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.
• Other Authors: UK Engineering and Physical Sciences Research Council, Scholarship from the University of Trento, Italy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2020
• Subjects: Multidisciplinary; Anguilla anguilla
• Online Access: http://dx.doi.org/10.1038/s41598-020-72957-w; https://www.nature.com/articles/s41598-020-72957-w.pdf; https://www.nature.com/articles/s41598-020-72957-w

Abstract 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 (t ac ), not considering coast and drift periods, (ii) estimate near-bottom velocities (U b ) 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 U b , t ac and T. Results showed that burst-and-coast swimming mode was increasingly adopted by glass eel, especially when U was higher than 0.3 ms -1 . Using U rather than U b 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), t ac 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 $${\rm{U}}_{\rm{b}}=0.174\cdot \left({{\rm{t}}_{\rm{ac}}}^{-0.36}\cdot {\rm{T}}^{0.77}\right)$$ U b = 0.174 · t ac - 0.36 · T 0.77 .