Download AEBR 344 Extent and intensity of bottom contact by commercial trawling in New Zealand waters, 1990–2022

This report presents the results of the updated trawl footprint in New Zealand waters within the Exclusive Economic Zone in waters open to trawling to a maximum depth of 1600 metres (fishable area).
Results are presented for the 1989–90 to 2021–22 fishing years for deepwater fisheries, and for the 2007–08 to 2021–22 fishing years for inshore fisheries, and combined inshore and deepwater (‘All stocks’) fisheries.
Statistics are presented on the measures of seabed contact for these groupings and include the area in square kilometres of the overall trawl footprints and aggregate (cumulative footprint) areas by year and all years combined. Other measures of contact also presented include the number of tows, the number of cells contacted (a 5 × 5 kilometre grid overlaid on the fishable area), and the number of ‘new’ cells contacted each year that had previously not been contacted.
This study also considered the above measures of contact when including midwater trawl used within five metres of the seabed and within ten metres of the sea bed. Methods were also developed to refine the placement of bottom-contacting trawl effort on underwater topographic features.
Results show that overall measures of contact have decreased in recent years for deepwater, inshore, and All stocks fisheries. Measures of contact increase little when including midwater trawl used within five metres and ten metres of the seabed. The development of methods to refine mapping of trawl effort to underwater topographic features shows promise but would benefit from external validation, perhaps through comparison with data held by the fishing industry.