Life history strategy of Leuciscus pyrenaicus (Cyprinidae) in intermittentstreams of the Guadiana basin (Portugal)

The aim of the study was to examine the ecology of Leuciscus pyrenaicus in intermittent streams in the middle reaches of the Guadiana basin, in southe rn Portugal, and examine the life history strategies this species adopts to survive the harsh environment conditions. Differences in growth and reprod uctive biology in three tributaries (Xevora, Caia and Degebe) were examined . L. pyrenaicus contributed up to 12% by number to the fish community, alth ough each population was dominated by small individuals. Males up to five y ears of age and females up to seven years were caught. Females attained a g reater size and age than males. The fastest growth rate was found in the Xe vora river, where this species dominated the community structure and its "p referred" habitat characteristics were evident, i.e., moderately flowing wa ter and coarse substrate. Changes in the gonadosomatic index (GSI) for sexu ally mature males and females suggest that gonad maturation occurs from Oct ober to April, and the spawning period is between April and July. Females f rom the Xevora river were more fecund and this was linked to the less harsh conditions found in this river. The species exhibits an r-selected life hi story strategy to survive the extreme environmental conditions in intermitt ent streams in the Guadiana basin.