The Effect of Unpredictable Chronic Stress on Rare Minnow (Gobiocypris rarus): Growth, Behaviour and Physiology

SIMPLE SUMMARY: The laboratory fish model plays an important role in modern scientific research. Ensuring the welfare of laboratory fish is beneficial to the repeatability of experimental results. Laboratory fish will face some stressors in the process of feeding and management, but there are few studies on this part. Our study shows that unpredictable chronic stress for 7 and 14 days can lead to a significant decrease in growth and cortisol levels of laboratory rare minnow. At the same time, the behaviour pattern and neurotransmitter response changed more significantly with the increase of time. Therefore, we should try to reduce the duration and intensity of these stressors to ensure their welfare needs in daily feeding management. ABSTRACT: Fishes often adjust their behaviour patterns and physiological responses to cope with changing environments, and different life experiences affect them differently. Fishes might adapt to short-term stress, whereas long-term unpredictable stress may lead to various adverse effects. Although some studies have constructed unpredictable stress models of fish, the effect of unpredictable chronic stress (UCS) in the laboratory is poorly understood in fishes. In the current study, we exposed adult rare minnow to an unpredictable chronic stress protocol over 7 and 14 days and measured their response in terms of growth performance, cortisol, neurotransmitter levels (DA, 5-HT, and related metabolites), and behaviour patterns to comprehensively assess the effects of UCS on laboratory rare minnow. We discovered that specific growth rates were significantly decreased, and cortisol levels were lowered in both 7-days and 14-days stress groups. In the behaviour test, the activity level of the 14-days stress group increased, but there was no significant difference in the number of crossings to the center areas, time spent in the center areas, or the speed. In addition, the levels of DA and 5-HT did not change in the stress groups, but the DOPAC and 5-HIAA levels in the 14 days stress group were significantly higher than those in the control group. These results suggested that UCS influences rare minnow growth performance, behaviour patterns, and cortisol levels, and similar stress should be minimised in the laboratory.