Salmon science

THE Talking Point on the salmon industry by Ian Johnston (Mercury, January 17) referenced research by the Institute for Marine and Antarctic Studies on the environmental interactions of salmon farming. This is a highly active area of research for IMAS, with more than 20 staff involved. The science we do is world-class and results are freely available to industry, government and community to enable discussion and decisions about the industry to be based on objective data.

Mr Johnston correctly notes that our research shows that salmon farming produces nitrogenous wastes which, in combination with other inputs into our waterways, can affect aquatic ecosystems.

However, the claim that “…eventually this causes a sudden catastrophic collapse in the ecosystem. All that is left is algal slime which does not support native fish communities” risks creating the impression that such an outcome is inevitable or has already occurred. Our research does not support either conclusion, in part because our data and results are used by industry and government to inform their efforts to avoid such outcomes.

Mr Johnson calls for a process of adjusting fish stocking levels to protect the marine environment surrounding fish farms. This process is in place and nitrogen outputs from farms are routinely monitored, with threshold levels for regulation based on IMAS science. This takes account of changes in water chemistry and the benthic ecosystem beyond the farm lease. If nitrogen outputs exceed these limits the government regulator requires farms to respond, including with destocking or adjusting feed inputs.

Professor Caleb Gardner IMAS Fisheries and Aquaculture

Centre