Drivers of long-term change in the Foveaux Strait oyster fishery (OYU 5) including the effects of disease and dredging essential oyster habitat are investigated. High densities of oysters are determined by recruitment and mortality from Bonamia exitiosa. Regular recruitment to the population shows productivity of the oyster fishery is high and is not likely to have changed. Oyster factors, co-infections with other pathogens, and climatic variables may affect oyster mortality and recruitment.

The silver warehou stock assessment conducted in 2023 is described. The assessment was ultimately rejected by the Fisheries New Zealand Deepwater Working Group. The data inputs and model assumptions are described. The main problems encountered, concerning stock structure, CPUE, age data, and model specifications, and their possible solutions, are discussed.

The study investigates cryptic mortality (i.e., deaths that are not observed) of seabirds in New Zealand’s trawl fisheries, separately for net captures and warp cable strikes. For net capture-related mortality, the results suggest that, on average, mortality was 2.5 times higher than when only based on observed captures. For warp strikes, estimates varied based on data sources, highlighting the need for tailored data collection due to uncertainties and sparseness in the current dataset.

The Spatially Explicit Fisheries Risk Assessment framework has recently been updated and applied to assess the fisheries risk to seabird populations within the New Zealand EEZ. In the current report, the approach is applied to seabirds globally in the southern hemisphere. Catchabilities were estimated from New Zealand captures. Then global fishing effort and species distributions were collated and used to assess the risk to seabirds from predicted fisheries captures throughout their range.

Data on elver catches of longfin and shortfin eels from hydroelectric barriers were collected during the 2018–19 to 2021–22 seasons. Catches contained moderate shortfin numbers, but moderate-high longfin numbers. Combined recruitment indices from all sites and seasons showed that recruitment of both species is variable within and between sites but remained stable, consistent with previous studies, indicating that recruitment of elvers has remained stable within the time frames of the datasets.

This report summarises the ling stock off the west coast South Island (LIN 7WC) and fishery. It describes the spatial structure of the stock, biological parameters, and trawl and longline standardised catch per unit effort (CPUE). Statistical Area 032 was reassigned to LIN 7WC based on the continuity of catch locations. The trawl and longline fishery CPUE and survey biomass showed similar patterns from 2000, with a decline from 2012. All three indices were considered in the stock assessment.

This report investigated the spatial and temporal structure of arrow squid (Nototodarus sloanii and N. gouldi) in New Zealand. Five potential stocks were defined. Estimates of growth rate were consistent with previous estimates. Spatial-temporal standardised CPUE fortnightly indices were developed and could be predicted relatively well by environmental variables. Preliminary population models showed recruitment was well estimated but initial biomass was highly uncertain.

A Management Strategy Evaluation (MSE) was conducted for hoki based on the recent (2022) stock assessment model. The MSE evaluated a set of Harvest Control Rules that specified a target biomass range and varied annual fishery catches relative to fluctuations in eastern and western stock biomass.

This report summarises the stock assessment of hake off the west coast South Island (WCSI) in HAK 7 for the 2021–22 fishing year. The index of abundance was the WCSI trawl survey. Initial spawning stock biomass was estimated as 78 870 t (95% CIs 74 140–84 810) with current status of 39% B0 (95% CIs 30–52% B0). Five-year projections showed that biomass would increase under average recruitment but would remain flat if future recruitments were low and catches were the same as the TACC.

This report summarises the WCSI hake (HAK 7) fishery with spatial structure of the stock, biological parameters, and standardised catch per unit effort (CPUE). The CPUE indices were similar for the tow-by-tow data and the daily summary data and showed a similar trend to the Sub-Antarctic trawl surveys. In general, the CPUE indices had declined over the period of fishing but had levelled off in recent years as the total catch declined.

This report presents the NIWA analysis of simulated Indian Ocean Yellowfin tuna (IOYT) data as part of the 2022–23 International Approaches and Advancements in Spatial Stock Assessment workshop programme. Two stock assessment model structures were developed and evaluated and are the focus of this report: a single area model which used the aggregated datasets, and a fleets-as-areas model.

The present project provides an update to the pāua (Haliotis iris) stock assessment for quota management area (QMA) PAU 5D and tested control rules to aimed at rebuilding catch towards the Total Allowable Commercial Catch. The findings suggested that the stock has been rebuilding and is now as likely as not to be at the interim management target. The harvest control rule from 2016 was updated to include a lag year on increases and a maximum 5% limit on year-on-year increases.

Acoustic biomass surveys of orange roughy (Hoplostethus atlanticus) in ORH 3B North Chatham Rise spawning grounds, 4–8 July 2021, on FV Amaltal Apollo. Surveys were undertaken on Morgue and Graveyard hills in NWCR and on the Rekohu aggregation in ESCR. The survey was prematurely curtailed due to vessel engine failure. Ancillary biomass estimates for Rekohu and Spawn Plume aggregations were derived from hull-mounted echosounder snapshots undertaken by FV Amaltal Mariner and FV San Waitaki.