Publications

This report provides an update of the characterisation and catch per unit effort (CPUE) analysis for the blue cod fishery in the BCO 3 area (east coast South Island from Clarence River to Slope Point) up to the end of the 2023–24 (2024) fishing year. Blue cod were caught mainly by cod pot (63% of catch) and bottom trawl (24%), over the last 35 years. The bulk of the landings from cod potting were taken from Statistical Areas 024 (north Otago) and 026 (south Otago), which have contributed 66%, and 20% of the catch respectively, over the 35-year time series. For the last five years, area 026 has become the main contributor, accounting for 56% of the catch compared to 32% from 024. The cod pot vessel fleet has declined by about one half from about 30 to 15 vessels since 2007. CPUE indices (assumed to be proportional to abundance) were estimated using Generalised Linear Models (GLM) run for Statistical Areas 024 and 026, and these fluctuated but generally trended upward, peaking in 2014, before declining steeply. The trends in CPUE were mirrored by the abundance estimates from both the north and south Otago potting surveys over the overlapping period from 2010 to 2022, suggesting that blue cod abundance in the Otago fishery dropped sharply from 2013 to 2018.

As finfish farming in Aotearoa New Zealand moves further offshore into more open and dynamic marine environments, there is growing concern about how waste from these farms affects the seafloor and the animals that live there. In particular, large shellfish and other seabed-dwelling animals (known as epifauna) play important roles in healthy marine ecosystems, but little is known about how they respond to waste from offshore salmon farms in Aotearoa New Zealand.

This report, part of the Environmental Health Measures for Open Ocean Aquaculture project, aims to better understand these effects by investigating how three key species – the horse mussel (Atrina zelandica), scallop (Pecten novaezelandiae), and a brachiopod or lamp shell (Neothyris lenticularis) – respond to increasing levels of organic waste from salmon farms. We measured a range of physiological responses in these species at different levels of seabed waste and looked at how their responses relate to one another and to current indicators used in salmon farm monitoring.

Key findings

⦁ Statistical analyses show the levels of organic enrichment that cause changes in physiological functioning in the three key species – and possibly early signs of stress.
⦁ Many of the measured responses were closely linked, suggesting that a smaller set of indicators could reliably detect wider changes in organism health.
⦁ The study shows how the health of the key species can be used as an early-warning signal for broader ecosystem impacts.

The Environmental Health Measures for Open Ocean Aquaculture project is an important first step in developing reliable, ecologically meaningful tools to assess and manage the environmental effects of open ocean aquaculture. Future studies should test to see how well the indicators work with other species and at different farm sites with varying levels of enrichment.

This report describes research conducted in 2022, 2023, and 2024 to determine the age of southern bluefin tuna (Thunnus maccoyii; STN) caught in New Zealand’s surface longline (SLL) fishery. Ages were assessed using counts of opaque and translucent zones in STN otoliths (‘ear bones’). Otoliths used this this study were collected from fish heads supplied by Licensed Fish Receivers (LFRs), collected by observers onboard SLL vessels, or from sampling of the recreational fishery in a related Fisheries New Zealand project. A total of 150, 156, and 163 STN were aged in 2022, 2023, 2024, respectively. Assigned ages ranged from 2–26 years old, with most aged fish around 4–12 years old. An age-length key was constructed applied to the lengths of STN provided by LFRs to estimate the age structure of the SLL catch in each year. The information generated by this study will be used for assessments and fisheries management advice.

Roberts, J. (2025). Harbour use by Māui/Hector’s dolphin and commercial net fisheries. New Zealand Aquatic Environment and Biodiversity Report No. 363. 56 p.

This document provides a summary of existing information of the use of West Coast North Island (WCNI) harbours by Māui/Hector’s dolphins (Cephalorhynchus hectori) and by commercial net fisheries.

Based on this review, Māui/Hector’s dolphins were much more frequently encountered in the coastal domain of the WCNI. By comparison, sightings and acoustic detections in harbour areas were much more infrequent and almost entirely located inside fishing prohibition areas in harbour mouths.

Commercial net fishing effort was described using recent data collected using electronic monitoring, which includes the locations of all reported fishing events. The two main net fishing methods used in WCNI harbours are set-nets and ring-nets, which differ in terms of the gear used and the nature of fishing operations. The overlap of harbour-based set-net effort with the dolphins is likely to be very low. By comparison, the overlap with ring-net fishing with the dolphins is likely to be a little higher in some harbour mouths, although ring-net fishers must attend their gear throughout short deployments, so this method is considered less likely to capture Māui/Hector’s dolphins.

However, several opportunistic sightings of Hector’s and Māui dolphins were made in the summer of 2024/25 that suggest they can move further into harbours and rivers under certain conditions that are not well understood. Therefore, research for understanding the environmental drivers of occasional harbour/river use across the species would be beneficial for understanding when and how often this is most likely to occur and to minimise overlap with fishing.

Mangan, S.; Tait, L.W.; Wing, S.; D’Archino, R.; Neill, K.; Battershill, C.; Schiel, D.R.. (2025). The relationships between macroalgae and New Zealand's wild fisheries, key vulnerabilities and monitoring approaches.

This report reviews key national and international research on the ecological importance of macroalgae, such as kelp, in supporting fisheries in Aotearoa New Zealand. This research shows that macroalgae are important in providing habitat and contributing to coastal food webs, as well as playing a significant role in global carbon cycles. These ecological services contribute to macroalgal habitats that are integral to a number of important fishery species, such as kōura papatea (red rock lobster), pāua, and various finfish and bivalves, resulting in substantial economic contributions. For example, the 13 fisheries that are associated with kelp had a combined asset value of $NZD 5.2 billion in 2019.

But macroalgae are vulnerable to a number of significant stressors including rising temperatures, sedimentation, and kina grazing. To better understand the impacts of these large-scale environmental pressures and support effective monitoring and management, satellite remote sensing has been identified as a valuable tool because it enables the generation of updateable maps showing the extent of large canopy forming kelps. When combined with other monitoring methods, it can aid our understanding of macroalgal dynamics and further contribute to more informed ecosystem-based management of New Zealand’s coastal marine resources.

Finucci, B.; Bennion, M.; Chin, C.; Duffy, C.A.J.; Morrison, M.; Struthers, C. (2025). Identification and mapping of habitats of significance for sharks. New Zealand Aquatic Environment and Biodiversity Report No. 361. 248 p.

The aim of this project was to review existing literature and analyse data to identify areas that may be further identified as a habitat of particular significance (HoPS) for chondrichthyans (sharks, rays, and chimaeras). This project proposed 30 HoPS for 20 species of interest: six of the 20 species had at least one potential HoPS for spawning purposes identified and 10 species had at least one suspected potential HoPS identified. There were four species (blue shark, mako, porbeagle, basking shark) where potential HoPS could not be identified. No proposed HoPS is completely closed to fishing, and 22 proposed HoPS are completely open to fishing. All species evaluated here need further information to reduce knowledge gaps. Focal species and areas for future research, and alternative opportunities to collect data are discussed.