Modelling sea lice control by lumpfish on Atlantic salmon farms: interactions with mate limitation, temperature and treatment rules

Abstract

Atlantic salmon farming is one of the largest aquaculture sectors in the world. A major impact on farm economics, fish welfare and, potentially, nearby wild salmonid populations, is the sea louse ectoparasite Lepeophtheirus salmonis. Sea louse infestations are most often controlled through application of chemicals, but in most farming regions, sea lice have evolved resistance to the small set of available chemicals. Therefore, alternative treatment methodologies are becoming more widely used. One increasingly common alternative treatment involves the co-culture of farmed salmon with cleaner fish, which prey on sea lice. However, despite their wide use, little is understood about the situations in which cleaner fish are most effective. For example, previous work suggests that a low parasite density results in sea lice finding it difficult to acquire mates, reducing fecundity and population growth. Other work suggests that environmental conditions such as temperature and external sea louse pressure have substantial impact on this mate limitation threshold and may even remove the effect entirely. We used an Agent-Based Model (ABM) to simulate cleaner fish on a salmon farm to explore interactions between sea louse mating behaviour, cleaner fish feeding rate, temperature and external sea louse pressure. We found that sea louse mating has a substantial effect on sea louse infestations under a variety of environmental conditions. Our results suggest that cleaner fish can control sea louse infestations most effectively by maintaining the population below critical density thresholds.

In lumpfish We Trust? The Efficacy of Lumpfish Cyclopterus lumpus to Control Lepeophtheirus salmonis Infestations on Farmed Atlantic Salmon: A Review

“…Another possible way of increasing the understanding of underlying causes of variation in the efficacy of lumpfish is to use biological modeling techniques to explore the interactive effect of lumpfish grazing and mate limitation on sea louse population dynamics under different environmental scenarios. McEwan et al [42] used an agent-based model (ABM) to simulate cleaner fish on a salmon farm to explore interactions between sea louse mating behavior, cleaner fish feeding rate, temperature, and external sea louse pressure. They found that sea louse mating has a substantial effect on sea louse infestations under a variety of environmental conditions.…”

Markers for Global Climate Change and Its Impact on Social, Biological and Ecological Systems: A Review

“…Temperature increases predator attack rate and reduce prey vulnerability (Pepi et al, 2018). Fluctuation in temperature severely affects reproductive behavior in animals due to mate limitation (McEwan et al, 2019). Thermal extremes effect growth in animals (Nishizaki & Carrington, 2015) and reduce offspring fitness in a cold-climate mainly in viviparous lizards (Cunningham et al, 2018).…”

Web‐based application to guide sampling on salmon farms for more precise estimation of sea louse abundance

“…To manage sea louse infestation on salmon farms, farm operators use a variety of methods (Overton et al 2019), including, among others, parasiticides to kill the parasites, fallow periods between production cycles where farms are emptied of fish to interrupt the parasite's life cycle, mechanical delousing to remove sea lice from salmon, and cleaner fish that feed on sea lice attached on salmon. In many instances, neighboring salmon farms adopt integrated pest management (IPM) to limit the exchange of sea lice among farms (Brooks 2009) and reduce external infestation pressure (McEwan et al 2019). The success and maintenance of these interventions are contingent on an accurate and precise surveillance system.…”

“…In many instances, neighboring salmon farms adopt integrated pest management (IPM) to limit the exchange of sea lice among farms (Brooks 2009) and reduce external infestation pressure (McEwan et al. 2019). The success and maintenance of these interventions are contingent on an accurate and precise surveillance system.…”