Download AEBR 364 Environmental Health Measures for Open Ocean Salmon Aquaculture – Identifying thresholds for sub-lethal responses in the context of wider ecosystem change

As finfish farming in Aotearoa New Zealand moves further offshore into more open and dynamic marine environments, there is growing concern about how waste from these farms affects the seafloor and the animals that live there. In particular, large shellfish and other seabed-dwelling animals (known as epifauna) play important roles in healthy marine ecosystems, but little is known about how they respond to waste from offshore salmon farms in Aotearoa New Zealand.

This report, part of the Environmental Health Measures for Open Ocean Aquaculture project, aims to better understand these effects by investigating how three key species – the horse mussel (Atrina zelandica), scallop (Pecten novaezelandiae), and a brachiopod or lamp shell (Neothyris lenticularis) – respond to increasing levels of organic waste from salmon farms. We measured a range of physiological responses in these species at different levels of seabed waste and looked at how their responses relate to one another and to current indicators used in salmon farm monitoring.

Key findings

⦁ Statistical analyses show the levels of organic enrichment that cause changes in physiological functioning in the three key species – and possibly early signs of stress.
⦁ Many of the measured responses were closely linked, suggesting that a smaller set of indicators could reliably detect wider changes in organism health.
⦁ The study shows how the health of the key species can be used as an early-warning signal for broader ecosystem impacts.

The Environmental Health Measures for Open Ocean Aquaculture project is an important first step in developing reliable, ecologically meaningful tools to assess and manage the environmental effects of open ocean aquaculture. Future studies should test to see how well the indicators work with other species and at different farm sites with varying levels of enrichment.