Modelado de extremo a extremo para un enfoque ecosistémico de pesquerías en el Ecosistema de la Corriente de Humboldt

This work represents an original contribution to the methodology for ecosystem models' development as well as the rst attempt of an end-to-end (E2E) model of the Northern Humboldt Current Ecosystem (NHCE). The main purpose of the developed model is to build a tool for ecosystem-based management and decision making, reason why the credibility of the model is essential, and this can be assessed through confrontation to data. Additionally, the NHCE exhibits a high climatic and oceanographic variability at several scales, the major source of interannual variability being the interruption of the upwelling seasonality by the El Ni~no Southern Oscillation, which has direct e ects on larval survival and sh recruitment success. Fishing activity can also be highly variable, depending on the abundance and accessibility of the main shery resources. This context brings the two main methodological questions addressed in this thesis, through the development of an end-to-end model coupling the high trophic level model OSMOSE to the hydrodynamics and biogeochemical model ROMS-PISCES: i) how to calibrate ecosystem models using time series data and ii) how to incorporate the impact of the interannual variability of the environment and shing.Este trabajo representa una contribución a la metodología para el desarrollo de modelos ecosistémicos, así como el primer intento de desarrollar un modelo de extremo a extremo para el Ecosistema de la Corriente de Humboldt (NECH). El principal propósito del modelo desarrollado es construir una herramienta para el manejo ecosistémico, razón por la cual la credibilidad del modelo es esencial, y ésta puede ser evaluada mediante la confrontación con datos. Adicionalmente, el NECH muestra una alta variabilidad climática y oceanográfica a diversas escalas, siendo la mayor fuente de variabilidad interanual la interrupción de la estacionalidad del afloramiento por El Niño- Oscilación Sur, que tiene efectos directos en la sobrevivencia larval y el éxito del reclutamiento de peces. La actividad pesquera también puede ser altamente variable, dependiendo de la abundancia y accesibilidad de los principales recursos pesqueros. Este contexto genera las dos principales preguntas metodológicas abordadas en esta tesis, a través del desarrollo de un modelo de extremo a extremo por el acoplamiento del modelo de nivel trófico alto OSMOSE y el modelo hidrodinámico y biogeoquímico ROMS-PISCES: i) cómo calibrar modelos ecosistémicos usando series de tiempo y ii) como incorporar el impacto de la variabilidad interanual del ambiente y la pesca.Francia. Institut de recherche pour le développement (IRD). ARTS (Ayudas para la Realización de Tesis en el Sur)Tesi

Ecosystem Viable Yields

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with guaranteed biological safety levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem

Cambio de fase en el proceso de contacto sobre Zd

El proceso de contacto en un tipo de proceso de Markov en tiempo continuo para el cual el espacio de estados, también llamados configuraciones, es X = {0, 1} Z d y en el cual cada coordenada de una configuración del proceso pasa de 1 a 0 a una tasa constante igual a 1, y el paso de 0 a 1 es proporcional a la cantidad de unos en las coordenadas vecinas, siendo λ la constante de proporcionalidad que parametriza el modelo. En este trabajo se muestra que el proceso de contacto puede ser construido formalmente a partir de la descripción anterior de las tasas de transición entre las configuraciones, mostrando además que existe un único proceso de Markov definido por tales tasas. Se utilizaron algunas técnicas básicas para el estudio de sistemas de partículas en interacción (monotonicidad, acoplamiento, dualidad) que permitieron demostrar algunas propiedades del proceso de contacto, como la autodualidad y la monotonía de la ergodicidad con respecto al parámetro del proceso. El resultado principal es mostrar que en una dimensión (d = 1) existe un parámetro crítico finito (λc) que determina un cambio de fase para la ergodicidad del proceso, siendo ergódico si λ λc. Este resultado se generaliza para el proceso en d dimensiones, mostrando que el parámetro crítico λd está acotado por 1/ 2d ≤ λd ≤ 2/d .Tesi

Viability Kernel for Ecosystem Management Models

We consider sustainable management issues formulated within the framework of control theory. The problem is one of controlling a discrete--time dynamical system (e.g. population model) in the presence of state and control constraints, representing conflicting economic and ecological issues for instance. The viability kernel is known to play a basic role for the analysis of such problems and the design of viable control feedbacks, but its computation is not an easy task in general. We study the viability of nonlinear generic ecosystem models under preservation and production constraints. Under simple conditions on the growth rates at the boundary constraints, we provide an explicit description of the viability kernel. A numerical illustration is given for the hake--anchovy couple in the Peruvian upwelling ecosystem

Validación biogeoquímica de una simulación interanual del modelo acoplado ROMS-PISCES en el Pacífico Sudeste

Currently biogeochemical models are used to understand and quantify key biogeochemical processes in the ocean. The objective of the present study was to validate predictive ability of a regional configuration of the PISCES biogeochemical model on main biogeochemical variables in Humboldt Current Large Marine Ecosystem (HCLME). The statistical indicators used to evaluate the model were the bias, root-mean-square error, correlation coefficient and, graphically, the Taylor’s diagram. The results showed that the model reproduces the dynamics of the main biogeochemical variables (chlorophyll, dissolved oxygen and nutrients); in particular, the impact of El Niño 1997-1998 in the chlorophyll (decrease) and oxygen minimum zone depth (increase). However, it is necessary to carry out sensitivity studies of the PISCES model with different key parameters values to obtain a more accurate representation of the properties of the Ocean.Los modelos biogeoquímicos en la actualidad son utilizados para entender y cuantificar los principales procesos biogeoquímicos que suceden en el océano. El objetivo del presente estudio es validar estadísticamente la habilidad predictiva de una simulación del modelo biogeoquímico PISCES en reproducir la dinámica de las principales variables biogeoquímicas del Ecosistema de la Corriente de Humboldt (ECH). Para evaluar el modelo se utilizaron indicadores estadísticos: sesgo, error de la raíz del cuadrado medio, coeficiente de correlación y gráficamente el diagrama de Taylor. Los resultados muestran que el modelo es capaz de reproducir la dinámica de las principales variables biogeoquímicas (clorofila, oxígeno disuelto y nutriente), captando bien el impacto que tiene El Niño 1997-1998 en la clorofila (disminución) y profundidad de la zona mínima de oxígeno (incremento). Es necesario llevar a cabo estudios de sensibilidad del modelo PISCES usando diferentes valores de los principales parámetrospara obtener una mejor representación de las propiedades biogeoquímicas del océano

Sustainable Yields for Ecosystems. A Mathematical Viability Approach

We define the notion of sustainable yields for ecosystem, with particular emphasis on long-run consistency between ecological and economic conflicting objectives. We provide a way to compute sustainable yields by means of a viability analysis of generic ecosystem models with harvesting. We apply our approach to a Lotka–Volterra model of the anchovy–hake couple in the Peruvian upwelling ecosystem between the years 1971 and 1981. Our analysis suggests that, during the anchovy collapse, the fishery could theoretically have been viably managed to produce catches above the expected levels while ensuring biological conservation. Control theory and viability theory methods have allowed us to introduce ecosystem considerations, such as multispecies and multiobjectives, and have contributed to integrate the long term dynamics, which is generally not considered in conventional fishery management.Keywords: Fisheries Modeling, Fisheries Economics, Modeling and Economic Theor

Management Strategy Evaluation for Peruvian Anchoveta (Engraulis Ringens) Fishery

Management strategy evaluation (MSE) is a methodology which allows to compare the efficiency of different management strategies in order to ensure the sustainability, in particular those based on viable control theory. Classic strategies (like precautionary approach of the International Council for the Exploration of the Sea, ICES) were compared to strategies defined from a viability control model for the Peruvian anchovy, which provides the biomass levels B which can be sustainable managed (viability kernel) and its related sustainable yields. Five management strategies (E1--E5) were considered to define the total allowable catch Y* for the Peruvian anchovy (Engraulis ringens): E1) social quota (Y* = Ymin), E2) ICES precautionary quota, E3) maximum viable quota Y*=Ymax(B), E4) maximum precautionary viable quota and, E5) half precautionary viable quota. We used five indicators for sustainability, related to the risk of collapse and the mean and variability of yields and biomasses. Two scenarios for initial biomasses were considered (healthy stock and postcollapse recovering stock). The analyses were done with Monte Carlo simulations, with 10 000 simulations per scenario and strategy. Uncertainty was incorporated in the quota implementation, simulating the variability of discards and illegal catches. The effect of the enviroment during 1963-- 1984 was considered by changing the stock-recruitment parameters during El Niño events. We found that the half precautionary viable quota (E5) could avoid the anchoveta fishery collapse in 1972--1973, allowing yields greater than the social quota. Also, the ICES precautionary strategy (E2) did not ensure the sustainability of the stock during El Niño events. We determine that a one year fishery moratorium after the fishery collapse would have been necessary to return to the viability kernel, allowing a sustainable management thereafter. We conclude that the viability kernel and viable yields are useful tools for designing management strategies which ensure the sustainability of natural resources.Keywords: Fisheries Economics, Fish and Aquaculture Sectors Developmen

Integrated assessment model for the north-central stock of Peruvian anchoveta Engraulis ringens Jenyns

Se presenta un nuevo modelo integrado de evaluación para el stock norte-centro de la anchoveta peruana que permite reconstruir y hacer un seguimiento de la estructura de longitudes del stock desde un modelo basado en edades. El modelo fue calibrado usando estimados acústicos de biomasa y estructuras de tallas provenientes de cruceros científicos y de desembarques de la pesquería. Para la calibración se utilizó un algoritmo evolutivo con diferentes funciones de aptitud para cada variable calibrada (biomasas y capturas). Se presentan los estimados mensuales de biomasa total, biomasa desovante, reclutamiento y mortalidad por pesca obtenidos por el modelo de evaluación integrada para el periodo 1964-2008. Se encontraron tres periodos cualitativamente distintos en la dinámica de anchoveta, entre 1961-1971, 1971-1991 y 1991 al presente, que se distinguen tanto por las biomasas medias anuales como por los niveles de reclutamiento observado.ABSTRACT: A new integrated assessment model for the northern-central stock of Peruvian anchovy is presented, which allows the reconstruction and follow-up of the length structure of the stock using an underlying age structured model. The model was calibrated using acoustic estimates of biomass and length structure from scientific surveys and from the fishery landings. An evolutionary algorithm with different fitness functions for each variable was used for the calibration (biomass and yield). Monthly estimates of total biomass, spawning stock biomass and recruitment given by the model for 1964-2008 are presented. Three different periods in anchovy dynamics were recognized, between 1961-1971, 1971-1991 and 1991 to the present, with distinguishable mean annual biomasses and recruitment values.Boletín IMARPE vol.25, n°1-2, 2010, p. 49-5

Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends