Otolith Growth Rates Research Articles

Uncoupling of Somatic and Otolith Growth Rates in Arctic Char (Salvelinus alpinus) as an Effect of Differences in Temperature Response

Experiments were conducted to study the effect of temperature, fish size, and somatic growth rate on mean daily otolith growth rate in Arctic char (Salvelinus alpinus) fry fed maximum rations. Long-term experiments at two different temperatures (8 and 13 °C) showed exponential relationships between otolith weight and fish wet weight, with the exponent of wet weight for the higher temperature being significantly higher than for the lower temperature. Increasing exponents at each sampling date indicated a difference in growth rates of the char and its otoliths. Short-term experiments showed that specific growth rate of the fry at six different temperatures was that of an optimum curve whereas the otolith growth rate continued to increase with increasing temperatures. A clear uncoupling between otolith growth rate and fish growth rate was demonstrated whereas temperature and fish wet weight modeled otolith growth rate reasonably well. It was found that otolith growth rate expressed as daily increase in weight gave a model with better fit and higher generality than growth rate along various radii. Several examples of uncoupling between fish growth rate and otolith growth rate in the literature were reexamined, and an explanation of otolith growth rate in terms of a metabolic expression was suggested.

Growth and stock differentiation of kingklip(Genypterus capensis)on the south-east coast of South Africa

Much of the southern African kingklip Genypterus capensis catch is derived from the south-east coast, and the growth rate of the species from this area is presented. Females grew faster than males after attainment of maturity (± 60 cm Lt) and reached a greater age. The otoliths, on which this growth study was based, increase in length in relation to fish length in a diphasic, linear manner, growth of the otolith slowing down after maturity. From stock differentiation studies, on the basis of otolith morphology and growth rate, it is concluded that the south-east stock (that at the eastem side of the Agulhas Bank) is a third subpopulation of the species and that the stock on the western side of the Bank may well be too. There was no difference in the number of vertebrae between the southeast stock and the previously recorded Cape stock.