Rethinking swimming performance tests for bottom-dwelling fish: the case of European glass eel (Anguilla anguilla)

• Published in: Scientific Reports
• Main Authors: Vezza, P, Libardoni, F, Manes, C, Tsuzaki, T, Bertoldi, W, Kemp, P S
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Tac; Anguilla anguilla
• Online Access: http://hdl.handle.net/11572/276558; https://doi.org/10.1038/s41598-020-72957-w; https://www.nature.com/articles/s41598-020-72957-w#citeas

Systematic experiments on European eel (Anguilla anguilla) in their juvenile, early life stage (glass eel), were conducted to provide new insights on the fish swimming performance and propose a framework of analysis to design swimming-performance experiments for bottom-dwelling fish. In particular, we coupled experimental and computational fluid dynamics techniques to: (i) accommodate glass eel burst-and-coast swimming mode and estimate the active swimming time (tac), not considering coast and drift periods, (ii) estimate near-bottom velocities (Ub) experienced by the fish, rather than using bulk averages (U), (iii) investigate water temperature (T) influence on swimming ability, and (iv) identify a functional relation between Ub, tac and T. Results showed that burst-and-coast swimming mode was increasingly adopted by glass eel, especially when U was higher than 0.3ms-1. Using U rather than Ub led to an overestimation of the fish swimming performance from 18 to 32%, on average. Under the range of temperatures analyzed (from 8 to 18°C), tac was strongly influenced and positively related to T. As a final result, we propose a general formula to link near-bottom velocity, water temperature and active swimming time which can be useful in ecological engineering applications and reads as [Formula: see text].