A bioenergetics evaluation of temperature‐dependent selection for the spawning phenology by Snake River fall Chinook salmon

Abstract

High water temperatures can increase the energetic cost for salmon to migrate and spawn, which can be important for Snake River fall‐run Chinook salmon because they migrate great distances (>500 km) at a time when river temperatures (18–24°C) can be above their optimum temperatures (16.5°C). Average river temperatures and random combinations of migration and spawning dates were used to simulate fish travel times and determine the energetic consequences of different thermal experiences during migration. An energy threshold criterion (4 kJ/g) was also imposed on survival and spawning success, which was used to determine how prevailing temperatures might select against certain migration dates and thermal experiences, and in turn, explain the selection for the current spawning phenology of the population. Scenarios of tributary use for thermal refugia under increasing water temperatures (1, 2, and 3°C) were also run to determine which combinations of migration dates, travel rates, and resulting thermal experiences might be most affected by energy exhaustion. As expected, when compared to observations, the model under existing conditions and energy use could explain the onset, but not the end of the observed spawning migration. Simulations of early migrants had greater energy loss than late migrants regardless of the river temperature scenario, but higher temperatures disproportionately selected against a larger fraction of early‐migrating fish, although using cold‐water tributaries during migration provided a buffer against higher energy use at higher temperatures. The fraction of simulated fish that exceeded the threshold for migration success increased from 58% to 72% as average seasonal river temperatures over baseline temperatures increased. The model supports the conclusion that increases in average seasonal river temperatures as little as 1°C could impose greater thermal constraints on the fish, select against early migrants, and in turn, truncate the onset of the current spawning migration.

Energetic Status of Alaskan Chinook Salmon: Interpopulation Comparisons and Predictive Modeling Using Bioelectrical Impedance Analysis

“…To assess differences in energetic status within and among individual fish, sampling methods must be refined to decrease measurement variation. An important potential application of individual BIA data would be to measure the decrease in lipid content and increase in water content of individuals over spawning migrations to provide empirical estimates that could be used to inform bioenergetics models for salmon species (Plumb ). Additionally, improved methods for weighing large, live fish in the field will be important and we would suggest using a nonconductive board upon which to measure length, weight, and electrical variables.…”

Thermal heterogeneity, migration, and consequences for spawning potential of female bull trout in a river–reservoir system

“…The interaction between water temperature and regulated discharge can influence the behavior, growth, and spawning potential of fish (Plumb, 2018; Rand et al, 2006). This interaction can be more apparent in heterogeneous river–reservoir systems like the one used for our model simulations (Brekke et al, 2009; Johnson et al, 2004).…”

“…Modeling was focused on the specific requirements of females (due to their greater investment in gonads; Jørgensen et al, 2006; Rideout et al, 2005), and for all scenarios, we tracked growth, energy content, condition, age of first spawning, and frequency of repeated (or skipped) spawning. Results of this work build on previous work linking energy content to spawning potential of other fishes (e.g., Glebe & Leggett, 1981; Jørgensen et al, 2006; Plumb, 2018; Plumb, Blanchfield, & Abrahams, 2014), as well as insights on the prevalence of skipped spawning in iteroparous fishes (Bull & Shine, 1979; Rideout et al, 2005; Secor, 2008) to provide an integrated modeling framework for evaluating the reproductive consequences of alternative patterns of habitat use by bull trout in a river–reservoir system.…”

Variation in the Configuration of the Middle Snake River and Its Relationship to Prehistoric Fishing Site Locations

“…Temperature is perhaps the most obvious, and in many ways the most important parameter in determining water quality (Blakey 1966). Higher temperatures during migratory runs can increase energetic expenditures (Plumb 2018), but species also have optimal temperature ranges for spawning. Optimal temperatures for an adult chinook salmon are around 16.5°C; and fish that migrate too early or too late will likely die due to exhausting all energy reserves (Plumb 2018).…”

“…Higher temperatures during migratory runs can increase energetic expenditures (Plumb 2018), but species also have optimal temperature ranges for spawning. Optimal temperatures for an adult chinook salmon are around 16.5°C; and fish that migrate too early or too late will likely die due to exhausting all energy reserves (Plumb 2018). The Middle Snake River currently has monthly temperatures that are ideal for chinooks during a 5 to 7-month period, which covers the three migratory runs.…”