Physiological Stress Responses in Wild and Hatchery-Reared Rainbow Trout

Abstract

Stress‐induced changes in plasma cortisol, glucose, and chloride were more extreme in wild rainbow trout Salmo gairdneri than in hatchery‐reared fish subjected to confinement in a net and to electroshock. During 12 h of net confinement, plasma cortisol increased from resting levels of 10 ng/mL to 480 ng/mL in wild fish, and from 2 ng/mL to 155 ng/mL in hatchery fish. Plasma glucose was also higher in wild fish, increasing from 55 to 284 mg/dL, versus an increase from 58 to 196 mg/dL in hatchery fish. Plasma chloride decreased from resting levels of 132–135 meq/L to 53 meq/L in wild fish (and it continued a decline to 33 meq/L during the first 24 h after confinement), but only to 102 meq/L in hatchery fish. Both wild and hatchery‐reared fish required more than 24 h after they were removed from the net to recover resting levels of plasma constituents. Plasma concentrations of cortisol, glucose, and chloride were less altered in response to electroshock than they were in response to net confinement. One hour after galvanonarcosis, plasma cortisol concentrations in wild fish peaked at 234 ng/mL and remained moderately elevated for 4 d; cortisol in hatchery fish peaked at 70 ng/mL within 0.5 h of the electrical stimulus and then returned to resting levels within 1 h. No substantial changes in plasma glucose or plasma chloride occurred in either the wild or the hatchery‐reared rainbow trout after galvanonarcosis.

Physiological response of wild rainbow trout to angling: impact of angling duration, fish size, body condition, and temperature

“…Levels of plasma cortisol for rapid capture fish identified in this study were within the range of resting or baseline levels previously reported for rainbow trout (Woodward and Strange, 1987;Pankhurst and Dedual, 1994). However, levels of plasma lactate for rapid capture fish were higher than resting levels previously reported for wild (Pankhurst and Dedual, 1994) and hatchery (Milligan and Girard, 1993) rainbow trout.…”

“…The magnitude of a stress response and recovery time can vary depending on the severity and duration of stress, fish size, temperature, recovery conditions, developmental state, and origin of fish (e.g., stock or hatchery versus wild; Wydoski et al, 1976;Mazeaud et al, 1977;Woodward and Strange, 1987;Pickering and Pottinger, 1989;Pankhurst and Dedual, 1994;Carey and McCormick, 1998). Alagnak River rainbow trout with greater landing and handling times presumably experienced a greater peak plasma cortisol and lactate response and longer recovery period than fish captured more quickly.…”

“…An extensive amount of research has been conducted to evaluate the magnitude and duration of the physiological response of rainbow trout to exhaustive exercise in hatchery or laboratory environments (Wood et al, 1983;Woodward and Strange, 1987;Pickering and Pottinger, 1989). However, little in situ research has been completed on the physiological response of wild rainbow trout to angling in their natural environment.…”

Domestication effects on behavioural and hormonal responses to acute stress in chickens

“…It has been noted in other species, that domestication and increased tameness is genetically linked to a wide array of behavioural, physiological and developmental traits and that this may be mediated via HPA and HPG axis dynamics [60]. Domestication has led to attenuated HPA reactivity in all species studied so far, while basal HPA axis activity is not necessarily affected [10,20,[22][23][24]. Cockrem [61] concludes that domestic birds (chickens, Japanese quail) have lower CORT levels after stress compared to wild species of birds (Adelie penguin, Great tit), which is in line with our results.…”

“…Various studies have compared hypothalamic-pituitary-adrenal (HPA) axis reactivity of wild and domesticated animals and they suggest that attenuated HPA-axis reactivity in domesticates is common in many species including mice [19], rats [20], pigs [21], guinea pigs [10] silver foxes [22], mallard ducks [23] and salmonids [24]. Furthermore, activation of the HPA-axis suppresses the hypothalamic-pituitary-gonadal (HPG) axis in most animals through several mechanisms [25].…”