Regularities of Formation of Diversity of Life Strategy and Genetic Variability of The Kamchatka Rainbow Trout Parasalmo mykiss in a Local Population

Diversity of life history traits, growth, and lipid storage in migratory variants of steelhead and rainbow trout (Oncorhynchus mykiss) in Kamchatka, Russia

“…1). The river basin area is 1350 km 2 , with a low gradient (5 m•km -1 ), and base flows at the river mouth are 12 m 3 •s -1 (Pavlov et al 2005;Kuzishchin et al 2020b). This tundra-type river is ice covered between November and April, with the lowest flows in the winter and highest flows in the spring, and is a meandering channel with tanniccolored water and limited riparian woody vegetation.…”

“…The third "estuarine" contingent migrates to the estuary and nearshore environment for the summer, appearing in nearshore catches in the Sea of Okhotsk (K. Kuzishchin, unpublished data). Estuarine fish are thought to overwinter in deep sections of the estuary (Kuzishchin et al 2020b) based on otolith Sr:Ca profiles (n = 11, K. Kuzishchin, unpublished data) and the observation that low temperatures (−0.1 to −0.5 • C) and high salinity (22-26 ppt) in the Sea of Okhotsk would be uninhabitable for salmonids between December and March. The fourth contingent, known as "riverine-estuarine" fish, similarly migrate to the estuary for the summer, but return to the river each year to overwinter (Kuzishchin et al 2020b), a migration supported by otolith Sr:Ca profiles (Zimmerman et al 2003) as well as tagging and index netting in the estuary and river (K. Kuzishchin, unpublished data).…”

“…Following analysis methods established over five decades of research in Kamchatka (Kuzishchin et al 1999;Pavlov et al 2001;Kuzishchin et al 2020b), we used scale pattern analysis to classify each fish into one of the five contingents. The total age of each fish at the time of capture was based on the number of years of growth inferred from annuli.…”

“…In addition, scale pattern analysis has detected more complex and intermediate growth patterns attributed to migration between rivers, estuaries, and coastal waters (Pavlov et al 2001;. Thus partial migration of these contingents is associated with a range of feeding environments from the most resource-rich and diverse open ocean (Daly et al 2014) to coastal and freshwater environments, where O. mykiss appear to encounter prey in more limited and seasonal pulses (Kuzishchin et al 2020b).…”

“…We hypothesized that differences among O. mykiss life histories are mediated by both their growth environment and physiological state. To examine this hypothesis, we synthe-sized life history, demographic, and growth data previously collected for our study river (Pavlov et al 2001;Kuzishchin et al 2020b), applied genetic and stable isotope techniques to increase robustness of the data set, and analyzed new data on somatic lipid content. We predicted that life history contingents accessing the resourcerich oceanic environment would have faster growth and higher lipids than those associated with the more resourcelimited coastal environments, which in turn would grow faster and store more lipids than those feeding in freshwater environments.…”