bridge runs the Lake Polyphytos Bridge, part of the Athens-Kozani national road. Southeast of Veria, the Haliacmon enters the central Macedonian plains, an area of great importance to agriculture. It flows into the Thermaic Gulf west of the delta of the Axios (Vardar), northeast of the coastal town Methoni. Haliakmon's tributaries include Gramos, Ladopotamos, Pramoritsa, Grevenitikos, Venetikos and Tripotamos. The Haliacmon flows along the towns (in downstream order) Nestorio, Argos Orestiko, Neapoli, Paliouria, Velventos and Alexandreia. Wetland Haliakmon contains 33 kinds of fish. These include brown trout, gilt-head bream, sardine, carp, pike, eel, european anchovy, nursehound, bogue, garfish, red porgy, saddled seabream, angler, bream, mediterranean sand smelt, sand steenbras, mullus barbatus, freshwater bass, tuna, salmon, Mediterranean moray, weever, longfin gurnard, dogfish, dusky grouper, school shark and turbot. About 30 of them are indigenous, while the rest were introduced by human intervention. Many of them are considered scarce and one, mavrotsironi, lives nowhere else in the world, i.e. it is endemic. Μost of these kinds of fish have no commercial value but only biological, since they support the food web. Fish found in Haliakmon, like carp and rainbow trout, indicate that its water is still pure. Some eels are found in its estuaries, that cannot migrate, hindered by the dams. For amateur fishermen the river has been enriched with introduced rainbow trout, that is not easy to reproduce, so there is no danger of disturbance of the river's ecosystem. In the place where the river flows into the sea, there has been formed over the years an extended Delta of 4.000 hectares, because of the large dam that was constructed and retains much of the brought matters. As a result, silting has been greatly reduced and during the summer, when there is not much water, the sea enters and largely overwhelms the river bed. Flathead mullets and European seabasses are found in Haliakmon's Delta. In the shallow marine areas formed there, the fry of many Aegean Sea's fish finds a place to reproduce, while about 90% of Greece's mussels are produced in the Haliakmon-Axios (Vardar) Delta. Aliki Kitrous is an area of 254 hectares, where 15–20.000 tons of salt are produced per year. Many kinds of birds have been observed in Haliakmon's region. They use it for accommodation and overwintering, like the ducks, or to rest on their long migratory journey. There have been observed 215 kinds of birds and about