Download FAR 2024/37 Southern blue whiting (Micromesistius australis) stock assessment for the Campbell Island Rise for data up to the 2022–23 fishing year

Southern blue whiting (Micromesistius australis) is a fish species which, in New Zealand waters, is almost entirely restricted in distribution to sub-Antarctic waters.

They are dispersed over the Campbell Plateau and Bounty Plateau for much of the year, but during August and September they aggregate to spawn near the Campbell Islands, on Pukaki Rise, on Bounty Plateau, and near the Auckland Islands over depths of 250–600 m, where they are targeted by commercial trawl fisheries.

The size and health of the southern blue whiting stock at each spawning location is assessed separately. This report presents an assessment of the Campbell Island Rise stock.

The assessment made use of a statistical model informed by commercial catch history, the age distribution of fish in each year, and biomass estimates obtained from acoustic surveys, up to and including the 2022 fishing season (1 April 2022 to 31 March 2023).

Different assumptions applied to the assessment model were tested. Model outcomes were ‘robust’, i.e. did not change in a way that gave different perceptions of stock health depending on input assumptions made.

The base case assessment model (model judged as most plausible) suggested the spawning biomass of the Campbell Island Rise stock in 2022 was at 63% of pre-fishing levels. The stock is judged in good health if the spawning biomass is at or above 40% of pre-fishing levels.

Projections out to 2028, assuming constant catch equal to the average over the 2020 to 2022 fishing seasons (18 200 t), predicted biomass to decrease to 54% of pre-fishing levels by 2028. The biomass was expected to decline to 29% of pre-fishing levels by 2028 under an assumption of a constant catch equal to the current total allowable commercial catch (TACC) in 2022 (39 200 t).