Population dynamics and fishery benefits of a large legal size of a pelagic sportfish, the Talang queenfish, Scomberoides commersonnianus, in northern Australia

Abstract

The life history of an increasingly important pelagic commercial and sport fish, the Talang queenfish, Scomberoides commersonnianus, was studied in northern Australia to investigate the stock status and assess current management of the species using minimum legal lengths (MLL). Estimated von Bertalanffy growth parameters were L ∞ = 1404 mm FL, K = 0.10 year −1 and t 0 = −1.21 year −1. There was no significant difference in growth between sexes. Ages ranged from 1 to 11 years with age composition differing between the commercial (mainly 6–7 years) and sport fishery (mainly 2–4 years). Females matured ( L 50) at 635 mm FL and 4–5 years. Spawning occurred between August and March when mature females were estimated to produce 259,488–2,859,935 eggs per spawning. Natural mortality ( M) was estimated as 0.16–0.26 year −1, while the combined fishing mortality ( F current) from commercial and sport fisheries was 0.38–0.48 year −1. Yield-per-recruit analyses revealed that under current MLL limits (no MLL or 45 cm TL) and natural mortality ( M = 0.16, 0.2 and 0.26 year −1), F current exceeded the reference points F max (0.15–0.22 year −1) and F 0.1 (0.10–0.15 year −1), suggesting the stock may be growth overfished if the current situation remains unchanged. Although a stock–recruitment relationship is unknown, spawning stock biomass-per-recruit analysis indicates the stock may also be recruitment overfished since F current exceeded the reference points F 25% (0.19–0.24 year −1) and F 40% (0.11–0.15 year −1). Increasing the MLL corresponding to L 50 of females (70 cm TL) will greatly improve the yield and long-term sustainability of the stock, and also enhance the sport fishery by increasing the number of larger trophy fish.