Catch-at-age data are important for the stock assessment of fish species because they provide information on the strength and progression of age classes in the stock, including juveniles and fish that are large enough to be taken by commercial fishers. These data include information on fish length and age (from otoliths—the ear bones of fish) collected at sea by observers from the commercial catch.

This report provides analyses of catch-at-age from the bottom trawl fisheries for barracouta (Thyrsites atun, BAR) in BAR 5 (Southland) and for gemfish (Rexea solandri, SKI) in SKI 3 (southeast coast) and SKI 7 (Challenger) for the 2021–22 fishing year. These results are the second of a three-year catch-at-age series for these two species.

Data for the 2021–22 season included few barracouta under 60 cm, indicating either less fishing on smaller (and younger) barracouta, or a poor year class should be expected. Most of the barracouta were aged 2–5 years.

Gemfish from SKI 3 in the 2021–22 fishing year showed a range of fish sizes, with most between 45 and 52 cm, which corresponded to age 2 fish, and also at sizes that corresponded to ages 4–6.

Gemfish from SKI 7 were less variable in length and included some fish under 50 cm, mainly females, which corresponded to ages 0–1. Most of the gemfish in SKI 7 around 50 cm in length corresponded to age 2; this was a strong cohort, particularly for males. Females were generally larger (and older) than males in the bottom trawl catch, with a strong mode at ages 5–8 for the females.

A stock assessment survey of Foveaux Strait oysters (OYU 5) in February 2023 found numbers of commercial-sized, recruit, pre-recruit oysters, and small oysters had decreased by between 44.8% and 52.3% from 2022 numbers. Winter-spring disease mortality is the most likely cause. These decreases cannot be fully explained by fishery and survey data. Summer mortality from Bonamia increased from 5% in 2022 to 9% in 2023. Mostly large oysters died; 70% of oysters are below recruit-size. Spat settlement was high.

This report updates and summarises the observational and research data for southern blue whiting from 1990 to 2022. These data include the time series of relative abundance from acoustic surveys, trawl survey indices, and updated time series of length-at-age and catch-at-age from observer sampling of commercial catch.

New Zealand’s Hector’s dolphins are an endangered species. A key threat to their survival is entanglement in fishing gear, including trawl nets. In this study, we report on a field trial where underwater microphones (hydrophones) were fitted to trawling equipment and the echolocation clicks naturally produced by Hector’s dolphins were localised to determine how the dolphins interacted with the trawling equipment as it moved through the water. The hydrophones were protected within custom-built cages to withstand the physical stress associated with being attached to fishing equipment that is dragged along the seabed. The field trial was conducted off the coast of Timaru, New Zealand, in September and October 2022. While the hydrophones recorded dolphin sound underwater, a Fisheries New Zealand observer on the boat also looked out for dolphins.

The protective cages around the hydrophones proved effective and we were able to successfully localise dolphins. Dolphins were localised moving towards the mouth of the fishing net from various approach angles, and, on several occasions, we were able to successfully distinguish multiple dolphins each moving along different paths. Even though we only analysed a subset of the acoustic data from each trawl, dolphin clicks were detected acoustically during trawls on more occasions than the observer on the fishing boat was able to see dolphins. Unfortunately silt from the seabed entered some of the connections between the hydrophones and the acoustic recorder, which resulted in corrupted data on some days, but overall the field trial was successful.

This study showed that listening for the presence of dolphins can be more effective than looking for dolphins from a boat. We suggest that a combination of listening and looking for dolphins would be the most effective way to detect dolphins that might be near the fishing net. In the long term, the listening system described here could be developed into a real-time warning system that alerts the fishing vessel master when dolphins are close to the fishing net. If the vessel master is aware of the dolphins, they could avoid activities that result in high-risk of entanglement, such as sharp turns or drawing in the net at the end of the trawl. Dolphin detection could also help with targeted use of devices that encourage the dolphins to move away from the high-risk areas—such devices emit noise and should be used as little as possible to minimise noise pollution and disturbance to the dolphins.

Sea urchin barrens are sea urchin dominated areas of rocky reef that would normally support healthy kelp forest, but have little or no kelp due to overgrazing by sea urchins.

This review updates our understanding of sea urchin barrens in New Zealand and the role fishing plays in their establishment to date. It also identifies key work required to support management decisions, including collating data on the distribution of urchin barrens, reviewing information required to set catch limits for sea urchin predators, and developing regional management approaches.

We review published scientific literature on sea urchin barrens in New Zealand and the role of fishing in their development.

We also summarise results of a national workshop to support management of sea urchin barrens.

Research based on observations from marine protected areas suggests fishing of sea urchin predators is causing and/or maintaining sea urchin barrens in north-east New Zealand.

The extent of sea urchin barrens and contributing factors in other parts of New Zealand appear to vary, but there are few published studies on this.

Workshop discussions indicated an urgent need to develop a suite of management options to address sea urchin barrens at regional scales in collaboration with tangata whenua and stakeholders.

This report describes the survey estimates for blackfoot pāua landed by amateur fishers from land-based access points in the Kaikōura Marine Area and Oaro during a two-month open season from 15 April 2023. This was the second survey conducted to estimate amateur harvest of pāua in the Kaikōura Marine Area and the first to provide cumulative harvest estimates weekly during the open season. Harvest numbers were estimated for rock lobster, yellowfoot pāua, and kina.

For the Bay of Plenty base model run current biomass was estimated to be 68.4% B0 (median), with 95% credible interval 46.6–97.7% B0. For all five-year projection scenarios, there was a low probability that the target biomass would decline below the target level of 40% B0. A stock assessment was also attempted for a Ninety Mile Beach/East Northland/Hauraki Gulf stock, but was unsuccessful due to conflicts between the abundance and catch-at-age data.

Changes in blue cod populations off Canterbury and in the Marlborough Sounds has raised concerns about the impact of human stressors on these populations, but the relationship between most stressors and blue cod is unknown.

Information on blue cod abundance was matched with environmental data to understand the habitat characteristics important for blue cod adults and juveniles off three Canterbury sites; Banks Peninsula, Motunau, Kaikōura.

Changes in potential stressors to blue cod habitat were compared with blue cod population status over 20 years at the sites off Canterbury and in the Marlborough Sounds.

Blue cod were associated with areas where the seafloor is rough and complex (e.g., reef systems), where structural habitat was provided by plants and animals, and in areas with higher water clarity and lower temperature.

Blue cod population status was related to stressors from land use (e.g., coastal water quality), and increasing water temperatures in most locations, although the intensity of these stressors has varied substantially over time and among locations.

This information provides guidance on the scale and focus for future research and potential management opportunities to limit these stressors and ensure sustainability of the blue cod fishery.

This report presents the results of a field survey made in December 2022 to estimate the abundance of kina in Tory Channel, Marlborough Sounds (SUR 7A). Kina densities were determined along with roe biomass from dive and camera transects, with estimates of abundance utilising high resolution bathymetry data. Total biomass of kina in the survey area was estimated to be 595 t, with a CV of 19%; the biomass of kina roe was estimated to be 62.9 t, most of which was in the highest quality category.

This report summarises population models for arrow squid in the Subantarctic. The models captured the main biological processes adequately. Recruitment estimates were robust to model assumptions and structure. However, absolute estimates of biomass were highly uncertain. The potential for in-season management was tested. Proxies that could be used to compare current relative exploitation rates with past conditions were also investigated; these could be used for hindcasting.

Fisheries stock assessments were undertaken for SCI 1 and SCI 2. The SCI 1 assessment was rejected by the Fisheries New Zealand Deepwater Working Group due to sensitivity to the trawl survey catchability prior. The SCI 2 assessment was accepted, but with a lower quality rating due to unresolved conflicts in data inputs. For SCI 2 current status in 2022 was estimated to be 56% B0 and likely within 47–66% B0. Projections were not carried out with either assessment.

This study used a model of individual eco-physiological response to environmental and climate factors to derive population level outcomes of fish stocks. These simulations were used to investigate how fisheries stock assessments are influenced by climate and bottom-up variability in production parameters. The assessments generally provided unbiased estimates of stock status even though there were annual and decadal fluctuations in all production-related parameters.

The Foveaux Strait oyster (OYU 5) stock assessment model was reviewed. Development of a disease sub-model to provide projections of future disease mortality will greatly improve assessments. B0 and stock reference points may be overestimated. Conceptual models of climatic, environmental, habitat, disease, and biological drivers of oyster production highlight several knowledge gaps. An understanding of disease processes and new time series data will underpin better stock projections.