Vicente D. Estruch

Determination of Lmax for Atlantic Bluefin Tuna, Thunnus thynnus (L.), from Meta-Analysis of Published and Available Biometric Data

A meta-analysis of the straight fork lengths (herewith abbreviated as L) of 2,458,028 Atlantic bluefin tuna, Thunnus thynnus (L.), taken from 224 scientific publications and unpublished L data from scientific organizations and fishing companies spanning most of the known Atlantic and Mediterranean Atlantic bluefin tuna fisheries dating from 1605 to 2011, give L values ranging from L min = 20 cm and L max = 330 cm. The results indicate that the parameter L ∞ = 318.85 cm of the growth equation used by ICCATs Standing Committee on Research and Statistics Atlantic bluefin tuna assessment group for the eastern stock (Lt = 318.85 [1 – e−0.093 (t + 0.97)]) lies within the confidence limits of the maximum Ls presented in the study: L max = 319.93 ± 11.3 cm, confirming that this equation perfectly fits the biology of the growth of this species. These conclusions are also valid for the equation for the western stock (Lt = 314.90 [1 – e−0.089 (t +1.13)]). The ICCAT Atlantic bluefin tuna database contains numerous records of Atlantic bluefin tuna L outside the biological feasibility, and solutions are provided to recognize and remove these outliers based on the application of fixed values of Fultons condition factor (K) between 1.4 and 2.6 and appropriate L-W relationships to correct this situation in the future.

On the Variability of the Length–Weight Relationship for Atlantic Bluefin Tuna, Thunnus thynnus (L.)

Following extensive review, a model of the Atlantic bluefin tuna (ABFT), Thunnus thynnus (L.), length–weight relationship for the eastern Atlantic and Mediterranean (RW = 0.0000188 SFL3.01247; Ec 1) is presented on the basis of samples of ABFT spawners, with an average value of index K = 2.03 ± 0.15SD, collected by the Atlantic traps of Portugal and Spain in the Strait of Gibraltar (1963; 1996–1998; 2000–2012), and a set of samples of juvenile fishes from ICCAT–GBYP (n = 707). The resulting model (Ec 1), together with the model used for the eastern stock assessment (RW = 0.000019607 SFL3.0092; Ec 2) and a recently adopted by ICCAT Standing Committee on Research and Statistics (SCRS) (RW = 0.0000315551 SFL2.898454; EAST) are analyzed in using a bi-variant sample [SFL (cm), RW (kg)] of 474 pairs of data with the aim of validating them and establishing which model(s) best fit the reality represented by the sample and, therefore, will have the greatest descriptive and predictive power. The result of the analysis indicates that the model EAST clearly underestimates the weight of spawning ABFT and that model Ec 2 overestimates it slightly, being model Ec 1 that best explains the data of the sample. The result of the classical statistical analysis is confirmed by means of the quantile regression technique, selecting the quantiles 5, 25, 50, 75, and 95%. Other fisheries and biological indicators also conclude that the model EAST gradually underestimates the weight of ABFT spawners (of 2–3 m) by 9–12.5 %, and does not meet the criterion that for RW = 725 kg (Wmax), SFL = 319.93 ± 11.3 cm (Lmax).

Analysis of the Length–Weight Relationships for the Western Atlantic Bluefin Tuna, Thunnus thynnus (L.)

Abstract The recently adopted model by ICCAT Standing Committee on Research and Statistics (SCRS) for the western Atlantic bluefin tuna (ABFT), Thunnus thynnus (L.) (RW = 0.0000159137 SFL3.020584, WEST), together with the model used to date (RW = 0.0000152 SFL3.0531, Ec 1) is analyzed in using a bi-variant sample (SFL (cm), RW (kg)) of 698 pairs of data (K = 2.02 ± 0.23 SD) in order to validate them and to establish the model that fits best the reality represented by the sample and, therefore, will have the greatest descriptive and predictive power. The result of the analysis indicates that the adopted model WEST clearly underestimates the weight of spawning ABFT being model Ec 1 that best explains the data of the sample. The result of the classical statistical analysis is confirmed by means of the quantile regression technique, selecting the quantiles 5%, 25%, 50%, 75%, and 95%. Other biological and fisheries indicators also conclude that the model WEST gradually underestimates the weight of ABFT spawners (of 2–3 m) by 11–13%, does not meet the criterion that for RW = 725 kg (Wmax), SFL = 319.93 ± 11.3 cm (Lmax), and the average value of K (1.77) obtained for a wide range of size–weight values, using WEST model, represents ABFT in low fattening condition.

Review of Recent Studies on the Absolute and Relative Growth of Atlantic Bluefin Tuna: Similarities with the Pacific Bluefin Tuna

Abstract This study aims to clarify some aspects of the growth of Atlantic bluefin tuna, Thunnus thynnus (L.), (ABFT) mainly regarding parameters of the growth equation and of relative growth, in this case length-weight relationships. There is a great volume of literature on these matters and there is a danger that the resulting confusion may give rise to mistaken decisions. In spite of the publication of 55 articles on absolute growth (FL > 50 cm), which contain a total of 43 growth equations, no consensus has yet been reached within the ABFT assessment group (AG) of the SCRS on parameters such as Lmax and L∞. The results of the present study indicate that the L∞ = 314.9 cm of the growth equation used for the western stock by the AG from 2010 (Lt = 314.9 [1 – e–0.089 (t + 1.13)]), which was discarded in 2016, lies within the confidence limits of the maximum Ls presented in this study (Lmax= 321.4 ± 8.7 cm), confirming that this equation fit the biology of the ABFT growth. With regard to the length–weight relationships, 38 articles (FL > 50 cm) have been consulted containing a total of 71 equations, but in spite of this the models adopted by the AG in 2014 underestimate the weight of spawners (>2 m) in high fattening phase by up to 23%. The coincidence of the length–weight model for the ABFT western stock, discarded by the AG in 2014, with that of Pacific bluefin tuna, Thunnus orientalis (T & S), (PBFT) indicates that both species must have the same growth, something that is not surprising since both were the same species until 2003. Other coincidences, such as the trend of condition factor K in adults and the growth in the first months of life, could ratify it. In the Pacific Ocean, where far fewer growth studies have been made on PBFT than on ABFT in the Atlantic and Mediterranean, the management of growth models for the purposes of stock assessment in the International Scientific Committee (ISC) makes more sense than that carried out by the SCRS on this matter.

Relationship between weight and linear dimensions of Bluefin tuna (Thunnus thynnus) following fattening on western Mediterranean farms

This study presents various models based on formulae relating weight and dimensions (length, height and width) of Bluefin tuna, Thunnus thynnus (L.), fattened in captivity. The main aim of establishing these expressions is to design tools for indirectly predicting the weight of a Bluefin tuna from measurements of one or more dimensions obtained using non-invasive methods such as stereoscopic cameras. Measurements of maximum length, height and width following slaughter were taken of fish fattened in captivity (n = 2078). Different relationships drawn from the dimensions of the tuna against their weight are fitted with part of the data collection and later checked against a reserved sample set. The resulting formulae are compared with the formulae most commonly used in the case of wild tuna. The results of this study confirm that, for tuna fattened in cages, the availability of more than one dimension to estimate weight improves the predictive power of the model and reduces error in the estimate.

Life cycle assessment applied to different citrus farming systems in Spain and Italy

ABSTRACT The increasing environmental awareness of the actors of agro-food supply chains has led to the implementation of new tools to analyze the impacts generated during agricultural practices. The impacts depend not only on the production system but also on the farmer’s management choices, in terms of input allocation, and on the production site, in terms of soil and climate conditions. In order to assess the environmental impact of conventional and organic farming systems on citrus growing in Italy and Spain, a life cycle assessment method has been implemented. The results show the organic system to be more sustainable than conventional and they could be useful indicators for correcting and modifying agricultural practices.

Prácticas de Matemáticas 2: de la clase tradicional a la clase inversa

Haciendo honor a Confucio cuando dijo “Me lo contaron y lo olvide, lo vi y lo entendi, lo hice y lo aprendi”, y gracias a los esfuerzos de la Universitat Politecnica de Valencia por potenciar las metodologias activas como punto de partida en la construccion de los aprendizajes, el Flipped Teaching o clase inversa esta tomando una especial relevancia en nuestras asignaturas, dado que da gran importancia al trabajo que comunmente se hacia en casa, como era la resolucion de problemas, y que ahora se aborda en el aula, donde el papel del profesor es el de orientador mas que de transmisor de conocimientos. En esta metodologia se rebaja el protagonismo del docente para hacer mas enfasis en el del alumno y su aprendizaje. Los estudiantes pueden preparar la teoria en casa con anterioridad, aprovechando la clase presencial para realizar actividades mas practicas, trabajos en grupo y aclarar las dudas que les vayan surgiendo en la resolucion de problemas en tiempo real, a traves de la colaboracion con sus companeros de equipo junto con las orientaciones del profesor, constituyendo todo este proceso una parte muy significativa en su aprendizaje. En este trabajo, describiremos la experiencia llevada a cabo para invertir la clase en la asignatura Matematicas 2 del primer ano del Grado en Ingenieria de Sistemas de Telecomunicacion, Sonido e Imagen, resultado de dos proyectos de innovacion educativa. Palabras clave: Flipped Teaching, metodologias activas, trabajo en grupo, Matematicas.

Luces y sombras del Flipped Teaching con estudiantes de primero de turismo

Este trabajo se ha realizado gracias al apoyo del Vicerrectorado de Estudios, Calidad y Acreditacion de la UPV al Proyecto PIME 2016-2017 “Puesta en marcha de diversas experiencias con el enfoque Flipped Teaching en asignaturas de Matematicas y Fisica”.