A machine learning algorithm was developed to analyse underwater videos and to detect the presence of macroalgae. Three habitat-forming algae Ecklonia radiata, Lessonia variegate, and Carpophyllum spp. were successfully identified. The machine learning models can be readily applied to ongoing monitoring programmes to rapidly determine and map the distributions of key macroalgal indicator species along coastlines. Monitoring data are critical to documenting changes in our coastal communities.

A descriptive analysis of the catch and effort data for hake on the Chatham Rise (HAK 4 and part of HAK 1) and standardised CPUE analyses for the Chatham Rise hake fishery from 1989–1990 to 2018–2019 are presented. CPUE indices for eastern Chatham Rise and whole-of Chatham Rise showed decreasing trends until around 2012 after which there was an increasing trend. The western index gave an initial increasing trend.

The 26th trawl survey in a time series to estimate the relative biomass of hoki and other species on the Chatham Rise was carried out from 4 January to 3 February 2020. Estimated biomass of hoki in core (200–800 m) strata was 89 557 t (CV 14.4%), a decrease of 27% from 2018. This decrease was largely driven by a low biomass estimate for 2+ (2017 year-class) hoki. The biomass of 1+ hoki (2018 year-class) was relatively high while the biomass of hoki ages 3+ years and older increased by 26%.

A statistical model is proposed to estimate the catch efficiency (the proportion of fish biomass within the gear affected area that is retained by that fishing event) from catch-effort data for multiple fisheries and gear types operating simultaneously throughout the New Zealand EEZ. The model was applied to nine fish species to provide estimates of the catch efficiency for each species and gear type.

This report documents the age determination protocol for ling (Genypterus blacodes). It describes the most recent scientific methodologies used for otolith preparation and interpretation, ageing procedures, and the estimation of ageing precision. Digital images of otolith sections illustrate the zone interpretation used to determine fish age. Difficulties and idiosyncrasies related to ageing prepared otoliths are also documented.

A collation of published references (for 1769 to 2015) on the identity and biology of New Zealand marine fishes, their fossil and archaeological record, and the commercial and recreational fisheries they support. Accounts of resource ownership and fisheries management are also covered. The bibliography has four components: a systematics section (by species); the references; appendices for University theses, Parliamentary papers, and ‘Museum Marine File’ articles; and subject and name indexes.

This report documents activities, timing, samples, and data collected during the two-week survey in August 2020 to continue the Chatham Rise seamount recovery survey series. The survey used primarily a towed camera system with high definition digital video and still cameras. It focused on the Graveyard seamounts (55 camera transects), but survey work was carried out also on seamounts in the Andes area (24 camera transects, 3 epibenthic sled tows), and Epilogue Seamount (1 camera transect).

Quantifying and understanding current and historic changes in commercial trawl gear selectivity is important for both effective use of CPUE indices, as well as assisting with innovation in fisheries to improve selectivity and reduce unwanted bycatch. This report details the outcomes of a desk-based study of trawl gear information currently available, and a workshop held in June 2019 to determine what attributes should be collected from fishers to better understand trawl selectivity.

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Seafood NZ, Eagle Technology House: 0930 – 1430