrating the use of all the functions step by step.

Coral reefs are under increasing threat, and the loss of reef-associated fishes providing valuable ecosystem services is accelerating. The monitoring of such rapid changes has become a challenge for ecologists and ecosystems managers using traditional approaches like scuba divers performing underwater visual censuses (UVC) or diver operated video recording (DOV). However, the use of small, low-cost robots could help tackle the challenge of such monitoring, provided that they perform at least as well as diver-based methods. To address this question, tropical fish assemblages from 13 fringing reefs around Mayotte Island (Indian Ocean) were monitored along 50 m-long transects using stereo videos recorded by a semi-autonomous underwater vehicle (SAUV) and by a scuba diver (Diver Operated stereo Video system, DOV). Differences between the methods were tested for complementary fish assemblage metrics (species richness, total biomass, total density, Shannon diversity and Pielou evenness) and for the number and size of nine targeted species. SAUV recorded on average 35% higher biomass than DOV which in turn recorded on average 12% higher species richness. Biomass differences were found to be due to SAUV monitoring larger fishes than DOV, a potential marker of human-related fish avoidance behaviour. This study demonstrates that SAUV provides accurate metrics of coral reef fish biodiversity compared to diver-based procedures. Given their ability to conduct video transects at high frequency, 100 m depth range and at a moderate cost, SAUV is a promising tool for monitoring fish assemblages in coral reef ecosystems.

Underwater cameras are widely used to monitor marine biodiversity, and the trend is increasing due to the availability of cheap action cameras. The main bottleneck of video methods now resides in the manual processing of images, a time-consuming task requiring trained experts. Recently, several solutions based on Deep Learning (DL) have been proposed to automatically process underwater videos. The main limitation of such algorithms is that they require thousands of annotated images in order to learn to discriminate classes (here species). This limitation implies two issues: 1) the annotation of hundreds of common species requires a lot of efforts 2) many species are too rare to gather enough data to train a classic DL algorithm. Here, we propose to explore how few-shot learning (FSL), an emerging research field, could overcome DL limitations. Few-shot learning is based on the principle of training a Deep Learning algorithm on “how to learn a new classification problem with only few images”. In our case-study, we assess the robustness of FSL to discriminate 20 coral reef fish species with a range of training databases from 1 image per class to 30 images per class, and compare FSL to a classic DL approach with thousands of images per class. We found that FSL outperform classic DL approach in situations where annotated images are limited, yet still providing good classification accuracy.