Evaluación del lavado gástrico como herramienta para el análisis de la dieta en trucha común

Se ha estudiado la eficacia del método de extracción del contenido estomacal mediante el procedimiento de lavado estomacal a través de una bomba diseñada a partir del modelo original de Seaburg (1957). La efectividad del método no esta relacionada con el tamaño del pez, sino más bien con las propias características morfológicas de las presas, el estado de repleción del estómago y el grado de digestión del alimento. Así, la efectividad del método está inversamente relacionada con el estado de repleción. Además, presas de gran tamaño y que presentan estructuras rígidas como los Aeshnidae y los Tricópteros con estuches son más difíciles de expulsar. No obstante, las diferencias observadas en la efectividad de expulsión entre presas con las mismas características se deben al diferente grado de digestión de las mismas. Aún así, la efectividad media del método es elevada y superior al 80 %. Se trata pues de una metodología relativamente sencilla y eficaz, por lo que su uso es adecuado para la obtención de muestras de contenido estomacal en juveniles y adultos de trucha común.The efficacy of the method of extracting stomach content, by means of the procedure of stomach washing through a pump, based on Seaburg's original model (1957), has been studied. The effectiveness of the method is not related to the size of the fish, but rather to the prey's own morphological characteristics, the degree of repletion of the stomach and the extent of digestion of the food. Thus, the effectiveness of the method is inversely related to the degree of repletion. Furthermore, bigger prey having rigid structures, such as Aeshnidae and Caddisflies with cases are more difficult to expel. However, the observed differences in the effectiveness of expulsion between preys with similar characteristics are due to the extent of their digestion. Nevertheless, the average effectiveness of the method is high and in excess of 80 %. It is therefore a relatively simple and effective methodology and the reason why its use is appropriate for obtaining stomach content samples in young and adult brown trout

Turistas indeseados: ritmo de entrada de especies exóticas en los medios acuáticos gallegos en el último siglo

Galicia (NW Spain) has a dense river network constituted by small coastal rivers, which present a high number of freshwater endemics. However, in the last two decades there has been a steep increase on the records of freshwater invaders on the region, and these constitute an important threat for its freshwater biodiversity. Most of the exotic species present in Galicia have been previously recorded in other areas of the Iberian Peninsula. The temporal analysis of the evolution of the records of invasions in Galicia and in the rest of the Iberian peninsula, shows that the tendency adjust to a decreasing linear regression, with species introduced after 1995 in other Iberian areas being almost immediately present also in Galicia. Detailed analysis of pathways of introduction underlines the important role of aquarium trade on these results, which needs to be regulated if we want to stop or at least retard the introduction of new invasive species on freshwater habitats