Life history and production of epeorus torrentium Eaton (Ephemeroptera: Heptageniidae) in a north Iberian stream

The life history and secondary production of E. torrentium were investigated at three sites along a small Spanish stream. This species had an univoltine winter life history with recruitment from June to November. It showed asynchronous development, which is consistent with the unpredictable environment where they dwell. E. torrentium showed higher density, biomass and production at the headwater site than at the downstream sites, but the annual production/biomass ratios followed the opposite spatial trend. Thus, the spatial pattern of production of this species was more related to shifts in population biomass than to changes in growth rates.