[Phototaxis of Anguilla marmorata based on fish attracting technology of eel passage]

Light trap is commonly used in protecting Anguilla marmorata resource and improving the attraction of eel passage entrance. In this study, a self-made multifunctional round pool was used to explore the phototaxis of elvers (A. marmorata) under three conditions. 3 W underwater landscape lamp was used as the light source. The results showed that the percentages of juvenile A. marmorata occurrence in light zone and dark zone were (8.7±0.3)% and (3.6±1.7)%, (8.4±0.2)% and (5.0±1.4)%, (9.0±0.2)% and (1.9±1.3)% respectively under three conditions. Moreover, most glass eel distributed in the light zone, while elver (or elver develop) distributed in the dark zone. The primary regions of fish occurrence and its percentages were yellow zone [(29.4±4.9)%], red zone [(24.1±3.9)%)] and purple zone [(17.2±4.0)%] for condition one, yellow zone [(29.4±3.3)%], purple zone [(25.2±3.7)%] and red zone [(18.2±2.9)%] for condition two, and red zone [(33.3±2.3)%], purple zone [(25.6±3.8)%] and yellow zone [(20.7±5.7)%] for condition three. Correspondingly, the top three regions of fish first entering were red, yellow and purple, red, purple and yellow, and red, purple and yellow, respectively. The number of entering and exiting for fish in those three color zones was between blue-green zone and colorful zone. Visual fatigue would occur for elvers with continuous exposure to red light or yellow light. Our results suggested that the phototaxis of elvers is dependent on their developmental stages. Glass eels have phototaxis and seem to be more interesting in red, yellow, and purple light. Light guidance fish is available in the entrance of eel passage, which can help glass eels find the migration channels.