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High stocking density affects cortisol secretion and tissue distribution in brook charr, Salvelinus fontinalis
1Department of Zoology, University of Guelph, Ontario, Canada.
The Journal of Endocrinology
|February 1, 1990
Summary
High stocking density in brook charr increases spontaneous cortisol secretion. While ACTH stimulates cortisol, high density fish show a blunted response, suggesting altered liver metabolism as an adaptation.
Area of Science:
- Aquatic Animal Physiology
- Fish Endocrinology
- Stress Physiology in Aquaculture
Background:
- High stocking densities in aquaculture can induce stress in fish.
- Cortisol is a key stress hormone in fish, regulating physiological responses.
- Understanding the impact of stocking density on cortisol dynamics is crucial for fish welfare.
Purpose of the Study:
- To investigate the effect of stocking density on cortisol secretion and clearance in brook charr (Salvelinus fontinalis).
- To examine the responsiveness of interrenal cells to adrenocorticotropic hormone (ACTH) under different stocking densities.
- To explore potential adaptations in cortisol metabolism at the hepatic level.
Main Methods:
- Preparation of head kidney tissue containing interrenal cells from brook charr at low (30 kg/m3) and high (120 kg/m3) stocking densities.
- Measurement of spontaneous cortisol secretion rates.
- Stimulation of cortisol secretion using adrenocorticotropic hormone (ACTH) at varying concentrations.
- Assessment of cortisol metabolic clearance rates and tissue uptake using [3H]cortisol.
Main Results:
- Brook charr at high stocking density exhibited higher spontaneous cortisol secretion.
- ACTH stimulation resulted in lower cortisol secretion in high-density fish compared to low-density fish.
- No significant difference was observed in the metabolic clearance rate of cortisol between stocking densities.
- High stocking density led to rapid hepatic uptake and catabolism of cortisol, suggesting altered liver metabolism.
Conclusions:
- Elevated stocking density induces chronic stress, evidenced by increased spontaneous cortisol secretion in brook charr.
- High stocking density may lead to a desensitization of the interrenal cells to ACTH stimulation.
- Rapid cortisol catabolism in the liver of high-density fish represents a potential adaptive mechanism to manage elevated cortisol levels, possibly altering hepatic metabolic activity.