title: The invisible fish: hydrodynamic constraints for predator-prey interaction in fossil fish Saurichthys compared to recent actinopterygians.
abstract: Recent pike-like predatory fishes attack prey animals by a quick strike out of rest or slow movement. This fast-start behaviour includes a preparatory, a propulsive and a final phase, and the latter is crucial for the success of the attack. To prevent prey from escape, predators tend to minimise the duration of the interaction and the disturbance caused to surrounding water in order to not be detected by the prey's lateral line sensory system. We compared the hydrodynamic properties of the earliest fossil representative of the pike-like morphotype, the Triassic actinopterygian Saurichthys, with several recent pike-like predators by means of computational fluid dynamics (CFD). Rainbow trout has been used as a control example of a fish with a generalist body shape. Our results show that flow disturbance produced by Saurichthys was low and similar to that of the recent forms Belone and Lepisosteus, thus indicative of an effective ambush predator. Drag coefficients are low for all these fishes, but also for trout, which is a good swimmer over longer distances but generates considerable disturbance of flow. Second-highest flow disturbance values are calculated for Esox, which compensates the large disturbance with its extremely high acceleration performance (i.e. attacks at high speeds) and the derived teleostean protrusible mouth that allows prey catching from longer distances compared to the other fishes. We show CFD modelling to be a useful tool for palaeobiological reconstruction of fossil fishes, as it allows quantification of impacts of body morphology on a hypothesised lifestyle.
authors.affiliation: TU Bergakademie Freiberg, Geologisches Institut, Bereich Paläontologie/Stratigraphie, Bernhard-von-Cotta-Str. 2, Freiberg 09596, Germany Kazan Federal University, Institute of Geology and Petroleum Technologies, 4/5 Kremlyovskaya St., Kazan 420008, Russia i.kogan@gmx.de steffen.pacholak@mailserver.tu-freiberg.de.
authors.forename: Ilja
authors.initials: I
authors.lastname: Kogan
authors.affiliation: TU Bergakademie Freiberg, Institut für Mechanik und Fluiddynamik, Lampadiusstr. 4, Freiberg 09596, Germany TU Bergakademie Freiberg, Institut für Numerische Mathematik und Optimierung, Akademiestr. 6, Freiberg 09569, Germany i.kogan@gmx.de steffen.pacholak@mailserver.tu-freiberg.de.
authors.forename: Steffen
authors.initials: S
authors.lastname: Pacholak
authors.affiliation: TU Bergakademie Freiberg, Geologisches Institut, Bereich Paläontologie/Stratigraphie, Bernhard-von-Cotta-Str. 2, Freiberg 09596, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Licht
authors.affiliation: TU Bergakademie Freiberg, Geologisches Institut, Bereich Paläontologie/Stratigraphie, Bernhard-von-Cotta-Str. 2, Freiberg 09596, Germany Kazan Federal University, Institute of Geology and Petroleum Technologies, 4/5 Kremlyovskaya St., Kazan 420008, Russia.
authors.forename: Jörg W
authors.initials: JW
authors.lastname: Schneider
authors.affiliation: TU Bergakademie Freiberg, Institut für Mechanik und Fluiddynamik, Lampadiusstr. 4, Freiberg 09596, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Brücker
authors.affiliation: Sebastian Brandt arts, Im Schlufter 13, Kornhochheim 99192 , Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brandt
keywords: Ambush predators; CFD; Fossil fish; Locomotion; Palaeontology; Saurichthys