Sampling protocol for skeletal structures of North Atlantic albacore tuna (Thunnus alalunga) and ageing interpretation

This paper presents a standardized protocol for sampling skeletal hard parts (dorsal fin ray and otoliths), preparation and age interpretation of albacore first dorsal fin ray. Ageing of albacore is focused in interpretation and reading of annual temporal marks (translucent bands) in first ray of dorsal fin. Preparation of fin ray sections (spines) is presented in detail using two different methods. The spines are usually cut individually using a low speed cutter. Depending of the size of spines, a new procedure has been developed for small spines based on encasing spines in a matrix of plastic resin allowing multiple spines cutting. Interpretation of growth marks on spine sections is explained and examples are presented for a range of size of albacore aged using this method.Ce document présente un protocole standardisé pour l’échantillonnage des pièces dures du squelette (rayon de la nageoire dorsale et otolithes), la préparation et l’interprétation de l’âge du rayon du premier rayon de la nageoire dorsale du germon. La détermination de l’âge du germon se centre sur l’interprétation et la lecture des marques temporelles annuelles (bandes translucides) du premier rayon de la nageoire dorsale. La préparation des sections du rayon de la nageoire (épines) est présentée en détail à l’aide de deux méthodes différentes. Les épines sont généralement sectionnées individuellement en utilisant un couteau basse vitesse. Selon la taille des épines, une nouvelle procédure a été élaborée pour les petites épines, consistant à enfermer les épines dans une matrice en résine plastique qui permet le découpage de plusieurs épines. L’interprétation des marques de croissance sur les sections des épines est expliquée et des exemples sont donnés pour une gamme de tailles de germon dont l’âge a été déterminé à l’aide de cette méthode.En este documento se presenta un protocolo estandarizado para el muestreo de partes duras del esqueleto (otolitos y rayo de la aleta dorsal) y para la preparación e interpretación de la edad del primer rayo de la aleta dorsal del atún blanco. La determinación de la edad del atún blanco se centra en la interpretación y lectura de las marcas temporales anuales (bandas traslucidas) en el primer rayo de la aleta dorsal. Se presenta en detalle la preparación de las secciones del rayo de la aleta (espinas) utilizando dos métodos diferentes. Las espinas suelen cortarse generalmente de forma individual utilizando un cortador de baja velocidad. Dependiendo del tamaño de las espinas, se ha desarrollado un nuevo procedimiento para las espinas pequeñas, que consiste en introducir las espinas en una matriz de resina plástica que permite cortar espinas múltiples. Se explica la interpretación de las marcas de crecimiento en las secciones de espinas y se presentan ejemplos para una gama de tallas de atún blanco cuya edad se determinó utilizando este método

Light Scattering from Nonequilibrium Concentration Fluctuations in a Polymer solution

We have performed light-scattering measurements in dilute and semidilute polymer solutions of polystyrene in toluene when subjected to stationary temperature gradients. Five solutions with concentrations below and one solution with a concentration above the overlap concentration were investigated. The experiments confirm the presence of long-range nonequilibrium concentration fluctuations which are proportional to $(\nabla T)^2/k^4$, where $\nabla T$ is the applied temperature gradient and $k$ is the wave number of the fluctuations. In addition, we demonstrate that the strength of the nonequilibrium concentration fluctuations, observed in the dilute and semidilute solution regime, agrees with theoretical values calculated from fluctuating hydrodynamics. Further theoretical and experimental work will be needed to understand nonequilibrium fluctuations in polymer solutions at higher concentrations.Comment: revtex, 16 pages, 7 figures. J. Chem. Phys., to appea

Dynamics of fluctuations in a fluid below the onset of Rayleigh-B\'enard convection

We present experimental data and their theoretical interpretation for the decay rates of temperature fluctuations in a thin layer of a fluid heated from below and confined between parallel horizontal plates. The measurements were made with the mean temperature of the layer corresponding to the critical isochore of sulfur hexafluoride above but near the critical point where fluctuations are exceptionally strong. They cover a wide range of temperature gradients below the onset of Rayleigh-B\'enard convection, and span wave numbers on both sides of the critical value for this onset. The decay rates were determined from experimental shadowgraph images of the fluctuations at several camera exposure times. We present a theoretical expression for an exposure-time-dependent structure factor which is needed for the data analysis. As the onset of convection is approached, the data reveal the critical slowing-down associated with the bifurcation. Theoretical predictions for the decay rates as a function of the wave number and temperature gradient are presented and compared with the experimental data. Quantitative agreement is obtained if allowance is made for some uncertainty in the small spacing between the plates, and when an empirical estimate is employed for the influence of symmetric deviations from the Oberbeck-Boussinesq approximation which are to be expected in a fluid with its density at the mean temperature located on the critical isochore.Comment: 13 pages, 10 figures, 52 reference

Application of age-length-keys to estimate catch-at-age for the North Atlantic albacore (Thunnus alalunga) stock

This document presents the results of applying two different methods to estimate catch-at-age for North Atlantic albacore (Thunnus alalunga). The Spanish albacore surface fishery size frequency data from 2003 to 2005 have been analyzed by means of MULTIFAN and age-lengthkeys (ALKs) have been derived from readings of sections obtained from sampled dorsal spiny rays of catch landed.Ce document présente les résultats de l’application de deux méthodes différentes visant à estimer la prise par âge pour le germon de l’Atlantique Nord (Thunnus alalunga). Les données de fréquences de tailles de la pêcherie de surface espagnole ciblant le germon de 2003 à 2005 ont été analysées à l’aide de MULTIFAN et des clefs âge-taille ont été calculées (ALKs) d’après la lecture des sections obtenues des rayons épineux de la dorsale échantillonnées de la prise débarquée.Este documento presenta los resultados de aplicar dos métodos distintos para estimar la captura por edad del atún blanco del Atlántico norte. La distribución por talla de las capturas comerciales de las flotas españolas de superficie fue analizada con MULTIFAN. Las claves talla edad fueron obtenidas por medio de la lectura de secciones de radios espinosos muestreados a partir de las capturas comerciales