World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 27 Incentives and Obstacles to Reducing Plastic Debris Waste management plans for handling and disposal of solid wastes are mandatory in only some countries and farmers are asked to identify high-risk activities and materials that may result in introduced waste or represent a hazard for people. Incentivizing such behavior may be necessary in areas where there are grandfathering advantages for early movers, although it may simply be regulated and enforced in regions where the industry is fully developed and organized and the resilience of the production sector will not be too strongly impacted. For example, pre- and post-storm checklists are an important consideration for cage and rope production at sea, identifying suitable gear and points of risk. As climate change is driving more intense and more frequent storms, however, this is a challenge that could be addressed by marking or tagging gear for identification when lost. This approach is currently being tested in the commercial fishing industry. There are lessons to be learned from the experiences of farmers who undertake inventories and activities such as post-storm checklists, to engender a cultural shift towards improved waste management. Typically, this is focused only on macroplastics and to date there are not similar dedicated regulations for microplastics. Although farmers are keen to address marine litter and plastic waste, microplastics are not generally of interest because they represent issues that are currently considered almost impossible to manage at the farm level. The limitations of recycling also represent a challenge for farmers. For example, plastic products used in aquaculture operations frequently contain chemical additives that cannot be handled by all recycling facilities or include biofouling that may limit the ability to recycle the material. Most recycled plastics from aquaculture operations will be repurposed into materials for the construction industry. Many countries currently lack capacity or access to recycling facilities and governments should consider ensuring that recycling capacity grows to meet increased demand from industries such as aquaculture. Actions to limit the use of plastic are of interest but all plastics cannot be removed from aquaculture operations without economically viable solutions as alternatives. To be successful, there is a need to bridge gaps between practitioners and regulators to ensure that industry needs are considered and the cost incurred by changes in operations are shared among all stakeholders. Biodegradable Plastic Alternatives for Aquaculture Although not a specific focus of the roundtable, delegates participating in discussions showed interest in the potential for bioplastics and degradable plastics in the context of aquaculture (as user or producer). This topic will need further discussion. From the perspective of sustainable development, there is a research and development focus on biodegradable plastics with additional potential for expansion into bioplastics. All over the world these solutions are now being explored. These plastics may be developed as part of recycling strategies and bioplastics may be produced from organic wastes or seaweeds. Such development allows production of plastics that are capable of degrading over a fewweeks. However, much more research is needed in this field to better understand the challenges and viability as an effective solution, especially with regards to supporting the necessary scaling up of such production and the evaluation of such products for use in aquatic environments. In many respects, there is a will from the aquaculture industry to use bioplastics and biodegradable plastics but the means is not yet there and much more research is needed to replace some of the non- replaceable plastics used nowadays. Although too much is unknown at this stage regarding the potential for alternative materials, if the industry can demonstrate a demand, there is scope for development and implementation of new engineering and technology solutions. Needed Research and the Path Towards Standardization The impacts of plastics on aquaculture production are complex, with animals affected differently depending on species, size and life stage of the farmed animal, size of the plastics and the mix of chemicals they may contain. Mesoplastics may not represent a risk to farmed aquatic animals because they are unable to pass alimentary and respiratory barriers because of their large size. However, aggregations of microplastics in the stomach and intestines can result in reduced nutritional state and scope for growth in some species but not in others. In contrast, a varied picture is presented by ultrafine micro- and nanoplastics that are able to cross the gut barrier and have been linked to changes in growth and tissue formation in some species. In addition, there is current debate surrounding the transfer to organisms of harmful chemical additives to plastics, including those no longer produced but still existing in plastics lost at sea and hydrophobic contaminants (e.g. polycyclic aromatic hydrocarbons; PAHs) already present in the natural environment that preferentially adsorb to plastics in the water column. Although there is the potential for these chemicals to be assimilated by an animal upon ingestion, this effect may be limited by the amount of time that the plastic is ( C O N T I N U E D O N P A G E 2 8 ) Examples of plastics debris collected as part of a Marine Clean-up Day organized by the Maritime and Port Authorities of Singapore. The southern areas of Singapore are not intensively farmed and and therefore most debris cannot be attributed to aquaculture (Photo: G. Drillet).