Oxidative Stress in Pacific Salmon (Oncorhynchus spp.) during Spawning Migration

Abstract

The energetic and physiological challenges of spawning migrations in semelparous Pacific salmon (Oncorhynchus spp.) have been well characterized. However, the accompanying costs associated with oxidative stress during this nonfeeding migration and the potential connection to senescence have not been explored. Oxidative stress is caused by an imbalance between free radical production and absorption, leading to irreparable cellular damage that accumulates over time and contributes to senescence. The objective of this study was to determine whether oxidative stress occurs during migration between river entrance and spawning for maturing pink salmon (Oncorhynchus gorbuscha), a semelparous species. Samples of plasma, liver, heart, brain, red muscle, and white muscle were collected from individual pink salmon at both the beginning and the end of the freshwater migration and then assayed for antioxidant capacity as well as for oxidative DNA damage. Antioxidant capacity and DNA damage changed between sites on a tissue-specific basis, demonstrating that oxidative stress may be experienced differentially between tissues. Consistent with our prediction, DNA damage was higher and antioxidant capacity lower in plasma (an integrative measure of body condition) and heart tissue at the spawning grounds compared with river entrance. The increased oxidative stress of these tissues is correlated with the senescence and deterioration associated with a semelparous reproductive strategy. However, similar changes were not seen in liver, red muscle, or white muscle. More surprisingly, the antioxidant capacity was higher and DNA damage was lower in the brains of spawning migrants at the spawning grounds than at river entrance. The latter results highlight the importance of tissue-specific variability in understanding the role that oxidative stress may play in spawning migration success.

Are there intergenerational and population-specific effects of oxidative stress in sockeye salmon (Oncorhynchus nerka)?

“…Our study showed that the liver might also be preferentially protected in populations making longer distance migrations, as antioxidant capacity was higher and oxidative stress lower in Stellako River compared to Chilko River. Wilson et al (2014) also assayed liver tissue but found no difference between pre-and post-migration for oxidative stress, however the spawning migration studied in this case was only~100 km and may not be long enough to observe the changes detected in the longer distance migrations. Once sockeye salmon fry complete yolk-sac absorption and emerge from the gravel redds, they must migrate to rearing areas (Quinn, 2005).…”

“…Creek spawning grounds to compare oxidative stress pre-and postspawning migration (Wilson et al, 2014). Wilson et al (2014) found that brain tissue had both higher antioxidant capacity and lower DNA , and oxidative stress represented as a ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) (C) for pre-fertilized eggs (PF), eggs at 24 h post-fertilization (24 HPF), eyed embryos (EYE), hatchlings (HA) and emergent fry (EMG, full yolk sac absorption) reared from female sockeye salmon captured at Harrison River (hashed bars), Chilko River (light gray bars), or Stellako River (dark gray bars) spawning sites.…”

“…Wilson et al (2014) found that brain tissue had both higher antioxidant capacity and lower DNA , and oxidative stress represented as a ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) (C) for pre-fertilized eggs (PF), eggs at 24 h post-fertilization (24 HPF), eyed embryos (EYE), hatchlings (HA) and emergent fry (EMG, full yolk sac absorption) reared from female sockeye salmon captured at Harrison River (hashed bars), Chilko River (light gray bars), or Stellako River (dark gray bars) spawning sites. Letters represent significant differences between offspring developmental stages (p b 0.010, false discovery rate) and symbols represent significant differences between populations (p b 0.011, false discovery rate).…”

“…When subjected to low-water stress after starvation, juvenile Chinook salmon (Oncorhynchus tshawytscha) experienced higher oxidative stress than control fish (Welker and Congleton, 2004). Wilson et al (2014) found that oxidative stress occurred in a tissuespecific manner during migration in pink salmon (Oncorhynchus gorbuscha), and that some tissues may be differentially protected to ensure successful spawning. However, the aforementioned studies do not address how oxidative stress varies intraspecifically or in an intergenerational manner.…”

Oxidative Stress Induction in Monosex Nile Tilapia (Oreochromis niloticus, Linnaeus, 1758): A Field Study on the Side Effects of Methyltestosterone

“…It adversely impacted fish welfare on several levels as growth [15] reproduction [16], and immunity [17].…”