Moore, B.R.; Ó Maolagáin, C.; Spong, K. (2024). Commercial catch sampling for species proportion, sex, length, and age of jack mackerels in JMA 7 in the 2022–23 fishing year, with a summary of all available data sets. New Zealand Fisheries Assessment Report 2024/80. 37 p.

Jack mackerels support significant commercial fisheries in New Zealand, with over 75% of the total jack mackerel catch taken by trawl fisheries off the west coasts of the North Island and South Island, in the JMA 7 Quota Management Area. Three jack mackerel species are caught in New Zealand waters (Trachurus declivis, T. murphyi, and T. novaezelandiae) but commercial catches of jack mackerels are only recorded against the generic species code JMA. Therefore, species-specific catch information is not available from the fishery data. Estimates of proportions of the three Trachurus species in the catch, based on species code specific observer data are used to derive species-specific catch estimates from the JMA catch data.

This report updates the data collected by the New Zealand observer sampling programme from trawl landings of jack mackerels in JMA 7 with the data collected during the 2022–23 fishing year, including estimates of species proportions and the ratio of males and females in the landings, as well as the numbers caught by length and age.

Estimated proportions of catch by species based on observer data have historically shown that T. declivis comprises 61–73% of the catch for all statistical areas, followed by T. novaezelandiae at 21–33%, and T. murphyi at 2–8%. In 2022–23, proportions of T. declivis, T. novaezelandiae, and T. murphyi were 64%, 36%, and less than 1%, respectively.

In 2022–23, sampled T. declivis and T. novaezelandiae were close to a sex ratio of 1:1 while sex ratios for T. murphyi were skewed towards females (54%).

For T. declivis and T. novaezelandiae, observer data indicate decreasing proportions of larger and older fish in the commercial catch in recent years, whereas the length and age data for T. murphyi indicated the catch mainly comprised large, older fish, with very few observations of younger fish.

Beentjes, M.P.; Miller, P. (2024). Relative abundance, size and age structure, and stock status of blue cod off Motunau in 2024. New Zealand Fisheries Assessment Report 2024/79. 54 p.

South Island recreational blue cod (Parapercis colias) fisheries are monitored by Fisheries New Zealand using potting surveys. This report describes the results of the blue cod potting survey carried out off Motunau in North Canterbury during January 2024 – as well as for three previous surveys (2012, 2016, 2020). Estimates are provided for population abundance, size structure from fish length, and age structure from otoliths (ear bones collected for ageing), as well as population sex ratio, total mortality, and fishing mortality. In 2024 the sex ratio was 74% male, and the estimated fishing mortality was nearly four times the target reference level indicating that overfishing is occurring. Survey mean catch rates showed a progressive decline over time, dropping by 66% between 2012 and 2024. The sex ratio over the four surveys was dominated by males with no trend (i.e., 72–76% male). Fishing pressure has been concentrated on just a few older ages, and was considerably higher than the target reference for all the previous surveys.

Beentjes, M.P.; Page, M. (2024). Relative abundance, size and age structure, and stock status of blue cod off Kaikōura in 2023. New Zealand Fisheries Assessment Report 2024/78. 61 p.

South Island recreational blue cod fisheries are monitored by Fisheries New Zealand using potting surveys. The results of the Kaikōura surveys are important for assessing the status of the blue cod stock in this region.

This report describes the results of the random-site blue cod potting survey carried out in Kaikōura in December 2023 and compares these with the four previous surveys.

The length frequency distributions and mean length were generally similar among the five surveys. Survey mean catch rates show a progressive decline over time, dropping by 49% between 2011 and 2023. The sex ratio over the surveys was 47–60% male with indications that males are becoming more common in the population. The estimated fishing mortality (F) in 2023 was nearly double the target reference of F = 0.15 indicating that overfishing is occurring.

The catch rates of blue cod caught in the Hikurangi Marine Reserve over three surveys (2017, 2019 and 2023) indicate that abundance has not changed much over this period, and while greater than adjacent strata, abundance was only about one quarter of that in other parts of the survey area outside the reserve. Size of fish in the Marine Reserve was also not larger than in other parts of the survey area, but blue cod were of better condition.

Stevens, D.W.; Ballara, S.L.; Maurice, A.; Escobar-Flores, P.C.; Yeoman, J. (2024). Trawl survey of hoki and middle depth species on the Chatham Rise, January 2024 (TAN2401). New Zealand Fisheries Assessment Report 2024/77. 119 p.

The 28th trawl survey in a time series to estimate the abundance of hoki and other species on the Chatham Rise was carried out from 4 January to 3 February 2024. A total of 131 bottom trawls were successfully completed.

The estimated abundance of all hoki was about the same as the estimate from the previous survey in January 2022, while the estimate of juvenile (2 year old) hoki was average for the time series. The estimate of the youngest (1 year old) hoki was one of the lowest in the time series, suggesting this year class (fish born in 2022) was weak. The estimated abundance of hake increased by 26.5% from that in 2022 and was the highest estimate since 2009. The abundance of ling was about the same as in 2022 and the time series for ling shows no overall trend.

Most hoki were aged less than 5 years. Hake and ling ages were broad, with most hake aged between 4 and 13 years and most ling between 3 and 16 years old.

Acoustic data were collected throughout the trawl survey. The acoustic estimate of mesopelagic fish abundance (thought to be an index of the amount of food available to hoki) in 2024 was 13% lower than that in 2022, and below the average for the acoustic time-series (since 2001).