Age, growth and length-to-weight relationship of largehead hairtail (Trichiurus lepturus) in south-eastern Australia suggest a distinct population

The age, growth rates and length to weight relationships for the south-eastern Australian population of largehead hairtail (Trichiurus lepturus) were investigated for the first time. Age was estimated by counting annuli in sectioned sagittal otoliths, with a maximum age of 8 years estimated for males and females. We found no significant differences in the growth rates of males and females over the size (12–78 cm pre-anal length (PL)) and age (0–8 years) ranges sampled. However, females in our collection were larger on average than males, and all fish sampled >60 cm PL were female, suggesting that females may grow to larger sizes than males and that sampling of greater numbers of larger and older fish may be required in future. T. lepturus growth was described by the von Bertalanffy growth function parameters L∝ = 74.89 cm PL, K = 0.13yr−1 and t0 = −0.80 yr, with the L∝ being amongst the largest reported for the species. Growth was variable, with the sizes at any given age spanning up to 50 cm PL. Female T. lepturus increased in body weight relative to length faster than males, as has been reported in other populations. The length/weight relationship for the south-eastern Australian population was significantly different, with almost no overlap, from that reported for T. lepturus in the Arabian Sea. The substantial differences in growth rates, maximum sizes and body morphometrics of T. lepturus from south-eastern Australia in comparison to other populations globally are consistent with the hypotheses that it represents a distinct population, although investigations using additional population markers are required to verify this.