Meeting Abstract

S1-2.6  Jan. 4  Fish schooling: 3D kinematics and hydrodynamics HANKE, W.*; LAUDER, G.V.; Harvard University, Cambridge; Harvard University, Cambridge

Fish can aggregate to groups generally termed “shoals”. In case of polarized and synchronized swimming behaviour, these special shoals are termed “schools”. Aggregating into groups can have various advantages for fish, including energy saving due to hydrodynamic effects. The possibility that fish might gain an energetic advantage from hydrodynamic effects in a school has been discussed for decades and was partly supported by experiments that quantified the tail beat frequency of the school members, but remains controversial. We are using three synchronized megapixel digital video cameras to image small (5-6 individual) schools of giant danios (Devario aequipinnatus) swimming at a range of speeds (1-6 L/s) at 1000 Hz. Two cameras are used to record the three-dimensional position of individual fish in the school while the third camera records particle image velocimetry (PIV) images to quantify water flow within the school. Two lasers are used to generate orthogonal light sheets to minimize shadows within the school. Our PIV system uses a custom laser-scanning system to sweep the laser light sheet through the volume occupied by the school at a high rate. This allows near-volumetric analysis of fish school hydrodynamics. Preliminary results indicate that the danios in a school, although not sustaining a fixed spatial pattern, can obtain a slight hydrodynamic advantage from schooling at higher swimming speeds. More species remain to be investigated to reveal possible differences in species from different ecological niches.