Physiological stress responses to confinement in diploid and triploid Atlantic salmon

Abstract

Confinement of juvenile Atlantic salmon Salmo salar from four different populations (allfemale diploids, all-female triploids, mixed sex diploids and mixed sex triploids) either before (FW parr) or after (SW smolts) transfer to sea elevated plasma cortisol and plasma lactate from control levels irrespective of ploidy status. Both before and after confinement, plasma cortisol levels in SW smolts (6-174 ng ml 1 ) were higher than those in FW parr (4-58 ng ml 1 ), which possibly reflected the physiological challenge of acclimation to SW. Mixed sex populations of SW smolts had higher cortisol levels than all-female populations. The duration of confinement (1, 3 or 6 h) affected the magnitude of the plasma cortisol and lactate responses in SW smolts. Plasma cortisol levels in diploid and triploid SW smolts subjected to 2 h of confinement decreased to pre-stress levels within 6 h post-confinement. Plasma lactate levels were not significantly different from pre-stress levels 48 h after confinement. As no difference exists in primary and secondary stress responses of Atlantic salmon of differing ploidy status, it is unlikely that differences in mortality rates between diploid and triploid populations under commercial conditions can be attributed to differences in their physiological responses to periods of stress lasting up to 6 h. 2000 The Fisheries Society of the British Isles

Effects of skeletal deformities on swimming performance and recovery from exhaustive exercise in triploid Atlantic salmon

“…Somatic growth continues in triploids and flesh quality is maintained over the period when diploid fish are sexually maturing and undergoing associated reduction in flesh quality (Sadler et al 2000). However, despite the obvious advantages of using triploids, there are a number of problems associated with the commercial production of all-female triploid fish.…”

Questionnaire-based risk assessment for amoebic gill disease (AGD) and evaluation of freshwater bathing efficacy of reared Atlantic salmon Salmo salar

“…It is, therefore, likely that bathing is less effective in smaller size cages. This could be due to a range of factors such as confinement stress (Sadler et al 2000), dominant behaviour (MacClean & Metcalfe 2001) and inability for escapement possibly leading to an increased chance of AGD-affected fish infecting unaffected fish.…”

“…For example, there was a 13-fold increased likelihood of infection with Kudoa thyrsites for sexually mature salmon compared to sexually immature salmon (StHilaire et al 1998). Also, higher cortisol levels, a measure for primary stress responses (Sadler et al 2000), were found in mixed sex populations compared to allfemale populations. High cortisol levels have also been associated with immunosuppression (Bakke & Harris 1998, Sadler et al 2000.…”

“…Also, higher cortisol levels, a measure for primary stress responses (Sadler et al 2000), were found in mixed sex populations compared to allfemale populations. High cortisol levels have also been associated with immunosuppression (Bakke & Harris 1998, Sadler et al 2000.Paramoebae were found to remain at detectable levels, though at significantly lower numbers, up to 1100 m away from a farming site, which was the greatest distance measured (Douglas-Helders et al 2003a). Further, it was demonstrated that Neoparamoeba pemaquidensis did nor require contact with hosts for at least 14 d to remain infective when a high infection dose was used (Douglas-Helders et al 2003b).…”

“…It is, therefore, likely that bathing is less effective in smaller size cages. This could be due to a range of factors such as confinement stress (Sadler et al 2000), dominant behaviour (MacClean & Metcalfe 2001) and inability for escapement possibly leading to an increased chance of AGD-affected fish infecting unaffected fish.Higher reported initial oxygen saturation levels during bathing were negatively associated with the mortality rate in the WS but not the reported bathing frequency. The reported bathing frequencies were negatively associated with the higher reported oxygen level during the CS, but not the number of total mortalities.…”