Age and length-weight structure of local stocks of sockeye salmon Oncorhynchus nerka in some feeding-spawning lakes of Kamchatka Region

Age and length-weight structure of sockeye salmon spawners are considered for the feeding-spawning lakes of southeastern Kamchatka, as Dalneye (1976-2013), Blizhneye (1939-2013), and Listvenichnoye (1999-2013), and for Lake Sarannoye on Bering Island (1990-2013). By these data, the age of sockeye salmon maturing is: 2.2, 2.3 and 3.2 in Lake Dalneye, 1.2, 1.3, 2.1 and 2.2 in Lake Blizheye, 2.2, 2.3 and 3.3 in Lake Listvenichnoye, and 2.2, 2.3, 3.2 and 3.3 in Lake Sarannoye. These age groups dominate in the samples of spawning sockeye with the portion 70-90 %. Long-term dynamics of length and weight of sockeye spawners is distinguished by negative trends significant for the longest time-series in Lake Blizhneye and insignificant for the shorter one in Lakes Dalneye; the length of observations in Lakes Listvenichnoye and Sarannoye is not enough to reveal trends. Besides, cyclic variations with the period 5-10 years could be revealed for the long tome-series. As a rule, each cycle includes the phases of gradual decreasing and sharp increasing of length and weight. Year-to-year dynamics of the length-weight structure in the common period of observations is similar for all investigated lakes.