Biology and Status of Masu Salmon in Sakhalin, Russia

Masu salmon populations are found throughout Sakhalin, Russia, but never reach large numbers.  Two life history forms exist.  In the south, the returning adults are small (41.0 cm length, 1088 g weight and 1466 eggs). Anadromous forms spend 1 year at sea.  Periods of freshwater residency for these anadromous individuals varies (age 1+:  71.3%, age 2+: 28.7%). Anadromous populations are usually dominated by females (58.7%) owing to the presence of freshwater resident, precocial males. The main spawning grounds for masu occur in headwater s and small tributaries in southern Sakhalin.  Smolt production and adult returns have been monitored in Aniva Bay rivers.  According to our estimates, the average number of spawning masu salmon in Aniva Bay over the past 50 years has decreased by a factor of 5-8 times. The main threats to masu are illegal fishing and intense sport fishing. In addition, bycatch in the commercial pink salmon fishery occurs along the southwest coast.  Recreational fishing is clearly effecting these populations.  Efforts are underway to educate anglers about fishing impacts, but they have not been effective at reducing the threat.  Some hatchery programs now exist, but the contribution is small relative to the size of the wild population.