The 2022 stock assessment of pāua (Haliotis iris) for PAU 7

Most pāua (Haliotis iris) fisheries in Aotearoa New Zealand are managed with regular stock assessments that determine the stock status of a particular quota management area (QMA). Stock assessments are based on statistical models that estimate the current and projected stock status, and the exploitation rate of the portion of the population that is impacted by fishing.

The present assessment provides an updated assessment for QMA PAU 7, which was last assessed in 2016. The previous assessment found the stock to be near or below the soft limit, and the Total Allowable Commercial Catch (TACC) was subsequently reduced by 50% to allow the stock to rebuild. Shortly following this reduction, a large earthquake struck the Kaikōura region, affecting areas on the east coast of Te Waipounamu South Island that are within QMA PAU 7 (although this area did not form part of previous assessments). Following the earthquake, which caused large areas of uplift of intertidal and subtidal reefs above the high tide mark, the fishery within the affected area was closed; a further 10% of quota was shelved pending re-opening of the affected coastline for pāua fisheries.

The present assessment was initially carried out as single and multi-area assessments over sub-areas within QMA PAU 7. Areas in the initial assessment model were Cook Strait, Northern Faces (north coast Marlborough Sounds), and D’Urville Island. Due to the spatial closure following the earthquake, the east-coast component of the fishery was not assessed and is currently being monitored using dive surveys.

Models for sub-areas Northern Faces and D’Urville Island were only technically feasible under the assumption of low stock resilience (steepness). There is anecdotal evidence, corroborated by initial model runs, that these sub-areas are in an enduring state of low recruitment and low biomass with little sign of recovery. Nevertheless, the Shellfish Working Group concluded that the models are likely insufficiently informed about the cause of the lack of recovery. Therefore, the models were considered to be inadequate to support management advice for these sub-areas. There is currently little commercial catch in the Northern Faces and D’Urville Island sub-areas, suggesting that the lack or recovery may be due to environmental conditions or allee effects related to low spawning biomass. Neither of these phenomena can currently be informed with data in the assessment model.

The fishery was largely concentrated in the Cook Strait area, which has consistently been the largest component of the PAU 7 fishery. Although there have been relatively large reductions in overall catch from PAU 7 in recent years (i.e., post-2016), the concentration of fishing effort in Cook Strait has meant that overall take from the area has not been reduced proportionally. Nevertheless, the current status was estimated to still be below target, but CPUE and the fitted assessment suggested strong signs of rebuilding in this component of the fishery. This aspect was evident in the projected biomass suggesting a rebuild to target levels by 2026 under current catch levels of near 75 t per year under the agreed base case model. All model sensitivities confirmed this trend, with varying status estimates and rebuilding timelines depending on productivity assumptions.