Choosing best practices for managing impacts of trawl fishing on seabed habitats and biota

Abstract

Bottom trawling accounts for almost one quarter of global fish landings but may also have significant and unwanted impacts on seabed habitats and biota. Management measures and voluntary industry actions can reduce these impacts, helping to meet sustainability objectives for fisheries, conservation and environmental management. These include changes in gear design and operation of trawls, spatial controls, impact quotas and effort controls. We review nine different measures and actions and use published studies and a simple conceptual model to evaluate and compare their performance. The risks and benefits of these management measures depend on the extent to which the fishery is already achieving management objectives for target stocks and the characteristics of the management system that is already in place. We offer guidance on identifying best practices for trawl‐fisheries management and show that best practices and their likelihood of reducing trawling impacts depend on local, national and regional management objectives and priorities, societal values and resources for implementation. There is no universal best practice, and multiple management measures and industry actions are required to meet sustainability objectives and improve trade‐offs between food production and environmental protection.

Sustainable Exploitation of Dominant Fishes in the Largest Estuary in Southeastern China

“…As estuarine benthic species, A. hexanema and C. abbreviatus showed a wide niche breadth and high competitiveness in the Min River Estuary [20]. However, in recent years, the extensive use of bottom trawls seriously damaged the population, as well as the seabed environment [56]. Responsive management strategies should be implemented immediately before the population collapse of these species.…”

Impact of bottom trawling on sediment biogeochemistry: a modelling approach

“…Additionally, largest impacts occurred when increasing the trawling frequency from 0 to 1 trawling event per year, and the response of mineralization processes to increased trawling frequency was often non-linear, making them more difficult to predict. This would imply that management strategies aimed at maintaining the ecosystem functions provided by shelf sediments should be focused on spatial controls, bottom impact quotas, and effort control, rather than on technical improvements to the trawling gear that per definition require contact with the bottom to catch commercially viable target species (McConnaughey et al, 2020). An effective strategy limits the impacted surface area, and allows carbon stocks and faunal communities in the sediment to recover from a disturbance, resulting in the recovery of vital biogeochemical functions such as denitrification and carbon burial.…”

“…To reduce fishing impacts, alternative bottom trawl gears such as pulse fishing gears are being investigated (Van Marlen et al, 2014;McConnaughey et al, 2020). With pulse gears, the heavy tickler chains are replaced by electrodes, which emit electrical pulses that induce a cramping response in flatfish (Soetaert et al, 2015).…”

Effects of pollution on marine organisms

“…Gorgonian coral species in canyon systems of the western Ligurian Sea (northwestern Mediterranean Sea) were found to be negatively impacted by one or more types of derelict fishing gear, with fishing nets causing the greatest impact at most study sites (Giusti et al, 2019). McConnaughey et al (2019) reviewed nine different management measures and voluntary industry actions to reduce adverse impacts from bottom trawl fishing and found that risks and benefits of such efforts depend on the specific fishery and the characteristics of the ecosystem; no universal best practice was apparent due to the diversity of policy drivers that influence the management of fisheries and their environmental impact. In the Northwestern Hawaiian Ridge and Emperor Seamounts, despite significant evidence of adverse impacts from decades (1960s-1980s) of bottom trawling and coral tangle net fishing including scarred hard bottom habitat, coral rubble, and lost fishing gear, Baco, Roark, and Morgan (2019) reported multiple signs of recovery in benthic seamount communities that have been protected for more than 30 years.…”