Life-History Pattern of the Iberian Toothcarp Aphanius Iberus (Pisces, Cyprinodontidae) From a Mediterranean Estuary, the Ebro Delta (Spain)

Abstract

The life-history pattern was studied of an endangered endemic cyprinodontid from the Iberian peninsula, Aphanius iberus (Cuvier & Valenciennes, 1846), found in a Mediterranean estuary, the Ebro delta. Maximum ages observed were 1 + in both sexes. The seasonal growth period started in March and continued until September. The females reached larger sizes than the males, as they have a higher rate of growth and live longer. The largest sizes found were 45 mm versus 38 mm. A. iberus is a multiple spawner that releases batches of eggs between May and August but with few eggs each time (varying from 10 to 30). Despite this continuous release of eggs two moments appeared to stand out as more important. After the reproduction period the parental cohort reduced drastically. The relationship between fecundity (F) and total length (mm) was represented by the formula: F = 8.358 x 10 -9 x L t 6.343 . The biology of the Iberian toothcarp is characterized by fast growth, early maturity, high reproductive effort, multiple spawning and reduced longevity. This may be a good life strategy for small fish species in unstable environments, such as estuaries, where adult mortality is high, variable or unpredictable. It allows them to exploit favourable environmental conditions, which occur in a specific, reduced period; practically all the population is renewed during this period.