Sea lice is the name given to a wide range of marine parasitic copepods in different parts of the world. In the UK, we use the term for species belonging to the caligid genera Lepeophtheirus and Caligus. They are naturally found as parasites of many fish species and can cause serious damage to the fish host and even mortality if infection levels are high. I
n Scotland, Ireland, Norway, Canada and Chile, infection of fish in cage culture and the costs associated with managing infection levels continues to be a huge economic burden to the industry and an emotive issue due to environmental concerns. Some caligid species cause many problems to fish culture in other parts of the world. For example, Caligus orientalis is one of the most important pathogens of brackish water farms in East Asia.
The Parasitology Research Group of the University of Stirling and our Marine Environmental Research Laboratory have maintained a programme of continuous research in order to tackle the issues met by the aquaculture industry. Aspects of sea lice biology, morphology, life-cycle, genetics, pathology and management have been studied by our researchers and students. 
Many control measures and treatments used by industry were first pioneered , developed or assessed by the group and include single year class stocking, fallowing and the use of chemotherapeutants such as hydrogen peroxide, emamectin benzoate (Slice® Intervet Schering Plough), azamethiphos, teflubenzuron, diflubenzuron and cypermethrin.
In recent years the industry has become increasingly reliant on the relatively few available licenced treatments that are now available for treating sea lice. This has led to concerns of resistance emerging in sub-populations of lice to these treatments. Our ongoing work is looking at this problem with industry partners to confirm the existence of resistance, to identify the mechanisms and to develop alternative treatments and management solutions.
To enable the testing of potential new products against sea lice, we maintain our own population of Lepeophtheirus salmonis, the sea louse responsible for causing the most problems in European mariculture, within our marine facilities. We have developed in vitro techniques and in vivo challenge models to specifically test the actions of chemotherapeutants against sea lice. Our lice were originally taken from a site where no treatments had been used and have been maintained through many generations without treatments in order that they can be considered naïve to potential parasiticides.