Assis, C. A. (1990).  Threats to the survival of anadromous fishes in the River 
Tagus, Portugal. Journal of Fish Biology.  37 (Suppl. A):225-226.
	
Most European anadromous fish are threatened species. This investigation 
concerns the River Tagus (Iberian Peninsula). Four anadromous fish spp occur in 
this basin but they no longer reach the upper (Spanish) part. In Portugal, the 
sea lamprey, Petromyzon marinus (Petromyzontidae), and the twaite shad, Alosa 
fallax (Clupeidae), are still common, the allis shad, Alosa alosa (Clupeidae), 
is rapidly declining and the river lamprey, Lampetra fluviatilis 
(Petromyzontidae), is rare. The sturgeon, Acipenser sturio (Acipenseridae), no 
longer occurs in the River Tagus. In the Tagus basin there are countless sources 
of all types of industrial and urban pollution. Although most anadromous fish 
species used to live in the whole Tagus basin, reaching its Spanish portion, 
they are now limited to the lower 200 km of the main Tagus River. This 
limitation is due to two dams which are impassable barriers, either because the 
fishways, when they exist, are not suitable for these anadromous species or 
because they are currently not in use. The reservoir at Castelo de Bode contains 
a land-locked population of allis shad. This population, due to its lower 
condition, size and weight has a low commercial value. The impact caused by 
fishermen on the anadromous fish stocks is important at two levels, both leading 
to low recruitment.