mercedes herrera

ABSTRACT The age, growth and reproduction of Leuciscus pyrenaicus (Günther, 1868), an endemic cyprinid from the Iberian Peninsula, was studied from November 1987 to September 1989 in a small seasonal tributary of the Guadalquivir river basin. Maximum fork lengths observed were a 160 mm male with six scale annuli and a 171 mm female aged 7 +. Maximum ages observed were 7 + in males and 8 + in females. There were no significant differences in the annual growth increments between sexes. Seasonal growth period started in March and continued for 5 to 6 months. Mean lengths of 1 + specimens onwards diminished during summer and/or autumn. Males and females matured in their third and fourth year of life respectively. The overall sex ratio (272 males: 310 females) differed significantly from equality. Spawning began in May and ended in July. L. pyrenaicus is a multiple spawner that releases a minimum of two batches of eggs per female each year. Eggs in each batch were similar in both size (egg diameter) and number released. The relationship between fecundity (Fee) and fork length (mm) was represented by the formula: Fec=1.96 10−3 L2.50.

ABSTRACT The age, growth and reproduction of Chondrostoma polylepis willkommi, an endemic cyprinid from the Iberian Peninsula, was studied for 2 years in a seasonal stream in the Guadalquivir River basin. Annual growth was low. Maximum ages observed were 5+ in males and 7+ in females. There was no significant difference in growth between sexes. Seasonal growth period started in May and continued for 2 to 6 months depending on age. The mean lengths of 1 + and 2+ age-groups decreased once the growth period had finished, probably related to reproductive stress and adverse ecological conditions, and this could explain the occurrence of Rosa Lee's phenomenon. Both sexes matured at the end of their second year of life (1+). There was a significant difference from 1: 1 in the overall sex ratio of 334 males to 464 females. Reproductive period started in March and lasted until May. Ch. p. willkommi was a multiple spawner that released two batches of eggs per female each year. The regression between fecundity (F) and fork length (l., mm) was: F=6.20 103 L.2.78. In females from age 2 + onwards, relative annual investment in somatic growth and reproduction was equivalent, implying that the same energy was allocated to reproduction as to maintenance/growth. Compared with other Ch. polylepis populations, the life-history patterns of this population, located in a small and seasonal stream in a southern latitude, were characterized by a low annual growth, a trade-off between reproduction and growth/maintenance, early maturity, low number of age-groups and high fecundity from multiple spawnings.

Abstract The age, growth and reproduction of an Atlantic population of Atherina boyeri is discussed on the basis of an examination of 2510 specimens from the Guadalquivir river (37 N, 6 25′ W). The life-span was short with a winter age structure of 80· 4% in 0+ group, 13· ...