This project used simulation modelling to explore potential bias in snapper SNA 8 stock assessments when there has been a change in stock productivity (i.e., regime-shift), as may be expected under climate change.

Three SNA 8 stock productivity-change scenarios were investigated: the first assumed an upward shift in productivity after 2000; the second assumed a downward productivity shift after 2000; the third had no productivity shift.

Various SNA 8 stock assessment models were run under these productivity shift scenarios including one that explicitly allowed for a post-2000 productivity shift. Assessment bias was investigated specific to two important management metrics: current-stock-biomass; current-stock-status (being the ratio of current-stock-biomass to stock virgin (unexploited) biomass).

All assessment models produced unbiased estimates of current-stock-biomass under the no-regime-shift scenario. Only the post-2000 productivity shift model produced unbiased current-stock-biomass estimates under increasing and decreasing productivity scenarios.

All model current-stock-status estimates were biased under increasing and decreasing productivity scenarios. Although the post-2000 productivity shift model current-stock-status estimates were markedly less biased that those of the other models. An important finding from the study was all models were substantively less biased in their estimates of current-stock-biomass than current-stock-status.

An important conclusion from the simulation work was that we should not be using model predicted stock-status ratios as stock assessment measures when it is suspected that stock productivity is likely to have changed. Instead, we should be placing more ‘faith’ in assessment model predictions of current-stock-biomass and therefore be measuring sustainability solely against these estimates.

The red rock lobster supports the most valuable inshore commercial fishery in New Zealand.

This fishery has been managed with catch quotas in nine Quota Management Areas (QMAs), which are usually treated as independent populations or stocks.

To estimate those quotas, a stock assessment is done for each QMA approximately every five years. These stock assessments include a review of the previous stock assessments and data inputs, the addition of new data, data processing, and development of a new stock assessment model.

This document describes the development of a new stock assessment model for the CRA 6 stock (the Chatham Islands).

The stock assessment estimated that since 1995, the stock size has steadily increased and is projected to increase over the next five years assuming current catches and recent recruitment patterns.

Most fishing methods catch target and non-target (unwanted) species, and unwanted catch may be returned to the sea in some cases.
Fishers and observers record catches of target and non-target species, and the amount of catch returned to the sea (discards).

Total non-target catch and discards for key species and species groups reported in the hoki, hake, ling, silver warehou, and white warehou (HHLSW) fishery from fishing years 2003 to 2022 were estimated with a statistical model.

Hoki and other target species make up most of the catch in this fishery, and key non-target species inluded javenlinfish, rattails, and sharks.
Gemfish showed a significant increasing trend in the amount of non-target catch reported, and sharks and slickheads showed significant decreasing trends.

The amount of catch that is discarded compared with the target catch is lower for this combined fishery than for other fisheries that are monitored.

Monitoring levels of catch and discards is important for understanding the impact of fishing on the environment.

Two oreo species, black oreo and smooth oreo, are commercially important in New Zealand waters. Oreos are deepwater fish and so are not very productive which means they can be easily over-exploited.

Management is based on setting catch quota for each oreo management area, but some areas have localised fisheries which are assessed separately to avoid over-exploitation.

To assess if catch quotas are sustainable, abundance trends are produced from acoustic surveys and/or catch per unit effort (CPUE) series from the commercial fisheries within a quantitative assessment.

Reductions in fishing effort and quotas have made acoustic surveys too expensive to fund from a levy on catch quotas and CPUE series in several areas have gone from accepted to rejected as a reliable indication of stock abundance trend, so quantitative assessments have been curtailed.

This study considered a range of different assessment methods and their data requirements in anticipation of lower-level monitoring and, for each oreo fishery, presents the monitoring and assessment options.

For two management areas (OEO 3A and OEO 4), acoustic surveys are still considered feasible if redesigned to reduce costs. Quantitative assessments are also considered possible and a method to explicitly consider spatial variation of CPUE within the area is demonstrated in this work as a way to improve the CPUE input data.

For the other main management area (OEO 6), none of the localised areas have sufficient data to continue quantitative assessments and, possibly, insufficient data for any other type of lower-level assessments.

The red rock lobster supports the most valuable inshore commercial fishery in New Zealand. This fishery has been managed with catch quotas in nine Quota Management Areas (QMAs), which are usually treated as independent populations or stocks.

To estimate those quotas, a stock assessment is done for each QMA approximately every five years. These stock assessments include a review of the previous stock assessments and data inputs, the addition of new data, data processing, and development of a new stock assessment model.

This document describes the collation and review of inputs for the 2023 stock assessment of CRA 6 (the Chatham Islands).

The trawl footprint describes how much seabed area has been contacted by trawling gear in New Zealand’s territorial sea (TS) and exclusive economic zone (EEZ), but it does not provide a measure of the effect of fishing on seabed communities.

This project used the trawl footprint information, in addition to other sources of information on impacts of contact by trawl gear on seabed fauna, to quantify the potential impacts to seabed communities and habitats.

Fishing gear types were first described and categorised, and footprints for each category of gear were produced. Two published impact assessment methods were applied to the TS and EEZ. The methods had different strengths and weaknesses and the outputs of the two methods were found to be complementary to one another.

The first method applied, the MRSP approach, combines information on gear categories, expert opinion on the vulnerability of seabed fauna to trawl gear, and the bottom contact footprint of trawl fishing. This approach does not consider how the fauna recover over time.

The second method, the relative benthic status (RBS) approach, uses information on the proportion of the seabed area swept by trawls and published information for depletion and recovery rates for seabed fauna considered to be particularly vulnerable to trawling. This method predicts a future state for the seabed fauna assuming no change to fishing effort.

This project provides outputs for both methods that can be used in conjunction with distribution data for seabed fauna to assess impacts of trawling and inform spatial planning processes.

Recognising the shortcomings of the MRSP and RBS approaches, two further approaches were explored and developed using data from the Chatham Rise. One approach aimed to enhance the RBS method by making this more relevant to local seabed fauna by using bycatch data from the Chatham Rise instead of relying on information from international sources. The results were encouraging but indicated that further method development is required.

The second approach expanded a previously applied spatio-temporal modelling approach to assess impacts to fauna thought to be useful indicators of potential trawling effects. It was found that this approach, as with the others, was limited by the available data, and further development is required to improve the utility of this approach in the future.

This report presents results of the 2022 inshore trawl survey of the west coast North Island (WCNI), the 9th in a time series starting in 1989, but with a 19-year gap between 1999 and 2018 surveys.

The survey extends from Scott Point on Ninety Mile Beach to Mana Island covering a depth range from 10–200 m north of Cape Egmont and 10–100 m to the south. Since 2018, there has been no sampling within 2–4 nautical miles of the coast between Maunganui Bluff and the Waiwhakaiho River, New Plymouth, a no-trawl area established to protect the Māui dolphin.

Everything that is caught in the trawl is sorted, identified, and weighed, and length and maturity data are collected for selected species and otoliths (fish ear stones) for ageing the four main species of interest: snapper, red gurnard, John dory, and tarakihi. The trawl survey provides time series of relative biomass estimates and age, length, and maturity stage information used for stock assessments and fisheries management advice for key inshore species.

In 2023, 95 phase one stations were successfully completed followed by four phase two stations completed to improve the coefficient of variation for tarakihi.

There were 72 species recorded in total, with snapper by far the most abundant. Biomass estimates (in tonnes) for the key species across the whole survey were: snapper, 8396.3 t ; red gurnard, 1160.5 t; tarakihi, 447.6 t ; John dory, 305.3 t.

The 2022 snapper biomass estimate was lower than that from the 2019 and 2020 surveys, but still significantly higher than the historical surveys in the 1990s. There were high numbers of juvenile snapper under 5 years old but a lower number of adult fish. The variability in adult snapper biomass in this survey may be due to fish moving inshore into shallow water to spawn, or may reflect the highly patchy distribution of snapper at this time of year.

The biomass estimate for adult red gurnard was relatively stable, but the biomass of smaller fish was substantially below historical estimates.

Snapper are the most important recreational fish species in New Zealand and are often released back to the sea after capture.
Little is known about the survival of fish after they are released.
NIWA conducted a study using volunteer fishers to catch 960 snapper at different depths and with different hook placements.
The captured snapper were kept in holding nets and monitored by NIWA divers over several days.
Fish hooked in the lip had a low chance of dying if caught at shallow depths, but the chance of dying increased as depth increased.
Fish hooked elsewhere on the body had a higher chance of dying, with those hooked deep in the gut having the highest chance of dying.
This study suggests that fishing practices can impact fish survival, but there are ways to potentially reduce post-release mortality.
Understanding how fishing affects fish survival is therefore an important consideration for catch and release fisheries and when setting catch limit regulations.

This report updates and summarises the commercial catches, standardised catch per unit effort (CPUE), and observer and research data for hoki (Macruronus novaezelandiae) caught commercially during the 2021–22 fishing year.

These data include time series of length-at-age and catch-at-age from observer and land-based sampling of commercial catch. Length and age data from spawning and non-spawning fisheries are compared with those from previous years.

The overall catch in the 2021–22 fishing year was lower than the catch in 2020–21. Catches in 2021–22 decreased in most areas (west coast South Island, Cook Strait, Chatham Rise, Sub-Antarctic, and east coast North Island) and increased in the east coast South Island and Puysegur fisheries. The CPUE indices varied by area but were all at or above the long-term average.

Catch-at-age data are important for the assessment of fish stocks because they provide information on the year class strength of age classes caught and are used in analyses of trawl surveys and commercial fisheries. Most of the catch in 2021–22 was of fish 45–90 cm length from the 2006–2019 year classes.

The 2014 and 2015 year classes were important in all areas except for the Chatham Rise, and the 2016 and 2017 year classes were low in all the main fisheries. The 2018 and 2019 year classes appeared strong in the WC.north, SA.snares, SA.auck, CR.shallow, and CR.deep sub-fisheries.

Biomass indices from research surveys and results from other research on hoki in the most recent year are also briefly described. Data in this report were incorporated in the model for the hoki stock assessment in 2023.

A 2013 workshop Future proofing New Zealand’s shellfish aquaculture: Monitoring and adaptation to ocean acidification, brought together experts from government, the aquaculture industry and science organizations from the US and NZ to raise awareness of ocean acidification within the NZ aquaculture community, identify ways to protect the aquaculture industry and develop US-NZ scientific cooperation to address OA. Papers presented at the workshop and points raised during discussion are summarised.

With funding from Fisheries New Zealand and support from the Department of Conservation (DOC), we trialled attaching short-term (24 hours) suction-cup recording tags (DTAGs) to Hector’s dolphins in Te Koko-o-Kupe/Cloudy Bay.

We wanted to determine if DTAGs are a possible tool for monitoring this endangered species and could help answer research gaps identified by DOC’s Threat Management Plan and Research Strategy.

We found these suction-cup DTAGs had little to no impact on Hector’s dolphin behaviour.

We tagged 11 dolphins, and their tags stayed attached for 1.5 to 24 hours.

We gathered over 83 hours of data on this species, including the first ever three-dimensional recordings of Hector’s dolphin underwater, their night-time movements, and recordings of the different sounds they make and hear during a typical day.

Overall, such insights about these dolphins can influence how we manage them in relation to their various threats.

The Marine Ecology Research Group used detailed field surveys to assess the recovery of the inshore coastal ecosystem affected by the cataclysmic 2016 Kaikōura earthquake.

The earthquake caused seismic uplift from 0.5 to 6.4 m along 130 km of coastline and resulted in widespread die-offs of important flora and fauna and permanent losses to critical habitats.

There was much concern for the fate of diverse intertidal and subtidal communities, which include culturally and commercially important fisheries, such as pāua, and other habitat-forming species like bull kelp.

Shore-based and dive surveys tracked the abundance of over 120 marine species at 16 sites for more than six years. Findings depict major physical and ecological changes over time across sites.

The complex dynamics of recovery are described in detail in this report and clearly show that the effects from this disturbance to the Kaikōura coastal ecosystem are both significant and ongoing.

This long-term study is the first of its kind and provides a detailed data set and quantitative baselines that will help inform future coastal management decisions.

This report describes catch-at-age distributions for hake (Merluccius australis) and ling (Genypterus blacodes) from commercial fisheries for the 2021–22 (2022) fishing year, to update an ongoing time series.

These distributions are based on length data and otoliths (ear bones for ageing fish) collected by observers from commercial fishing and research trawl data.

Catch-at-age data are important for the assessment of fish stocks because they provide information on the year class strength of age classes caught and are used in analyses of trawl surveys and commercial fisheries.

The precision target (coefficient of variation) was met for analyses of hake commercial trawl Sub-Antarctic and west coast South Island fisheries but not for the Sub-Antarctic trawl survey. The target precision was met for the Chatham Rise and Sub-Antarctic ling commercial trawl fisheries, and the Sub-Antarctic trawl survey, but not for the west coast South Island commercial trawl fishery. The target precision was met for the west coast South Island and Sub-Antarctic ling longline fisheries analysed.

Further observer data collection in certain areas and months are recommended to improve the precision of the hake and ling time series in future analyses.

Increasingly frequent and intense extreme weather events such as Cyclone Gabrielle are likely to impact seafloor marine ecosystems by accelerating soil erosion and sediment transport to the ocean by rivers.

The objective of this project was to understand sediment impacts from the February 2023 Cyclone Gabrielle event on marine environments of the Hawke’s Bay and Gisborne regions to enable rapid fisheries management decisions.

We conducted two vessel surveys in June and October 2023 focusing on offshore seabed environments deeper than 15 metres. As part of these surveys we mapped selected areas of the seafloor, surveyed life on the seabed using a towed underwater camera, and obtained sediment core samples.

An ocean current and sediment transport model was designed and implemented to investigate the transport and deposition of sediments after Cyclone Gabrielle. Concentrations of suspended sediments and other parameters in the surface ocean along the east coast of the North Island were estimated from satellite images. This satellite information was used to inform the sediment transport model and to characterise the spatial extent and longevity of the offshore sediment plumes generated by Cyclone Gabrielle. A Seafloor model was used to explore impacts and recovery of seafloor ecosystems following the cyclone.

The analysis of satellite images suggest that the influence of Cyclone Gabrielle lasted approximately two to three months across the Hawke’s Bay and Gisborne coastal marine areas, with surface ocean parameters largely returning to normal by May. The concentrations of suspended sediment at the ocean surface in February were significantly elevated, but they did not exceed values typical of winter months.
Seabed mapping revealed areas of significant sediment erosion, and deposition up to about one metre in thickness, at Pania Reef, Tangoio Reef and Clive outfall area in Hawke Bay. Elsewhere, sediment core observations suggested the presence of fresh muddy deposits of up to about 15 centimetres. Swell waves were resuspending muddy sediments at shallow locations for several months after the cyclone, as was evident by the low underwater visibility during camera deployments.

The abundance and diversity of the sediment fauna sampled in Hawke’s Bay and Gisborne before (2010) and after Cyclone Gabrielle (June and October 2023) tended to increase away from the shore and into deeper waters. Sediment fauna were less abundant in June 2023 when compared with 2010, but appeared to be recovering by October 2023.

Seafloor animal and plant communities are highly likely to have been impacted by sediments at 11 of the 36 locations we surveyed using the towed underwater camera, as assessed by observations including (1) fresh mud layer on the seafloor, (2) animal/plant life in poor condition, and/or (3) absence of seaweed at shallow depths. However, for most of these locations a direct link to Cyclone Gabrielle cannot be demonstrated because no information on the distribution of seafloor organisms is available from before the cyclone. The likely exception is Wairoa Hard in Hawke Bay, where available information shows that kelp and sponges were present before the cyclone but were almost completely or completely absent after the cyclone. Whether this loss of habitat has led to reductions in associated fish populations is unclear.

Although limited by the availability of data, the ocean current and sediment transport model produced realistic predictions of suspended sediment concentrations and deposition at the seafloor. In the days following the cyclone, sedimentation in Hawke Bay was predicted to occur mainly close to shore in the western and central parts of the bay. In the Gisborne region, there was deposition of up to about 10 centimetres of sediments offshore of Poverty Bay and along a narrow band of the coast to the north near Tokomaru and Tolaga bays. These model predictions are broadly consistent with observations from the sediment core samples.

The Seafloor model showed small declines in structure-forming organisms such as sponges for Hawke’s Bay following Cyclone Gabrielle. These declines were not substantial, most likely because the region is already impacted by decades of fishing and increased sedimentation. The Seafloor model predicted weaker cyclone impacts for Gisborne than Hawke’s Bay and indicated that continued trawling may slow down recovery of seafloor communities following extreme weather events.

The lack of pre-cyclone information was a major obstacle in assessing the potential impacts of the cyclone on seabed ecosystems. Information collected as part of this project now form a valuable baseline that will inform future impact assessments in the region. Another limitation is the inability to use towed cameras to survey inshore habitats for extended periods because of poor underwater visibility. A precautionary approach could be warranted in the period following an extreme weather event until key habitats and ecosystems can be surveyed, and fish stocks and catch levels should be carefully monitored in the years following the event.

Sediment transport modelling is a promising tool for rapidly identifying areas most at risk from sedimentation following extreme weather events. However targeted sampling of sediment and water parameters under normal and flood conditions would help improve the accuracy and reliability of model predictions. The Seafloor model could be used to explore how spatial changes in fishing effort could enhance recovery following extreme weather events and could be improved through better information on the distribution of seafloor sediment and reefs and their associated animal and plant communities, particularly in the Gisborne region.

The impact of extreme weather events is made worse by decades of increased sedimentation in New Zealand’s marine environments. Addressing the long-term issue of sedimentation in marine ecosystems and the impacts of extreme weather events will require addressing the factors that have made New Zealand’s catchments more prone to erosion.

The red rock lobster supports the most valuable inshore commercial fishery in New Zealand. This fishery has been managed with catch quotas in nine Quota Management Areas (QMAs), which are usually treated as independent populations or stocks.

To estimate those quotas, each population is fully assessed every five years, requiring a lot of time and effort by a team of at least five researchers working on the review of the previous assessments and data inputs, the addition of new data, data processing, and development of a new assessment.

Every year, instead of a full assessment, a rapid update assessment is done for each of the stocks that were not assessed that year.

A rapid update repeats the previous full assessment model, only updating data inputs, which significantly speeds up the required process to provide advice about stock status in the interim years between full assessments.

This document describes the operation of the stock assessment rapid updates completed in 2023 for six stocks that can be used to guide management decisions of New Zealand red rock lobster QMAs.

For the beginning of the 2023–24 fishing year, all red rock lobster stocks evaluated were estimated to be above sustainable levels.