Over the past decades, an increasing number of fish species have undergone strong decrease in their abundance due to various human activities. Such activities may prevent the free movement of fish, generates pollution and habitat loss, overfishing and many additional problems. To overcome these demographic declines, numerous stocking programs have been implemented to sustain fish populations worldwide. This is the case of the Muskellunge (Esox masquinongy) in the province of Québec, Canada. The species is renowned for his trophy-size specimens which are highly prized by anglers. However, Muskellunge has undergone strong decline in abundance during the first half of the 20th century in the waters of the St. Lawrence River, especially in the greater Montréal region. Consequently, Muskellunge from Ontario and New York State were used for stocking over 1.5 million of individuals from 1950 to 1997. From 1950 to 1965, eggs initially taken from the Chautauqua Lake (New York State, USA) were transferred to the Lachine government hatchery in Québec where fry were reared before being released into the St. Lawrence River, several of its main tributaries and inland lakes. From 1965 to 1986, adults from Lake Joseph were used as source for stocking. Finally, from 1986 to 1997, eggs from Lake Tremblant were used. Muskellunge populations from Joseph and Tremblant Lakes were originally introduced with fish from the Lake Chautauqua source.