The effect of temperature and substrate on the development of the cortisol stress response in the lake sturgeon, Acipenser fulvescens, Rafinesque (1817)

Abstract

Lake sturgeon, Acipenser fulvescens, are considered threatened or endangered throughout most of their North American Range. Current hatchery rearing for re-stocking programs utilise conventional methods with little to no understanding of the relationship between rearing conditions and the development of the hypothalamic-pituitary-interrenal (HPI) stress axis. In the present study we examined the effects of substrate type and temperature on the development of the HPI stress axis in prolarval and larval lake sturgeon. Lake sturgeon raised over either gravel or no substrate did not consistently show an increase in whole body cortisol at the prolarval stage. However, after the onset of exogenous feeding a consistent increase in whole body cortisol following a stress was evident. Lake sturgeon larvae raised in gravel substrate demonstrated a sustained increase in whole body cortisol for at least 240 min post stress whereas whole body cortisol in larvae raised in no substrate returned to baseline within 240 min post stress. Lake sturgeon larvae raised at 9, 12 and 15°C exhibited markedly different cortisol responses with baseline whole body cortisol being, 38.6 ± 3, 5.67 ± 0.41 and 25.38 ± 2.84 ng.g−1 respectively. Furthermore, the chase induced increases in whole body cortisol at the larval stage were significantly different for each temperature treatment. These experiments demonstrate that physical environment has a significant impact on the development of the HPI stress axis in lake sturgeon.