The changing war on sea lice: the rise of non-drug based treatments

Authors: Pietrak, Michael; BRICKNELL, IAN - University Of Maine

Submitted to: World Aquaculture Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2017
Publication Date: 2/20/2017
Citation: Pietrak, M.R., Bricknell, I. 2017. The changing war on sea lice: the rise of non-drug based treatments. World Aquaculture Society Meeting.

Interpretive Summary:

Technical Abstract: Sea lice are likely the single most economically costly pathogen that has faced the salmon farming industry over the past 40 years. Estimates of the global cost of sea lice to the industry have grown from $480 million USD in 2006 to $742 million USD in 2012. Not only has the cost to industry increased over time, but the tools for managing lice have evolved as well. Initially, fish were treated with the organophoshates trichlorfon and dicholrvos. Both of these chemotherapeutants have been replaced by a number of other chemotherapeutants due to environmental impacts and reduced efficacy. This second generation of lice drugs include a range of compounds including organophosphates, avermectins, pyrethroids, insect growth regulators and hydrogen peroxide. Many of this second generation of sea lice drugs have also shown signs of resistance over the past decade despite efforts to prolong their effective lifespans. During the 1990’s and 2000’s many farming regions adopted various forms of Integrated Pest Management Plans (IPMPs) in order prolong the life span of available chemotherapeutants. These initial IPMPs relied on tactics such as coordinated farm and bay wide treatments, use of cleanup treatments to reduce populations heading into winter and rotation of chemotherapeutant use where possible. In addition, growers responded to sea lice and other pathogen outbreaks with improved bio-security. The combination of biosecurity and IPMPs ushered in a host of new husbandry practices designed to minimize the spread of pathogens. Changes such as single year class stocking, reduced stocking densities, fallowing, and various bay management strategies all were introduced to help improve the general wellbeing and health of farmed fish. During this time one of the first non-chemotherapeutic, strictly lice management strategies was introduced; the use of wrasse as cleaner fish. The technique was relatively wide spread throughout European farming regions though not adopted on all farms. The rise of wide spread resistance and reduced efficacy of many of the current chemotherapeutants has lead an explosion of new research in non-chemotherapeutic ways to manage sea lice. New management tools include plankton net skirts, snorkel cages, additional species of cleaner fish, lice killing lasers, hot water baths, use of mussels, vaccines, functional feeds, and selective breeding to name just some new tools. The proliferation of new non-chemotherapeutic management strategies highlights the industries’ shifting strategy away from the historic strategy of using a few chemotherapeutic treatments towards IPMPs that encompass an ever larger and evolving set of non-chemotherapeutic management strategies. These new tactics bring a number of practical and economic challenges to the modern salmon farmer looking to effectively manage sea lice while maintaining or reducing the cost of production.