Towards cost‐effective biofouling management in salmon aquaculture: a strategic outlook

Abstract

Biofouling is an ongoing challenge for marine salmon aquaculture, impacting farming operations, fish health and welfare. Current mitigation strategies employed in Norway and Scotland rely mainly on the use of antifouling coatings and reactive removal of biofouling. These approaches are not only costly and of limited efficacy, but also pose active risks and likely contribute to mortality of fish during grow‐out at sea. Given the inefficiencies of current biofouling management approaches and the industry’s objectives for growth and sustainability, a strategic assessment of future avenues for biofouling management is needed. We here present such an assessment and outline three novel biofouling management strategies that, once implemented, could facilitate improved fish health and welfare, reduced environmental impacts and benefits to the public perception of fish farming. These strategies are based on: (i) efficient antifouling coatings; (ii) antifouling combined with intermittent cleaning; and (iii) grooming of nets. We discuss the advantages, challenges and research and development needs associated with the realisation of these strategies. Drawing on experiences from agricultural systems and invasive species management, we show how the costs involved in the implementation of new strategies will over time be offset by the direct and indirect benefits arising from a reduction in environmental and fish health impacts and an increase in the industry’s social licence to operate.

Managing Biofouling on Submerged Static Artificial Structures in the Marine Environment – Assessment of Current and Emerging Approaches

“…Structures associated with aquaculture were most amenable to treatment, reflecting their size, the nature of farm activities that often allow structures to be treated when stock are temporarily absent from structures or sites, and possible removal to the water surface or land for treatment. It also reflects the significant amount of mitigation investment by this industry given the direct and quantifiable impacts of biofouling on their operations (Adams et al, 2011;Fitridge et al, 2012;Bloecher and Floerl, 2020). We note, however, that many permanent structures associated with aquaculture (such as anchors and pylons) face the same issues as other SSAS.…”

“…Determining whether SSAS management measures are cost effective is straightforward where direct benefits of managing biofouling accumulation can be quantified. For example, reduced biofouling could lead to increased yield or a superior product from a marine farm (Bloecher and Floerl, 2020). For a drilling rig or power plant, a greater number of operational days per year could be realized if delays or temporary shutdowns associated with biofouling impacts are avoided.…”

“…Similarly, Kostenko et al (2019) reported on the use of ROVs to inspect and clean vessel submerged surfaces using laser radiation. Remotely operated brush systems are used to remove fouling from finfish farm production nets (e.g., Bloecher and Floerl, 2020). It is reasonable to expect that systems could be developed to continuously inspect and clean other categories of SSAS.…”

“…Direct operational impacts are the primary driver of management to reduce the likelihood of these types of impacts. Bloecher and Floerl (2020) calculated direct biofouling management costs for a typical Norwegian salmon farm (eight production pens) to be US$420,000 to $493,600 per production cycle (excluding farm personnel costs), equating to 2.2% of production costs for individual sites. Biofouling species common to aquaculture structures can act as reservoirs and amplifiers of pathogens (Costello et al, 2021), which can impact stock or broader disease dynamics within a seascape.…”

“…A broad range of approaches has been used to manage biofouling growth on marine farm stock and infrastructure (Table 1), including the use of biocidal paints (de Nys and Guenther, 2009;Bannister et al, 2019), high pressure jets/power washing (Forrest and Blakemore, 2006), chemical sprays and dips (Denny, 2008;Guenther et al, 2011;Fitridge et al, 2012), encapsulation (Atalah et al, 2016), and removal for cleaning (e.g., cleaning of finfish farm predator nets). Physical and mechanical removal of biofouling are the main management approaches for shellfish aquaculture, while finfish operations tend to use antifouling coatings (e.g., copper-based paints), undertake regular net changes and/or cleaning and, in rarer cases, use biological control (Fitridge et al, 2012;Georgiades et al, 2016;Bloecher and Floerl, 2020).…”