Selectivity, pulse fishing and endogenous lifespan in Beverton-Holt models

Optimal management in a multi-cohort Beverton-Holt model with any number of age classes and imperfect selectivity is equivalent to finding the optimal fish lifespan by chosen fallow cycles. Optimal policy differs in two main ways from the optimal lifespan rule with perfect selectivity. First, weight gain is valued in terms of the whole population structure. Second, the cost of waiting is the interest rate adjusted for the increase in the pulse length. This point is especially relevant for assessing the role of selectivity. Imperfect selectivity reduces the optimal lifespan and the optimal pulse length. We illustrate our theoretical findings with a numerical example. Results obtained using global numerical methods select the optimal pulse length predicted by the optimal lifespan rule

A systematic approach to plant-wide control based on thermodynamics

Abstract In this work, a systematic approach to plant-wide control design is proposed. The method combines ingredients from process networks, thermodynamics and systems theory to derive robust decentralized controllers that will ensure complete plant stability. As a first step, the considered process system is decomposed into abstract mass and energy inventory networks. In this framework, conceptual inventory control loops are then designed for the mass and energy layers to guarantee that the states of the plant, both in terms of extensive and intensive properties, will converge to a compact convex region defined by constant inventories. This result by itself does not ensure the convergence of intensive variables to a desired operation point as complex dynamic phenomena such as multiplicities may appear in the invariant set. In order to avoid these phenomena, thermodynamics naturally provides the designer, in these convex regions, with a legitimate storage or Lyapunov function candidate, the entropy, that can be employed to ensure global stability. Based on this, the control structure design procedure is completed with the realization of the conceptual inventory and intensive variable control loops over the available degrees of freedom in the system. To that purpose, both PI and feedback linearization control are employed. The different aspects of the proposed methodology will be illustrated on a non-isothermal chemical reaction network

First Assessment of the Impacts of the COVID-19 Pandemic on Global Marine Recreational Fisheries

This work is the result of an international research effort to determine the main impacts of the COVID-19 pandemic on marine recreational fishing. Changes were assessed on (1) access to fishing, derived from lockdowns and other mobility restrictions; (2) ecosystems, because of alterations in fishing intensity and human presence; (3) the blue economy, derived from alterations in the investments and expenses of the fishers; and (4) society, in relation to variations in fishers’ health and well-being. For this, a consultation with experts from 16 countries was carried out, as well as an international online survey aimed at recreational fishers, that included specific questions designed to capture fishers’ heterogeneity in relation to behavior, skills and know-how, and vital involvement. Fishers’ participation in the online survey (5,998 recreational fishers in 15 countries) was promoted through a marketing campaign. The sensitivity of the fishers’ clustering procedure, based on the captured heterogeneity, was evaluated by SIMPER analysis and by generalized linear models. Results from the expert consultation highlighted a worldwide reduction in marine recreational fishing activity. Lower human-driven pressures are expected to generate some benefits for marine ecosystems. However, experts also identified high negative impacts on the blue economy, as well as on fisher health and well-being because of the loss of recreational fishing opportunities. Most (98%) of the fishers who participated in the online survey were identified as advanced, showing a much higher degree of commitment to recreational fishing than basic fishers (2%). Advanced fishers were, in general, more pessimistic about the impacts of COVID-19, reporting higher reductions in physical activity and fish consumption, as well as poorer quality of night rest, foul mood, and raised more concerns about their health status. Controlled and safe access to marine recreational fisheries during pandemics would provide benefits to the health and well-being of people and reduce negative socioeconomic impacts, especially for vulnerable social groups.Versión del edito

Development and validation of a clinical score to estimate progression to severe or critical state in Covid-19 pneumonia hospitalized patients

The prognosis of a patient with Covid-19 pneumonia is uncertain. Our objective was to establish a predictive model of disease progression to facilitate early decision-making. A retrospective study was performed of patients admitted with Covid-19 pneumonia, classified as severe (admission to the intensive care unit, mechanic invasive ventilation, or death) or non-severe. A predictive model based on clinical, analytical, and radiological parameters was built. The probability of progression to severe disease was estimated by logistic regression analysis. Calibration and discrimination (receiver operating characteristics curves and AUC) were assessed to determine model performance. During the study period 1,152 patients presented with Covid-19 infection, of whom 229 (19.9%) were admitted for pneumonia. During hospitalization, 51 (22.3%) progressed to severe disease, of whom 26 required ICU care (11.4); 17 (7.4%) underwent invasive mechanical ventilation, and 32 (14%) died of any cause. Five predictors determined within 24 hours of admission were identified: Diabetes, Age, Lymphocyte count, SaO2, and pH (DALSH score). The prediction model showed a good clinical performance, including discrimination (AUC 0.87 CI 0.81, 0.92) and calibration (Brier score = 0.11). In total, 0%, 12%, and 50% of patients with severity risk scores ≤5%, 6-25%, and >25% exhibited disease progression, respectively. A simple risk score based on five factors predicts disease progression and facilitates early decision-making according to prognosis.Carlos III Health Institute, Spain, Ministry of Economy and Competitiveness (SPAIN) and the European Regional Development Fund (FEDER)Instituto de Salud Carlos II

Selectivity, pulse fishing and endogenous lifespan in Beverton-Holt models

Optimal management in a multi-cohort Beverton-Holt model with any number of age classes and imperfect selectivity is equivalent to finding the optimal fish lifespan by chosen fallow cycles. Optimal policy differs in two main ways from the optimal lifespan rule with perfect selectivity. First, weight gain is valued in terms of the whole population structure. Second, the cost of waiting is the interest rate adjusted for the increase in the pulse length. This point is especially relevant for assessing the role of selectivity. Imperfect selectivity reduces the optimal lifespan and the optimal pulse length. We illustrate our theoretical findings with a numerical example. Results obtained using global numerical methods select the optimal pulse length predicted by the optimal lifespan rule

Development of an User-Friendly Virtual Environment for Design and Simulation of Food Processing Plants: Appli- cation to the Valorization Process of Fish Skins to Obtain Gelatines

Abstract The aim of this work is to develop a visual interface including the most representative processes in the gelatin production from fish skin. Connecting different components from a library implemented in EcosimPro, users can easily configure a virtual plant according to their requirements, and test different scenarios attending to the quantity and quality of the raw material (normally subject to seasonal variations). In this way, it is possible to analyze the consumption of water, energy and reactives, as well as the quality and quantity of the product obtained by given variations in the inputs and/or the operational parameters. The approach is multipurpose, combining elements of design and simulation. INTRODUCTION One of the strategies towards a responsible management of fisheries, is to promote policies of by-catch no-discard and zero-waste production both on-board and in-land. Such policies must be accompanied, for the sake of sustainability, by up-grading strategies for the fish wastes and by-products. In this context, the gelatin obtained from fish skin is not only a way of valorization, but a potential alternative to mammalian gelatin. Fish skin is a good source of collagen, the precursor of gelatin, and fish gelatin extraction has been reported for a number of ray finned fishes (cod, tuna, pollock, sole, tilapia ...) and chondrichthyes (namely shark and ray). Collagen is not soluble in water, but its fibers shrink at hot temperature producing water soluble gelatin. The core of the gelatin production process consists basically in the extraction of the denatured collagen macromolecules from the skin to an aqueous solution, and presents variations depending mainly on the characteristics of the raw material and the desired quality of the product. We have created a model library with the most representative processes in the gelatin production. In this way, users can easily configure, using the components included in the library, a virtual plant according to their requirements. The model library has been implemented in Ecosimpro, which is a powerful modelling tool for many fields including food processing industr

Network theory in control engineering: applications in dynamic analysis and process control

[EN] Processes in chemical, food or biotechnology industry, as well as many of the mechanisms characteristics of system biology, belong to the so-called process systems class. In this contribution, use is made of a number of previous results that combine aspects from systems and graph theory with methods from thermodynamics and reaction networks to set up the basis on which to develop a formal and generalized representation of processes in terms of complex networks. This representation –partially developed by other authors- not only allows the unification of a wide number of apparently diverse processes, but also provides an efficient and systematic approach to undertake decentralized control problems as well as advanced dynamic analysis (including bifurcation analysis).[ES] Los procesos de la industria química, alimentaria o biotecnológica, así como muchos de los mecanismos propios de la biología de sistemas, pertenecen a la clase de los llamados sistemas de proceso. En esta contribución se hace uso de un conjunto de resultados previos que combinan aspectos de la teoría de sistemas y grafos, con métodos de termodinámica y de redes de reacción para así sentar las bases sobre las que elaborar una representación formal y generalizada de procesos en términos de redes complejas. Esta representación -parcialmente desarrollada por los autores- además de unificar un amplio número de procesos aparentemente diversos, proporciona una sistemática eficiente con la que abordar los problemas de control descentralizado y análisis dinámico avanzado (incluyendo el análisis de bifurcación).Los autores agradecen la financiación recibida del Gobierno Español (Proyecto MCyT PPQ2001-3643 y DPI2004-07444-C04-03) y de la Xunta de Galicia (PGIDIT02-PXIC40209PN).Antelo, LT.; Otero-Muras, I.; Banga, JR.; Alonso, AA. (2009). La Teoría de Redes en Ingeniería de Control: Aplicación al Análisis Dinámico y al Control de Procesos. Revista Iberoamericana de Automática e Informática industrial. 4(1):24-34. http://hdl.handle.net/10251/146234OJS24344

An integral and sustainable valorisation strategy of squid pen by-products

The aim of this study was to present a sustainable valorisation approach of Loligo opalescens squid pen by-products by optimal production of chitin and chitosan biopolymers and recycling of the generated effluents. The integral recovery of squid pens started with the optimization of the deproteinization process to isolate chitin, including less hazardous enzymatic alternatives to conventional chemical treatments. Response surface methodology analysis yielded optimal conditions of 53.2 °C/pH 8.84 for Alcalase, 54.7 °C/pH 9.16 for Esperase and 0.2 M NaOH/27.5 °C for alkaline hydrolysis. The generated effluents were a good source of organic nitrogen (squid peptones) for the culture of a lactic acid bacterium (Pediococcus acidilactici), with biomass and metabolite productions comparable to commercial Man, Rogosa, Sharpe medium. Secondly, optimal process time and alkali concentration for the chemical deacetylation of chitin were established at 16 h/64% NaOH, obtaining high purity chitosan (deacetylation degrees >92%, molecular weights -Mn- ranging from 139 to 300 kDa). Optimized chitin and chitosan processes led to lower energetic costs. Alkaline effluents from chitosan production were applied as a reagent in the selective precipitation of chondroitin sulphate from enzymatic hydrolysates of shark cartilage by-products. Finally, the goodness of the proposed valorisation strategy was evaluated by developing a Material Flow Analysis.The authors thank to Ana Durán, Margarita Nogueira, Araceli Menduíña and Javier Fraguas for their excellent technical assistance. This research was funded by the projects IBEROS (0245_IBEROS_1_E, POCTEP 2015), CVMar+I (0302_CVMAR_I_1_P, POCTEP 2015) and BLUEHUMAN (EAPA_151/2016, UE-INTERREG Atlantic Area Programme). RNC thanks the Portuguese Foundation for Science and Technology (IF/00373/2014).info:eu-repo/semantics/publishedVersio

The landing obligation in European fisheries: discard reporting by observer programs and automatic technology

Fisheries observers and landing obligation Otter bottom trawl targeting demersal species in north Iberian waters is a mixed fishery which takes place throughout the year targeting European hake, anglerfish, megrim, horse mackerel and blue whiting. An standardized scientific observer program is carried out to analyze and raise the data to obtain discard estimates for stock assessment every year. In this work, a dedicate observer program was set up to study the application of the landing obligation in coastal trawling fleet. The study involves both scientific oceanographic vessels and commercial vessels to characterize discards and record unwanted species occurrence. Observer trials and an automatic observer were used to test the potential use of discard recording by fishermen and scientist to comply with landing obligation regulation