Age-Based Population Dynamics of the Four-Rayed Rattail Coryphaenoides subserrulatus From the Chatham Rise, New Zealand

Abstract

This study explores the age-based population dynamics of the four-rayed rattail Coryphaenoides subserrulatus, a bycatch species from the Chatham Rise orange roughy (Hoplostethus atlanticus) fishery. Age and size distribution of C. subserrulatus ranged from 2 to 27 years, and 139 mm to 366 mm (TL), respectively. The sampled population was female-dominated, especially in the older and larger classes, with a sex ratio of 1.69 females per 1 male (F:M = 1.69:1). Von Bertalanffy growth function (VBGF) analysis showed asymptotic length of 337.02 mm for females and 312.84 mm for males. Likelihood Ratio Test (LRT), and 95% confidence ellipses conducted on VBGF parameters of L∞ and K, confirmed female growth to be significantly different than male. Length–Weight relationship analysis showed this species to have a negatively allometric growth coefficient (b = 2.69), which indicates prioritisation of growth over condition. Annual mortality rate was estimated at 14.39% (yr−1), indicating a stable population under unfished conditions. This study contributes to the understanding of the population dynamics of C. subserrulatus in New Zealand waters, adding to the existing knowledge on the ecology of this deep-sea bycatch species.