Earthquake effects on abalone habitats and populations in southern New Zealand

Abstract

The 2016 Mw 7.8 Kaikōura earthquake lifted 140 km of coastline on New Zealand’s South Island by up to 6.4 m. This caused extensive mortality and destruction of habitat critical for early life stages of blackfoot abalone Haliotis iris (called pāua), a species of cultural and commercial importance. The fishery for pāua was closed, at considerable financial loss to local communities. This study determined the extent to which habitats and populations of pāua survived along the coastline. With aerial imaging, the coast was categorised into broad habitats at a 10 m scale. This was used to select areas for in situ assessments of pāua populations and specific habitat features at 26 sites over 1.5 yr. We quantified key habitat features to identify correlates and potential drivers of pāua abundance and distribution. We found that despite extensive habitat degradation from uplift, erosion and sedimentation, abundant pāua in size classes <30 mm shell length indicated that successful settlement and juvenile recruitment had occurred soon after the earthquake. Pāua up to 170 mm shell length also survived in shallow habitats. A generalized linear mixed model showed that pāua were negatively influenced by the degree of uplift, and positively associated with the cover of unconsolidated layered rocks. Juvenile pāua (<85 mm) abundance was greatest at sites with <2.5 m of uplift. There was further recruitment 1.5 yr post-earthquake and evidence of good growth of the previous year’s cohort. Despite major disruption to this coastline, there appears to be very good potential for recovery of pāua and the fishery.