Blue carbon accounting as metrics to be taken into account towards the target of GHG emissions mitigation in fisheries

Abstract

The adoption of the 2030 Agenda for Sustainable Development must address the balance between sustainable growth and tackling climate change. In this context, forests can help to reduce greenhouse gas (GHG) emissions, unfortunately, equivalent solutions in the ocean are often overlooked. Moreover, the complexity in determining the real impact of fishing on the environment is not a trivial issue. Thus, the aim of this study is to broaden the scope and analyse, for the first time, the entire carbon cycle associated with the life cycle of a fish: Scomber scombrus from a fishery located in the Cantabrian Sea (Spain). From this carbon cycle assessment, it is estimated that fishing activity has prevented 871.7 t of carbon (in terms of blue carbon) from being sequestered each year. This value comes from the fraction of fish that would have died of natural causes if they had not been caught, reaching the seabed, and undergoing remineralisation processes of the carbon content of their bodies. Beyond these results, it is vital to implement a series of actions with the aim of counteracting the amount of carbon that could have been sequestered on the seabed by the natural death of the fishes if they had not been caught. To this end, it is shown that the implementation of technical improvements to the vessels, the replacement of the current fuel used and the rearrangement of shipping routes in combination with an extension in the closed fishing season and a commitment to an omnivorous diet, allows for a reduction in carbon flow of almost 90 % of the blue carbon that has been prevented from being sequestered by fisheries. A consequential approach can then identify the influence of the proposed changes on their corresponding carbon flows for use as decision criteria in regulating fisheries and environmental management policies.