Sustainable production and use of cleaner fish for the biological control of sea lice: recent advances and current challenges

Abstract

Currently, cleaner fish are one of the most widely used sea lice control strategies in Atlantic salmon aquaculture. Two species are currently being farmed in North Atlantic countries, ballan wrasse () and lumpfish (), and the sector in most countries is rapidly expanding towards self-sufficiency. The species are very different both in terms of their biology and life histories and, consequently, production and husbandry methods must be tailored to each species. There are numerous health challenges currently experienced in both species, with bacterial and parasitic diseases being the most prevalent, and cohabitation with salmon may increase the risk of disease. Good husbandry and routine health monitoring are essential, although treatment is often required when disease outbreaks occur. Ballan wrasse and lumpfish are both proven to be effective salmon delousers, although delousing efficacy can be variable in farmed fish; the provision of suitable habitat and acclimation to net-pen conditions may encourage natural behaviours, including delousing, and the use of operational welfare indicators can highlight potential welfare issues. Cleaner fish research is progressing rapidly, although much of the basic knowledge regarding the species' biology remains unknown. The simultaneous domestication of two new marine aquaculture species is a significant challenge demanding sustained effort and funding over a prolonged period of time. Research must focus on enhancing the robustness of the farmed stocks and increasing hatchery outputs to meet the urgent demands from the salmon sector and protect wild stocks from overfishing.

Health assessment of the cleaner fish ballan wrasse Labrus bergylta from the British south-west coast

“…Widely used chemicals for the removal of lice, such as the orally administered emamectin benzoate, marketed as SLICE ® , and bath-administered hydrogen peroxide H 2 O 2 , are showing reduced efficacy (Jones et al 2013, Helgesen et al 2015, and in recent years attention has shifted to biological control using cleaner fish, in particular wrasse (Labridae spp.) and lumpfish Cyclopetrus lumpus L. (Brooker et al 2018a).…”

Vibrogen‐2 vaccine trial in lumpfish (Cyclopterus lumpus) against Vibrio anguillarum

“…Sea–lice is the greatest health challenge limiting production of the Canadian Atlantic salmon ( Salmo salar ) aquaculture industry since the 1970s (Brandal & Egidius, ; Fisheries & Oceans Canada, ; Mustafa, Rankaduwa, & Campbell, ; Nilsen, Nielsen, Biering, & Bergheim, ; Powell et al, ; Torrissen et al, ). Sea–lice is a copepod ectoparasite (Aaen, Helgesen, Bakke, Kaur, & Horsberg, ; Hamre et al, ; Nilsen et al, ; Wootten, Smith, & Needham, ) that immune compromises the fish host, increasing susceptibility to viral and bacterial infections (Brooker et al, ) and causing significant losses and high treatment costs (Costello, ; Fisheries & Oceans Canada, ). It has been estimated that sea–lice infection results in up to a 16% reduction in production biomass, which is approximately equivalent to a 9% loss in farm revenues (Abolofia, Wilen, & Asche, ).…”

“…Lumpfish, a native fish to the North Atlantic Ocean, perform well in cold environments (Imsland et al, ; Reynolds, Eliassen, Elvergård, Foss, Vikingsstad, & Imsland, ) and are the most common farmed and utilized cleaner fish species in the North Atlantic region (Boyce, Ang, & Prickett, ). Commercial production of lumpfish has grown exponentially in the last few years (Brooker et al, ; Powell et al, ), and in Newfoundland, Canada, lumpfish aquaculture has become an emergent industry (Boyce et al, ).…”

“…Bacterial diseases are the primary challenge for lumpfish delousing performance and survival rates at sea cages (Brooker et al, ; Powell et al, ). The most frequent bacterial pathogens affecting lumpfish are Vibrio anguillarum and Aeromonas salmonicida (Gulla, Sorum, Vagnes, & Colquhoun, ; Hedeholm, Blicher, & Grønkjær, ; Ronneseth, Haugland, Colquhoun, Brudal, & Wergeland, ).…”

“…Aquaculture losses due to V. anguillarum have been reaching magnitudes as high as 100% (Austin, Austin, Sutherland, Thompson, & Swings, ; Larsen, Pedersen, & Dalsgaard, ; Reynolds, ). V. anguillarum was first isolated from infected eels during 1909 (Naka & Crosa, ) and since then has been reported in several fish species, including lumpfish (Brooker et al, ; Hickey & Lee, ). V. anguillarum outbreaks in lumpfish have been detected in Scotland, Norway and Canada (Breiland et al, ; Gulla et al, ; Marcos‐Lopez, Donald, Stagg, & Mccarthy, ; Powell et al, ; Vasquez et al, ).…”