Life-history characteristics of Theodore’s threadfin bream, Nemipterus theodorei (Ogilby, 1916), and the yellow-lip butterfly bream, Nemipterus aurifilum (Ogilby, 1910), from southern Queensland, Australia

Abstract

Theodore’s threadfin bream (Nemipterus theodorei) and the yellow-lip butterfly bream (Nemipterus aurifilum) are two of the most common nemipterids in eastern Queensland. These two species are caught incidentally and at times retained for sale as ‘permitted’ species in Australia’s largest trawl fishery, the Queensland East Coast Otter Trawl Fishery (QECOTF). Despite their prevalence, little biological information is available for these species. This paper reports key life-history characteristics of these nemipterids. Growth and length-at-maturity parameters were estimated from samples collected in southern Queensland. Growth parameters were estimated using back-calculation of fork length (FL) from otolith increment data and modelled within a Bayesian framework to overcome bias resulting from the small number of larger, older animals in the retained bycatch. The von Bertalanffy growth function (VBGF) was identified as the most appropriate growth model with significant differences in sex-specific growth rates evident for both species. Maximum ages were six and four years for N. theodorei and N. aurifilum respectively, with individuals maturing within their first year of life. The length-at-maturity for females was 91 mm FL and 77 mm FL for N. theodorei and N. aurifilum respectively. Increased reproductive activity was observed in the austral spring and summer months. The results from this study can be used to assess the ecological risk posed to these species by the QECOTF.