Pacific Salmon and Steelhead: Life in a Changing Winter Ocean

Abstract

How Pacifi c salmon and steelhead (Oncorhynchus spp.) respond to climate-driven changes in their oceanic environment is highly uncertain, in part due to limited information on winter distribution in international waters (high seas) of the North Pacifi c Ocean and Bering Sea. We review what is known and summarize what should be known to properly address the question: Where do Pacifi c salmon go in the high seas during winter and why, and how might this be aff ected by climate change? Historical high-seas research (1950s-1970s, all seasons) discovered that there are species and stock-specifi c distributions in the high seas; winter survey results provided some clues as to important winter locations and dominant oceanographic features of winter habitat. In succeeding decades , new fi sheries-oceanographic survey methods, stock-identifi cation techniques, remote-sensing technologies, and analytical approaches have enabled us to expand our knowledge of the winter distribution and ecology of salmon, although empirical data are still very limited. In general, we learned that the "why" of ocean distribution of salmon is complex and variable, depending on spatio-temporal scale and synergies among heredity, environment, population dynamics, and phenotypic plasticity. The development of quantitative multispecies, multistage models of salmon ocean distribution linked to oceanographic features would help to identify key factors infl uencing winter distribution and improve understanding of potential climate change eff ects.

Examining Life History Shifts and Genetic Composition in a Hatchery Steelhead Population, with Implications for Fishery and Ocean Selection

“…; Myers et al. ). Changes in predator distribution have also been associated with ocean warming (Peterson et al.…”

Opening the black box: New insights into the role of temperature in the marine distributions of Pacific salmon

“…The Importantly, the models developed in this work are effectively averaging over any ontogenetic (French et al, 1976;Myers et al, 2016;Neave et al, 1976) and stock-specific (Espinasse et al, 2020;McKinnell et al, 1997;Shelton et al, 2021;Urawa et al, 2009;Weitkamp & Neely, 2002) distribution patterns, which may themselves be related to differences in temperature preferences among ages and populations, that complicates effective prediction of spatial responses to climate variation. The distribution models and temperature preferences estimated here are intended to represent general basin-wide patterns for each species that can act as a new baseline from which to develop investigations into the influences of F I G U R E 5 Change in thermal habitat suitability scores by month (rows) and species (columns), calculated using the SST effect curves estimated in Model 3 standardized to a [0,1] scale, between mean sea surface temperature conditions matching a cold (1983)(1984)(1985)(1986) and warm (2013-2016) period for sockeye (left), chum (middle) and coho (right) salmon.…”

“…When all the estimated thermal niche metrics are considered, our results suggest and Trudel (2014). Past work has suggested that immature sockeye salmon are distributed further south and in warmer water than older, maturing fish (Myers et al, 2016). Therefore, it is possible that this pattern is the result of ontogenetic effects, other factors like stockspecific dynamics or migration patterns, or, more likely, some combination of these.…”

“…Salmon also serve as an indicator of a changing North Pacific. As salmon migrate across great distances (Myers et al, 2009(Myers et al, , 2016, their growth and survival reflects ocean conditions acting at multiple spatiotemporal…”

“…org/ enfor cemen t-activ ities/ ). Trudel, 2014Trudel, , 2015Myers et al, 2016;Welch et al, 1998) While various environmental data associated with these catch records were collected at times, only SST was regularly recorded.…”