The environmental impacts of pelagic fish caught by Scottish vessels
Introduction
The direct effects of climate change are already apparent, e.g. crop failures due to adverse weather conditions (Lizumi and Ramankutty, 2015), increasing sea levels (Nicholls and Cazenave, 2010), species distribution shifts (Dulvy et al., 2008) and pollinator decline (Kerr et al., 2015). The need to limit the global temperature increase to 1.5 degrees C has become a worldwide imperative (IPCC, 2018). This has resulted in growing scientific and political pressure to reduce global greenhouse gas (GHG) emissions in an effort to mitigate the adverse effects and keep the net warming of the planet below 1.5 C° (UN, 2018). Consequently, there has been international co-ordination to meet this goal, as is evident from recent large-scale international pledges and agreements to mitigate emissions, such as the Paris Agreement (UNFCCC, 2015).
Food-related GHG emissions are responsible for approximately 20–30 % of all anthropogenic global GHG emissions, with 14.5 % attributed to livestock alone (Garnett et al., 2016). As a result, there is growing interest in identifying climate smart food production (Klytchnikova et al., 2015) and a desire to quantify and reduce GHG emissions related to agriculture, fishing and aquaculture (Audsley et al., 2009; Garnett, 2011; Smith et al., 2013). GHG emissions are estimated by life cycle assessment (LCA) (Avadí and Fréon, 2013; Garnett, 2014; Nijdam et al., 2012), whereby standardised techniques are used to estimate the climate-related and environmental impacts of a system or product, and to identify the main contributing factors. This standardised approach allows for greater comparability of the environmental impacts of different food products and helps to identify strategic options for food policy and for working towards the goal of net zero carbon emissions.
An important food source worldwide, seafood from both wild capture fisheries and aquaculture accounts for approximately 17 % of the global population’s dietary animal protein intake (FAO, 2018). For over two fifths of the world’s population this figure increases to 20 % of dietary animal protein intake (FAO, 2018). Improving fishing technology, such as the use of sonar to locate fish schools as well as improvements in fishing gear and engine design, has resulted in increasing quantities of seafood being harvested with decreasing effort and reduced danger to those involved. This expansion has not come without its own problems (e.g. the collapse of commercial fisheries, Myers et al., 1997), resulting in changes in the behaviour of apex predators (Estes et al., 1998), and extreme ecosystem shifts caused by the collapse of a food web (Pandolfi, 2005). As such, there are now safeguards in many countries to minimise the negative impacts of fishing and create sustainable and well managed fish stocks and stable marine environments (for example, national and international fishing quotas, no-take zones).
However, as the population continues to increase there is growing pressure on fisheries and all other food systems to continue to meet demand (Garcia and Rosenberg, 2010; Godfray et al., 2010). Given the projected population growth by 2050 and the commitment to meeting the UN sustainable development goals (UN, 2019), strategies for climate smart food systems need to be identified and developed. Climate smart food systems are those which meet the following criteria: they are either carbon neutral or relatively low in GHG emissions, they are resilient against climate change and extreme weather events and they have the ability to be sustainably increased to meet growing demand (World Bank Group, 2015).
The contribution of marine and freshwater food production systems to a nation’s carbon footprint (CF) has been historically overlooked in global and national estimates. However, aquatic systems are now the focus of interest for many studies seeking to quantify the CF and other environmental impacts of various seafood products worldwide (Hilborn et al., 2018). A recent review by Parker et al. (2018) concluded that only 4 % of emissions from global food production can be attributed to fisheries. This is in sharp contrast to approximately 60 % of emissions from livestock (Garnett et al., 2016) though it should also be noted that considerably more terrestrial meat is eaten than fish worldwide. These comparisons highlight the importance of wild capture fisheries for contributing to climate smart food production. Considerable variation is observed between different fisheries, with fish species, fishing method, and region all known to have an effect on the CF of a particular species (Hilborn et al., 2018; Parker et al., 2018). Currently, there is a basic need for region-specific CF data for the most commercial fisheries.
LCA is the widely accepted methodology used to quantify the full environmental effects of seafood production from cradle (beginning of life cycle) to grave (disposal or recycling), or any subset within. Interest in LCA and carbon profiling in the seafood industry began in the late 1990s and early 2000s (e.g. Thrane, 2004; Ziegler et al., 2003). In the early years a lack of standardisation resulted in considerable variation in methodologies which made cross-comparison between studies difficult. Since then, the publication of the International Standard series 14000, e.g. 14,040 and 14044, (International Organisation for Standardisation, 2006a, b), specific guidelines (BSI, 2012), as well as general agreement within the scientific community has helped to Improve the issue of comparability. Two components of comparability are those of consistent system boundaries (the aspects of the product life cycle included in the assessment) and allocation (the term used for the partitioning of environmental impacts between products and co-products). Current approaches in LCA allow specific comparisons to be facilitated by using consistent system boundaries and offering guidelines towards details such as the issue of allocating emissions between co-products. There are two general types of LCA: attributional LCA (ALCA) and consequential LCA (CLCA). ALCAs are the most common and report a system’s impacts at a given point in time, whereas CLCA explores possible changes in a system which may potentially alter impacts.
LCAs that have previously been undertaken for modern fisheries generally indicate that the capture process is the single most significant factor contributing to emissions over a product’s entire lifespan (Avadí and Fréon, 2013; Hilborn et al., 2018), though its significance varies from fishery to fishery (Ziegler and Valentinsson, 2008). This variation is strongly related to the use of fuel during fishing (Hospido and Tyedmers, 2005; Parker et al., 2018) and general fishing efficiency (Ziegler and Valentinsson, 2008). Because of the importance of fuel economy on the GHG emission rate, influencing factors (such as the fishing method) can also have a large effect on a fishery’s CF and other environmental impacts (Thrane, 2004; Tyedmers, 2000; Tyedmers et al., 2005; Vázquez-Rowe et al., 2010). Other studies have identified refrigeration leakage as also being of significance, particularly in the category of CF or Global Warming Potential (GWP) as it is often referred to in LCA papers (Vázquez-Rowe et al., 2010; Ziegler et al., 2011). The link between fuel usage and fishing efficiency also can be credited with the connection between environmental impacts and fishing method. Several studies have highlighted that efficiencies in catch rate vary across fisheries and gear types (Madin, 2015; Parker and Tyedmers, 2014). In some cases these can vary markedly even between geographically close regions (Iribarren et al., 2011; Ramos et al., 2011).
Small pelagic fisheries are generally considered to be one of the lowest impact fisheries, with purse seining often highlighted as being the most fuel efficient fishing method (Hilborn et al., 2018; Parker et al., 2018; Parker and Tyedmers, 2014). The pelagic mid-water trawl fishing method is more variable with some studies estimating it to be twice as high in terms of fuel burned per tonne of fish landed compared to purse seining (Parker and Tyedmers, 2014) although other studies having found it to be comparable (Jafarzadeh et al., 2016; Schau et al., 2009). Bottom trawling is found to be one of the most fuel intensive fishing methods (Schau et al., 2009; Winther et al., 2009), up to five times less efficient than purse seining in some instances. Crustacean fisheries are reported to have the highest GHG emissions documented to date (Parker et al., 2018).
Scottish vessels catch approximately 65 % of total fish caught in the UK (MMO, 2017). The largest and most valuable industry sector is the pelagic sector, making up 64 % of all Scottish landed fish, with a value of £202 million in 2018 (Scottish Government, 2019b). The Scottish pelagic fleet is comprised of modern, large, refrigerated seawater pelagic trawl vessels and purse seiners. These vessels target primarily Atlantic mackerel (Scomber scombrus), Atlantic herring (Clupea harengus) and blue whiting (Micromesistius poutassou). These are landed at processing plants in Scotland, Norway, Denmark and Ireland and the products are sold worldwide almost exclusively for human consumption. Of the four major fisheries targeted by the Scottish pelagic fleet (North East Atlantic mackerel, North Sea herring, Atlanto-Scandian herring and North East Atlantic blue whiting) all but Atlantic mackerel currently have MSC certification (MSC, 2020a, b; MSC, 2020c, d), and are harvested at or below maximum sustainable yield (MSY) level as per ICES guidance (European Comission, 2019). The mackerel fishery, however, had its MSC status suspended in March 2019 (along with all other fisheries for the North East Atlantic mackerel stock), due to reputed overharvesting (Ramsden, 2019).
Despite the importance of Scottish pelagic fisheries to the UK and their role as a worldwide producer of pelagic fish, there is little region-specific data describing the contributions of Scottish-caught pelagic fish towards country-specific and global GHG emissions, or other climate related environmental impacts. Furthermore, given the government’s commitment to reaching net zero carbon emissions (Scottish Government, 2019a) there is strong incentive for the industry to quantify the environmental impacts of Scottish caught pelagic fish and how it can contribute to achieving the goal of net zero carbon.
This study aims to quantify the environmental impacts of Scottish caught pelagic fish using ALCA. In order to do this it will: i) identify the main contributing factors causing the impacts; ii) estimate temporal and inter-vessel variability; and iii) determine how the environmental impacts compare to other seafood LCA studies.
Section snippets
Methods
The Scottish pelagic fleet is made up of 22 vessels, predominantly pelagic trawl vessels ranging from 44 to 79.8 m in length. Three vessels use both the pelagic trawl and purse seining method to target different fisheries. Of the 22 fleet vessels, 50 % of the fleet participated in this study (n = 11). This sample contained vessels from two out of three home ports (72 % Shetland and 27 % Peterhead). As Fraserburgh vessels are geographically close to Peterhead and known to follow similar fishing
Results
The results of each of the selected impact categories used in the LCA analysis for the study fleet are shown in Table 2. Each impact category is displayed in its own units relative to a kilogram of whole fish landed. The accumulative CF (here the GWP) was 0.452 kg CO2 eq. per kilogram of whole fish landed for the Scottish pelagic fleet.
The LCA component analysis (Fig. 2) indicates that the single biggest contributing factor to GWP, and all other impact categories investigated, is the use of
LCA component analysis
Fuel usage was the largest contributing factor in all impact categories, consistent with other studies (Avadí and Fréon, 2013; Parker, 2012; Parker et al., 2018). Fuel was consistently >92 % of the contribution to any impact category. In GWP it contributed ∼96 % of the overall impact. Earlier studies have found refrigeration to be a large contributor to environmental impacts (Iribarren et al., 2011; Winther et al., 2009), particularly GWP. However, our study found the assumed leakage rate to
Conclusion
Using standardised methodology for quantifying impacts (ACLA) this study has found Scottish-caught pelagic fish (herring, mackerel and blue whiting) to have a low CF and environmental impact when compared to other similar seafood including farmed salmon, demersal fish and shellfish. Given that seafood products generally have a low CF in comparison to other animal proteins (Garnett et al., 2016; Parker et al., 2018), Scottish-caught pelagic fish can be considered a climate smart, low carbon food
Funding
This research was undertaken as part of PhD studies and funded by the following institutions: Scottish Pelagic Sustainability Group, Shetland Islands Council, University of Aberdeen, University of the Highlands and Islands, Shetland Fish Producers’ Organisation.
CRediT authorship contribution statement
Frances Sandison: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Visualization, Project administration. Jon Hillier: Conceptualization. Astley Hastings: Methodology, Writing - review & editing. Paul Macdonald: Conceptualization, Writing - review & editing, Funding acquisition. Beth Mouat: Writing - review & editing, Funding acquisition. C. Tara Marshall: Conceptualization, Writing - review & editing, Funding acquisition,
Declaration of Competing Interest
This work was undertaken as part of PhD studies and funded by the following institutions: Scottish Pelagic Sustainability Group, Shetland Islands Council, University of Aberdeen, University of the Highlands and Islands, Shetland Fish Producers’ Organisation.
Acknowledgements
The authors would like to thank all industry stakeholders that provided information for this study, and give special thanks to Steve Mackinson and Ian Gatt (Scottish Pelagic Fishermen’s Association) for their advice and support. We are grateful to Dr. F. Ziegler and another anonymous reviewer for their detailed and constructive critiques.
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2023, Science of the Total EnvironmentCitation Excerpt :Table 7 shows some references from literature. Jafarzadeh et al. (2016) reported a value of 0.35 kg fuel/kg small pelagic landed using trawls, in addition to a consumption of only 0.05 kg fuel/kg fish landed by coastal seine methods, in opposite with the findings of (Sandison et al., 2021) and (Furuya et al., 2011), who obtained a FUI of 0.04 and 0.08 using trawls for the capture of pelagic species. In the Avadí and Fréon (2013) review the kg fuel/kg of small pelagic fish with purse seine was equal to 0.07.