Using otolith dimensions and weight to quickly and inexpensively predict ge in tigertooth croaker, (Otolithes ruber)

In this study 82 tigertooth croaker (Otolithes ruber) (Bloch & Schneider, 1801) specimens were collected by trawling and trapping (Gargur) in Bushehr province, Bandar Genaveh, to investigate the relationship of the otolith dimensions and weight with the age of croaker. Scales and otolithes were used to aging fish. Pearson correlation coefficients were calculated for age, weight, length, width and thickness of otolith. Among all measured parameters, otolith length (r=0.930) and weight (0.926) showed the strongest correlation with age. Then different regression models was tested to predict the dependent variable (age) from the independent variable(s) (otolith weight and dimensions). Finally, simple linear regression {Age=0.343 × (Otolith Length)-1.793}, and multiple linear regression {Age=2.185 × (Otolith weight) + 0.191 (Otolith Length)-0.687}, were fitted statistically. Then the same models were derived from the 60% subsample (n=50) and age of residuals were estimated from this models. In this study, the model-estimated ages and the observed ages determined by the readers were not significantly different (P<0.05); however, the multiple linear regression was the better predictor of age. In conclusion, due to difficulty of weighing otolith and need to accurate scale, the simple linear regression (using otolith length to predict age) could be recommended.