Stock assessment of Queensland east coast prickly redfish, herrmanni curryfish and vastus curryfish with data to December 2023

Abstract

Prickly redfish, herrmanni curryfish and vastus curryfish are species of sea cucumber from the family Stichopodidae. All three species have a broad Indo-Pacific distribution and are found in multiple countries with coral reef ecosystems. All three species occur across the GBR but at varying depth ranges: 10-30 m for prickly redfish, 0-25 m for herrmanni curryfish and 0-8 m for vastus curryfish.

This is the first stock assessment conducted on Queensland east coast prickly redfish, herrmanni curryfish and vastus curryfish by Fisheries Queensland.

All assessment inputs and outputs are referenced on a calendar year basis (that is, ‘2023’ means January 2023–December 2023).

This assessment used a one-sex age-structured population model and a delay-difference model which led to similar results. The outputs of the age-structured model are presented as the main results for all three species in this assessment.

The assessment incorporated commercial catch and effort data spanning 1995 to 2023 as well as length composition data and estimates of absolute abundance from recent surveys undertaken in 2023. No recreational or Indigenous catch data were available and catches from these sectors are considered negligible. There are no discards due to the highly selective nature of the fishery.

Several Stock Synthesis scenarios were run to examine the implications of different fixed model parameters such as steepness (h) and natural mortality (M) on model outcomes. All scenarios were optimised using Markov chain Monte Carlo (MCMC) to better explore the robustness of the models. From these exploratory scenarios a final base case was chosen for each species. The base case Stock Synthesis results indicated that the biomass ratio of prickly redfish at the beginning of 2024 was between 73% and 116% of unfished levels. The base case Stock Synthesis results indicated that the biomass ratio of herrmanni curryfish at the beginning of 2024 was between 81% and 141% of unfished levels. The base case Stock Synthesis results indicated that the biomass ratio of vastus curryfish at the beginning of 2024 was between 65% and 124% of unfished levels.