This paper describes a non-invasive method for estimating gross brain size in small fish with semi-transparent heads, using system camera equipment. Macrophotographs were taken fromabove on backlit free-swimming fish undergoing light anaesthesia. From the photographs, the width of the optic tectum was measured. This measure (TeO-measure) correlates well with the width of the optic tectum as measured from out-dissected brains in both brown trout fry and zebrafish (Pearson r > 0.90). The TeO-measure also correlates well with overall brain wet weight in brown trout fry (r = 0.90), but less well for zebrafish (r = 0.79). A non-invasive measure makes it possible to quickly assess brain size froma large number of individuals, as well as repeatedly measuring brain size of live individuals allowing calculation of brain growth.
Näslund, J. (2014). A simple non-invasive method for measuring gross brain size in small live fish with semi-transparent heads. PeerJ, 2014(1). https://doi.org/10.7717/peerj.586