The impact of mobile demersal fishing on blue carbon in seabed sediments:Fisheries Industry Science Partnerships scheme (FISP) report

Seabed sediments are one of the largest stores of organic carbon, and as such are an important stock of natural capital as this process aids in carbon sequestration. Recent scientific papers have raised concern over the potential impacts of mobile bottom gears on sediment carbon, suggesting that bottom trawling leads to a remineralisation of this organic carbon, and therefore reducing net uptake of CO2 from the atmosphere. Empirical data on the effect of bottom fishing on seabed organic carbon and its potential to be mineralised are mixed in outcome, and so more empirical data in needed from a range of fishing gears and habitat types to fully inform any potential management decision. In April 2023 experimental fishing was conducted by a beam trawler and scallop dredger off the southwestern coast of England to measure how, and if, organic carbon in the sediment is affected if resuspended and subsequently remineralized. We found no clear evidence of reduction in organic carbon due to trawling and dredging in the low carbon (mean 0.13 % Corg), coarse sediments (sandy gravels) of the study area. Potential signals of sediment resuspension were observed, but no consistent or significant signals of clear organic carbon resuspension and remineralisation from the carbon and nutrient analysis on water samples were found. We suggest that the underlying sedimentary environment results in low organic carbon content with naturally high remineralisation rates, which made the experimental fishing conducted limited in its potential direct effect on sedimentary carbon and remineralisation, and the ability of detecting any potential fishing effect difficult to detect

Workshop on Assessing the Impact of Fishing on Oceanic Carbon (WKFISHCARBON; outputs from 2023 meeting)

Rapports Scientifiques du CIEM. Volume 6, nº 12The Workshop on Assessing the Impact of Fishing on Oceanic Carbon (WKFISHCARBON) was set up to provide ICES and stakeholders with a summary of knowledge on the role of fishing in the process of carbon budgets, sequestration and footprint in the ocean. The workshop addressed the potential impact of fishing on the biological carbon pump (BCP), the possible impacts of bottom trawling on carbon stores in the seabed, as well as considering emissions from fishing vessels. The overall aim was to generate proposals on how to develop an ICES approach to fishing and its role in the ocean carbon budget, and to develop a roadmap for a way forward. The main findings were that knowledge of the BCP in the open ocean was reasonably well developed, but that key gaps existed. In particular, information on the biomass of mesopelagic fish and other biota, and of some of the key processes e.g. fluxes and fish bioenergetics. Knowledge is much weaker for the BCP in shelf seas, where the bulk of fishing occurs. In particular, while biomass of fish was often well quantified, unlike the open ocean, the understanding of the important processes was lacking, particularly for the fate of faecal pellets and deadfall at the seabed. There is extensive scientific knowledge of the impact of fishing on the seabed, but what is un-clear is what it means for seabed carbon storage. There have been numbers of studies, which give a very divided view on this. There has also been open controversy about this in the literature. Physical disturbance to the seabed from fishing can affect sediment transport and has the potential to facilitate remineralization, but precise impacts will depend on habitat, fishing métier, and other environmental factors. From this, it is clear that more research is needed to resolve the controversy, and to quantify the impacts from different fishing gears and on different substrates or habitats in terms of carbon storage. There has been much more research on minimizing fuel use by fishing vessels, and hence emissions, but this has mainly focused on fuel efficiency, fuel use per unit of landed catch, and less on the total emissions. Baselines for fuel use are available at the global level, but are lacking at the national and vessel level. There is a need for standardization of methodologies and protocols, and for improving the uptake of fuel conservation measures by industry, as well as for improving the uptake of existing and potential fuel conservation and efficiency measures by industry. Finally, a roadmap was proposed to develop research and synthesis, on the understandings of the processes involved, the metrics and how to translate this into possible advice for policy-makers. To that end, a further workshop was proposed in 2024.info:eu-repo/semantics/publishedVersio