Abstract
AbstractBiofouling 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.
Highlights
Net cleaning technology mostly relies on pressurised water expelled from rotating discs mounted onto a ‘cleaning rig’ that moves along the inside of pens and washes biofouling organisms off the nets (Fig. 1)
We describe and project the potential savings that the pursuit of improved biofouling management may achieve, over and above initial investments required to change from the current status quo
Strategy 3: grooming of nets without antifouling. This strategy is based on a net that can be cleaned at high frequency (‘groomed’) to prevent the maturation of the biofouling community and minimise the amount of material removed and released, including materials that may be harmful to the fish
Summary
Biofouling, the growth of organisms on submerged structures (Fig. 1), is a serious challenge for global marine salmon aquaculture (Fitridge et al 2012; Bannister et al 2019). Floerl reduce their delousing activity in the presence of biofouling as an alternative food source (Deady et al 1995; Eliasen et al 2018). This concern is possibly the strongest driver for biofouling mitigation on pen nets in Norway (Bouwman 2020). There is increasing uncertainty and controversy around the perceived interference of biofouling on cleaner fish performance (Eliasen et al 2018; Leclercq et al 2018) as well as the continuation of their use as control agents due to welfare concerns (Hjeltnes et al 2019; Mo & Poppe 2019) and poor demonstrated efficacy at full commercial scale (Barrett et al 2020; Overton et al 2020). The coordinated release of gametes during farming operations such as net cleaning can further facilitate their establishment in adjacent natural environments (Carl et al 2011; Mineur et al 2012; Simkanin et al 2012)
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