Cold-blooded aquatic vertebrates that swim with fins and breathe with gills are called fish. Rui is a carp fish. Small and light carp are called minor carp (bata, ghania) and large and heavy carp are called major carp (rui, katla, mrigel). Under normal conditions, roe fish fry are 35–45 cm (1–1.5 ft) long and weigh 700–800 g. But the fish of Halda river weigh 2-2.5 kg in a year. Therefore, the price of hatching fish or hatching eggs of Halda river is 60-65 thousand taka per kg. Dr. Siddiq Publications