The Experts below are selected from a list of 2694 Experts worldwide ranked by ideXlab platform
E Ciccotti - One of the best experts on this subject based on the ideXlab platform.
-
quantifying 60 years of declining european eel anguilla anguilla l 1758 fishery yields in mediterranean coastal lagoons
Ices Journal of Marine Science, 2016Co-Authors: Emilius A Aalto, F Capoccioni, Marcello Schiavina, C Leone, E CiccottiAbstract:The European eel Anguilla anguilla is thought to be in a multi-decadal decline across its range. Although its northern Atlantic sub-populations are well-studied, little is known about the historical trend and current status of eel stock in the Mediterranean Sea. To fill this gap, we gathered catch data for 86 lagoon fisheries in nine countries across the Mediterranean basin and analysed historical trends and geographical and environmental patterns. We found a region-wide decline in eel catch, beginning in the mid-1970s and exceeding the simultaneous decline in non-eel fisheries, as well as lower productivity in larger lagoons and those in the southern Mediterranean. Additionally, we developed a population dynamics model to provide a preliminary estimate of pristine, potential, and actual Escapement of spawning adults (silver eels) across the Mediterranean basin under historical and current conditions. Model results suggest that current Escapement is 35% of Escapement at pristine biomass levels, ,40% target set by EC regulation 1100/2007. Furthermore, we estimate that a complete closure of lagoon fisheries would achieve 57% of pristine Escapement under current recruitment levels. Though preliminary, this analysis represents a first step towards a full assessment of the role of the Mediterranean subpopulation in overall eel stock recovery.
-
l anguilla europea nel bacino idrografico marta bolsena valutazioni preliminari di colonizzazione ed emigrazione ai fini della gestione per la salvaguardia della biodiversita integrating river restoration and sustainable management of eel fishery in a lake river system in the mediterranean region a small scale case study to support eel conservation at global scale
2014Co-Authors: E Ciccotti, Chiara Leone, Daniele Bevacqua, G De Leo, L Tancioni, F CapoccioniAbstract:The European eel is a diadromous species for which a urgent conservation issue exists since its entire population has been declining at least since the 1980s. For this species, an economically and culturally important fishery resource throughout Europe, a framework has been set up for management and conservation, based on allowing an adequate Escapement of silver eel biomass form continental waters to the sea. Aim of this work was the setting up of a methodological framework for the management of eel local stocks at the catchment scale, based on integrating habitat restoration and sustainable management of fisheries. The reference system is the Bolsena lake, a natural growing habitat for eel, with its emissary, the river Marta that flows in the Mediterranean sea and whose course is fragmented by a number of dams. Following interventions to restore physical as well as hydraulic continuity of the river, samplings were carried out on the river and in the lake. A detailed demographic model was developed to allow to simulate the fishery yields and silver eel production under different recruitment and management scenarios, as a tool to assess Escapement from the system and thus compliance to the management target The simulations yielded interesting results concerning potential Escapement from the lake in pristine conditions, estimated in 36,7 t, compared to conditions of high harvest level. The actual level is estimated in 23,7 t, more than 60 % of the pristine level: this represents nevertheless a potential Escapement, that could become effective, leaving unchanged the present level of fishery effort, if the connection between lake and river was definitively reestablished. The opportunity of an integrated approach to management at the catchment scale is evidenced for eel: for this species local scale actions shall hopefully contribute to conservation at the global scale.
Giulio A De Leo - One of the best experts on this subject based on the ideXlab platform.
-
multi objective assessment of conservation measures for the european eel anguilla anguilla an application to the camargue lagoons
Ices Journal of Marine Science, 2007Co-Authors: Daniele Bevacqua, Paco Melia, Alain J Crivelli, Marino Gatto, Giulio A De LeoAbstract:Bevacqua, D., Melia, P., Crivelli, A. J., Gatto, M., and De Leo, G. A. 2007. Multi-objective assessment of conservation measures for the European eel (Anguilla anguilla): an application to the Carmargue lagoons. - ICES Journal of Marine Science, 64: 000-000: -.The European eel (Anguilla anguilla) stock has declined since the early 1970s and is currently considered to be outside safe biological limits. The European Commission has proposed a regulation (COM 2005/472 final) to establish measures for the recovery of the stock, with the aim of achieving an Escapement to the sea of 40% of the adult eel biomass (with respect to undisturbed conditions) from each river basin. The proposed regulation imposes an effective reduction of fishing activities until implementation of an approved eel management plan. We use a demographic model, explicitly accounting for age, length, and sex structure, and important features of the continental phase of eel life cycle, to assess the effectiveness of the proposed regulation. We explore alternative management options with reference to the Camargue (southern France) eel population. Using multi-criteria methods, we compare different fishing policies with respect to two potentially conflicting objectives: preserving a sufficient spawner Escapement and guaranteeing an acceptable harvest to fishers. We show that the current fishery is inefficient and that appropriate management policies (such as limiting the fishing season and increasing the mesh size of fishing gear) are likely to have a doubly positive effect, by achieving the conservation target of the regulation and increasing fisher revenues.
Thomas P Quinn - One of the best experts on this subject based on the ideXlab platform.
-
climate and conspecific density trigger pre spawning mortality in sockeye salmon oncorhynchus nerka
Fisheries Research, 2017Co-Authors: Michael D Tillotson, Thomas P QuinnAbstract:Abstract Pre-spawning mortality (PSM) has been occasionally observed in association with high densities of adult Pacific salmon ( Oncorhynchus spp.), but because large Escapements are rare, the phenomenon remains poorly understood. A large spawning Escapement (∼12 times the 54 year median, and 3X the previous maximum) to a small stream in Alaska provided a unique opportunity to explore the factors that contribute to density-driven spawning ground mortality. After comparing patterns of mortality in 2014 with over 20 years of prior abundance and environmental data, we identified low dissolved oxygen (DO) as likely contributing to PSM. We then utilized a fish habitat-DO model to explore the roles of density-dependent and -independent factors in reducing DO. Stream flow and spawning density were identified as primary drivers of oxygen availability. Despite suboptimal oxygen levels the salmon did not die abruptly. Rather, on average they lived as long as in previous years (mean = 9.99 d), but many (55%) failed to complete spawning prior to death. Our results suggest that this mortality was ultimately a density-dependent process, exacerbated by low-flow conditions. Given projected effects of climate change on river flows and temperatures, similar events may occur more frequently in parts of the range of salmon where abundances remain high.
-
quantifying six decades of fishery selection for size and age at maturity in sockeye salmon
Evolutionary Applications, 2009Co-Authors: Neala W Kendall, Jeffrey J Hard, Thomas P QuinnAbstract:Life history traits of wild animals can be strongly influenced, both phenotypically and evolutionarily, by hunting and fishing. However, few studies have quantified fishery selection over long time periods. We used 57 years of catch and Escapement data to document the magnitude of and trends in gillnet selection on age and size at maturity of a commercially and biologically important sockeye salmon stock. Overall, the fishery has caught larger fish than have escaped to spawn, but selection has varied over time, becoming weaker and less consistent recently. Selection patterns were strongly affected by fish age and sex, in addition to extrinsic factors including fish abundance, mesh size regulations, and fish length variability. These results revealed a more complex and changing pattern of selective harvest than the ‘larger is more vulnerable’ model, emphasizing the need for quantified, multi-year studies before conclusions can be drawn about potential evolutionary and ecological effects of fishery selection. Furthermore, the results indicate that biologically robust Escapement goals and prevention of harvest of the largest individuals may help prevent negative effects of size-selective harvest.
B. Knights - One of the best experts on this subject based on the ideXlab platform.
-
On the application of models of European eel (Anguilla anguilla) production and Escapement to the development of Eel Management Plans: the River Severn
ICES Journal of Marine Science, 2007Co-Authors: M. W. Aprahamian, Alan Walker, B. Williams, A. Bark, B. KnightsAbstract:Aprahamian, M. W., Walker, A. M., Williams, B., Bark, A., and Knights, B. 2007. On the application of models of European eel (Anguilla anguilla) production and Escapement to the development of Eel Management Plans: the River Severn. - ICES Journal of Marine Science, 64: 1472-1482.The European eel stock has declined significantly since the 1980s, and the Eel Recovery Plan of the European Commission requires Member States to develop river basin Eel Management Plans (EMPs) that will achieve an Escapement of silver eels that equals or exceeds 40% of the Escapement biomass that would be produced in the absence of human activities. However, because silver eel Escapement is not quantified within the UK, a modelling approach is required to estimate potential and actual Escapement, and to assess the likely effects of management measures. We focus on two approaches developed in the UK, the Reference Condition Model (RCM) and the Scenario-based Model for Eel Populations (SMEP), and illustrate how such approaches can be used in EMPs using selected data from the River Severn. The RCM results indicate that the yellow eel population in the River Severn basin may be just 30-40% of the potential density indicated by reference conditions derived from a selection of rivers between the late 1970s and the early 1980s. The challenges of applying a model designed to be as realistic of eel production as possible, and the limited data on natural eel habitat and eel production in the Severn, preclude a SMEP analysis similar to that of the RCM, but simulations based on a simplified basin description and eel survey data from the early 1980s illustrate the potential of this model to assess compliance and test management scenarios.
Daniele Bevacqua - One of the best experts on this subject based on the ideXlab platform.
-
l anguilla europea nel bacino idrografico marta bolsena valutazioni preliminari di colonizzazione ed emigrazione ai fini della gestione per la salvaguardia della biodiversita integrating river restoration and sustainable management of eel fishery in a lake river system in the mediterranean region a small scale case study to support eel conservation at global scale
2014Co-Authors: E Ciccotti, Chiara Leone, Daniele Bevacqua, G De Leo, L Tancioni, F CapoccioniAbstract:The European eel is a diadromous species for which a urgent conservation issue exists since its entire population has been declining at least since the 1980s. For this species, an economically and culturally important fishery resource throughout Europe, a framework has been set up for management and conservation, based on allowing an adequate Escapement of silver eel biomass form continental waters to the sea. Aim of this work was the setting up of a methodological framework for the management of eel local stocks at the catchment scale, based on integrating habitat restoration and sustainable management of fisheries. The reference system is the Bolsena lake, a natural growing habitat for eel, with its emissary, the river Marta that flows in the Mediterranean sea and whose course is fragmented by a number of dams. Following interventions to restore physical as well as hydraulic continuity of the river, samplings were carried out on the river and in the lake. A detailed demographic model was developed to allow to simulate the fishery yields and silver eel production under different recruitment and management scenarios, as a tool to assess Escapement from the system and thus compliance to the management target The simulations yielded interesting results concerning potential Escapement from the lake in pristine conditions, estimated in 36,7 t, compared to conditions of high harvest level. The actual level is estimated in 23,7 t, more than 60 % of the pristine level: this represents nevertheless a potential Escapement, that could become effective, leaving unchanged the present level of fishery effort, if the connection between lake and river was definitively reestablished. The opportunity of an integrated approach to management at the catchment scale is evidenced for eel: for this species local scale actions shall hopefully contribute to conservation at the global scale.
-
multi objective assessment of conservation measures for the european eel anguilla anguilla an application to the camargue lagoons
Ices Journal of Marine Science, 2007Co-Authors: Daniele Bevacqua, Paco Melia, Alain J Crivelli, Marino Gatto, Giulio A De LeoAbstract:Bevacqua, D., Melia, P., Crivelli, A. J., Gatto, M., and De Leo, G. A. 2007. Multi-objective assessment of conservation measures for the European eel (Anguilla anguilla): an application to the Carmargue lagoons. - ICES Journal of Marine Science, 64: 000-000: -.The European eel (Anguilla anguilla) stock has declined since the early 1970s and is currently considered to be outside safe biological limits. The European Commission has proposed a regulation (COM 2005/472 final) to establish measures for the recovery of the stock, with the aim of achieving an Escapement to the sea of 40% of the adult eel biomass (with respect to undisturbed conditions) from each river basin. The proposed regulation imposes an effective reduction of fishing activities until implementation of an approved eel management plan. We use a demographic model, explicitly accounting for age, length, and sex structure, and important features of the continental phase of eel life cycle, to assess the effectiveness of the proposed regulation. We explore alternative management options with reference to the Camargue (southern France) eel population. Using multi-criteria methods, we compare different fishing policies with respect to two potentially conflicting objectives: preserving a sufficient spawner Escapement and guaranteeing an acceptable harvest to fishers. We show that the current fishery is inefficient and that appropriate management policies (such as limiting the fishing season and increasing the mesh size of fishing gear) are likely to have a doubly positive effect, by achieving the conservation target of the regulation and increasing fisher revenues.