Fon, A., Thomson, S., Purvis, E., Marulli de Barletta, C., & Voice, R. (2022 ). Mud crab sustainability: Avon Heathcote Estuary Ihutai.

Commissioned by the Avon-Heathcote Estuary Ihutai Trust, this research project investigated the sustainability of the mud crab species; Halicarcinus whitei, Hemiplax hirtipes, and Helice crassa in Te Ihutai estuary. This was important because climate change induced sea level rise poses a significant risk to estuarine habitats in Te Ihutai and across the world. Without action, the inundation of mud crab habitat could cause the local extinction of these three species. The aim of this project was therefore to answer the research question: ‘What are the Avon-Heathcote estuarine margin conditions and are they suitable for mud crab retreat in the face of climate change?’.

To answer this question, the researchers used a combination of sediment sampling, GIS analysis, literature review, and reported sightings to determine the current estuarine margins, determine habitat preferences of each crab species, and make predictions about future suitable habitats. Overall, they found that the current estuarine margins provided suitable habitat for each crab species, and that the main limiting factor in habitat suitability was the presence of infrastructure and tidal zones dictating where mud crabs could migrate to. Consequently, it was recommended that future research consider how mud crabs might naturally reach new habitats in the future and whether human action will be required to help crabs migrate to new habitats.