Is caudal fin colour in tigerfish Hydrocynus vittatus a sex or population trait?

Abstract

Tigerfish caudal fin colours vary from yellow to red, with distinct dissimilarities previously noted. To understand these colour differences, tigerfish were collected during 2008 to 2010 from four southern African populations in the Upper Zambezi River (ZAM), Okavango Delta (OKA), Pongolapoort Dam (POD) and Phongolo River (POR), and caudal fin colouration was classified according to pattern and sex. Muscle and liver tissue were assayed by starch electrophoresis. Caudal fin colour in OKA, ZAM and POD showed significant differences between sexes. Genetics revealed closer relationships between OKA and ZAM, substantiated by their recurrent and historical links, and between POD and POR, as expected for a dam and associated river. There is an association between the genetic and geographical distance of tigerfish populations, but variation in caudal colour in this species can most likely be attributed to their environment, territorial dominance and sexual behaviour.