Caractérisation biologique et variation des captures de la grande alose (Alosa alosa) par unité d'effort sur le fleuve Adour (Pyrénées Atlantiques, France)

Abstract

The study of logbooks from commercial fishermen on the Adour River and commercial samples allowed characterization of the allis shad population (Alosa alosa L.) caught during the period 1988-91. A better knowledge of the influence of hydroclimatic factors (rate of river flow and intensity of tidal coefficient) on the catchability of the species in that river was also obtained. Allis shad are mainly recruited to this fishery from the beginning of April to the end of May: Between 78 and 89% depending on year. Males in the population were on average younger than females. However, at the same age, males were significantly smaller in size and in weight than females. These results reinforce the knowledge already obtained on French stocks in the Loire and Gironde river networks. During the main exploitation period of allis shad, we noted the influence of the rate of flow and tidal coefficients on catch per unit effort (kg per trip) variations. Analysis performed either with Correspondence Analysis or with Generalized Linear Model indicated that an increase of catch per unit effort (CPUE) is associated with the increase in the tidal coefficient. The rate of flow was considered to be a secondary factor of variation. © 1994 IFREMER-Gauthier-Villars.