LIFE-HISTORY PATTERN OF THE IBERIAN TOOTHCARP APHANIUS-IBERUS (PISCES, CYPRINODONTIDAE) FROM A MEDITERRANEAN ESTUARY, THE EBRO DELTA (SPAIN)

The life-history pattern was studied of an endangered endemic cyprinod ontid from the Iberian peninsula, Aphanius iberus (Cuvier & Valencienn es, 1846), found in a Mediterranean estuary, the Ebro delta. Maximum a ges observed were 1(+) in both sexes. The seasonal growth period start ed in March and continued until September. The females reached larger sizes than the males, as they have a higher rate of growth and live lo nger. 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 cont inuous release of eggs two moments appeared to stand out as more impor tant. After the reproduction period the parental cohort reduced drasti cally. The relationship between fecundity (F) and total length (mm) wa s represented by the formula: F = 8.358 x 10(-9) x L-t(6.343) The biol ogy of the Iberian toothcarp is characterized by fast growth, early ma turity, high reproductive effort, multiple spawning and reduced longev ity. This may be a good life strategy for small fish species in unstab le environments, such as estuaries, where adult mortality is high, var iable or unpredictable. It allows them to exploit favourable environme ntal conditions, which occur in a specific, reduced period; practicall y all the population is renewed during this period.