Age, growth and reproduction of Cobitis paludica in a seasonal stream

Abstract

In the Iberian endemic loach Cobitis paludica, in a small seasonal tributary of the Guadalquivir River, 65–70% of the total growth in length occurred in the first year of life. The maximum ages observed were 3+ years in males and 4+ years in females. Both sexes matured at the beginning of their second year of life. There was a significant difference from 1: 1 in the overall sex ratio of 412 males to 674 females. Spawning began in late March and ended in July. Cobitis paludica is a multiple spawner that releases a minimum of two batches of eggs per female each year. Once spawning had started, however, there was no recruitment from the stock of transparent oocytes to the mature stock. The number of eggs decreased from the first batch to the second, but there was no significant difference in the mean egg diameter between batches. Compared with other populations of this species, the present population, from a low latitude, is characterized by a low number of age groups, fast growth, early maturity and high fecundity in multiple spawnings. These life‐history characteristics are typical of species in unstable environments, where adult mortality is high, variable or unpredictable.