The aim of this project was to provide a summary on the use of salt supplementation of dairy cows to mitigate N leaching and nitrous oxide emissions and to recommend how salt supplementation could be incorporated into OverseerFM. The project confirmed that salt supplementation is most effective in reducing N leaching when used during autumn. It recommends that evaluating changes to the default N loading rate in OverseerFM be the next step.

MacGibbon, D.J.0F; Beentjes, M.P.; Escobar-Flores, P. (2024). Inshore trawl survey of Canterbury Bight and Pegasus Bay, April–June 2024 (KAH2402). New Zealand Fisheries Assessment Report 2024/87. 150 p.

This report presents results from the 15th east coast South Island inshore trawl survey in 2024, which continues a time series started in 1991.

The survey series covers the area from Waiau River to Shag Point, at depths from 30 to 400 metres (core strata), and estimates biomass for many species but is optimised for the target species: dark ghost shark, giant stargazer, red cod, spiny dogfish, sea perch, and tarakihi. Since 2007, four strata in depths from 10 to 30 m have been included in the survey to better cover the depth range of elephantfish and red gurnard, which were added as target species.

Data collected include length, weight, and maturity data for selected species, and collection of otoliths (fish ear stones) of the key species for ageing. 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 2024, 106 stations were successfully carried out. Almost all target and key non-target QMS species in 2024 declined in biomass from 2022, several of them substantially. For red cod, sea perch, and tarakihi, biomass estimates were the lowest in the time series, and for spiny dogfish, barracouta, lemon sole, and ling, estimates were the second lowest in the series. However, different target species show different biomass trends over the time series. Dark ghost shark shows an overall increasing trend. Elephantfish is variable through time. Giant stargazer has varied but is currently relatively high. Red cod has been decreasing over time. Red gurnard has been increasing with some variability. Sea perch shows no clear trend. Spiny dogfish has fluctuated but shows an overall declining trend. Tarakihi shows an overall declining trend. Overall, there was no evidence for extreme catchability in 2024 for the eight target species within the core plus shallow strata. A variety of trends is also seen for eight other key non-target species.

This SLMACC project followed on from a 25-year study of farm system impacts following land use and management change in the 260-hectare Mangaotama catchment farm (within the former Whatawhata Research Centre). The project has supported an improved understanding of the costs and benefits associated with land use and management change in pastoral hill country, occurring over time scales of multiple decades.