Influence of Ambient Salinity on Osmoregulation and Cortisol Concentration in Yearling Coho Salmon during Stress

Abstract

Yearling coho salmon Oncorhynchus kisutch acclimated to fresh water or seawater were subjected to severe chronic confinement stress in fresh water, seawater, or a medium (one‐third‐strength seawater) that was approximately isosmotic to the fishˈs blood. Plasma osmolarity, Na, K, Ca, Mg, and cortisol and blood hematocrit were measured in fish sampled at 1, 7, 24, and 48 hours after stress began. Plasma osmolarity and electrolyte concentrations increased during stress in seawater, but generally decreased during stress in fresh water. Osmotic imbalance did not occur in fish that were stressed in one‐third seawater. Hematocrit increased in fish stressed in fresh water and decreased in fish stressed in seawater. Fish acclimated to fresh water tended to regain osmotic balance within 48 hours when stressed in fresh water, but in seawater they died. Fish acclimated to seawater tended to regain osmotic balance within 48 hours when stressed in seawater, but in fresh water a compensatory trend was not evident. Confinement stress greatly amplified the osmotic imbalance after fish were transferred from fresh water to seawater compared with that in unconfined fish. Plasma cortisol concentrations increased during stress for all groups; however, fish stressed in one‐third seawater had lower concentrations of cortisol than the other groups within 7 hours after stress began. Received February 8, 1983 Accepted August 7, 1983

Effects of commercial live transportation and preslaughter handling of Atlantic salmon on blood constituents

“…Additionally, the significant difference was also observed in Na + and Cl -ion concentrations after pumping suggests a net transepithelial fluxe of Na + and C1 -change in these euryhaline fish during stress (Redding and Schreck 1983).…”

“…Earlier studies have also demonstrated that blood osmolality and electrolyte concentrations are similarly affected when fish are handled and transported (Redding andSchreck 1983, Urbinati et al 2004). Osmotic perturbations during stress are affected directly by changes in branchial permeability to water and electrolytes (Redding and Schreck 1983) and the magnitude and direction of stress-induced osmotic imbalance depends, at least partly, on water salinity. Fish stressed in seawater tend to gain electrolytes and lose water (Redding andSchreck 1983, Urbinati et al 2004).…”

“…Osmotic perturbations during stress are affected directly by changes in branchial permeability to water and electrolytes (Redding and Schreck 1983) and the magnitude and direction of stress-induced osmotic imbalance depends, at least partly, on water salinity. Fish stressed in seawater tend to gain electrolytes and lose water (Redding andSchreck 1983, Urbinati et al 2004).…”

The effect of allostatic load on hypothalamic–pituitary–interrenal (HPI) axis before and after secondary vaccination in Atlantic salmon postsmolts (Salmo salar L.)

“…This seemed to be supported by the fact that secondary and tertiary stress responses as plasma chloride, magnesium, fin rot and mortality, were significantly increased in the "stress and vaccine" group compared to the "vaccine and stress" and the control group. Earlier studies have shown that cortisol is often associated with the detrimental effects of stress including: decreased growth rates, reproductive dysfunction (Morgan et al 1999;Schreck et al 2001;Mommsen et al 1999), increased incidence of disease (Barton 2002;Davis et al 2002Davis et al , 2003Einarsdottir et al 2000a;Einarsdottir et al 2000b;Weyts et al 1999), reduced seawater tolerance (Ventura et al 2011;Iversen et al 2009;Mommsen et al 1999;Redding and Schreck 1983;Sandodden et al 2001) and survival (Iversen et al 2005;Portz et al 2006;Finstad et al 2003;Iversen et al 1998;Hasan and Bart 2007). It has also been suggested that if the fish is not permitted enough time to recover completely after stress, a second, normally nonfatal, stressful occurrence could be fatal (Carmichael 1984), as observed in this experiment.…”

Plasma prolactin and cortisol concentrations of stressed coho salmon, Oncorhynchus kisutch, in fresh water or salt water

“…It is possible, of course, that this hormone is playing some other, nonhydromineral (Clarke and Bern, 1980) or immunologic role after stress in either medium. Similarly, the hyperkaliemia following stress in either FW-or SWadapted fish could reflect compensation for stress-induced acid-base imbalance (Redding and Schreck, 1983;Turner et al, 1983).…”