Suchergebnisse

Disentangling the influence of demographic parameters and the role of density dependence on species' population dynamics may be challenging, especially when there are fractions of the population that are unobservable (e.g. dispersers, non-breeders). Additionally, due to the difficulty of gathering data at large spatial scales, most studies ignore the global dynamic of a species, which would integrate heterogeneity in local dynamics and remove the noise of dispersal. We developed a global scale, integrated population model (IPM), to disentangle the main demographic drivers of population dynamics in a long-lived colonial seabird. We used 28 years of Audouin's gull demographic data encompassing 69 local patches (90% of the world population). Importantly, we took into account the unobservable fraction of non-breeders and also assessed the strength of density dependence for this fraction of the population. As predicted by life histories of long-lived organisms, temporal random variation in survival was highest for immatures (), and lowest for adults (). Large temporal fluctuations in the probability of taking a sabbatical from reproduction would partly explain constancy in adult survival, adults probably refraining from breeding when environmental conditions were harsh. Thus, skipping breeding would be a bet hedging strategy for long-lived organisms having many reproductive chances during their lifespan. Immature survival and fertility were the main drivers of population dynamics during the study period (r2= 0.83 (0.77-0.87) and 0.73 (0.63-0.79) respectively). We found strong evidence of density dependence, not only due to the number of breeders (r2= -0.34 (-0.43 -0.24)) but also to that of sabbaticals (r2= -0.18 (-0.33 -0.01)). Even though population dynamics of long-lived organisms are very sensitive to changes in adult survival, we show here that in the absence of strong environmental perturbations affecting this life history trait, fluctuations in population density in those species may be driven by variations of immature survival and fertility. The species is showing a 5% of annual global decrease during the last ten years, and we propose an updated species conservation status. Integrated models based on long term monitoring at a global scale may enhance our ecological and evolutionary understanding of how demographic drivers influence population dynamics. ; M. Genovart is supported by a postdoctoral contract co‐funded by the Regional Government of the Balearic Islands and the European Social Fund. Funds were partially provided by the Spanish Ministry of Economy (ref. CGL2013‐42203‐R and CGL2017‐85210‐P) and the European Union (H2020 RIA‐ MINOUW Grant, ref. H2020‐ 634495). ; Peer reviewed

Several studies of marine top predators, above all of seabirds, have analyzed the effects of either individual age or environmental fluctuations on reproduction; nevertheless, little is known about the age patterns in breeding performance in a variable environment. To investigate the simultaneous influence of age and environmental conditions on laying dates and egg volumes, we tested different climate and food availability indices in a transequatorial migratory seabird using female data from a 23-year study. Our results show an improvement in breeding parameters with age (i.e., earlier laying dates and greater egg volumes) but no pattern of senescence in older age groups. The best models showed an interaction of time and age in breeding performance, i.e., the age pattern of breeding performance changed each year likely as a result of environmental variability. Nevertheless, climatic indexes used here explained part of that annual variability: NAO and SOI index accounted for 24 and 20% of deviances in laying dates and egg volume, respectively. Part of that unexplained variability might be related to other processes such as intermittent breeding and the individual quality of breeders, which were not assessed in our study. ; Funds were provided by the Balearic Government (FEDER program) and the Spanish Ministry of Economy and Competitiveness (ref. CGL2013-42203-R). ; Peer reviewed ; Peer Reviewed

Este artículo contiene 9 páginas, 3 figuras, 1 tabla. ; Social interactions, through infuence on behavioural processes, can play an important role in populations' resilience (i.e. ability to cope with perturbations). However little is known about the efects of perturbations on the strength of social cohesion in wild populations. Long-term associations between individuals may refect the existence of social cohesion for seizing the evolutionary advantages of social living. We explore the existence of social cohesion and its dynamics under perturbations by analysing long-term social associations, in a colonial seabird, the Audouin's gull Larus audouinii, living in a site experiencing a shift to a perturbed regime. Our goals were namely (1) to uncover the occurrence of long-term social ties (i.e. associations) between individuals and (2) to examine whether the perturbation regime afected this form of social cohesion. We analysed a dataset of more than 3500 individuals from 25 years of monitoring by means of contingency tables and within the Social Network Analysis framework. We showed that associations between individuals are not only due to philopatry or random gregariousness but that there are social ties between individuals over the years. Furthermore, social cohesion decreased under the perturbation regime. We sustain that perturbations may lead not only to changes in individuals' behaviour and ftness but also to a change in populations' social cohesion. The consequences of decreasing social cohesion are still not well understood, but they can be critical for the population dynamics of social species. ; Funding came from the Spanish Ministry of Science (CGL2017-85210) and Grant PICS INTERACT n°07699 (2016, CSIC-CNRS). MG was partially supported by the European Union (MINOUW Project, H2020-634495). ; Peer reviewed

Discards from fisheries are the most important predictable anthropogenic food subsidies (PAFS) that are being incorporated into marine ecosystems. Changes on their availability and predictability can help us to understand the role that food availability (i.e. an important indicator of the carrying capacity) plays at different ecological levels, from individual fitness to community dynamic and ecosystem functioning. For several reasons, seabirds are an excellent model for evaluating the ecological effects arising from a lack of discards: 1) they are one of the most important discard scavengers, 2) they are easy to monitor and 3) they are apical predators are globally distributed, which makes them suitable health indicators of ecosystems. Here we review the existing information on seabird-discard interactions to identify the main knowledge gaps and propose new challenges for improving our understanding of the general role of food availability. We conclude that the new policies on the ban of fishery discards that are being progressively implemented in the European Union, Norway, Chile and New Zealand offer a suitable experimental scenario for improving our understanding of how a large decrease in the carrying capacity may alter demographic parameters such as survival, dispersal and reproduction, the resilience of populations against perturbations and the role of individual specialization in the foraging process. ; Los descartes pesqueros constituyen el recurso antropogénico predecible (PAFS) más importante que está siendo incorporado en los ecosistemas marinos. Cambios en su disponibilidad y predictibilidad pueden ayudar a entender mejor el papel ecológico de la disponibilidad de alimento (i.e. un importante indicador de la capacidad de carga) a diferentes niveles, desde la eficacia biológica individual hasta la dinámica de poblaciones o el funcionamiento de los ecosistemas. Las aves marinas constituyen un modelo excelente para estudiar los efectos ecológicos derivados de la falta de descartes por diversas razones: las aves marinas: 1) se encuentran entre los principales carroñeros de descartes, 2) son fáciles de monitorear y 3) son depredadores apicales globalmente distribuidos, lo cual las convierte en buenas indicadoras de la salud del ecosistema. En el presente estudio revisamos la información existente sobre las interacciones ecológicas entre las aves marinas y los descartes de la pesca, con el fin de identificar los principales vacíos de conocimiento y plantear retos futuros de cara a mejorar nuestra comprensión sobre el papel ecológico que tiene la disponibilidad de alimento. Concluimos que las políticas actuales en materia de prohibición de descartes que están siendo implementadas en la Unión Europea, Noruega, Chile o Nueva Zelanda, ofrecen un escenario ideal para mejorar nuestra comprensión sobre cómo una reducción de la capacidad de carga puede alterar parámetros demográficos tales como la supervivencia, la dispersión y la reproducción, la resiliencia de las poblaciones frente a perturbaciones y el papel de la especialización individual en el proceso de forrajeo.

Summary: Discards from fisheries are the most important predictable anthropogenic food subsidies (PAFS) that are being incorporated into marine ecosystems. Changes on their availability and predictability can help to understand the role that food availability (i.e. an important indicator of the carrying capacity and the individual fitness) plays at different ecological levels, from individual fitness to community dynamic and ecosystem's functioning. Seabirds constitute an excellent model to evaluate the ecological effects derived from a lack of discards for several reasons: seabirds are 1) one of the most important discard scavengers, 2) easy to monitor and 3) apical predators globally distributed, which makes them suitable ecosystem's health indicators. Here we review the existing information on seabirds-discards interactions to identify main knowledge gaps and to propose new challenges to improve our understanding on the general role of food availability. We conclude that the new policies on the ban of fishery discards that are being progressively implemented at the European Union, Norway, Chile or New Zealand offer a suitable experimental scenario to improve our understanding on how a large decrease in the carrying capacity may alter demographic parameters such as survival, dispersal and reproduction, the resilience of populations against perturbations as well as the role of individual foraging specialization processes. ; Peer reviewed

ACKNOWLEDGEMENTS Funds for this study were supplied by the Spanish Ministry of Economy and by the European Social Fund (grant ref.: CGL2013-42203-R). The study also received funding from the European Commission's Horizon 2020 Research and Innovation Programme under Grant Agreement no. 634495 for the project Science, Technology, and Society Initiative to Minimize Unwanted Catches in European Fisheries (MINOUW). MG and ASA are supported by postdoctoral contracts co-funded by the Regional Government of the Balearic Islands and the European Social Fund. Two reviewers helped to improve the manuscript. ; Peer reviewed ; Publisher PDF

Este artículo contiene 18 páginas, 7 figuras, 8 tablas. ; Fisheries have an enormous economic importance, but reconciling their socio-economic features with the conservation and sustainability of marine ecosystems presents major challenges. Bycatch mortality from fisheries is clearly among the most serious global threats for marine ecosystems, affecting a wide range of top predators. Recent estimates report ca. 200,000 seabirds killed annually by bycatch in European waters. However, there is an urgent need to rigorously estimate actual mortality rates and quantify effects of bycatch on populations. The Mediterranean Sea is one of the most impacted regions. Here, we estimate for the first time both bycatch mortality rates and their population-level effects on three endemic and vulnerable Mediterranean taxa: Scopoli's shearwater, Mediterranean shag, and Audouin's gull, that die in different types of fishing gears: longlines, gillnets and sport trolling, respectively. We use multi-event capture–recapture modelling to estimate crucial demographic parameters, including the probabilities of dying in different fishing gears. We then build stochastic demography models to forecast the viability of the populations under different management scenarios. Longline bycatch was particularly severe for adults of Scopoli's shearwaters and Audouin's gulls (ca. 28% and 23% of total mortality, respectively) and also for immature gulls (ca. 90% of mortality). Gillnets had a lower impact, but were still responsible for ca. 9% of juvenile mortality on shags, whereas sport trolling only slightly influenced total mortality in gulls. Bycatch mortality has high population-level impacts in all three species, with shearwaters having the highest extinction risk under current mortality rates. Different life-history traits and compensatory demographic mechanisms between the three species are probably influencing the different bycatch impact: for shearwaters, urgent conservation actions are required to ensure the viability of their populations. Results will be very useful for guiding future seabird conservation policies and moving towards an ecosystem-based approach to sustainable fisheries management. ; Regional Government of the Balearic Islands; European Social Fund; Spanish Ministry of Economy, Grant/Award Number: CGL2013-42203-R; European Union, Grant/Award Number: H2020- 634495 ; Peer reviewed

World-wide, many seabirds are affected by fisheries in opposing ways: as a source of mortality from bycatch, but also by providing discards as a predictable and abundant food resource. This applies to the Balearic shearwater Puffinus mauretanicus, the most endangered European seabird, whose time to extinction was estimated at only ˜40 years a decade ago. Since the previous assessment, new data and more sophisticated demographic modelling have become available, and new fishing policies from the European Union (Common Fisheries Policy, CFP) will apply, posing different scenarios for the viability of the species. Thus, there is both an urgent need and an opportunity for a more reliable update of the conservation status of the species. Demographic data were collected between 1985 and 2014 at one of the world's largest colonies. Most demographic parameters were estimated using multievent capture–recapture modelling. Some parameters, such as bycatch rate, immature individual survival and recruitment, were estimated for the first time. We incorporated estimates into stochastic population models to forecast time to extinction and assess the viability under different management scenarios, accounting for upcoming fishing policies. Adult survival was much lower than expected (0·809, SE: 0·013) and largely influenced by bycatch, which accounted for a minimum of 0·455 (SE: 0·230) of total mortality. Breeding success was positively correlated with discard availability. Recruitment started at low rates in 3-year-old birds (0·030, SE: 0·0455), increasing in following age classes and was almost complete at 6 years. Under the present scenario, we predict a time to extinction of 61 years (95% CI: 55–69). Synthesis and applications. Population projections suggest that the actual impact of fisheries on Balearic shearwaters is unsustainable and the imminent discard ban under the new Common Fisheries Policy may accelerate the declining trend. This study demonstrates that reducing the bycatch rates of fisheries is an unavoidable and urgent conservation measure for avoiding the extinction of the species. We also advise setting up demographic long-term studies, to allow researchers to diagnose, with reliability, the effectiveness of management actions. These actions will also benefit many other marine top-predator species affected by this anthropogenic impact. ; Funds were provided by FEDER programme (Balearic Government), the Spanish Ministries of Economy and Competitiveness (ref. CGL2013-42203-R) and Agriculture, Food and Environment, the H2020 framework EU programme (MINOUW project) and Fundación Biodiversidad. ; Peer Reviewed

Este artículo contiene 7 páginas, 3 figuras. ; Predators are an important ecological and evolutionary force shaping prey population dynamics. Ecologists have extensively assessed the lethal effects of invasive predators on prey populations. However, the role of non-lethal effects, such as physiological stress or behavioural responses like dispersal, has been comparatively overlooked and their potential population effects remain obscure. Over the last 23 years, we developed a mark-recapture program for the Audouin's gull and an intensive carnivore monitoring program to assess how the appearance and invasion of the study site by carnivores affects population dynamics. We evaluate changes in turnover of discrete breeding patches within the colony, age structure and breeding performance. Once carnivores entered the colony, the number of occupied patches increased, indicating a higher patch turnover. Breeders responded by moving to areas less accessible to carnivores. More importantly, the presence of carnivores caused differential (and density-independent) breeding dispersal: experienced, better-performing breeders were more likely to leave the colony than younger breeders. This differential dispersal modified the age structure and reduced the reproductive performance of the population. Our results confirm the importance experience in the study of populations. The role of differential dispersal for animal population dynamics might be more important than previously thought, especially under scenarios of global change. ; RESET (ref.CGL2017-85210-P), FPU (ref. FPU2012-000869), IBISES (ref. CGL2013-42203-R) and MINOW (ref. H2020- 634495). ASA and MG are supported by a postdoctoral contract co-funded by the Regional Government of the Balearic Islands and the European Social Fund (ref. PD/003/2016 and PD/023/2015). ; Peer reviewed

Este artículo contiene 12 páginas, 5 figuras, 5 tablas. ; Recently isolated populations offer a good biological model to infer the evolutionary forces responsible for the current divergences across populations. We coupled genetic, morphometric, ecological, and demographic analyses from three island populations of the endemic Balearic Wall Lizard, Podarcis lilfordi, (Balearic archipelago, Spain) to infer the mechanisms underlying the observed differences in body size. For each population, we described plant community structure, derived a biotic capacity index, and used individual-based data on 1369 lizards captured and released during 6 yr (2009–2015) to estimate population density and body growth patterns. We used genetic data collected on 80 individuals (~27 for each population) to infer genetic divergences across islets and population history. Body size divergences cannot be explained by the ecological or population characteristics. Individual growth was slower in the smallest island, where lizards reached the largest average body size. In addition to having the highest density, results suggested that resource availability does not constrain asymptotic body size, but the speed at which individuals reach it does. The Approximate Bayesian Computation used to infer population history from genetic data supported the occurrence of two bottlenecks in the islet with the highest anthropogenic footprint. We emphasize the need to integrate ecological and genetic data and the importance of considering the effects of past human disturbance as an additional force in being able to model present island fauna. ; GT was supported by I. Hendriks. AR was supported by a JAE fellowship from the Spanish Council of Research. Ethics Committee for Animal Experimentation (CEEA) of Balearic Islands University (Spain) approved the protocol. The authorization to capture and handing animals was given by the Balearic Islands Government (ref: CEP 06/2015). ; Peer reviewed

Marine megafauna, including seabirds, are critically affected by fisheries bycatch. However, bycatch risk may differ on temporal and spatial scales due to the uneven distribution and effort of fleets operating different fishing gear, and to focal species distribution and foraging behaviour. Scopoli's shearwater Calonectris diomedea is a long-lived seabird that experiences high bycatch rates in longline fisheries and strong population-level impacts due to this type of anthropogenic mortality. Analyzing a long-term data set on individual monitoring, we compared adult survival (by means of multi-event capture-recapture models) among three close predator-free Mediterranean colonies of the species. Unexpectedly for a long-lived organism, adult survival varied among colonies. We explored potential causes of this differential survival, by: (1) measuring egg volume as a proxy of food availability and parental condition; (2) building a specific longline bycatch risk map for the species; and (3) assessing the distribution patterns of breeding birds from the three study colonies via GPS tracking. Egg volume was very similar between colonies over time, suggesting that environmental variability related to habitat foraging suitability was not the main cause of differential survival. On the other hand, differences in foraging movements among individuals from the three colonies expose them to differential mortality risk, which likely influenced the observed differences in adult survival. The overlap of information obtained by the generation of specific bycatch risk maps, the quantification of population demographic parameters and the foraging spatial analysis should inform managers about differential sensitivity to the anthropogenic impact at mesoscale level and guide decisions depending on the spatial configuration of local populations. The approach would apply and should be considered in any species where foraging distribution is colony-specific and mortality risk varies spatially. ; Funds were partially provided by the Spanish Ministry of the Economy (ref. CGL2013-42203-R), Consell Insular of Minorca, Universidade da Coruña and Xunta de Galicia (reference GRC2014/050) and the European Union (H2020 RIA- MINOUW Grant, ref. H2020- 634495). GPS-tracking work was supported by two EC-funded LIFE Projectsconducted by SEO/BirdLife: LIFE04NAT/ES/000049 (Marine IBAs in Spain; 2004–2009) and LIFE07NAT/E/000732 (INDEMARES; 2009–2014). ; Peer reviewed

Este artículo contiene 27 páginas, 2 tablas, 5 figuras. ; Shearwaters and petrels (hereafter petrels) are highly adapted seabirds that occur across all the world's oceans. Petrels are a threatened seabird group comprising 124 species. They have bet-hedging life histories typified by extended chick rearing periods, low fecundity, high adult survival, strong philopatry, monogamy and long-term mate fidelity and are thus vulnerable to change. Anthropogenic alterations on land and at sea have led to a poor conservation status of many petrels with 52 (42%) threatened species based on IUCN criteria and 65 (52%) suffering population declines. Some species are well-studied, even being used as bioindicators of ocean health, yet for others there are major knowledge gaps regarding their breeding grounds, migratory areas or other key aspects of their biology and ecology. We assembled 38 petrel conservation researchers to summarize information regarding the most important threats according to the IUCN Red List of threatened species to identify knowledge gaps that must be filled to improve conservation and management of petrels. We highlight research advances on the main threats for petrels (invasive species at breeding grounds, bycatch, overfishing, light pollution, climate change, and pollution). We propose an ambitious goal to reverse at least some of these six main threats, through active efforts such as restoring island habitats (e.g., invasive species removal, control and prevention), improving policies and regulations at global and regional levels, and engaging local communities in conservation efforts. ; AR and FR were supported by Juan de la Cierva programme, Spanish Ministry of Economy, Industry and Competitiveness (IJCI-2015-23913 and IJCI-2015-24531). ML was funded by the Ramón y Cajal programme (RYC-2012-09897), Spanish Ministry of Economy, Industry and Competitiveness. WM was supported by an NSERC Discovery grant. MG was partially supported by the European Union (MINOUW Project, H2020-634495). JMA and VC were supported by ZEPAMED Project, Pleamar programme, Fundación Biodiversidad, Spanish Ministry of Ecological Transition. ; Peer reviewed