Comparing stress responses of F1 and domesticated striped bass ( Morone saxatilis ) following a repeated acute stressor

Abstract

Finfish aquaculture requires routine practices such as handling, grading, transport and general system maintenance that may induce repeated stress and lead to suboptimal production. Stress responses are under neuroendocrine control and divert an animal's energy reserves away from normal bodily functions such as growth, immune system maintenance, and reproduction and direct them towards coping with the stressor (Pickering, 1993). If the adaptive response is successful, a return to pre-stressed conditions (homeostasis) is achieved, but if the stressor is too severe or long-lasting, the coping mechanisms become maladaptive and detrimental to the fish's performance (Barton, 2002;Barton & Iwama, 1991).The common response to stressors (General Adaptation Syndrome (GAS; Selye, 1950Selye, , 1973 in fish and other vertebrates has been well studied and consists initially of neural activation of the hypothalamus-pituitary-interrenal gland (HPI) axis and release of catecholamines, followed by production of the glucocorticoid, cortisol (Mommsen et al., 1999;Wendelaar Bonga, 1997). Elevated circulating cortisol levels have primarily been used as an indicator of aquaculture-induced stress because of its predictive responsiveness and relative ease of measurement (Barton & Iwama, 1991).Correlations between elevated cortisol and long-term performance traits (growth, disease susceptibility), however, are often not evaluated and have been inconsistent when analysed (Kenter et al., 2019).

Water temperature explains part of the variation in basal plasma cortisol level within and between fish species

“…This is nevertheless consistent with the results of the studies carried out in R. quelen , where no effect of age on basal cortisol levels was found (Barcellos et al ., 2012; Koakoski et al ., 2012). Furthermore, habituation to environment and/or stress is known to decrease the cortisol level, including cortisol release in fish (Barton et al ., 1986; Houslay et al ., 2019; Kenter et al ., 2021). We thus expected that larger fish ( i.e ., older and experienced fish regarding stress) would be less affected by environmental factors and respond less to stress than smaller (younger) fish.…”

“…Furthermore, habituation to environment and/or stress is known to decrease the cortisol level, including cortisol release in fish (Barton et al, 1986;Houslay et al, 2019;Kenter et al, 2021). We thus expected that larger fish (i.e., older and experienced fish regarding stress) would be less affected by environmental factors and respond less to stress than smaller (younger) fish.…”