Publications

New Zealand’s jack mackerel fisheries comprise three closely related species of pelagic fish, two native species (yellowtail and greenback jack mackerels), and the Chilean jack mackerel that periodically arrives in New Zealand waters from the wider South Pacific. Although catch limits are set for the species group, the abundance of each species must be monitored separately.

Off the west of New Zealand (JMA 7), jack mackerels are caught by a midwater trawl fishery with target fishing focussed in the Taranaki Bight. Observer sampling information allows the catches of the three species to be separated. Greenback jack mackerel currently make up about 80% of the catch, with yellowtail jack mackerels most of the remainder.

As part of its management within the Quota Management System, jack mackerel abundance in JMA 7 is monitored using catch-per-unit-effort (CPUE) from the midwater trawl fishery. In this report, this information is given for 1990 to 2024.

Both greenback and yellowtail jack mackerels were likely to be at or above target levels in 2024. In the case of greenback jack mackerels, the assessment is considered to apply to the species in both the JMA 3 and JMA 7 areas as there are indications they are a single population.

Potting has recently become an important method of catching ling in many areas around New Zealand, alongside the traditional trawl and bottom longline fisheries.

Ling potting is now being undertaken by a fleet of dedicated vessels, many of which are using collapsible, cylindrical pots that are deployed on a long backbone.

This report summarises the development of the fishery using standard data sources, and identifies where further data are required. Some of these data needs can be met by modifications to the Electronic Reporting of potting.

Scientific publishing is widely perceived to be in a state of crisis. A contributing factor is reproducibility: the extent to which the results can be replicated is key to assessing the reliability of a study. Reproducibility rates have often been found to be low, a situation complicated by the fact that many studies provide insufficient details of their methods.

For the last decade, we have been using a framework that allows us to fully reproduce the results of analyses of fisheries data. Key features are that the analyses are fully defined in code and run within a consistent computing environment. The approach has proven to be transferable, with the framework being adopted in a range of other disciplines.

Incentivising the broader adoption of fully reproducible analyses would assist in re-establishing trust in scientific publications, addressing the “reproducibility crisis”reproducibility crisis while also providing a basis for strengthened peer review processes and increasing the likelihood that questionable research practices are identified.

Implementing fully reproducible analyses has some overhead, especially where the software tools that support the approach are unfamiliar. We have found that the benefits of openness, transparency, and efficiency, together with increased collaboration, make this overhead worthwhile.

Arrow squid represent an important fishery resource, but their fast growth and relatively short lifespan make stocks difficult to assess and manage. This study focused on developing a novel method to distinguish different squid cohorts based on size and catch-per-unit-effort (CPUE), across different areas and over time. Using information from trawl fisheries on the Stewart-Snares-shelf and at Auckland Islands, the assessment assumed two dominant cohorts in each area, occurring in autumn (early season) and spring (late season). This assumption was used to develop a mixture model (i.e., a probabilistic model) to determine the proportional contribution of each cohort to a given fishing event, which, in turn, allowed simultaneous estimation of CPUE for each cohort. The model indicated consistent depletion (i.e., decreases in squid over time) for the late-season cohort, but there was no consistent trend for the early-season cohort. This proof of concept highlights the potential to further develop this approach for providing stock assessments for squid in these trawl fisheries.

The snapper fishery in Fisheries Management Area 2 (SNA 2) occurs on the east coast of the North Island, primarily from Hawke Bay to East Cape. Snapper in this area is mainly taken as bycatch in trawling that targets tarakihi or gurnard.

Snapper in the north of the SNA 2 area (north of the Māhia Peninsula) and southern part of the area (mainly Hawke Bay) are separate biological stocks. As part of its management within the Quota Management System, snapper abundance in the north and south of SNA 2 is monitored using catch-per-unit-effort (CPUE) from bottom trawl fisheries and, in this report, CPUE series are provided for the period 2002 to 2024, a one-year update from the previous analysis.

Snapper abundance in both the north and south of SNA 2 has increased between 2016 and 2024: by more than three times in the north and by almost eight times in the south. Snapper in the southern area was assessed as Very Likely (> 90%) to be at or above the target level in 2023–24.

The fishery for jack mackerels in JMA 3, which includes the southern part of New Zealand’s EEZ, was characterised using data from 1989 to 2024.

There was little target fishing for jack mackerels in JMA 3 until the 1990s when the area was at the forefront of the “invasion”invasion of Chilean jack mackerel into New Zealand waters. A target fishery subsequently developed, mainly using midwater trawling. Catches declined during the 2000s, but have been stable since 2010.

Because of low observer coverage, a statistical model was developed to estimate the catches of the Chilean jack mackerel and the native greenback jack mackerel in the JMA 3 fisheries (the other native species, yellowtail jack mackerel, is largely absent in JMA 3). Catches estimated using this model demonstrated that the Chilean jack mackerel comprised the majority of the JMA 3 catch until the 2020s.

The species modelling also allowed the development of standardised catch-per-unit-effort series that were intended to provide an indication of trends in abundance, with a focus on the status of the native greenback jack mackerel. However, data on the size and age composition of the catch suggested that greenback jack mackerel in JMA 3 is not an independent stock, but comprises larger and older fish that likely originated in another area.

As a working hypothesis, greenback jack mackerel in JMA 3 were linked to the stock in JMA 7, and CPUE from that area was used to conclude that the stocks in both areas were Likely to be at or above the target.

Chilean jack mackerel are not considered to be a self-sustaining stock in New Zealand waters, but thereare some indications of ongoing arrivals from wider Pacific stock, at a lower level than in the 1990s. In particular, most jack mackerels caught around the Chatham Islands are Chilean jack mackerels.

Alfonsino stocks in the Quota Management System include two related species, but most of the catch is of splendid alfonsio, Beryx splendensBeryx splendens, a species that occurs globally but with poorly understood population dynamics.

The New Zealand alfonsino fishery occurs off the southern east coast of the North Island, and on the eastern Chatham Rise, north and south-east of the Chatham Islands. Alfonsino is caught by a mix of bottom and midwater trawling.

Analyses of commercial catch rates have demonstrated that alfonsino abundance trends are different in the four main areas of the fishery. The reasons for the differing trends are not well understood. More extensive biological sampling, aimed at monitoring the age structure of alfonsino in the different areas over time, is recommended.

This study evaluated using fish length to adjust catch limits for a jack mackerel species in New Zealand waters, with a view to developing simple length metrics to help manage this species. The effectiveness of length-based management depended greatly on biological factors like recruitment, growth, and natural mortality. Current uncertainties about these factors make length-based rules less reliable than expected. Alternative approaches using age data might provide a better way to support sustainable management of this species.

The FLA 2 Quota Management Area extends southwards from the central east coast of the North Island around to the Taranaki coast. The main flatfish fishery within this area has been in Hawke Bay, but there are smaller fisheries in Wellington Harbour, off the Kapiti coast, and in the north Taranaki Bight.

Flatfish stocks comprise a group of eight flatfish species. Recent changes in reporting regulations mean that comprehensive catch reporting for these individual species has been in place since late 2021. The distribution of the different species was examined at a countrywide level, as well as at a detailed level within the FLA 2 area.

The FLA 1 fishery is dominated by yellow-bellied flounder, while New Zealand sole and sand flounder are the main species caught in FLA 2, and lemon sole is the main species caught in FLA 3. FLA 7 currently has the most diverse catch composition, although sand flounder and New Zealand sole appeared to dominate the FLA 7 catch historically.

In FLA 2, monitoring of stock abundance previously used a combined flatfish catch-per-unit-effort-series from flatfish target bottom trawl fishing. However, a decline in flatfish target fishing required a re-evaluation of the monitoring approach.

Catch-per-unit-effort-series beginning in 2008 were adopted for combined flatfish, New Zealand sole, and sand flounder in Hawke Bay. These stocks were assessed as being as likely as not to be at or above the management target.

Gemfish (southern kingfish) are found throughout New Zealand waters and are generally caught by trawl fisheries in depths from 150 to 500 metres. There are two New Zealand stocks of gemfish, with the northern stock caught off both coasts of the North Island and a southern stock caught around the South Island.

A trawl fishery targeting the northern gemfish stock developed in the 1980s. Catches peaked in the early 1990s, but a decline in stock abundance led to a series of reductions in catch limits. Monitoring, using catch-per-unit-effort (CPUE), has demonstrated that abundance of the northern stock of gemfish increased substantially since the mid 2010s. New catch-at-age data from the target trawl fisheries were compiled for the 2012, 2014, and 2022 fishing years.

This report details a new, full quantitative stock assessment for the northern gemfish stock undertaken in 2023. The model estimated that northern genfish abundance increased throughout the mid-late 2000s, following higher recruitment in the late 1990s and early 2000s, then increased further during 2019–2023 following strong recruitments in 2013–2017. In 2023 abundance was estimated to be around the average level that would occur in the absence of fishing. This estimate is uncertain because the gaps in age sampling mean that the size of recent recruitments is uncertain, but it is likely that the stock can support higher catches, at least in the short term. It appears that gemfish stocks are sustained by intermittent periods of high recruitment.

The snapper fishery in Fisheries Management Area 2 (SNA 2) primarily occurs from Hawke Bay north to East Cape, on the east coast of the North Island. Snapper in this area are mainly taken as bycatch in trawling that targets tarakihi or gurnard.

As part of its management within the Quota Management System, snapper abundance in the north and south of SNA 2 is monitored using catch-per-unit-effort (CPUE) from bottom trawl fisheries and, in this report, this information is given for 2002 to 2023.

Snapper abundance in both the north and south of SNA 2 has increased between 2016 and 2023: by more than three times in the north and by almost eight times in the south. Snapper in the southern area was assessed as Very Likely (> 90%) to be at or above the target level in 2022–23.

Blue mackerel (coded as EMA) are a widely distributed, small pelagic fish. In New Zealand they are mainly caught in commercial fisheries on the east and west coasts of the North Island.

In the Taranaki Bight, on the west coast of the North Island, and the northern west coast of the South Island (management area EMA 7), blue mackerel are taken by the midwater trawl fishery that primarily targets jack mackerels. The catch of blue mackerel is a mix of target catch and bycatch. Some catch is also taken by purse seining.

As part of its management within the Quota Management System, blue mackerel abundance in EMA 7 is monitored using catch-per-unit-effort (CPUE) from the midwater trawl fishery. In this report, this information is given for 2003 to 2022. In 2022 the EMA 7 stock abundance was assessed to be slightly above the target level.

The “petrel project” continued the use of on-board cameras to monitor seabird captures in the small-vessel bottom longline fishery off the north-east of New Zealand. Results demonstrated the value of the video observation data in providing data that were representative of the fishery, and the importance of assessing the variation between reviewers in their ability to make observations from the footage. Footage was reviewed to May 2022 and, for the first time, included reviewing footage from the winter months (June–October) in addition to the November–May period when black petrels and flesh-footed shearwaters are breeding in the area. Models using the video observation data estimated 40 black petrel captures, and 159 flesh-footed shearwater captures, in all bottom longline fishing in Fisheries Management Area 1 during the 2021–22 fishing year. The estimated captures of black petrels were lower than previous estimates, which were based on observed data only, but estimated captures of flesh-footed shearwaters were similar. Additional blind reviews were carried out of footage where captures occurred to allow estimation of reviewer skill. Of the five reviewers involved in the project, two reviewers detected over 90% of the seabird captures, but one reviewer detected fewer than 50% of the captures.

The environmental and ecosystem information needs of fisheries managers and other stakeholders were assessed through a workshop and survey. We concluded that reporting the environmental impacts of fishing by fishery, rather than species, was the best approach.

Similar approaches to defining fisheries are used in New Zealand and internationally. However, when projects do not use the same definition for a fishery this complicates compiling results at the fishery level.

A well-defined, and comprehensive, classification is recommended for future reporting. It should be hierarchical, allowing groups to be merged or split as required.

Existing resources can be built upon to efficiently implement a new framework for annual, fishery-level reporting.

Red gurnard is an important component of inshore trawl fisheries around New Zealand. Off the central east coast of the North Island (GUR 2), the target bottom trawl fishery for gurnard is focused in Hawke Bay, with bycatch in the deeper tarakihi target fishery representing around a third of the catch.

Abundance of red gurnard in GUR 2 is monitored using catch-per-unit-effort (CPUE) from the inshore trawl fishery, and a CPUE-based target abundance level has been established to facilitate its management within the Quota Management System. In this report, this information is given for 1990 to 2023. In 2023 red gurnard was assessed as being likely to be at or above the target.

Gurnard abundance appears to be cyclical, with increases and decreases occurring over 5–7 year periods. Fine-scale changes in the distribution of red gurnard within Hawke Bay and the neighbouring coastal areas are also evident in tow-level data available since 2008, with the population moving between deeper and shallower areas. In 2022 and 2023 red gurnard appear to have had a deeper distribution, but it is unclear if this is related to the impacts of Cyclone Gabrielle.

New Zealand’s jack mackerel fisheries comprise three closely related species of small pelagic fish, two native species (yellowtail and greenback jack mackerels) and the Chilean jack mackerel that periodically arrives in New Zealand waters from the wider South Pacific stock. Although catch limits are set for the species group, the abundance of each species must be monitored separately.

Off the west of New Zealand (JMA 7), jack mackerels are caught by a midwater trawl fishery with target fishing focussed in the Taranaki Bight. Observer sampling information allows the catches of the three species to be separated, but previous assessments have encountered problems with data interpretation and quality.

As part of its management within the Quota Management System, jack mackerel abundance in JMA 7 is monitored using catch-per-unit-effort (CPUE) from the midwater trawl fishery. In this report, this information is given for 1990 to 2022, and concerns with data quality were addressed. Stock targets were adopted for the two native species. Greenback jack mackerel was assessed as being likely to be at or above the target in 2022, while yellowtail jack mackerel was very likely to be at or above the target.

Information on the age composition of fish catches is desirable for undertaking fully quantitative stock assessments.

Monitoring, using catch-per-unit-effort (CPUE), has demonstrated that abundance of the northern stock of gemfish increased substantially since the mid 2010s.

This has led to interest in undertaking more detailed stock assessment modelling. To support this modelling, catch-at-age data were compiled for the 2012, 2014, and 2022 fishing years.

Otoliths (fish ear bones, the structures used for assessing fish age) were available from sampling of landings from the northern gemfish target trawl fishery in 2012 and 2014. New sampling of this fishery was carried out in 2022 by Fisheries New Zealand observers.

Samples from these three years were aged, with care taken to ensure that the techniques and results were comparable with those used to provide earlier age data for gemfish.

In 2012 and 2014, nine- to ten-year-old females and eight- to nine-year-old males were the most common age classes in the catch.

Younger male and female gemfish dominated the catch in 2022. Few of the age classes sampled in 2022 had been sampled in previous years.

Rig (lemonfish) is a coastal shark species caught in fisheries around New Zealand. Commercial catches in the central east coast North Island fisheries (SPO 2) have exceeded the Total Allowable Catch Limit in 2022 and 2023 as a result of increased rig catches in the set net fishery that targets school shark and rig.

Given this over-catch, a rapid update of the catch-per-unit-effort (CPUE) index from bottom trawl—that is used for monitoring abundance of rig in SPO 2—was carried out. Rig abundance in 2023 had increased to 1.7 times the target abundance, and the stock was assessed as very likely to be at or above the target level.

Near-shore catch rates of rig in Hawke Bay were reduced in 2023, potentially due to Cyclone Gabrielle impacts.

Rig (lemonfish) is a coastal shark species caught in fisheries around New Zealand. Commercial fishers target rig (coded as SPO) in set nets, bottom trawl, and Danish seine nets. It is the most common shark species caught by recreational fishers.

As part of its management within the Quota Management System, rig abundance in five areas is monitored using catch-per-unit-effort (CPUE) from bottom trawl and set net fisheries and, in this report, this information is given for 1990 to 2021. Off the South Island, rig is also monitored by trawl surveys.

Around the north of the North Island, rig abundance targets have not been established, but trends can be monitored. In the Firth of Thames, rig abundance increased during 2013 to 2019, then decreased, but remained above average. On the west coast of the North Island abundance was stable or increasing in the various areas assessed.

Off the central and southern east coast of the North Island, rig abundance has increased since 2009 and in 2021 was 2.5 times the target abundance.

Rig abundance off the South Island east coast appeared to have increased between 2017 and 2021, but the 2021 trawl survey index was imprecise and the stock was assessed as being at or about its target level. Abundance off the South Island south coast was also found to have increased, and this stock was also assessed as being at or about its target level in 2021.

For the South Island west coast, and the southern Taranaki Bight, recent CPUE indices increased while the trawl survey showed an increase from the mid-2010s then a decrease. The stock was considered to be at the target level in 2021.

Gemfish (southern kingfish) are found throughout New Zealand waters and are generally caught by trawl fisheries in depths from 150 to 500 metres. There are two New Zealand stocks of gemfish, with the southern stock caught around the South Island and a northern stock caught off both coasts of the North Island.

The trawl fisheries taking gemfish around the South Island were described for the period 1989–90 to 2019–20, using commercial catch and effort and observer data. Eleven standardised catch-per-unit-effort (CPUE) analyses were investigated as potential abundance series. South Island gemfish are thought to mainly live in the waters south of Stewart Island during the spring and summer and to migrate in the winter to the west coast of the South Island to spawn. Gemfish on the east coast of the South Island appear to be less abundant than on the west and south coasts of the South Island and their spawning migration patterns are not well understood.

Catches of southern gemfish were high in the 1980s and their abundance dropped by the early 1990s. Catch limits were curtailed, and commercial catches dropped to low levels from the late 1990s to the early 2010s. From the mid-2010s gemfish were increasingly caught in fisheries targeting hoki and squid.

All the analysed data sets indicated that the relative abundance of South Island gemfish had substantially increased, beginning in the mid-2010s. However, the size of increase was not consistent among the various indices and areas, and a CPUE based management reference point was not established.

Black petrel (Procellaria parkinsoniProcellaria parkinsoni) and flesh-footed shearwater (Ardenna carneipesArdenna carneipes) are two of the seabird populations assessed as being at greatest risk from incidental captures in fisheries. These seabirds breed in north-eastern New Zealand, and are caught primarily by bottom longline vessels fishing in that area. In order to develop a methodology for monitoring seabird captures from video footage, and to gather data on capture rates, video cameras were used to film the hauling station on bottom longline vessels fishing within Fisheries Management Area (FMA) 1, off the north-east coast of New Zealand. This programme has been developed in collaboration with the fishers, who have volunteered their time and the use of their vessels.

Since 2016–17, this programme has been used to monitor between nine and twelve of the most active vessels in this fishery. In this report we present the results of the 2018–19 and 2019–20 data collection programme. Data were collected during 2019–20 as part of this project, with previous footage and data being made available by Trident Systems.

The electronic monitoring (EM) systems used for collecting footage consisted of a single camera on each vessel, positioned on a boom outboard from the hauling station. During 2019–20, a wheelhouse unit was used to record the footage, with the footage transferred into a review system using USB devices. Selected footage was reviewed to identify seabird captures, with selections sometimes being reviewed multiple times for quality control. Any seabird captures identified were then reviewed by a specialist to confirm the identification.

Footage collection during 2019–20 was impacted by several operational issues: the camera housings developed cracks that let water inside the housings; noisy fans and bright lights resulted in the crew switching the EM systems off, initially by removing fuses because switches were not installed; the system clock on one vessel failed leading to incorrect footage timings; and the coronavirus pandemic prevented system maintenance and data transfer during the lockdown period. In addition, one vessel had a fire as a result of damage to the EM system power cable which had a poorly located fuse. Despite these issues, footage was collected from 645 fishing events during November to May 2019–20 (17.7% of all bottom longline fishing events in FMA 1 over the period). In the snapper fishery (i.e., snapper target bottom longline events), footage was captured for 25.8% of the hooks set over this period, with 23.8% being reviewed for seabird captures. In contrast, 8.1For the preceding season (November to May 2018–19), the footage collected by Trident Systems covered 700 bottom longline fishing events in FMA 1 (20.1%). In the snapper fishery, footage was captured for 26.2% of the hooks set over this period, with 24.7% being reviewed for seabird captures. Human observers were assigned to vessels in the snapper fishery for the period in which 7.4% of hooks were set.

In total, 65 seabird captures were recorded by video monitoring during 2019–20 (one of which was on a fishing event outside FMA 1), with a capture rate of 0.032 captures per 1000 hooks. The highest number of captures recorded from a single vessel was 24 captures. Flesh-footed shearwater was the most frequently caught species (48 captures), followed by black petrel (13 captures). By using a statistical model, fitted to data from four years of video observation, to scale up these observed captures to the whole fishery, there were estimated to have been 296 (97.5% c.i.: 166 to 519) seabird captures in all bottom longline fishing in FMA 1 between October 2019 and May 2020. This corresponded to a capture rate of 0.038 (95% c.i.: 0.021 to 0.067) seabird captures per 1000 hooks set.

Over the 2019 and 2020 fishing years, there were 251 seabird captures reported by fishers from bottom longline fishing within FMA 1. Of these captures, 127 were reported from vessels participating in the video monitoring trial (a capture rate of 0.0148 seabird captures per 1000 hooks). There were 124 captures reported from other vessels, with a capture rate of 0.0078 seabird captures per 1000 hooks. The rate of reporting by vessels participating in the trial was around twice as high as the rate of reporting by other vessels.

The multiple reviews identifed an issue with the review accuracy. There were many seabird captures that were missed during the first review of the footage (there were 51 captures on footage that was multiple-reviewed, and of these 20 were on sections of footage that had no capture detected by the first reviewer). The video monitoring programme is reliant on the accuracy of the video review, and without the multiple review this would have led to significant under-reporting of seabird captures. Overall, however, despite the operational challenges, and despite the discrepancies seen in multiple reviews, the programme demonstrates that video monitoring can be used to collect data on seabird captures in bottom longline fisheries. The programme has allowed the effective coverage in snapper bottom longline fisheries to be expanded well beyond what has been possible with a traditional observer programme. The ability to assess the reviewer accuracy is unique to video observation; there is no equivalent assessment of the accuracy of data from traditional observer coverage. As the technology and the systems continue to develop, it is likely that the efficiency and accuracy of the video-monitoring will increase.

Gemfish (SKI) was introduced to the Quota Management System on 01 October 1986. Originally the SKI stocks were specifically silver gemfish, Rexea solandriRexea solandri, but in 2005 the scope was widened to include Rexea spp. generally. Catches are assumed to be comprised almost exclusively of Rexea solandri, but some catch of long-finned gemfish (R. antefurcataR. antefurcata) may occur in the northern fisheries within the SKI 1 and SKI 2 Quota Management Areas, which are considered to include a single biological stock of R. solandri.

The northern gemfish fisheries developed in the 1960s and 1970s, with catches increasing substantially during the 1980s. Declining catches in the 1990s preceded a series of cuts in the Total Allowable Catch. In SKI 1 and SKI 2, gemfish are taken primarily by bottom trawling between 300 and 500 m, and landed unprocessed. The target fishery has been undertaken by larger “inshore”inshore vessels but, as the stock has rebuilt, gemfish have been caught in the more traditional inshore fisheries, particularly the tarakihi fishery.

Gemfish were historically targeted from the Wairarapa Coast, in SKI 2, round to the west coast of the North Island, off Ninety Mile Beach; however, after the catch reductions in the early 2000s, targeting became focussed in the western Bay of Plenty. In SKI 1, the target fishery continued to take the majority of the gemfish catch until 2015, whereas in SKI 2 bycatch has dominated since 2005.

The last fully-quantitative assessment of northern gemfish was in 2008, and the stocks are currently classified as Group 2 stocks to be monitored with relative abundance indices based on standardised catch-per-unit-effort (CPUE). However, developing appropriate CPUE indices proved challenging for a period as a result of the significant changes in the fishery in the early 2000s. A CPUE index for SKI 2 was accepted in 2014 and, during 2020–2022, new indices have been developed. An index based on tarakihitarget effort throughout SKI 1 and SKI 2 and beginning in 1990 is considered to index the sub-adult and adult fish, while an index of adult stock abundance beginning in 1994 has been developed using gemfish and hoki target effort off the North Island east coast.

Abundance of sub-adult and adult fish declined from 1990 to 2000, then slowly increased for the following 15 years before a more rapid increase in abundance was observed between 2016 and 2018, peaking in 2020. Abundance of adult fish, measured by the gemfish-hoki index, subsequently increased substantially over the period 2017–2022.\(B_{MSY}\) compatible reference points have been agreed by the Fisheries Assessment Plenary, with the geometric mean CPUE from the gemfish and hoki target series for the period 2004 to 2017 adopted as the soft limit reference point. The target is assumed to be twice the soft limit value. The northern gemfish stock was assessed as Likely (>60%) to be above the target reference point in 2021, and abundance has increased further in 2022.

There are concerns that observer sampling for catch composition in the JMA 7 trawl fishery has not always implemented the intended approach of sampling throughout the processing of the catch. If any stratification of the catch within the trawl persists through to when the catch is processed, then sampling at a single time (such as the beginning of processing) may result in biased estimates of species composition.

To address this concern, two observer trips were carried out where observers took up to four speciated length-frequency sub-samples of jack mackerel during the processing of catches and recorded additional information about the sub-sampling process. After initial data screening, 50 tows with sub-samples were available for analysis.

Species proportions were estimated for each sub-sample and for the aggregated sample for each tow. Chi-squared tests were used to compare numbers of each species in the sub-samples with the tow-level proportions, and a bootstrapping approach was used to compare differences in the estimated proportions when expressed in terms of estimated species weights. Although differences in species proportions were detected between some sub-sample estimates and the tow-level estimates, these were not related to the time during processing at which the sub-samples were taken. Similarly, differences between sub-sample and tow-level estimates of the mean size of each species were not related to time of sampling.

While gathering of the speciated length-frequency sample at several times during processing of the catch is good practice, this trial suggests there is limited risk that tow-level estimates will be significantly biased if observers have deviated from this instruction and gathered a single sample at one point in the tow. These results are consistent with a similar study in the Bering Sea trawl fishery.

It is recommended that sub-sample information is routinely collected in future sampling, to ensure that checks for potential stratification in the catch can be conducted routinely.

The fisheries taking trevally (Pseudocaranx dentexPseudocaranx dentex, TRE) in Quota Management Area (QMA) TRE 2 are described from 1989–90 to 2016–17 based on statutory commercial catch and effort data held by Fisheries New Zealand. TRE 2 comprises waters off the eastern and southern North Island from Cape Runaway south around to Mana Island off the west coast. Trevally is caught as by-catch throughout TRE 2. However, the majority of the TRE 2 catch is taken by the mixed-species (red gurnard, snapper, trevally and tarakihi) bottom trawl fishery within Hawke Bay and Poverty Bay. Over the period examined, the annual TRE 2 catch fluctuated between 187 and 417 tonnes, regularly exceeding the 241 tonne Total Allowable Commercial Catch. TRE 2 is thought to be part of TRE 1 biological stock in the Bay of Plenty with large changes in catch and abundance in TRE 2 attributed to the movement of fish into and out of this QMA.

This study examines TRE 2 relative abundance using a TRE 2 bottom trawl catch-per-unit-effort (CPUE) index, including data to the end of the 2016–17 fishing year. The CPUE indices were derived using a delta approach that incorporated Generalised Linear Models of the occurrence of trevally in the trawl catch (binomial model) and the magnitude of positive trevally catches (Weibull model). The CPUE index shows large fluctuations in abundance between 1989–90 and 2007–08. Since the last analysis (with data to 2009–10) the CPUE indices have been relatively stable, with an increasing trend from 2008–09 to 2016–17. This increase is corroborated by a tow-based series using data collected on Trawl Catch Effort Returns from 1 October 2007.

Experimental fishing was undertaken off the south Canterbury coast in January 2019 to compare the performance of an MHS1480 specification Modular Harvesting System (MHS) with a conventional 4 inch mesh trawl net typically used in the South Island inshore trawl fishery. The purpose of the study was to test an alternate-tow approach to assess the performance of an MHS trawl relative to a conventional trawl net.

A key feature of the trial design was to ensure, as far as possible, that each tow made with one gear type was matched with a corresponding tow made with the other gear type under similar circumstances. The alternate-tow design generates data that can be analysed using efficient paired-comparison type methodologies.

The criteria for assessing the performance of new trawl technologies require consideration of a number of factors including catch rates and catch composition. Catch rates are relevant to the benthic impacts associated with a given catch. Higher catch rates attain a given yield with less trawling effort and consequently lower benthic impacts. Catch rates of barracouta achieved by the two gear types were compared using a Bayesian Generalised Linear Mixed Model (GLMM) and a non-parametric bootstrap approach.

Methods for comparing the length distributions of red gurnard, tarakihi and sea perch retained by the two nets were also explored. Splines fitted to bootstrapped proportions of catch at length on MHS tows provide a measure of MHS selectivity relative to the conventional net. Potential differences between the gear types in the proportions of fish retained below a specific cut-off length, such as a minimum legal size (MLS), were investigated using a parametric test and non-parametric bootstrapping.

Despite a modest sample size of 11 tow-pairs, data collected during the trial were sufficient to demonstrate some clear differences between the two gear types:the barracouta catch rate of the conventional 4 inch mesh net is significantly higher than the MHS net;the barracouta catch rate of the conventional 4 inch mesh net is significantly higher than the MHS net;the MHS net retains fewer tarakihi less than 20 cm; andthe MHS net retains fewer tarakihi less than 20 cm; andgiven the fish available to the trial, MHS catches included a lower proportion of tarakihi below the 25 cm minimum legal size.given the fish available to the trial, MHS catches included a lower proportion of tarakihi below the 25 cm minimum legal size.

Red gurnard retained by the two gear types on the trial had very similar size distributions. However, small gurnard were not caught by either gear so the trial was not informative about expected relative gurnard retention in areas where small gurnard are available. Sampling of sea perch lengths was insufficient to draw any conclusions about relative length-specific sea perch retention. The analyses presented indicate that the alternate-tow design tested on the trial provides a sound basis for comparing new trawl designs with current gear. We consider that:the GLMM and bootstrapping approaches are both suitable for comparing catch rates. The GLMM approach may be slightly more flexible when comparing catch rates from tows targeting different species;the GLMM and bootstrapping approaches are both suitable for comparing catch rates. The GLMM approach may be slightly more flexible when comparing catch rates from tows targeting different species;for comparisons of relative size-based retention of the two gear types, relative selectivity is more informative and more generally applicable than the approaches that compare proportions below a specific length;for comparisons of relative size-based retention of the two gear types, relative selectivity is more informative and more generally applicable than the approaches that compare proportions below a specific length;for species where a minimum legal size is specified, it is nevertheless helpful to have an indication of the proportion of catch above or below the MLS. The non-parametric bootstrap for proportion below the MLS is recommended for this purpose.for species where a minimum legal size is specified, it is nevertheless helpful to have an indication of the proportion of catch above or below the MLS. The non-parametric bootstrap for proportion below the MLS is recommended for this purpose.

The additional data collected on the trial (over and above the statutory data) on fish lengths and total catch of all species was important for undertaking these analyses. Although 11 tow-pairs was sufficient to draw some clear conclusions regarding catch rate and size retention of specific species from the trial, the sample sizes required in future comparisons will depend on the magnitude of the differences between gears and the level of certainty required by decision makers. The Statistics, Assessments and Methods Working Group has suggested that an allowance for up to 30 tow-pairs is considered in planning future trials, with real-time monitoring and analyses of data to understand what, if any, differences are emerging between gears.

The analysis methods recommended above can be adapted to consider data from multiple trials, including the use of multiple vessels to increase sample sizes, if required.

During 2019, the statutory reporting requirements for the inshore trawl fleet changed with the introduction of electronic reporting (ER) for the reporting of fishing activity, catches, the at-sea disposal of catches, and landed catches. This study provides a review of the catch and effort data collected from the inshore trawl fleet following the completion of the first full year of implementation of the ER regime (the 2019/20 fishing year) to evaluate the potential impact on the derivation of CPUE indices for a range of inshore finfish species.

Simple comparisons of the overall (landed) catch composition from each fishery did not reveal appreciable differences in the fisheries between the two time periods, indicating that there was no substantive change in the operation of the fisheries. However, some differences in the distributions of fishing depth and location were apparent between the two time periods. Trawl duration was also variable between the two reporting periods. However, it is likely that such differences are more related to the inter-annual variability in the operation of the inshore trawl fisheries than attributable to the change in reporting regime.

The reporting of the (estimated) weight of species catches from individual trawls was limited to a maximum of 8 species for the TCER form and five species from the TCEPR form. ER has resulted in the more comprehensive reporting of trawl catches, with up to 15–20 species reported from some trawls. For the dominant species, there is no indication of a change in the reporting of the magnitude of (estimated) catches from individual trawls. However, the trawl catches of less important species were more frequently recorded following the introduction of ER. This change has the potential to introduce biases into the analysis of catch and effort data. The current “best practice”best practice of applying “two-stage”two-stage or “hurdle”hurdle models in the modelling of CPUE is likely to compensate for some of the changes in reporting, whereby changes in the indices from the positive catch model counter changes in the occurrence model. However, for lower tier species (species catch ranking 6–8) the change in reporting may significantly bias the CPUE models. These biases may be addressed, at least in part, by truncating the ER trawlbased catch data to approximate the level of catch reporting from the preceding period (i.e., limited to the top 5 or 8 species).The new reporting regime is also likely to have improved the reporting of the legally discarded catches, particularly for the non-QMS species, as indicated by an increase in the frequency of catch reporting via Disposal reports. These changes in the reporting of catch disposals are also likely to have improved the reporting of spiny dogfish and Schedule 6 species catches. These changes in reporting will need to be considered in future analyses of catch and effort data for those species.

Currently, there are four main e-logbook systems in operation in the inshore trawl fisheries. There was no indication that catch and effort reporting differed appreciably between the platforms. A more comprehensive appraisal of the various systems would require a review the specifications, operation, and instructions for each platform, although the technical details of each system were not available for the current study. Any future developments of the ER platforms need to be fully documented to enable an assessment of potential changes in the collection of catch and effort data from the trawl fisheries.

The introduction of electronic reporting (ER) of statutory catch, effort, and landings data across all New Zealand commercial fisheries has the potential to change the nature of the data collected and so disrupt the use of the statutory data in fisheries monitoring and management.

A period of parallel reporting of fishing effort, using the statutory paper forms while implementing early adoption of ER using one of the available reporting software platforms, was carried out with participation primarily from fishers active in the northern snapper (SNA 1) fishery. Twenty vessels actively participated in the trial, providing 294 vessel-days of parallel reporting data. After filtering ER events generated as a result of software testing, the trial dataset consisted of 461 matched fishing events reported via both the statutory paper regime and using the ER regime prior to its statutory adoption.

For trawl and bottom longline data, there were indications that electronic reporting was helpful in reducing transcription errors in event times and positions, because these were automatically captured by the reporting software. However, errors in fishing duration could still arise if fishing events were not recorded as starting or ending at the correct time, and the possibility of errors in gear and target species codes remained. Thus, checking and grooming of these fields as part of routine analyses will still be required.

A key result from the perspective of standardised catch per unit effort (CPUE) analyses was that there is no evidence of systematic change in the recording of fishing effort (duration, hooks) or estimated catches for either trawl or bottom longline fishing. It is likely that this was due to the maintenance of event-based data formats (i.e., individual trawls and longline sets) in the ER regime that are similar to the formats introduced to inshore fisheries via the paper-reporting regime in 2007/08.

For some other fishing methods, such as Danish seine, the changes in data format are more dramatic, requiring event-by-event reporting rather than daily aggregated data. However, in the SNA 1 area, Danish seine fishers were already reporting event-by-event data via the paper forms. Danish seine data are not currently used in New Zealand for generating CPUE indices, so changes in format are less material.

Overall, the study indicates no major concerns for the generation of trawl or bottom longline fishery CPUE indices with continuity across the change in reporting regime. However, although improvements in positional and event time data are evident, the possibility of data entry errors in other fields remains. Some subtle changes in recording may become apparent over time, due to fishers adapting to the new reporting methodology. There is evidence that fishers are making use of the ability to record estimated catches of more species using the ER system; this may improve the recording of smaller catch volumes and so reduce the difference between estimated catch totals and trip landings. The “real-time”real-time nature of ER data implies that further error checking and correction processes could be introduced to assist fishers in providing cleaner data, for example by rapidly querying unusual values. Nevertheless, checking and grooming of the input data as a key stage in fisheries data analyses will remain important.

This study encountered a number of challenges in participation and logistics that could be addressed in future studies. A key limitation is that only one ER software package was used in the trial, and the possibility remains that different ER implementations may result in differences in the submitted data. It should also be noted that the parallel reporting period used in this trial was necessarily limited in duration and coverage, and occurred at a time when the ER systems were still being finalised. In addition, parallel reporting as a technique has limits due to the risk that the reported data may not be fully consistent with the data that would be provided if the systems were operated alone (i.e., data from one report could be simply carried across to the other system). Thus, although this trial suggests that data for CPUE analyses can largely be considered as continuous through the change in reporting regime, ongoing awareness of the potential for changes in the nature of the data is required, in particular as part of data characterisations that support CPUE analyses.

An alternate-tow comparison of conventional mesh trawls and the inshore-specification Modular Harvest System (MHS) net was undertaken in the hoki fishery off the east coast of the North Island. Thirty-six tows, in eighteen matched tow pairs, were carried out. Tows within a pair fished the same tow line with the different gears. Alternate tows took place on subsequent days of the trial. Other than date, other effort-related parameters of the tows within the pair were matched as closely as possible. The experimental fishing took place over four trips in May-June 2020.

Length-frequency sampling was carried out for hoki, gemfish, and ling on each tow. When catch volumes were small the entire catch was measured, but larger catches were subsampled with a target sample size of 200 hoki or 100 fish of the other species. Catch data were collected via the vessel’s Electronic Reporting (ER) system with catch of all species recorded for experimental tows. The sampling was carried out by a Fisheries New Zealand observer, with data recorded using an electronic device (“YUMA”YUMA device) used by the observer programme. ER data were provided daily, and observer data were provided after each trip. This allowed trial progress to be monitored in “real-time”real-time and an assessment made of when adequate data had been collected. In general, trial logistics were successful, although there were some minor differences in catch data record-keeping and problems with exported data from the observer’s YUMA device that could be improved in future trials.

Data were analysed following the approaches developed by Chambers et al. (2021). Specifically, Bayesian generalised linear mixed models were used to fit catches with tow pair as a random effect. Analysis of the length data focused on proportional catch at length (“relative selectivity”relative selectivity) with uncertainty in the proportion caught by MHS assessed by bootstrapping. A key difference in the methodology was scaling the sample data to the tow weight, because it was not possible to measure all fish caught.

The MHS1480 was originally engineered for inshore fisheries where a minimum of 125 mm mesh is required. Catch rates of hoki were lower with the MHS than with the 100 mm mesh trawl that is the minimum standard in the fishery, but the difference was not significant at the 95% level. Catch rates of gemfish were significantly lower and there was also evidence that the first tow in a pair had a lower catch rate of gemfish. Catch rates of ling did not differ between the two gears.

The relative selectivity analyses indicated that the MHS caught significantly fewer hoki in the 65 cm to 85 cm range, although the differences in proportional catch at length were generally not significant after accounting for the difference in fishing power. After accounting for the reduced catch rates of gemfish, no differences in size selectivity for gemfish or ling were apparent between the methods.

This report provides an overview of electronic monitoring programmesfor New Zealand fisheries carried out during the 2016 to 2018 fishing years. These were delivered by seafood industry science provider, Trident Systems. The focus of this report is to provide a summary of the coverage achieved by the programmes, and to identify lessons learnt that may assist in the implementation of future programmes.

The report is structured as follows:Section 1 describes the information needs that led to the development of electronic monitoring systems by Trident, the key innovations that were pursued, and the trials carried out prior to the implementation of operational programmes from 2015;Section 2 documents the technologies and processes used to deliver the programmes and highlights some of the key lessons learned with respect to the system hardware;Section 3 characterises the snapper 1 (SNA 1) fleet, which was the core focus of the programmes;Section 4 documents the coverage achieved by the SNA 1 Vessel Monitoring System programme, which implemented tracking of all SNA 1 vessels;Section 5 documents the coverage, in terms of both footage obtained and footage reviewed, of the SNA 1 trawl video observation programme from 2016 to 2018, which focussed on quantifying the returns of snapper below the minimum legal size (MLS), denoted SNX, to the sea;Section 6 provides a trip-level comparison of the quantities of sub-MLS snapper estimated from the video observation process with vessel estimates;Section 7 documents the coverage of the “petrel project”petrel project in 2017 and 2018 which focussed on identifying seabird captures in inshore bottom longline fisheries in Fisheries Management Area (FMA) 1;Section 8 describes lessons learned in the operational logistics of the programmes, focussing on the SNA 1 trawl programme;Section 9 discusses the nature and management of data from video observation programmes;Section 10 summaries key coverage statistics and identifies key learnings from the implementation of the programmes.

The three key programmes successfully achieved a high level of coverage of the FMA 1 trawl and longline fisheries, introducing innovative monitoring technologies that have facilitated significant new data collection from these fisheries.

The SNA 1 Vessel Monitoring System provided tracking data from up to 80% of fishing events by the SNA 1 fleet. Because this figure excludes vessels that were able to provide tracking data to the Ministry for Primary Industries from existing tracking systems this represents a minimum bound on the coverage achieved.

The SNA 1 trawl video observation programme obtained footage from 33.6% of trawl events in FMA 1 during the 2016 fishing year. In the 2017 and 2018 fishing years, when the programme was fully operational, footage was obtained from 75.5% and 78.6% of FMA 1 trawl events, respectively. The focus of the programme was the SNA 1 fishery, but the nature of the fishery meant that the majority of the FMA 1 trawl fisheries were covered by the video observation programme, with the exception of the scampi fishery. Footage was selected for review using a randomised block design and, in the 2016, 2017 and 2018 fishing years, 15.5%, 23.9% and 21.1%, respectively of FMA 1 fishing events were included within the reviewed footage. The project has produced a rich dataset that deserves further analysis, but it is nevertheless clear that vessel estimates of SNX are broadly consistent with those made by video observation. Overall video observation estimates of SNX returns by SNA 1 trawl vessels exceeded vessel estimates by about 16.8%.For the 2017 and 2018 fishing years, the petrel programme obtained footage from 24.2% and 23.9%, respectively of FMA 1 bottom longline events, with 15.6% and 12.3% of events in the reviewed footage.

A range of “lessons learned”lessons learned are described, in the expectation that this will assist in the ongoing development and deployment of technological solutions that contribute to meeting fisheries management information needs.