E. Trip, D. Raubenheimer, K. Clements, J. Choat
Marine and Freshwater Research, 62, pp. 176-186, (2011)
Butterfish, Edge type analysis, Mating system, Oxytetracycline, Relative gonad weight, Reparameterised von Bertalanffy growth function, Size- and age-at-maturity, Size- and age-at-sex change
A common view is that, in marine fishes, herbivory and sex change are
subject to physiological constraints at high latitudes, which are likely
to affect growth rates and reproductive outputs. The present study
examines the reproductive demography of Odax pullus, an
herbivorous and protogynous species of temperate New Zealand. We
establish an otolith-based methodology for age estimation and
investigate sex-specific growth, longevity and age-based reproductive
events. Individuals achieved a maximum age of 11 years, reached 85% of
adult body size (455 mm FL) within the first 3.5 years of life, were
sexually mature by the age of 1.1–1.5 years and changed sex at 2.8–3.5
years, indicating fast simultaneous somatic and reproductive growth.
There was no significant difference in growth or body size between the
sexes. Ovary weight of spawning females increased significantly with
size and age, suggesting the presence of size- and age-fecundity skews
underlying the absence of sex change in larger and older females. Testes
of reproductively active males comprised less than 1% of bodyweight,
suggesting pair-spawning and little sperm competition. The present study
provides metrics to support comparisons of the demography of this
temperate protogynous and herbivorous labrid across spatial or temporal
strata.