Structure of spawning school of chum salmon Oncorhynchus keta from Olutorsky Bay of the Bering Sea (Northeastern Kamchatka)

Relation between biological parameters of Pacific salmons of the genus Oncorhynchus and their population dynamics off the northeastern Kamchatka Peninsula

“…In odd years, the proportion of 4 year old breeders increased, whereas 5 year old breeders were markedly dominant in even years. This probably results from the stronger competition for food in years of high pink salmon abundance (i.e., odd years), which forces a large proportion of chum salmon breeders to remain in the sea and return for spawning only when they are one year older (Klovach and El'nikov, 2013a). The lowest abundance of breeder chum salmon over the 7 years of this study was recorded in the year of the highest pink salmon abun dance (2011), and the smallest female body weight was recorded the next year (simultaneously with the high est proportion, 85%, of 5 year old breeders).…”

“…The amplitudes of interannual changes in these parameters are greater in chum salmon than in pink salmon. In our opinion, this difference is deter mined by both the different age structure of catches 160 120 80 40 0 2 0 0 9 2 0 0 1 1 9 9 3 1 9 8 5 1 9 6 9 1 9 5 3 1 9 3 7 1 9 6 1 1 9 4 5 1 9 7 7 Year Catch, t 200 (а) 2 0 0 8 2 0 0 0 1 9 9 2 1 9 8 4 1 9 6 8 1 9 5 2 1 9 3 6 1 9 6 0 1 9 4 4 1 9 7 6 (b) and the interannual changes in the body weight of fish of different age (Klovach and El'nikov, 2013a). In addition, two seasonal forms, the earlier and the later, different in biological parameters and spawning ecol ogy, have been distinguished in chum salmon of Oly utorsky Gulf, and their periods of migration into rivers overlap (Klovach and El'nikov, 2013a).…”

“…In our opinion, this difference is deter mined by both the different age structure of catches 160 120 80 40 0 2 0 0 9 2 0 0 1 1 9 9 3 1 9 8 5 1 9 6 9 1 9 5 3 1 9 3 7 1 9 6 1 1 9 4 5 1 9 7 7 Year Catch, t 200 (а) 2 0 0 8 2 0 0 0 1 9 9 2 1 9 8 4 1 9 6 8 1 9 5 2 1 9 3 6 1 9 6 0 1 9 4 4 1 9 7 6 (b) and the interannual changes in the body weight of fish of different age (Klovach and El'nikov, 2013a). In addition, two seasonal forms, the earlier and the later, different in biological parameters and spawning ecol ogy, have been distinguished in chum salmon of Oly utorsky Gulf, and their periods of migration into rivers overlap (Klovach and El'nikov, 2013a). Figure 7c shows that the average MI of females decreases in the sequence of even years: from 12.4 in 2008 to 11.5 in 2010 and 9.9 in 2012; by contrast, this parameter grad ually decreases in the series of odd years: from 10.3 in 2007 to 10.5 in 2009 to 12.5 in 2011.…”