Science Centres: Aquatic Biodiversity and Biosecurity

NIWA scientists working with Auckland Regional Council staff to sterilise and clear gill nets at Lake Wainamu.

NIWA scientists, working with the Department of Conservation, commercial fishers, and regional council staff, have found a salty solution to the problem of how to effectively and conveniently sterilise freshwater fishing nets.

The nets must be sterilised to ensure fishers, researchers, and water managers don’t inadvertently spread pest fish and weeds. The standard method is air drying, but this usually requires nets to be laid out in a dry spot overnight – not ideal for damp conditions or when nets have to be re-used quickly.

DoC and the Foundation for Research, Science & Technology commissioned NIWA to test potential alternatives on key aquatic pests. The winning treatment: soak nets for one hour in concentrated saltwater (70 grams of salt per litre, or 1 part salt to 14 parts water by volume).

Susceptible pest fish species include catfish, goldfish, koi carp, gambusia, perch, rudd, and tench; susceptible aquatic weeds include curly pondweed, elodea, egeria, hornwort, hydrilla, and lagarosiphon.