Nicolas Bez

Institute of Research for Development | IRD · UMR 248 MARBEC

We propose an innovative and generic methodology to analyse individual and collective behaviour through individual trajectory data. The work is motivated by the analysis of GPS trajectories of fishing vessels collected from regulatory tracking data in the context of marine biodiversity conservation and ecosystem-based fisheries management. We build...

This study introduces the concept of portfolios of distribution maps, which consist of the reduced set of empirical orthogonal maps that best explain spatial biomass distributions of a given species over time. The approach is demonstrated for the distributions of common octopus (Octupus vulgaris) off Mauritania over the last thirty years. The maps...

Graph models are standard for representing mutual relationships between sets of entities. Often, graphs deal with a large number of entities with a small number of connections (e.g. social media relationships, infectious disease spread). The distances or similarities between such large graphs are known to be well established by the Graphlet Correla...

Analysis of spatiotemporal observations often leads to decomposition of the problem into a spatial part multiplied by a temporal part (factorization). Principal component analyses produce factors that are temporally uncorrelated but that remain spatially correlated, leading to incomplete factorization. Min–max autocorrelation factors developed many...

This study introduces the concept of map portfolio as the set of principal maps that best explain the spatial distributions of a given species over time. An application is developed on octopus’s distribution off Mauritania over the past thirty years. The maps that make up the portfolio are the subset of the empirical orthogonal maps that allow to r...

Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distributi...

Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distributi...

Nurseries are crucial habitats that play an important role for many marine fish species; which rely on them to complete their life cycle. Juvenile stages of dab (Limanda limanda), plaice (Pleuronectes platessa) and sole (Solea solea) present in the English Channel are common in the Seine estuary nursery grounds. To further explore the estuary's nur...

Here, we present an approach to identify partners at sea based on fishing track analysis, and describe this behaviour in several fleets: pelagic pair trawlers, large and small bottom otter trawlers, mid-water otter trawlers, all in the North-East Atlantic Ocean, anchovy purse-seiners in the South-East Pacific Ocean, and tuna purse-seiners in the we...

Fisheries observer programs represent the most reliable way to collect data on fisheries bycatch. However, their limited coverage leads to important data gaps that preclude bycatch mitigation at the basin scale. Habitat models developed from available fisheries observer programs offer a potential solution to fill these gaps. We focus on tropical tu...

Here we present an approach to identify partners at sea based on fishing track analysis, and describe this behaviour in six different fleets: 1) pelagic pair trawlers, 2) large bottom otter trawlers, 3) small bottom otter trawlers, 4) mid-water otter trawlers, all operating in the North-East Atlantic Ocean, 5) anchovy purse-seiners in the South-Eas...

Spatial indicators are widely used to monitor species and are essential to management and conservation. In the present study, we tested the ability of 11 spatial indicators to quantify changes in species’ geographic patterns: (1) spatial displacement of a patch of biomass (‘shift’), (2) a spatial decrease in a patch, accompanied either by a loss of...

Coordinated movements of seabirds exploiting a prey patch are known to increase prey encounter and capture rates of individuals. These behaviours, based on effective cooperation between seabirds, have only been reported at small scale, i.e. the scale of the prey patch. However, the efficient prey exploitation by seabirds in vast oceans require larg...

In movement ecology, the few works that have taken collective behaviour into account are data-driven and rely on simplistic theoretical assumptions, relying in metrics that may or may not be measuring what is intended. In the present paper, we focus on pairwise joint-movement behaviour, where individuals move together during at least a segment of t...

Spatial indicators are used to quantify the state of species and ecosystem status, that is the impacts of climate and anthropogenic changes, as well as to comprehend species ecology. These metrics are thus, determinant to the stakeholder’s decisions on the conservation measures to be implemented. A detailed review of the literature (55 papers) show...

Review of previous works using the spatial indicators. Works are organized by subject, with a brief quantitative description on the indicators used, the inclusion of the areas of influence in its calculations (if it is mentioned and whether the details for calculation were provided), the species, temporal interval considered, type of sampling and a...

Options on the estimation of the areas of influence. (DOCX)

Illustration of spatial indicators. Illustration of some spatial indicators mentioned in the text: Gini index, Lorenz curve and spreading area (upper panel), center of gravity, inertia and isotropy (lower panel). (DOCX)

PCA with complete matrix (species and years). (DOCX)

In movement ecology, the few works that have taken collective behaviour into account are data-driven and rely on simplistic theoretical assumptions, relying in metrics that may or may not be measuring what is intended. In the present paper, we focus on pairwise joint-movement behaviour, where individuals move together during at least a segment of t...

Seabirds are known to concentrate on prey patches or at predators aggregations standing for potential feeding opportunities. They may search for prey using olfaction or by detecting visually feeding con-specifics and sub-surface predators, or even boats. Thus, they might form a foraging network. We hypothesized that conditionally to the existence o...

Analysis of VMS data could provide a reliable alternative for conducting pelagic stock assessments. For example, the fisheries community has been preparing GPS data for fishing vessels for some years. For the most part, the methods developed here are based on Markovian or semi-Markovian hierarchical models. This allowed us to show the informative p...

Scientific monitoring of fishery resources is difficult or, in some cases, impossible or too costly. When completed, they provide only one (or two) biomass estimate per year. The development of approaches based on interpreting vessel behavior to infer prey abundance would provide a reliable alternative to provide in-real-time indices of abundance a...

L’Association Française d’Halieutique réunit environ 200 scientifiques français de divers organismes d’enseignement supérieur et de recherche, de diverses disciplines, tous intéressés par l’halieutique (la science de la pêche, mais aussi des ressources aquatiques exploitées, des écosystèmes qui les supportent et des systèmes d’exploitation). Tous l...

Since the mid-1990s, drifting Fish Aggregating Devices (dFADs), artificial floating objects designed to aggregate fish, have become an important mean by which purse seine fleets catch tropical tunas. Mass deployment of dFADs, as well as the massive use of GPS buoys to track dFADs and natural floating objects, has raised serious concerns for the sta...

The European Research project " Catch, Effort, and eCOsystem impacts of FAD-fishing " (CECOFAD) set out to improve our understanding of the use of drifting fish-aggregating devices (DFADs) in tropical purse seine tuna fisheries in open ocean ecosystems. Data from unofficial technology information related to FAD-fishing were retrieved and the change...

In this introductory paper we highlight key questions that were discussed during the symposium on “Status, functioning and shifts in marine ecosystems” organized by the Association Française d’Halieutique (French Association for Fisheries Sciences, Montpellier, France, July 2015). This symposium illustrated that fisheries science is now working at...

An improved knowledge of habitat utilization by demersal species is a pre-requisite for their spatial management. Based on scientific survey data collected over the period 1994-2010, the present study investigates relationships between 4 environmental factors and 10 demersal species in the Gulf of Lions (northwestern Mediterranean Sea). Generalized...

Since the mid 1990s, the use of drifting Fish Aggregating Devices (dFADs) by purse seiners, artificial objects specifically designed to aggregate fish, has become an important mean of catching tropical tunas. In recent years, the massive deployments of dFADs, as well as the massive use of tracking devices on dFADs and natural floating objects, such...

Increasing human pressures and global environmental change may severely affect the diversity of species assemblages and associated ecosystem services. Despite the recent interest in phylogenetic and functional diversity, our knowledge on large spatio-temporal patterns of demersal fish diversity sampled by trawling remains still incomplete, notably...

In the open ocean, movements of migratory fish populations are typically surveyed using tagging methods that are subject to low sample sizes for archive tags, except for a few notable examples, and poor temporal resolution for conventional tags. Alternatively, one can infer patterns of movement of migratory fish by tracking movements of their preda...

Mapping diversity indices, that is estimating values in all locations of a given area from some sampled locations, is central to numerous research and applied fields in ecology. Two approaches are used to map diversity indices without including abiotic or biotic variables: (i) the indirect approach, which consists in estimating each individual spec...

In the open ocean, movements of migratory fish populations are typically surveyed using tagging methods that are subject to low sample sizes for archive tags, except for a few notable examples, and poor temporal resolution for conventional tags. Alternatively, one can infer patterns of movement of migratory fish by tracking movements of their preda...

The objective of the European Research project " Catch, Effort, and eCOsystem impacts of FAD-fishing " (CECOFAD) is to improve our understanding of the use of fish-aggregating devices (FAD) in tropical purse seine tuna fisheries on open-sea ecosystems. Due to the relevance of accurate indices of abundance derived from catch per unit of effort, the...

The desire to predict the consequences of global environmental change has been the driver towards more realistic models embracing the variability and uncertainties inherent in ecology. Statistical ecology has gelled over the past decade as a discipline that moves away from describing patterns towards modelling the ecological processes that generate...

Since the mid 1990s, drifting Fish Aggregating Devices (dFADS), artificial objects specifically designed to aggregate fish, have become an important mean of catching tropical tunas in the Indian Ocean for the purse seine fleet. In recent years, the massive deployments of dFADs as well as the massive use of tracking GPS and echosounder buoys on dFAD...

Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpredictable and challenging. In the Gulf of Lions (nor...

We analyse fish diversity by a multiple indices and scales approach over 19 years.•Species richness and evenness are proxies of phylogenetic and functional components.•Species richness reveals hotspots for different spatial scales contrary to evenness.•All diversity components remains stable over the last two decades.

Sardinella spp. are the main species fished in Mauritanian waters. Logbook data (1991–2009) were used to standardise CPUE. This clearly revealed that the abundance of sardinella peaked in the warm season(July–September) which is the main, if not the only significant spawning season for round sardinella.This study does not directly confirm or falsif...

In North West Africa, pelagic fisheries are an essential economic sector. However, the scientific community fails to perform satisfactory assessments of key pelagic species like sardinella, owing to a lack of relevant indices of abundance to tune the model. This paper provides an alternative acoustic index based on a semiquantitative modelisation o...

The objective of the European Research project " Catch, Effort, and eCOsystem impacts of FAD-fishing " (CECOFAD) is to improve our understanding of the use of fish-aggregating devices (FAD) in tropical purse seine tuna fisheries on open-sea ecosystems. Due to the relevance of accurate indices of abundance derived from catch per unit of effort, the...

The objective of the European Research project " Catch, Effort, and eCOsystem impacts of FAD-fishing " (CECOFAD) is to improve our understanding of the use of fish-aggregating devices (FAD) in tropical purse seine tuna fisheries on open-sea ecosystems. Due to the relevance of accurate indices of abundance derived from catch per unit of effort, the...

Natural floating objects (e.g., logs) have always been a component of the habitat of tropical tunas. However, the introduction of fish aggregating devices (FADs) modifies this environment. To assess the changes due to the deployment of FADs, we compared the spatial distribution of natural and artificial floating objects (FADs), using data from obse...

Amandè, M. J., Chassot, E., Chavance, P., Murua, H., Delgado de Molina, A., and Bez, N. 2012. Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean. – ICES Journal of Marine Science, 69: . Estimating bycatch, i.e. the incidental catch of non-target marine animals and undersized individuals of target species, by...

Sustainability of living resource exploitation relies on an ecosystem management approach. Within tropical tuna purse seine fisheries using fish aggregating devices (FADs), such an approach incorporates the reduction of bycatch, in particular vulnerable species such as elasmobranchs. The levels of total bycatch (in mass) from fishing operations usi...

This study analyzes the temporal variability/stability of the spatial distributions of key exploited species in the Gulf of Lions (Northwestern Mediterranean Sea). To do so, we analyzed data from the MEDITS bottom-trawl scientific surveys from 1994 to 2010 at 66 fixed stations and selected 12 key exploited species. We proposed a geostatistical appr...

Annual maps of anglers. Kriged annual maps of both anglers (Lophius budegassa and Lophius piscatorius) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of Mediterranean horse mackerel. Kriged annual maps of Mediterranean horse mackerel (Trachurus mediterraneus) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of Atlantic horse mackerel. Kriged annual maps of Atlantic horse mackerel (Trachurus trachurus) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of grey gurnard. Kriged annual maps of grey gurnard (Eutrigla gurnardus) log-density (Z) from 1994 to 2010. (PNG)

Correlation circles from the EOF analysis. The correlation circle depicts the contribution of each descriptor (i.e. the years) to the two first axes of the Empirical Orthogonal Functions (EOF). Higher the contribution of a given descriptor to the first EOF axis, longer the arrow. Here, all the descriptors have positive and high contributions to the...

Gravity centers and inertia. For each key species, gravity centers (crosses) and inertia axes of annual log-density maps, from 1994 to 2010. (TIF)

Annual maps of red mullet. Kriged annual maps of red mullet (Mullus barbatus) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of horned octopus. Kriged annual maps of horned octopus (Eledone cirrhosa) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of small-spotted catshark. Kriged annual maps of small-spotted catshark (Scyliorhinus canicula) log-density (Z) from 1994 to 2010. (PNG)

Annual maps of cuttlefish. Kriged annual maps of cuttlefish (Sepia Elegans) log-density (Z) from 1994 to 2010. (PNG)