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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.