Effects of stocking density during simulated transport on physiology and behavior of largemouth bass (Micropterus salmoides)

Citation

Yang Y, Narayan E, Rey Planellas S, Phillips CJC, Zheng L, Xu B, Wang L, Liu Y, Sun Y, Sagada G, Shih H, Shao Q & Descovich K (2024) Effects of stocking density during simulated transport on physiology and behavior of largemouth bass (Micropterus salmoides) [Transport in Largemouth bass]. Journal of the World Aquaculture Society, (e13054). https://doi.org/10.1111/jwas.13054

Abstract
The live transport of farmed fish is an important practice in Chinese aquaculture due to consumer preferences in its domestic market. However, live transport can be stressful for fish and may cause many welfare issues. This study aimed to examine the effects of transport density on the welfare of largemouth bass (Micropterus salmoides). Adult fish were allocated to four experimental treatments in a two-factor design (N = 5 groups per treatment). Factor one was stocking density of either 39 (low density) or 78 (high density) g L1. Factor two was transport, with half of the fish groups exposed to simulated transport stress for 3 h using a motion platform, and the other half kept in static tanks for the same length of time. Baseline behavior and physiology were determined from a subset of fish after acclimation but before selection into groups and application of transport. To determine the effects of transport, stocking density, and their interaction on the experimental groups, physiological sampling and behavioral recording were car- ried out immediately after simulated transport, and water quality was measured both before and after transport. Changes in water quality were observed between two timepoints, with decreased dissolved oxygen levels and increased water temperature. Total ammonia nitrogen levels significantly increased in all treatments over time, particu- larly in the high-density groups. Fish ventilation rates were significantly elevated in the groups kept at a high stocking density regardless of whether they also experienced trans- port stress. Fish transported at a high stocking density also showed more fear-related behaviors such as freezing and thigmotaxis than non-transported groups. Serum cortisol, catalase, and aspartate transaminase levels were signifi- cantly higher in the transported treatment groups compared to the baseline fish, but no difference was found for serum glucose, lactate, and glutathione peroxidase. We concluded that 3 h of simulated transport was stressful to largemouth bass kept at 78 g L1, as evidenced by altered fish physio- logical and behavioral indicators of stress, as well as deterio- rated water quality. Additionally, we identified a positive correlation between serum and skin mucus samples for cor- tisol, glucose, and lactate in transported fish, providing important information for developing less invasive methods for the welfare assessment of largemouth bass.

Keywords
Agronomy and Crop Science; Aquatic Science

Journal
Journal of the World Aquaculture Society, Issue e13054