Potential ecological and economic impacts of sea lice from farmed salmon on wild salmon fisheries Yajie Liu a, ⁎, Ussif Rashid Sumaila b , John Paul Volpe c a Department of Economics, Norwegian University of Science & Technology, Dragvoll University Campus, Building 7, Level 5. N-7491, Trondheim, Norway b Fisheries Economics Research Unit, Fisheries Centre, University of British Columbia, 2202 Main Mall, Vancouver BC, Canada V6T 1Z4 c School of Environmental Studies, University of Victoria, PO Box 3060 Stn CSC, Victoria, BC, Canada V8W 3R4 abstract article info Article history: Received 22 August 2010 Received in revised form 22 December 2010 Accepted 25 April 2011 Available online 12 June 2011 Keywords: Sea lice induced mortality Recruitment Discounted profit Pink and chum salmon Fixed harvest rate Fixed escapement policy This paper examines the possible ecological and economic effects of sea lice from salmon farms on wild salmon populations and fisheries. A bioeconomic model is developed incorporating an age-structured population dynamics model of wild pink and chum salmon with mortality caused by farm-derived sea lice. Our model incorporates capture fisheries under two management policy scenarios. Results suggest that the ecological and economic effects are minor when the sea lice induced mortality rate is below 20%, while they can be severe if the mortality is greater than 30%. Sea lice have greater ecological and economic impacts on pink salmon than on chum salmon. The impact of farm lice epizootics on wild salmon is greater under a fixed exploitation rate than under a target escapement policy. As a result, a precautionary principle should be adopted, and appropriate management schemes and policy strategies should be developed to minimize these effects. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Aquaculture has been the fastest growing food producing sector in the world over the last few decades. It is very likely that aquaculture will continue its growth in the future to meet potential increased global demand in seafood due to growing populations and preferences for healthy food such as salmon, but may not at a fast pace as expected (Liu and Sumaila, 2008). Being one of highly valuable carnivorous fish species, salmon has been commercially grown in several countries worldwide. The farmed salmon production has exceeded the wild salmon catch since 1998. According to FAO statistics, in 2008 the world farmed salmon production is about 1.5 million tons with a farmed gate value of 7.2 billion US dollars while the salmon production (also including trout and smelts) from wild capture is only 0.8 million tons. The environmental concerns associated with aquaculture such as pollution, disease spreading and escapees, however, may strike its future development. In the case of salmon aquaculture one of these negative externalities affecting its development is the impact of sea lice infection on wild salmon population and fisheries. The dramatic decline in pink salmon (Oncorhynchus gorbuscha) populations around the Broughton Archipelago, British Columbia (BC) in 2002 triggered a debate over the role of sea lice (Lepeophtheirus salmonis and Caligus clemensi) originating from salmon farms on wild salmon populations. Numerous studies have been conducted in both laboratory and field environments to explore the connections between farm-derived sea lice and wild salmon populations in BC (e.g., Beamish et al., 2006; Brooks, 2005; Brooks and Jones, 2008; Krkošek et al., 2005, 2006, 2007; Morton et al., 2004, 2008). Some argue that salmon farms intensify the level of sea lice in surrounding waters, leading to serious infection of wild juvenile pink and chum salmon, possibly resulting in increased mortality and declines in wild salmon populations (e.g., Krkosek et al., 2007, 2005, 2006; Morton et al., 2004, 2008; Morton and Routledge, 2005). Others claim that factors other than sea lice (e.g., ocean conditions) may play more important roles because these populations fluctuate widely on their own from year to year, and sea lice are natural parasites (e.g., Brooks, 2005; Brooks and Jones, 2008; Brooks and Stucchi, 2006; Noakes et al., 2000). Sea lice, including L. salmonis and C. clemensi, are naturally occurring parasites in the coastal marine waters of BC (Margolis and Arthur, 1979; McDonald and Mrgolis, 1995). Returning wild adult salmon such as pink, chum (Oncorhynchus keta), and sockeye (Oncorhynchus nerka) can carry high levels of adult sea lice (Beamish et al., 2005). Lice on farm salmon may not originate on the farm; rather, the farms may amplify those originating in the wild (Bakke and Harris, 1998; Beamish et al., 2005). Farmed salmon are typically reared in open net cages with no solid barriers to separate farmed salmon from the surrounding environment. The high density of salmon within the net cages ensures completion of the louse cycle, leading quickly to amplified pathogen concentrations within the farm and increased infection risks to nearby wild salmon populations (Krkošek et al., 2005, 2006; Morton et al., 2004; Noakes et al., 2002). Ecological Economics 70 (2011) 1746–1755 ⁎ Corresponding author. Tel.: +47 73 59 19 37; fax: +47 73 59 69 54. E-mail addresses: yajie.liu@svt.ntnu.no (Y. Liu), r.sumaila@fisheries.ubc.ca (U.R. Sumaila), jpv@uvic.ca (J.P. Volpe). 0921-8009/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolecon.2011.04.017 Contents lists available at ScienceDirect Ecological Economics journal homepage: www.elsevier.com/locate/ecolecon