Estudi de l'estratègia reproductora d'una població nativa d'alburn (Alburnus alburnus)

Abstract

The bleak Alburnus alburnus (L.) is a cyprinid species inhabiting mainly lentic environments. Its diet is based on zooplankton and land insects and its reproductive period takes place during the seasons of spring and summer. This species, native to most of Europe, was introduced in the Iberian Peninsula in the 90’s, where it has spread becoming invasive. On the one hand, this study expects to examine the biological treats of one native population of bleak from Saône River, located at east of France. On the other hand, the aim is to compare this species biological treats with other native populations from the southeast of France (Chappaz et al., 1987) and introduced populations in the Iberian Peninsula. Specifically, populations from the Catalonia internal basins (Masó, 2012), from the Atlantic slope rivers and from river Ebro (Latorre, 2013). The specimens were captured by electrical fishing, during the spring of 2014. Lately, the specimens were processed in the laboratory so it was possible to analyse the following biological traits: total length (TL), total weight (TW), gonads weight (WG), minimum length at maturity (Lmm) for females, sex ratio, gonadosomatic index (GSI) and Le Cren (LK) and Fulton (K) index condition. Moreover, population size and age structure were determined too and fecundity and mean egg diameter were determined for females. It seems that the ecological conditions of the basin are determinant of the populations’ status. After comparing the populations, it can be deduced that in stable lentic environments, bleak establishes easily and presents a minimum length at maturity similar to the native ones and low values of GSI and gonads weight. However, in changeable environments, the populations are under expansion phase, with a lower minimum length at maturity and a higher reproductive potential. Thus, although the population from Saône River presents high values of GSI and gonads weight, the females’ minimum length of maturation allows for deducing that the population could be well established. Between native populations, the one from Saône River shows lower fecundity values and less growth. The results suggest that these biological treats are determined by various factors, such as bleak’s diet, among others. Additionally, the zone of the river where bleak is found could be another determining factor for growth and fecundity. Moreover, the differences observed in the maximum ages of each population could be explained by the mentioned factors and the environmental conditions of the zone