title: The influence of body size on the intermittent locomotion of a pelagic schooling fish.
abstract: There is a potential trade-off between grouping and the optimizing of the energetic efficiency of individual locomotion. Although intermittent locomotion, e.g. glide and upward swimming (GAU), can reduce the cost of locomotion at the individual level, the link between the optimization of individual intermittent locomotion and the behavioural synchronization in a group, especially among members with different sizes, is unknown. Here, we continuously monitored the schooling behaviour of a negatively buoyant fish, Pacific bluefin tuna (N = 10; 21.0 ∼ 24.5 cm), for 24 h in an open-sea net cage using accelerometry. All the fish repeated GAU during the recording periods. Although the GAU synchrony was maintained at high levels (overall mean = 0.62 for the cross-correlation coefficient of the GAU timings), larger fish glided for a longer duration per glide and more frequently than smaller fish. Similar-sized pairs showed significantly higher GAU synchrony than differently sized pairs. Our accelerometry results and the simulation based on hydrodynamic theory indicated that the advantage of intermittent locomotion in energy savings may not be fully optimized for smaller animals in a group when faced with the maintenance of group cohesion, suggesting that size assortative shoaling would be advantageous.
authors.affiliation: Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan takujinodan@gmail.com.
authors.forename: Takuji
authors.initials: T
authors.lastname: Noda
authors.affiliation: National Research Institute of Far Seas Fisheries, FRA, Shizuoka 424-8633, Japan.
authors.forename: Ko
authors.initials: K
authors.lastname: Fujioka
authors.affiliation: National Research Institute of Far Seas Fisheries, FRA, Shizuoka 424-8633, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Fukuda
authors.affiliation: Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Mitamura
authors.affiliation: Field Science Education and Research Center, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Ichikawa
authors.affiliation: Field Science Education and Research Center, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Arai
mesh_terms: D000818:Animals; D049628:Body Size; D010140:Pacific Ocean; D013550:Swimming; D014413:Tuna / Q000502:physiology*
keywords: behavioural synchrony; biologging; reality mining; size assorted; three dimensional