In the early 1960s, the population of White Sea marine three-spined stickleback (Gasterosteus aculeatus), a key forage fish, declined drastically, and the species almost completely disappeared from catches. The population started to recover in the late 1990s, and its abundance has increased exponentially since then. Using contemporary and historical data, we contrast the age structure of spawning stock and fish growth before and after the population decline. Most stickleback spawners in 2009–2011 were 2 and 3 years old, with the 3-year-old fish being more abundant. The proportion of 2-year-old fish in recent catches is higher than that 50 years ago, indicating some rejuvenation of the population after the prolonged decline. Moreover, White Sea sticklebacks in the present population grow faster than those in the 1950s. The observed shifts are concurrent with the long-term changes in the temperature regime in the coastal areas of the White Sea, which determine zooplankton abundance and the duration of the feedi