Primary and secondary indices of stress in the progeny of rainbow trout (Oncorhynchus mykiss) selected for high and low responsiveness to stress

Abstract

A series of pooled gamete matings was carried out employing eggs and milt from mature male and female rainbow trout selected for a consistently high‐ or low‐responsiveness to stress, as indicated by post‐stress plasma cortisol elevation. Development of the progeny was closely monitored and the responsiveness to stress of the progeny of high‐responding parents and the progeny of low‐responding parents was assessed by two methods. For a period of 14 months, at approximately monthly intervals, the plasma cortisol elevation evoked by a standardized confinement stress was determined in fish from each group, and secondly, on one occasion, the time‐course of the plasma cortisol response to a 24‐h period of confinement was monitored. Progeny of high‐responding parents snowed a significantly greater cortisol response to stress than the progeny of low‐responding parents during both testing procedures. However, when the effect of a 14‐day confinement stress was examined, high‐responding progeny showed a more rapid recovery of plasma cortisol levels, while levels in the low‐responding progeny, although initially lower, showed a more sustained elevation. To assess the possible functional implications of these observations, circulating lymphocyte numbers, an immunologically important cortisol‐sensitive component of the blood cell complement, were determined. The duration of the lymphocytopenia observed following the onset of confinement was found to be related to the initial, not the sustained, cortisol response. These data suggest that manipulation of the sensitivity to stress of fish is feasible by selective breeding, but that careful.choice of the indices employed to identify traits considered desirable is necessary.

Divergence of endocrine and metabolic responses to stress in two rainbow trout lines selected for differing cortisol responsiveness to stress

“…However, it is difficult to assess which element of the combined stressor is most important in evoking this response. Similar observations were made during a previous study with rainbow trout selected for stress responsiveness (Pottinger et al, 1994b) and has been confirmed during a recent study with the same F2 lines (T. G. Pottinger and K. G. T. Pulman, unpublished observations). Further investigations are being made to establish whether the dynamics of change in plasma cortisol levels during stress in the HR and LR F2 lines has altered radically from that observed in the F1 lines.…”

Changes in blood cortisol, glucose and lactate in carp retained in anglers' keepnets

“…The reasons for this are unclear but may be related to the age, size or strain of the carp used in Experiment 2 which were different to those used in Experiments 1 and 3. The stress responsiveness of salmonid fish can vary between strains (Pickering & Pottinger, 1989;Pottinger & Moran, 1993;Pottinger et al, 1994) and the same is likely to be true of non-salmonid fish. There have been no reports that age and size are factors which affect stress responsiveness in fish although that possibility cannot be discounted.…”

ACTH does not mediate divergent stress responsiveness in rainbow trout

“…Recent studies have demonstrated that the stress responsiveness of individual rainbow trout, measured as the magnitude of increase in blood cortisol levels following exposure to a standardised confinement stressor, is to a large extent an individual characteristic (Pottinger et al, 1992(Pottinger et al, , 1994) with a moderate to high degree of heritability (Fevolden et al, 1999; offering the prospect of selection for stress tolerant fish. However, it is not yet known at what site(s) within the hypothalamus-pituitary-interrenal (HPI) endocrine cascade selection for responsiveness operates.…”