Determining the most suitable method of otolith preparation for estimating the age of tigerfish, hydrocynus vittatus in the Pongolapoort Dam, South Africa

Abstract

The growth, morphology and relative age estimates of the lapillus and asteriscus otoliths were studied to gain a better understanding of the development and ageing of tigerfish otoliths. Asteriscus and lapillus growth showed good to excellent linear relationships for thickness (r2 = 0.547), length (r2 = 0.741), diameter (r2 = 0.799) and mass (r2 = 0.929). Otolith vs. somatic growth showed the highest correlations between lapillus and standard lengths (r2 = 0.659) as well as asteriscus mass and standard length (61%). Subject to further testing, it is believed that these near-linear relationships show promise for future use in tigerfish ageing studies. The possibility of using otolith morphometrics in tigerfish ageing studies will not only be cheaper, faster and easier but also more precise by avoiding reader error and bias. Indices of bias and precision showed sectioned lapilli to be the most precise ageing technique in terms of between-reader (CV = 7.85%; APE = 5.55%) and between-structure (CV = 6.20; APE = 4.20%) analyses.