Evaluating strategies for managing anthropogenic mortality on marine mammals : an R implementation with the package RLA

Funding: ADERA provided support for salaries (MA).Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is one of the main causes of mortality of marine mammals worldwide. When quantitative conservation objectives and management goals are clearly defined, computer-based procedures can be used to explore likely population dynamics under different management scenarios and estimate the levels of anthropogenic removals, including bycatch, that marine mammal populations may withstand. Two control rules for setting removal limits are the Potential Biological Removal (PBR) established under the US Marine Mammal Protection Act and the Removals Limit Algorithm (RLA) inspired from the Catch Limit Algorithm (CLA) developed under the Revised Management Procedure of the International Whaling Commission. The PBR and RLA control rules were tested in a Management Strategy Evaluation (MSE) framework. A key feature of PBR and RLA is to ensure conservation objectives are met in the face of the multiple uncertainties or biases that plague real-world data on marine mammals. We built a package named RLA in the R software to carry out MSE of control rules to set removal limits in marine mammal conservation. The package functionalities are illustrated by two case studies carried out under the auspices of the Oslo and Paris convention (OSPAR) (the Convention for the Protection of the Marine Environment of the North-East Atlantic) Marine Mammal Expert Group (OMMEG) in the context of the EU Marine Strategy Framework Directive. The first case study sought to tune the PBR control rule to the conservation objective of restoring, with a probability of 0.8, a cetacean population to 80% of carrying capacity after 100 years. The second case study sought to further develop a RLA to set removals limit on harbor porpoises in the North Sea with the same conservation objective as in the first case study. Estimation of the removals limit under the RLA control rule was carried out within the Bayesian paradigm. Outputs from the functions implemented in the package RLA allows the assessment of user-defined performance metrics, such as time to reach a given fraction of carrying capacity under a given level of removals compared to the time needed given no removals.Publisher PDFPeer reviewe

Relative importance of different mecanisms underlying fish response to climate change

Climate change affects marine systems stability, in particular temperature increase induces a shift of the  fish  spatial  distribution  polewards.  Phenology  of  ecological  processes,  such  as  reproduction,  migration  seasons,  and  species  physiology  subject  to  temperature  increase  are  also  expected  to change. The ecosystem response to climate change implying all these processes remains unknown and difficult to estimate due to the numerous interactions between species. To better understand the relative  importance  of  the  different  processes  affected  by  climate  change,  we  use  the  multispecies model OSMOSE applied to the eastern English Channel and we simulated  two climate scenarios for 2040-2049  from    IPCC  (B1  and  A2).  For  this  study,  climate  change  is  assumed  to  affect  4  main processes:  the  primary  production,  reproduction  seasonality,  growth  and  spatial  distribution. Simulations followed a full factorial design in order to explore separate effects of each process as well as  their  combinations.  The  projections  of  IPCC  scenarios  on  the  system  showed  that  reproduction seasonality is the process affecting the most total and species biomasses, while spatial distribution has  a  moderate  effect  of  the  different  indicators  studied.  The  interactions  between  species  lead  to antagonistic  or  synergistic  combined  effects  of  the  different  processes.  When  considering  all processes simultaneously, the simulated state of the ecosystem in the 2040’s is characterized  by a decrease  of  predators’  biomass  weakening  the  system  and  leading  to  the  prevalence  of  some intermediate-level  predators.Les  effets  du  changement  climatique  sur  la  stabilité  des  systèmes  marins  sont  connus. L’augmentation de température entraine une redistribution spatiale des espèces vers les pôles de la planète. Il a également été démontré que la température pouvait influer les processus phénologique comme  la  migration  ou  la  reproduction.  Pour  comprendre  de  manière  précise  comment  le changement  climatique  affecte  les  divers  processus  qui  régissent  au  sein  des  espèces,  il  est nécessaire de tenir compte des interactions entre les espèces du système en plus des effets directs du changement climatique. Ainsi, il est proposé dans cette étude d’utiliser un modèle multispécifique forcé par 2 scenarios de changement climatique provenant des prévisions du GIEC pour les années 2040 à 2049. Les effets directs du changement climatique sont supposés, dans cette étude, affecter 4 processus, la production primaire, la saison de reproduction, la croissance et la distribution spatiale. Les 2 scenarios de changement ont été régionalisés au site d’étude, correspondant à la Manche-Est. La projection de ces scenarios nous montre que la saison de reproduction est le paramètre qui influe le plus sur la biomasse du système mais également pour chaque espèce. Les interactions entre les espèces  entrainent  des  interactions  entre  les  4  processus  de  type  synergique  ou  antagoniste.  Les projections du système pour les années 2040 corroborent les précédents résultats. Il est attendu de voir une diminution de l’abondance des ‘top-prédateurs’ et une augmentation de l’abondance de leur proies dû à la fragilisation que la perte prédateurs secondaire entraine

The Risky Decrease of Fishing Reference Points Under Climate Change

In Europe, implementation of sustainable fisheries management has been reinforced in the latest common fisheries policy, and presently marine fish stocks are mostly managed through assessment of their exploitation and ecological status compared to reference points such as Maximum Sustainable Yield (MSY). However, MSY and its associated fishing mortality rate FMSY are sensitive to both stock characteristics and environment conditions. In parallel, climate change impacts are increasingly affecting fish stocks directly and indirectly but might also change the exploitation reference points and the associated level of catch. Here we explored the variability of MSY reference points under climate change by using a multi-species model applied to the Eastern English Channel, a highly exploited semi-continental sea. The spatial individual-based OSMOSE explicitly represents the entire fish life cycle of 14 species interacting through size-based opportunistic predation. The model was first parameterized and run to fit the historical situation (2000–2009) and then used to assess the ecosystem state for the 2050–2059 period, using two contrasting climate change scenarios (RCP 4.5 and RCP 8.5). For each condition, a monospecific MSY estimation routine was performed by varying species fishing mortality independently and allowed estimation of reference points for each species. The FMSY estimated with OSMOSE were mostly in accordance with available values derived from stock assessment and used for fishing advice. Evolution of reference points with climate change was compared across species and highlighted that overexploited cold-water species are likely to have both MSY and FMSY declining with climate warming. Considering all species together, MSY under RCP scenarios was expected to be higher than historical MSY for half of them, with no clear link with species temperature preferences, exploitation status or trophic level, but in relation with expected change of species biomass under climate change. By contrast, for 80% of cases FMSY projections showed consistent decreasing pattern as climate conditions changed from historical to RCP scenarios in the Eastern English Channel. This result constitutes a risk for fisheries management, and anticipation of climate change impacts on fish community would require targeting a smaller fishing mortality than FMSY to ensure sustainable exploitation of marine stocks

Estimating a mortality threshold for the Belt Sea population of harbour porpoises

For small cetaceans bycatch in fishing gear is one of the largest threats towards their conservation. In order to effectively manage this threat, an estimation of the maximum number of animals that can be killed by anthropogenic activities each year is required. Such calculations rely on species or population specific information on population dynamics, and information on the current state of the population relative to carrying capacity. Here, we calculate the mortality limit for the Belt Sea population of harbour porpoises (Phocoena phocoena) based on a modified potential biological removal (mPBR) method. We estimate that for the population to reach the conservation objective set by ASCOBANS (the population should reach 80% of carrying capacity (assumed here to be 50,000 animals), with the assumption that this is achieved within 100 years with an 80% probability) a maximum of 29 animals can be removed annually. This removal rate applies a recover factor (Fr) of 0.1 that accounts for many uncertainties in population dynamics, abundance estimates, and the current removal rate and depletion level of the population. However, even using the highest possible Fr value (1.0) (which is not recommended for populations with unknown status and does not allow the population to reach the conservation objective), the mPBR limit of the population is 292, which is still significantly lower than the current estimated levels of bycatch in this population (~700 a year). Therefore, urgent action is required in order to ensure that this population is able to reach the conservation objective and achieve good environmental status under a range of European legislation.

Estimating a mortality threshold for the Belt Sea population of harbour porpoises

For small cetaceans bycatch in fishing gear is one of the largest threats towards their conservation. In order to effectively manage this threat, an estimation of the maximum number of animals that can be killed by anthropogenic activities each year is required. Such calculations rely on species or population specific information on population dynamics, and information on the current state of the population relative to carrying capacity. Here, we calculate the mortality limit for the Belt Sea population of harbour porpoises (Phocoena phocoena) based on a modified potential biological removal (mPBR) method. We estimate that for the population to reach the conservation objective set by ASCOBANS (the population should reach 80% of carrying capacity (assumed here to be 50,000 animals), with the assumption that this is achieved within 100 years with an 80% probability) a maximum of 29 animals can be removed annually. This removal rate applies a recover factor (Fr) of 0.1 that accounts for many uncertainties in population dynamics, abundance estimates, and the current removal rate and depletion level of the population. However, even using the highest possible Fr value (1.0) (which is not recommended for populations with unknown status and does not allow the population to reach the conservation objective), the mPBR limit of the population is 292, which is still significantly lower than the current estimated levels of bycatch in this population (~700 a year). Therefore, urgent action is required in order to ensure that this population is able to reach the conservation objective and achieve good environmental status under a range of European legislation.

Synthèse des données de l’Observatoire PELAGIS au sein du PNM des estuaires picards et de la mer d’Opale.

Les données de distribution, d’abondance et d’utilisation de la zone par la mégafaune marine sont aujourd’hui insuffisantes pour répondre aux questions de gestion et d’évaluation du Parc naturel marin des estuaires picards et de la mer d’Opale. Il existe des lacunes sur la fréquentation, notamment par les oiseaux marins ou le marsouin commun dans le périmètre du PNM EPMO et des sites Natura 2000. En amont du projet MAMO (Etude de la Mégafaune marine par observation Aérienne en Manche orientale, en particulier dans le Parc naturel marin des estuaires picards et de la mer d’Opale) et des survols saisonniers qui vont être réalisés au cours de deux années, ce rapport synthétise les données collectées par l’Observatoire PELAGIS ((UAR 3462, La Rochelle Université – CNRS) dans la zone d‘étude. Seules les données collectées selon un protocole standardisé sont retenues, c’est çà dire celles provenant du dispositif d’observation Mégascope à bord des campagnes halieutiques (IBTS, CAMANOC, CGFS) et celles collectées au cours des campagnes aériennes (SAMM, SCANS, LEDKOA). Ces données sont présentées sous forme de cartes de distribution saisonnière pour les principales espèces de mégafaune marine. En complément, les échouages de mammifères marins recensés dans la zone ont été extraits de la base de données du Réseau National de suivi des Echouages (RNE) depuis 1992. Bien que les résultats présentés ici révèlent des patrons de distribution pour certaines espèces, les couvertures spatiales et l’intensité d’échantillonnage étant dissemblables entre les campagnes et les saisons, les différences saisonnières observées doivent être interprétées avec précaution. Néanmoins, les résultats obtenus pour différentes espèces apparaissent en cohérence avec les patrons saisonniers connus, et dessinent ainsi une première image de la variabilité saisonnière de la mégafaune marine dans la zone d’étude

Estimating Bycatch From Non-representative Samples (II): A Case Study of Pair Trawlers and Common Dolphins in the Bay of Biscay

Marine megafauna plays an important functional role in marine ecosystems as top predators but are threatened by a wide range of anthropogenic activities. Bycatch, the incidental capture of non-targeted species in commercial and recreational fisheries, is of particular concern for small cetacean species, such as dolphins and porpoises. In the North-East Atlantic, common dolphin (Delphinus delphis, Linné 1758) bycatch has been increasing and associated with large numbers of animals stranding during winter on the French Atlantic seashore since at least 2017. However, uncertainties around the true magnitude of common dolphin bycatch and the fisheries involved have led to delays in the implementation of mitigation measures. Current data collection on dolphin bycatch in France is with non-dedicated observers deployed on vessels for the purpose of national fisheries sampling programmes. These data cannot be assumed representative of the whole fisheries' bycatch events. This feature makes it difficult to use classic ratio estimators since they require a truly randomised sample of the fishery by dedicated observers. We applied a newly developed approach, regularised multilevel regression with post-stratification, to estimate total bycatch from unrepresentative samples and total fishing effort. The latter is needed for post-stratification and the former is analysed in a Bayesian framework with multilevel regression to regularise and better predict bycatch risk. We estimated the number of bycaught dolphins for each week and 10 International Council for the Exploration of the Sea (ICES) divisions from 2004 to 2020 by estimating jointly bycatch risk, haul duration, and the number of hauls per days at sea (DaS). Bycatch risk in pair trawlers flying the French flag was the highest in winter 2017 and 2019 and was associated with the longest haul durations. ICES divisions 8.a and 8.b (shelf part of the Bay of Biscay) were estimated to have the highest common dolphin bycatch. Our results were consistent with independent estimates of common dolphin bycatch from strandings. Our method show cases how non-representative observer data can nevertheless be analysed to estimate fishing duration, bycatch risk and, ultimately, the number of bycaught dolphins. These weekly-estimates improve upon current knowledge of the nature of common dolphin bycatch and can be used to inform management and policy decisions at a finer spatio-temporal scale than has been possible to date. Our results suggest that limiting haul duration, especially in winter, could serve as an effective mitigation strategy. Data is available here to reproduce the method described in this paper : https://gitlab.univ-lr.fr/mauthier/cdptmbycatch

PROJET GALION. Gestion alternative de la pêcherie chalutière du Golfe du Lion

Améliorer la gestion des ressources marines est donc un impératif au maintien des entreprises de pêche, c’est pourquoi les pêcheurs chalutiers du golfe du Lion ont lancé l’initiative du projet GALION pour permettre de définir de nouveaux modes de gestion pour cette pêcherie. Le projet intègre plusieurs phases de collecte de données en mer dans le cadre d’un partenariat entre scientifiques, pêcheurs et économistes. Plusieurs actions sont menées au cours des trois années du projet : 1. Cartographier la distribution des captures et rejets. 2. Définir des habitats sensibles ou à risque. 3. Analyser la sélectivité des engins de pêche et leur impact économique. 4. Proposer des stratégies de pêche limitant les rejets. Ainsi le projet GALION vise à fournir aux pêcheurs une aide à la décision pour la meilleure stratégie de pêche à adopter. Ce projet est porté par l’AMOP, en partenariat avec l’Ifremer, le projet DISCARDLESS, le Cépralmar, Capacités Mer et SEANEO. Il a également bénéficié des soutiens financiers de l’association France Filière Pêche, de la Région Occitanie, de la Région Provence Alpes Côtes d’Azur, du Conseil Départemental du Gard et du Conseil Départemental de l’Hérault

A negative trend in abundance and an exceeded mortality limit call for conservation action for the Vulnerable Belt Sea harbour porpoise population

The management and conservation of biodiversity relies on information on both the abundance of species and the potential impact of threats. Globally, one of the largest threats towards marine biodiversity is bycatch in fisheries. Under the Marine Strategy Framework Directive (MSFD), EU Member States are required to assess the status of species, such as the harbour porpoise (Phocoena phocoena), in relation to their abundance and mortality due to bycatch every six years. The Vulnerable (HELCOM) Belt Sea population of harbour porpoise has been surveyed to determine its abundance six times using dedicated aerial or ship-based line-transect distance sampling surveys. Here, we estimated the first trend in population abundance over an 18 year period (2005-2022). Using the most recent abundance estimate, we computed a mortality limit applying the modified Potential Biological Removal (mPBR) method based on the regionally agreed conservation objective to restore or maintain 80% of carrying capacity over 100 years with an 80% probability. Over the past 18 years there has been a strong negative trend (-2.7% p.a.; 95% CI: -4.1%; + 1.3%) in abundance, with a 90.5% probability. The mortality limit was estimated to be 24 animals, which the current bycatch estimates (~900 porpoises/year from the commercial Danish and Swedish set net fishery fleets, with no data from Germany and other fishery types) exceed by far. The frequency and quality of data available on abundance for this population are higher than those available for the majority of marine species. Given the observed population decline and likely unsustainable levels of bycatch, the results presented here provide a strong basis to make informed, evidence-based management decisions for action for this population. Such action is needed urgently, before the dire situation of other porpoise species and populations around the globe is repeated