The sea in Tianjin. River swordfish is a freshwater fish, and Tianjin seaside is seawater, that is, salt water, which is not suitable for the growth of river swordfish, so Tianjin seaside does not produce river swordfish. Swordfish is a migratory fish species, which can be divided into river knife, sea knife and lake knife, especially the river knife that enters the river from the sea in February and March every year and goes upstream to the Yangtze River to lay eggs.