Estimation of age and growth in the St Joseph Callorhinchus capensis (Dumeril)

Abstract

Age and growth of Callorhinchus capensis (Order Chimaeriformes) are estimated from counts of serially deposited cones of dentine in the dorsal spine. Age estimates are validated by cone margin characteristics. Growth curves for females and males are described by the formulae L_t = 1 089,375(1−e^{0,0515(t+0,6O6)})^0,520 and L_t = 685,641(1−e^{0,171(t+0,721)})^0,593 respectively. The relationship between spine length and age for both sexes combined is described by the equation S_t = 162,594(1−e^{−0,254(t+1,434)}). Age to mass relationships differ greatly between sexes and are best described by a Von Bertalanffy curve for males, M_t = 2,155(1−e^{−0,483(t+13,131)}), and a linear relationship for females, M_t = 0,399(t+0,098). The relatively greater mass of older females reflects a large increase in female girth following the onset of sexual maturity.