Fisheries reports and stock statistics

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.

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.

Grüss, A.; Datta, S.; McGregor-Tiatia, V.; Holmes, S.J.; Davis, J.P.; Fulton, E.A.; Sainsbury, K.; Plagányi, É.E; Dolder, P.J.; Parsa, M.; Dambacher, J.M.; Gaichas, S.K.; Townsend H.; Pascoe, S.; Blanchard, J.L.; Parsons, D. (2025). Towards ecosystem-based fisheries management in New Zealand: an ecosystem approach to fisheries management case study in FMA 7. New Zealand Aquatic Environment and Biodiversity Report No. 360. 80 p.

Aotearoa New Zealand has committed to progress integration of broader ecosystem and environmental considerations in fisheries management. These efforts can start with an ecosystem approach to fisheries management, where these broader considerations are explicitly considered in analysis focused on management settings for individual fish stocks.

The research reported here identified and reviewed tools that could support greater analysis of ecosystem and environmental considerations in New Zealand’s current fisheries management framework.

The Fisheries Management Area 7 (west coast South Island) inshore mixed bottom trawl fishery was used as a case study for this research. Meetings with managers and key fishery stakeholders were held to establish key management questions around ecosystem and environmental considerations. This included understanding the effects of single species catch limits on other species in a mixed fishery, the ecosystem effects of environmental stressors such as sedimentation, and key predator-prey interdependencies. An international expert workshop was then held to identify tools which have been applied overseas to inform management advice on ecosystem and environmental considerations for fisheries.

There exists a diverse range of ecosystem simulation models, with different configurations, levels of complexity, information requirements, and management applications. Qualitative ecosystem models and ecosystem models of intermediate complexity are the most suitable ecosystem simulation models to assist the ecosystem approach to fisheries management in New Zealand, primarily because of their more limited data requirements and their ability to strongly engage resource managers and other stakeholders. Beyond ecosystem simulation models, tools called “métier analysis”, “principal component analysis” (“PCA”) and “heatmaps” provide additional technical options for supporting the ecosystem approach to fisheries management in New Zealand.

Our report also includes recommendations to facilitate the inclusion of ecosystem and environmental considerations in resource management, which were provided at the international expert workshop, and directions for future research.

New Zealand has developed a spatially explicit risk assessment framework to assess the impact of fishing on protected species. It has been applied to a variety of charismatic fauna that are potentially vulnerable to the effects of fishing, including sea lions, seabirds and dolphins. In the case of seabirds, many of the species caught incidentally by New Zealand vessels are also caught outside of the Exclusive Economic Zone by high seas fisheries, particularly surface longliners fishing for tuna at high latitudes. This has led the risk assessment framework to be developed in a manner that can include global fishing effort and using global species distribution maps.

The Commission for the Conservation of Southern Bluefin Tuna (CCSBT) is the regional fisheries management organisation responsible for managing southern bluefin tuna surface longline fisheries. New Zealand has a history of collaboration with the CCSBT to develop a risk assessment for seabirds in the southern hemisphere. The current project is the most recent update to that work. This report provides a review and update of the biological input data used for the risk assessment, as well as a brief outline of the fisheries data. The assessment results were presented at the Fifteenth Session of the Working Group on Ecologically Related Species in June 2024. Model outputs and results are provided in the CCSBT report from that meeting.

Tangata Whenua of Tutukaka, Ngunguru and Hora Hora seek to protect and enhance ecosystem health in their rohe. In February 2024, the Rehuotane Ki Tai 186a temporary closure was established within three nautical miles of the coast. The harvest for rock lobster, cockle, crab, garfish, mussel, octopus, pāua, pipi, rock oyster, sea cucumber, sea horse, sea snail, starfish and tuatua was prohibited and no fishing with nets was allowed in Tutukaka Harbour or the Ngunguru and Hora Hora estuaries.

The Whāngai Mokopuna Rohe Moana management group initiated this research project in conjunction with appointed Tangata Kaitiaki to identify areas of healthy kelp forest and the extent of kina barrens and to trial kina removals at two sites. A cost effective and repeatable “rapid assessment” survey method was developed using readily available mapping software and in-water observations.

A simple habitat classification system was used by two experienced freedivers who reported what they saw to the crew on the support boat. We surveyed 17 km of coastline in three days, recording the location of each observation. There were extensive mature or active kina barrens observed in water depths of 10 metres or less. These areas had low biodiversity and few reef fish.

Two areas were selected for clearance of kina using free divers. Most kina collected in August and during follow up clearance in November had edible roe. Most kina were culled in situ because dive time was limited and kina density was high but some kina were harvested and distributed to hapū members. The project demonstrated the effectiveness of the rapid assessment method and provided valuable insights for future community led surveys and restoration initiatives.

New Zealand has developed a spatially explicit risk assessment framework to assess the impact of fishing on protected species. It has been applied to a variety of charismatic fauna that are potentially vulnerable to the effects of fishing, including sea lions, seabirds and dolphins. In the case of seabirds, many of the species caught incidentally by New Zealand vessels are also caught outside of the Exclusive Economic Zone by high seas fisheries, particularly surface longliners fishing for tuna at high latitudes. This has led the risk assessment framework to be developed in a manner that can include global fishing effort and using global species distribution maps.

The Commission for the Conservation of Southern Bluefin Tuna (CCSBT) is the regional fisheries management organisation responsible for managing southern bluefin tuna surface longline fisheries. New Zealand has a history of collaboration with the CCSBT to develop a risk assessment for seabirds in the southern hemisphere. The current project is the most recent update to that work. This report outlines details of the method used for work that was presented at the Fifteenth Session of the Working Group on Ecologically Related Species in June 2024. Model outputs and results are provided in the CCSBT report from that meeting.

The Chatham Islands to the East of the South Island of New Zealand are in an area that has been identified as experiencing frequent marine heatwaves. We investigated the effect of changing sea surface temperatures on adult and sub-adult pāua (Haliotis iris) collected from Ascots Beach and Owenga Harbour in the Chatham Islands, between 2020 and 2022. Pāua at the two sites reacted differently to temperature changes based on microbial diversity and metabolic profile findings. Site specific differences were detected in histological assessments with pāua from Ascots Beach showing reproductive abnormalities and pāua from Owenga Harbour showing an increased presence of kidney stones.

This report describes application of a novel risk assessment approach to trawl bycatch (non-target) shark species. The assessment estimated the exploitation rate inflicted on each of twelve species by fishing in the New Zealand Exclusive Economic Zone. Although trawl catches predominated, all relevant fishing methods were included so that the total fisheries impact could be gauged. The exploitation rate is a measure of the proportion of the selected population biomass that is killed as a result of fishing, and includes those individuals that die even when returned to the ocean. The exploitation was compared to a theoretical productivity measure to estimate whether it was high enough to inflict long-term damage on the population. Elephantfish (Callorhinchus milii) and carpet shark (Cephaloscyllium isabellum) were identified as being at higher risk from fishing.

This report describes application of a novel risk assessment approach to pelagic bycatch (non-target) shark species. The assessment estimated the exploitation rate inflicted on each of six species by fishing in the New Zealand Exclusive Economic Zone. All relevant fishing methods were included so that the total fisheries impact could be gauged. The exploitation rate is a measure of the proportion of the selected population numbers that are killed as a result of fishing, and includes those individuals that die even when returned to the ocean. The exploitation was compared to a theoretical productivity measure to estimate whether it was high enough to inflict long-term damage on the population. Thresher shark (Alopias vulpinus), porbeagle (Lamna nasus) and mako shark (Isurus oxyrinchus) were identified as being at higher risk from fishing and risk for the protected basking shark (Cetorhinus maximus) and white pointer shark (Carcharodon carcharias) was lower but still non-negligible.

Offshore finfish farming is expanding in New Zealand, but we lack knowledge about how seabed habitats and their species will respond to organic enrichment (in the form of faeces and waste feed) from salmon farms. This report, part of the Environmental Health Measures for Open Ocean Aquaculture project, investigates these impacts through laboratory and field experiments on three species: horse mussels, brachiopods, and scallops. Lab trials tested responses to controlled levels of enrichment, while field trials monitored animals near an operational salmon farm in the Marlborough Sounds.

Key Findings
• Fatty acid tests showed that all species absorbed salmon waste, which affected their nutritional health.
• Breathing rates increased with enrichment in horse mussels and brachiopods, suggesting they were using more energy to survive.
• Changes in gene activity were strong in the lab but weaker in the field, potentially showing early warning signs of stress.
• Some animals developed health issues, including parasites in horse mussels and scallops, and tissue changes possibly linked to changes in their diet or normal variations in living functions.
• Overall, the effects did not cause death, with N. lenticularis showing higher tolerance than the two bivalve species.

This research reviewed current data and information about marine heatwaves in New Zealand and their potential effects on marine ecosystems and fisheries. A marine heatwave is a prolonged period of warmer-than-usual water. Such events are increasing in frequency and intensity globally. Aotearoa New Zealand (Aotearoa-NZ) has experienced several in the last decade, and marine heatwaves are predicted to become more frequent and intense, and to last for longer, in the future.

Scientific reports from overseas suggest that marine heatwaves could affect both individuals and populations, causing redistributions such as range expansions or contractions, and affect reproductive success and survival of early life stages. In Aotearoa-NZ, spatial redistributions have been observed but whether they were caused by environmental change is unknown or speculative. Fishes may also be impacted by marine heatwaves through ecosystem changes, in particular the distribution and abundance of prey, changes to biogenic habitat, and disease, as much as through direct physiological effects.

We reviewed published information on 32 species or species groups of importance to fisheries in Aotearoa-NZ. Documented evidence of the impact of marine heatwaves in New Zealand were only found for green lipped mussel, snapper, and king (chinook, quinnat) salmon. Some information was found for bluefin tuna, rock lobster, and snapper outside of Aotearoa-NZ. Further international studies documented impacts for some taxonomically related species of oyster, abalone (pāua), and squid.

Behrens, E.; Dunn M.R.; Holmes, S.J.; Cummings, V.J. (2025). Marine heatwaves and fisheries in Aotearoa New Zealand: observed and projected temperature anomalies and potential impacts by fisheries management area. New Zealand Aquatic Environment and Biodiversity Report No. 351. 58 p.

The ocean around Aotearoa New Zealand has been warming, and marine heatwaves have become more prevalent and more intense.
This project examines patterns in warming (the slow warming trend over time) and heatwaves (shorter periods that are exceptionally warm) around Aotearoa New Zealand.

Maps of past and future projected coastal and ocean temperatures are reported for “shallow” (0–200 m) and “deep” (200–1500 m) waters in the ten Aotearoa New Zealand Fisheries Management Areas.

Most coastal waters show a sea surface warming trend between 0.2–0.3°C per decade.

Coastal bottom temperatures are warming by about 0.1°C per decade.

Marine heatwaves are projected to get hottest around the North Island, and more frequent around the South Island.

The fish stocks more likely to be impacted by future temperature changes include: green-lipped mussels on the west coast of the North Island; pelagic mackerels and tunas around the North Island and the west coast of the South Island; pāua around the Chatham Islands; snapper and John dory around the North Island and the west coast of the South Island; and arrow squid off Southland and northern parts of the Sub-Antarctic.

We recommend these regions and fisheries would benefit from further and more detailed study to better understand the potential scale and implications of these impacts.

We have the most knowledge of how temperature influences some shellfish, but relatively little for most New Zealand finfish species. The threats from marine heatwaves to most species remain poorly known and speculative, simply because we don’t know much about the impacts of temperature on these species.

Carovano, K.,; Pierre, J., Fuller, J., Cozza, A., Wealti, M., Torgersion, E., Jones, Z. (2025). Electronic Automated Reporting System (EARS): Remote at-sea monitoring of seabird bycatch mitigation measures. New Zealand Aquatic Environment and Biodiversity Report No. 350. 47 p.

Methods to reduce and monitor seabird bycatch in tuna longline fisheries are subject to ongoing investigation globally. Proven methods to reduce seabird bycatch are available, while these may not be implemented at sea. This project progressed the development of a working benchtop prototype device designed to monitor deployment of a tori line (a line with streamers attached that is deployed astern the fishing vessel, and reduces the risk of seabird bycatch by deterring birds from attending longline gear during setting), night setting, and the presence of weights on longline branchlines. The benchtop prototype device was transformed into a unit designed for at-sea deployment and subjected to proof-of-concept at-sea testing. The seagoing prototype design incorporated two small IP cameras, a GPS antenna, a rotation sensor, and an externally produced tracking buoy intended to record the location of the terminal end of the tori line. Forty-five hours of camera imagery and associated data were collected from five longline sets during at-sea testing in New Zealand. Tori line deployment could be verified and longline setting time was recorded (relevant to monitoring night-setting). The tracking buoy located at the end of the tori line failed to record GPS information during testing. Therefore, the location of the terminal end of the tori line astern the vessel could not be determined. The project also encountered many logistical difficulties, in part due to taking place at the height of the COVID-19 pandemic. It is recommended that future research focus on the use of cameras (electronic monitoring) augmented with additional tools (e.g. sensors) to meet research objectives. Also, use of off-the-shelf components and the simplest possible hardware solution would be beneficial, to minimise points of failure and the costs of bespoke development.

Underwood, M.J.; Jones, E.G.; Roberts, J.O.; Wells, R. (2025). Review of New Zealand fur seal (Arctocephalus forsteri) mitigation technology. New Zealand Aquatic Environment and Biodiversity Report No. 349. 79 p

The New Zealand fur seal faces threats from disease, climate change effects on their prey, and interactions with commercial fishing. This project aimed to identify areas where New Zealand fur seals and fisheries interact and evaluate ways to reduce these interactions, while balancing conservation and fishing needs.

In some areas around New Zealand, at different times of the year, hoki, middle depth, southern arrow squid, and southern blue whiting trawl fisheries pose the highest fishery-risk to New Zealand fur seals. Lower risk are shark, flatfish, minor set net fisheries, and the southern bluefin tuna surface longline fishery.

A literature review examined potential options to reduce New Zealand fur seal interactions. For trawl fisheries, solutions included a Seal Exclusion Device (optimised for New Zealand fur seals), net binding during shooting, and net constriction during hauling. Acoustic devices, designed to cause a startled response in fur seals, showed promise for set net fisheries. Switching from set net to demersal longlining or potting might also be an option. In surface longline fisheries, covering the catch or using acoustic devices may be a solution, although have not commonly been used for seals and sea lions.

Mitigation success varies by target species, fishery, and gear type, so a one-size-fits-all approach is not effective. This study emphasises the need for research to develop and refine mitigation techniques specifically for New Zealand fur seals. Understanding the interactions between New Zealand fur seals and fishing operations is crucial for effective risk reduction.