DO EEL GRASS BEDS AND SALT-MARSH BORDERS ACT AS PREFERENTIAL NURSERIES AND SPAWNING GROUNDS FOR FISH - AN EXAMPLE OF THE MIRA ESTUARY IN PORTUGAL

The fish communities of the Mira estuary (Portugal) have been studied as a whole since 1986. It was possible to identify two different types of habitat that act as nursery areas and spawning grounds for a large number of fish species - the eel grass beds and the salt-marsh-border ed zone. The importance of these habitats is due, not only to the numb er of species present, but also to their abundance. However, as the ee l grass beds only extend over a small surface in the Mira estuary, the salt marshes become of vital importance for the marine fish, especial ly those with economical value. As several major modifications are pla nned for the Mira estuarine bed and valley in the near future, suggest ions are given in order to preserve the estuarine ecosystem equilibriu m.