estimation of the carbon footprint of the shetland fishery for · 4 1. introduction 1.1 background...
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Estimation of the carbon footprint of the Shetland fishery for
Atlantic mackerel (Scomber scombrus)
Author:
Frances Sandison, NAFC Marine Centre
Frances.sandison @uhi.ac.uk
Supervisors:
Paul Macdonald, NAFC Marine Centre
Chevonne Angus NAFC Marine Centre
Funders:
Arthur Laurenson Memorial Bursary, Scottish Fishermen’s Trust, Hunter & Morrison
Memorial Trust, NAFC Marine Centre.
NAFC Marine Centre
Port Arthur
Scalloway
Shetland
ZE1 0UN
email: [email protected]
web: www.nafc.ac.uk
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Contents
Executive Summary ....................................................................................................................................... 3
1. Introduction .......................................................................................................................................... 4
1.1 Background ................................................................................................................................... 4
1.2 An Overview of Carbon Footprinting and Life Cycle Analysis History .......................................... 5
1.3 Carbon Footprint Analysis in Capture Fisheries. ........................................................................... 7
1.4 Mackerel Biology and Stock Structure .......................................................................................... 9
1.5 The Scottish Mackerel Fishery .................................................................................................... 11
1.6 Aims and objectives of Project .................................................................................................... 13
2 Methods .............................................................................................................................................. 14
2.1 Data Collection ............................................................................................................................ 14
2.2 Data Analysis ............................................................................................................................... 16
3 Results ................................................................................................................................................. 17
3.1 Fleet Analysis .............................................................................................................................. 17
3.2 CF Individual Component Analysis .............................................................................................. 22
3.3 Seasonal Analysis ........................................................................................................................ 25
4 Discussion ............................................................................................................................................ 29
4.1 Discussion of Study Results ......................................................................................................... 29
4.2 Comparison of Results with Other Aquatic Meat Studies .......................................................... 31
4.3 Comparison of Results with Terrestrial Meat Studies ................................................................ 33
5 Conclusion ........................................................................................................................................... 35
6 References .......................................................................................................................................... 37
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Executive Summary
This study investigates the carbon footprint (CF) of the pelagic trawl Atlantic mackerel (Scomber
scombrus) fishery of the Shetland Isles over the period 2012-2014. The study has found the
Shetland Atlantic mackerel pelagic trawl fishery to have a comparably low CF at the point of
landing in comparison both to other fisheries and terrestrial meat systems to a similar end
point (0.41 t CO2e per tonne of fish landed). This was found to be in keeping with other
research which shows small pelagic species and pelagic trawl fisheries in general to have a low
CF value.
Fuel consumption was found to be the single biggest contributor to the overall CF and thus any
steps to further reduce fuel consumption will aid in lowering the fleet CF. Refrigerant leakage
was also found to play a large part in the current estimation of CF for the Shetland fleet.
However, this was caused by a minority of vessels and will no longer factor after the change in
regulations in 2015 requiring the out-phasing of R22 as a refrigeration system. This will result in
those vessels affected converting to the carbon neutral ammonia system utilised by the others,
thus removing refrigeration leakage and further reducing the fleet CF value.
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1. Introduction
1.1 Background
Today the fishing industry represents our last wild caught, large scale commercial foodstuff and
produces a commodity that is traded globally (Smith, et al, 2010). Fisheries provide protein rich
meat contributing to at least 15% of the average protein intake for half the global population
(FAO Fisheries and Aquaculture Department, 2012). Of the fish landed or reared, only about
20% goes into uses other than direct human consumption (e.g. as fish meal or oil). Additionally,
the fishing industry supports over 180 million jobs around the globe (FAO Fisheries and
Aquaculture Department, 2010).
The increasing reliance on fish as a food source has largely been made possible by improving
technology, although it has not come without its own problems (e.g. the collapse of commercial
fisheries - Myers, et al, 1997; resulting changes in the behaviour of apex predators - Estes, et al,
1998: and extreme ecosystem shifts caused by the collapse of a foodweb - Pandolfi, 2005). As
such, there are now numerous safe guards in place to try and minimise the negative effects of
fishing and create sustainable and well managed fish stocks and marine environments (for
example MSC certification, no take zones, international fishing quota). Despite this, one issue
that has, up until recent years, been widely overlooked by measures of fishing sustainability is
climate change. In recent years effects of climate change on various fisheries have been
reported. For instance, climate change was reported as one of the contributing causes of the
reduced sand eel population around Orkney and the Shetland Isles (RSPB, 2009). Future
projections suggest this could have much greater effects on a variety of commercial fish
species, with higher latitudes possibly seeing a 30-70% increase in catch potential and the
tropics seeing a drop in catch potential of around 40% (Cheung et al, 2010).
As well as being affected by climate change, fisheries themselves may be a strong contributor
to global warming emissions. Food production as a whole, including distribution and retail, is
responsible for a significant overall proportion of a country’s net greenhouse gas emissions and
general environmental impact (Foster, et al., 2006). The terrestrial meat industry alone, largely
due to beef production, is known to be the second highest cause of global greenhouse gas
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emissions after that of heating and electricity production (Rifkin, 2011). This ranks even above
the contribution caused by worldwide transport. However, the focus for greenhouse gas
emission has traditionally been on terrestrial meat production systems, and as a result there is
to date no widely accepted figure for the aquatic food industry as a whole.
There is a growing consumer led interest in ethical food production and consumption, with 67%
of UK consumers more likely to purchase a product with a low carbon footprint (Carbon Trust,
2012). There is also a growing political and scientific drive to sustainably manage resources.
Growing consumer awareness on the state of fish stocks has also led to the development of
indicators and certifications or labels that can help differentiate between sustainably managed
fisheries and those that are not sustainably managed. One of the major labels for this is the
Marine Stewardship Certification (MSC) of fisheries (MSC, 2011), which considers such factors
as fishing pressure on stocks as a whole and various issues associated with fishing practices (e.g.
as is seen in the Scottish North Sea haddock fishery (MSC, 2015). Such labels are often coveted
as they can potentially increase the value and marketability of the resource in all aspects of
retail. As it stands however, few if any of these measures of sustainability actually consider a
fisheries’ carbon footprint.
1.2 An Overview of Carbon Footprinting and Life Cycle Analysis History
A ‘carbon footprint’ (CF) or carbon profile, is the term used to refer to the quantity of carbon
dioxide and all other gas emissions that contribute to global warming, starting from the
creation of a product right through until the end of its life including its disposal or eventual
recycling. It is expressed in global warming potential (GWP) for every kilogram of gas emitted
over a fixed period (typically 100 years). This allows for the total emissions from a product to be
calculated and added together to give a single figure that can be directly compared to that of
other products. A summary of some of the most common greenhouse gas emissions and their
GWP over a century, based on the figures given by the IPCC (EPLCA 2009), is shown in Table 1.
Greenhouse gas emissions are caused through many different processes, the most notable of
which is the combustion of fossil fuels in heating and electricity production, transport and in
agricultural processes (Rifkin, 2011) .
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Table 1 Greenhouse gases and their associated GWP over a hundred year period as reported by the IPCC (EPLCA 2009).
Gas type Chemical formula GWP100
Carbon dioxide CO2 1
Methane CH4 25
Nitrous oxide N2O 298
HFCs - 124-14800
Sulphur hexafluoride SF6 22800
PFCs - 7390-12200
Life Cycle Assessment (LCA) is the standardized method for calculating environmental impact of
any product or service from the beginning of its life to the end, including its CF. It is defined and
outlined by the international organisation of standardisation, in their documents ISO 14044 and
14040 (BSI, 2006a; BSI, 2006b). Like a CF estimation, it follows a product through from
obtaining the raw materials to final disposal or recycling of waste. However, rather than focus
on the single impact category of global warming, it considers all possible environmental impacts
associated with the product chain. This can range from GWP to habitat destruction, with a
number of other impact categories in between. CF is considered an important category of LCA
and one of the main constituents of the overall impact (BSI, 2011).
It is generally considered to be best practice when assessing the environmental impacts of any
process to consider all possible impact categories over the entire lifespan of the product. Here
an impact category is defined as the possible consequences that could affect human health,
wildlife and sustainability. This prevents the shifting of burdens from one impact category to
the other. For example; farmed shrimp have been found to have lower directly associated
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greenhouse gas emissions than wild caught shrimp (Ziegler, et al., 2011). However, they are
linked to the increasing destruction of mangroves which are considered an important habitat
for many commercial fish species and thus may contribute to declining fish stock numbers,
(Mangrove Action Project, 2013). Nevertheless, businesses tend to prefer the easier to
understand and more marketable figure of a CF, which unlike the LCA, offers a single,
unambiguous end figure. Fortunately, as GWP makes up a large proportion of environmental
impact as a whole (Parker, 2012), a CF profile is accepted as a suitable first step in
environmental analysis of a product (BSI, 2011). Both CFs and LCAs can be considered in their
entirety (a cradle to grave approach) whereby the impacts/emissions of the product right from
the beginning of its life, including any material capital goods, through to its eventual
destruction or recycling are assessed. Alternatively, a segmented approach (cradle to gate) can
be assessed whereby the impacts of a product are considered for only part of the life cycle,
usually from the beginning of its life (including capital goods) through to the end of the first
stage, where it passes into a different system. In the context of fishing, an accepted cradle to
gate approach would consider the impacts of the fish from capture to landing or processing,
leaving distribution and retail as separate stages in the assessment to be considered later (BSI,
2011). The latter is often preferred by businesses as it allows them to be accountable only for
the emissions involved in their stage of the analysis, or it removes the issue of being unable to
quantify possible emissions downstream of their involvement with the product.
1.3 Carbon Footprint Analysis in Capture Fisheries.
The traditional view of assessing environmental impact in capture fisheries has often been
restricted to looking at fish stock levels, damage to the seabed, bycatch and effects of fishing
down the foodweb (as discussed in Avadi and Freon, 2013). Unfortunately however this narrow
focus has ignored several other important impacts, such as ocean acidification, toxicity and
climate change, which, although not caused solely by capture fisheries, do represent important
categories in a fishing LCA. LCA has been widely accepted as the more encompassing
framework to assess a seafood product from its beginning to its end (Pelletier, et al., 2007).
Creating carbon profiles for the fishing industry has gained interest and popularity over recent
years, with LCA and carbon emission analyses starting in the late 1990s to early 2000s, (e.g.
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Tharne, 2004; Ziegler, et al., 2003). However, a lack of standardisation and agreement on terms
and scope has resulted in a multitude of LCAs of differing magnitude and methodologies. The
release of the PAS 2050-2: 2012 (BSI, 2012) outlined specific guidelines for CF in the aquatic
sector, meaning that there are issues with comparing LCAs prior to this.
Many LCA studies of fisheries have shown that the capture process (summarised in Avadí &
Fréon, 2013) is the most significant contributor to greenhouse gas emissions over the whole life
cycle of the product. This appears to be overwhelmingly due to fuel emissions (Hospido &
Tyedmers, 2005) and as a result the method and gear used to catch the fish has a significant
effect on the overall CF, depending on their energy efficiency (e.g. Tharne, 2004; Tyedmers,
2000; Vázquez-Rowe, et al., 2010). Additionally some studies have found contributors such as
refrigeration leakage also are responsible for a considerable proportion of the overall footprint
(e.g. Zeigler et al, 2013; Vazquez-Rowe et al, 2010). The few studies that have not come to this
conclusion tend to involve either air transport or value added products. Because of this
correlation, Parker (2012) suggested that in studies without significant air travel or products
involving the addition of ingredients with high CFs in their own right, fuel use could be used as a
proxy for the CF of the overall product up to arrival at its intended destination.
The use of capital goods in studies, particularly with regards to vessel construction, has been
found to have a negligible contribution to overall LCA values (e.g. Ziegler, et al., 2003; Hospido
& Tyedmers, 2005; Hayman, et al., 2000) and, in line with PAS guidelines, it is often ignored
from the analysis. There has been some debate as to whether this is an accurate
representation, with some authors suggesting that the reported negligibility is due to an
oversimplification of quantification of construction materials (Iribarren, et al., 2010). However,
this argument is more aimed at other aspects of an LCA analysis, such as marine toxicity, than
carbon footprinting.
A number of studies suggest that emission rates vary from fishery to fishery, depending heavily
on the gear type used and the efficiency of the catch rate (e.g. Parker & Tyedmers, 2014; Madin
and Macreadie, 2015; Ziegler, 2007) and that some can have a very high emission rate while
others are particularly low (Madin and Macreadie, 2015). It is generally accepted that bottom
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trawlers have the highest fuel consumption and emission rate (Winther, et al, 2009), especially
in the shrimp and crustacean fisheries (Schau, et al., 2009). Research suggests that purse
seiners are generally the most efficient of the mainstream fishing methods with regards to
carbon emissions, and can be up to five times more efficient than bottom trawling in some
fisheries (Driscoll & Tyedmers, 2010). However, it is noted by some that this is more reflective
of their high rate of net haulage than actual fuel efficiency in terms of fuel combustion (Zeigler,
2007). Emission rates for pelagic trawls on the other hand are always significantly lower than
bottom trawling, but vary from being twice as high as purse seining (Parker & Tyedmers, 2014)
to being as efficient as it (Schau, et al., 2009). Zeigler et al, (2003) in particular warn against
generalising about gear efficiency across fisheries due to such discrepancies. As such, results
are best taken in context with other local fishing methods.
Artisanal fisheries have considerable variation in their carbon emission rate depending on
method and species targeted (Ziegler, et al., 2011), but are largely perceived to be the lowest
impact fishing method by the consumer. Little has been done on the emission rates in artisanal
fisheries including handline fisheries, though some studies have suggested that handlining is no
more efficient, or slightly less so than pelagic trawling or purse seining (Schau, et al., 2009).
However, small pelagic fisheries are reportedly the single most energy efficient of the
commercial fisheries (Parker & Tyedmers 2014).
1.4 Mackerel Biology and Stock Structure
Atlantic mackerel (Scomber scombrus) (Figure 1) is a small pelagic fish that is a member of the
tuna family, Scombridae. A migratory fish, they spend the majority of their life travelling in
large, fast moving shoals in mid-water, covering vast distances over the year as they move
between overwintering, spawning and feeding grounds. Considered a high source of omega
three fatty acids (NHS Choices, 2013) which are required by the fish for its high energy content
to fuel their migration and spawning, they are considered to be a healthy source of protein and
a valuable resource.
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Figure 1 Atlantic mackerel Scomber scombrus.
The North East Atlantic (NEA) mackerel stock is made up of three breeding populations – the
Western component, the North Sea component and the Southern component, (Simmonds
2001). Only the Northern component is thought to be genetically distinct from the other two,
although this distinction is debated by Jansen & Gislason (2013). The North Sea component of
the mackerel stock showed a dramatic decrease in the late 1960-1970’s, which was generally
believed to be the result of overfishing as well as indirect pressure on valuable prey species
such as herring. Low recruitment continued thereafter, though a recent study by Jansen (2014)
has suggested this is more reflective of a stock shift driven by changing water temperatures.
The three components are treated as a single management unit, as intermingling between the
populations make separate management impossible. As a result the stock is widely spread with
several known spawning areas (Figure 2).
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Figure 2 Spawning grounds (left) and landings for Atlantic Mackerel (Scomber scombrus) (right) by the Scottish Pelagic fleet in 2010 (Scottish Pelagic Sustainability Group 2014).
Mackerel from the North Sea component spend their winter months close to the Shetland Isles
and along the Norwegian deep, before travelling into the central area of the North Sea in spring
to spawn. The Western component however linger close to the continental slope (Scottish
Pelagic Sustainability Group, 2014), spawning around Ireland and west of the UK between
March-July, before travelling into the North Sea and Norwegian waters to mingle with the
North Sea stock, (Figure 2). As with the North Sea component, over the years some clear shift in
trends have been noted with the Western component and its migration time and path, moving
later in the year and into deeper waters. Spawning areas have also seen an expansion further
north and west of existing spawning grounds. ICES maintain that this is not reflective of changes
in climate so much as it is of changes in stock size (ICES, 2005).
1.5 The Scottish Mackerel Fishery
In recent years Atlantic mackerel has become the single most valuable species to the Scottish
fishing industry, making up about one third of the value of the total landings. In 2012 catches
totalled over 134,000 tonnes, valued at £131 million (Scottish Pelagic Sustainability Group,
2014), and it is still considered one of the healthiest commercial fisheries in Europe. Catches by
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the Scottish fleet largely consist of removals from the Western and North Sea components of
the stock. There are two main aspects to the fishery, the first being the much larger trawl
fishery which operates on a seasonal basis, from January- February targeting mackerel along
their migration route (with the west component of the stock moving from the continental shelf
where they overwinter towards the south and west of the UK and Ireland, and the North Sea
component moving from the Norwegian deeps into the central North Sea – Scottish Pelagic
Sustainability Group, 2014) and from October – November in Scottish waters. The second
aspect is the inshore fishery, which operates only a single season running from June-October.
Fishing is mainly conducted by pelagic trawl where a large trawl net is towed through the water
at the mid-water level. Unlike the better known bottom trawling method, this form of trawling
does not impact upon the seabed as it does not touch the sea floor and has a relatively low
bycatch rate. This is mainly due to the shoaling behaviour of the mackerel which allows pelagic
vessels to target a single shoal at a time. Shoals are mainly ‘relatively clean’, i.e. they consist of
only mackerel, but at different times of the year shoals may either be less dense or have higher
percentages of bycatch species within them. Wheelhouse equipment (sonar and echosounder)
enable the fishers to identify those shoals of mixed species and allows for them to be avoided,
resulting in a minimum bycatch (MSC, 2014).
The fish from the Scottish fishery are used solely in human consumption and transported to be
sold worldwide. In January 2009 the Scottish Pelagic Sustainability Group gained Marine
Stewardship Council (MSC) certification of the North East Atlantic mackerel fishery against the
MSC's standard for environmental and sustainable fishing (Seafish, 2013). This label was
suspended in 2012 after Iceland and Faroe allegedly compromised the sustainability of the
stock by increasing their quotas markedly without international agreement. International
debate continued until 2014 when an agreement was finally made between Faeroe, Norway
and the EU, with allowance made for Iceland should they wish to join later. This initial
agreement was set for five years during which time a long term management plan, agreed on
by the respective nations, is to be assessed by ICES in the hope of regaining MSC certification
(MSC, 2014).
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Unlike other national pelagic fleets, purse seining does not feature largely in the Scottish fleet,
instead it is predominantly undertaken by pelagic trawl. The eight vessels that make up the
Shetland pelagic trawler fleet are all refrigerated seawater vessels and make up a notable
proportion of the Scottish fleet. In these vessels the catch is pumped into large chilled seawater
tanks to keep it fresh prior to landing. The inshore fishery also adds to the mackerel quota
uptake, though at a considerably lower level, operating smaller handline or jigging vessels.
Mackerel caught by the Shetland trawlers are predominantly landed at processing plants in
Shetland, North East Scotland and in Norway. Shetland itself possesses one large scale
processing plant, Shetland Catch, which due to its proximity to seasonal shoaling pelagic fish
attracts landings from national and international vessels as well as some from the local fleet.
Smaller boats typically land their catches to the traditional fish markets on the island (Leiper, S.,
pers. comm.).
1.6 Aims and objectives of Project
Within the Scottish mackerel fishery the Shetland fleet is of relative importance, being awarded
a sizeable proportion of the quota – over quarter (26.89%) of the Scottish quota for the
Western component of the mackerel stock in 2014 (Shetland Fish Producers’ Organisation,
pers. comm.). Fishing takes place during October and November mainly in Scottish waters
(referred to herein as ‘late season’); and in January - February when stocks are on their feeding
migration (referred to herein as ‘early season’), which results in fishing activity moving as far as
south-west Ireland by February. There is an assumption within the pelagic sector in Shetland
that the mackerel fishery based in Shetland will have a relatively low CF given the modern
nature of the fleet and the use of high-tech equipment.
The aims of this project are as follows;
To investigate the CF of the mackerel fishery undertaken by Shetland’s pelagic trawl
fleet
To contrast the CFs of the pelagic trawl fleet in the two intra-annual mackerel seasons
To compare the CF of Shetland’s mackerel fisheries with that of terrestrial meat systems
and other commercial fisheries
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To investigate the CF of the smaller inshore Atlantic mackerel fishery and to contrast
this against the pelagic trawler CF
While a full LCA analysis should be considered for the future to prevent improvements in one
sector inadvertently causing higher impacts in another, at this stage a carbon profile is felt to be
the best first step for the analysis of the Shetland mackerel fishery.
2 Methods
2.1 Data Collection
For the initial stage of this study a cradle to gate CF study is proposed, focusing on the capture-
landing phase of the Shetland Atlantic mackerel fishery. In this instance the gate is defined as
the factory door, with only ship related emissions considered.
Both aspects of the Shetland fishery were intended to be included; the large scale pelagic trawl
fishery and the smaller handline fishery, with a retrospective approach used examining record
data to calculate the carbon footprints for the fisheries over the past three years (as in keeping
with the PAS guidelines). However it was discovered on implementation that this was not
feasible for the handline aspects of the fishery as the smaller vessel skippers did not typically
keep records to the detail required for a reliable estimation. For this reason, exploration of the
handline Atlantic mackerel fishery in Shetland was eliminated from this stage of the analysis.
For the pelagic trawler aspect, focus was primarily given to the overall carbon footprint. The
contrast between the two intra-annual fishing seasons was also explored to see if there was any
significant difference between them.
PAS guidelines (BSI 2012) suggest that for a fleet this size, all vessels should be included in
analysis for an appropriate confidence interval. However, as one of the vessels was registered
between two different ports, it was removed from further analysis to avoid unnecessary
complication.
The following data were collected for the seven suitable vessels;
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Fishing inputs
Consumables;
o Nets
o Rods/lines/hooks
o Ropes
o Metals
Cooling materials
o Refrigerants
Fuels/ Energy
Materials used for maintenance
o Lubricating oil
o Anti-fouling agents
o Cleaning agents
Fishing outputs
Catch
o Landed bycatch
Emissions
o Loss of refrigerants to atmosphere
o Emissions from fuel combustion
This data was obtained from primary sources, through interview/correspondence with the
skippers/engineers of the vessels as well as their shipping agents, and in some cases (as with
the details on nets – weight and consumption, and for the details on antifouling) companies
used for purchase of materials. Permission was obtained for access to ship records to allow
analysis of the raw data, either passed on through the shipping agents/companies or by access
to their online e-log records.
Where secondary data was required in the absence of reliable raw data (e.g. refrigerant
leakage), the range suggested by the Seafish carbon footprint analysis tool was used (Seafish,
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n.d.). A worst case scenario approach taken to allow for a conservative estimation (in keeping
with suggestions made by the PAS for unknown data) and the highest suggested figure used.
2.2 Data Analysis
In order to calculate the end figure of CF, landings per year for each of the vessels as well as
estimation of fuel spent per year were calculated the latter being taken from fuel purchase
records. For this an approximate quantity of litres purchased per year were calculated using
base price figures obtained from the fishing agent. These were then validated by comparison of
the calculated figures with a random selection of invoices. All compared figures were found to
be within acceptable parameters and thus deemed appropriate for use. The issue of fuel
purchased not directly equalling fuel spent was considered, however as averages were taken
over the full three year period, it was felt that any discrepancies between the two would equal
out overall.
From the total fuel spent over the year, this was allocated by percentage of landings (mass of
landed fish) between the different fish species, as per the PAS guidelines. The total fuel was
split between all species landed as a proportion of total landings for the time period looked at,
in order to account for emissions caused by the lengthy non-fishing periods and activities in
which auxiliary engines were continuously run to keep the main engines in working order or
where the ship was moved from port to port.
By allocating fuel with this method, landed bycatch could be removed from the analysis as it
had been already accounted for by subdivision of the landings and related emissions.
Additionally, as the fish were landed whole no calculation of percentage yield to fish caught
was necessary. Litres spent per tonne of mackerel landed could therefore be calculated with
relative ease. This was done at different levels dependent on the focus – per vessel, per trip,
per season, per year and average over the time period.
For consumables, estimates were obtained through the engineers and skippers and calculated
to give yearly averages, with the figures split again by allocation to each species percentage of
total landings for the year/time period and then calculated per tonne of mackerel landed. As
17
this had a very low contribution to the analysis, estimations were deemed suitable without
further validation.
The calculation of actual carbon footprint was done by the Seafish online emission profiling
tool, though the final figure (given in kg of CO2 equivalent emitted per tonne of fish landed) was
then converted to tonne of CO2 equivalent (t CO2e) per tonne of fish landed to allow for easier
comparison with other studies. Assessment was made of the overall fleet average figures,
individual vessel average figures and both individual and fleet average figures per year. For the
seasonal comparison, fuel spent over the collective fishing seasons over the study period was
contrasted with landings per species within the specified season. The Pearson correlation test
was used to determine if there was a significant relationship between the end carbon footprint
and: landings; fuel consumption; fuel intensity, as well as between fuel consumption and
landings.
3 Results
3.1 Fleet Analysis
An overall estimated carbon footprint for the Shetland pelagic trawler fleet’s Atlantic mackerel
fishery was calculated by accumulating the data for all seven vessels followed in the study over
the three year period and then averaging. The estimated average carbon footprint is shown in
Figure 3.
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Figure 3 Estimated average footprint for the Shetland pelagic trawler fleet 2012-2014.
The average estimated carbon footprint for the entire Shetland pelagic trawler fleet between
the years of 2012 and 2014 is 0.407 t CO2e. Of this, the majority (0.283 t CO2e) is caused by the
fuel consumption in the fishery. The contribution of the refrigerants in the overall footprint is
notable. However, upon closer inspection this contribution is caused solely by two of the seven
vessels in the fleet (Figure 4). In contrast the contribution to the footprint by the vessels fishing
gear and maintenance is minimal (0.002 t CO2e).
Materials: Vessel, fishing gearand maintenance
0.002
Refrigerant emissions in fishery 0.122
Fuel consumption in fishery 0.283
0
0.1
0.2
0.3
0.4
0.5
0.6To
nn
e C
O2
equ
ival
len
t
Fleet Average
Average carbon footprint for the Shetland Pelagic Trawler fleet 2012-2014
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Figure 4 Estimated overall average carbon footprint for the Shetland pelagic trawler fleet 2012-2014.
There is clear inter-vessel fluctuation in CF, with the lowest carbon footprint belonging to
Vessel 4 (0.287 t CO2e) and the highest to Vessel 6 (0.645 t CO2e). However both Vessel 6 and
7’s comparatively higher overall footprint is caused largely by the emissions from refrigeration
leakage. Emissions caused purely by fuel combustion places them below all five other vessels
(0.215 t CO2e and 0.204 t CO2e respectively), with refrigeration leakage adding an additional
0.429 t CO2e /0.426 t CO2e respectively to their overall CF figure.
Annual inter-vessel fluctuations in CF for the period 2012 to 2014 are shown in Figure 5. There
are notable fluctuations in CF across vessels and years. No real trend can be seen between the
initial two years of the study (2012-2013) as some vessels’ annual footprints increase while
other’s decrease, with the overall averages being quite similar (0.455 t CO2e and 0.448 t CO2e).
However, there is a marked reduction in the average for 2014 (0.356 t CO2e) and, with the
exception of Vessel 7, all vessels show a clear reduction in CF for this year. In 2014 fuel
1 2 3 4 5 6 7
Materials: Vessel, fishing gear andmaintenance
0.002 0.002 0.002 0.001 0.002 0.002 0.001
Refrigerant emissions in fishery 0 0 0 0 0 0.429 0.426
Fuel consumption in fishery 0.317 0.359 0.337 0.286 0.322 0.215 0.204
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Ton
ne
CO
2eq
uiv
alen
t
Vessel
Average overall carbon footprint for the Shetland Pelagic Trawler Fleet 2012-2014
Fuel consumption in fishery Refrigerant emissions in fishery Materials: Vessel, fishing gear and maintenance
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consumption emissions are lower for all vessels except vessel 7, explaining its overall increase
in CF.
Vessel length did not have a considerable effect on CF, however refrigeration was found too.
The two oldest vessels (Vessels 6 and 7), built prior to a change in refrigeration policy in 2000,
were still utilising the R22 refrigeration method over the study period, resulting in much higher
refrigeration figures than the other vessels.
21
Figure 5 Estimated individual carbon footprints for the Shetland pelagic trawler fleet 2012(top),
2013 (middle) and 2014 (bottom)
1 2 3 4 5 6 7 Average
Materials: Vessel, fishing gear andmaintenance
0.002 0.002 0.002 0.001 0.002 0.002 0.001 0.002
Refrigerant emissions in fishery 0 0 0 0 0 0.429 0.429 0.122
Fuel consumption in fishery 0.35 0.411 0.273 0.381 0.393 0.239 0.174 0.331
00.10.20.30.40.50.60.70.8
Ton
ne
CO
2eq
uiv
alle
nt
Vessel
2012
1 2 3 4 5 6 7 Average
Materials: Vessel, fishing gear andmaintenance
0.002 0.002 0.002 0.001 0.002 0.002 0.001 0.002
Refrigerant emissions in fishery 0 0 0 0 0 0.429 0.429 0.122
Fuel consumption in fishery 0.37 0.393 0.414 0.267 0.522 0.196 0.174 0.324
00.10.20.30.40.50.60.7
Ton
ne
CO
2eq
uiv
alle
nt
Vessel
2013
1 2 3 4 5 6 7 Average
Materials: Vessel, fishing gear andmaintenance
0.002 0.002 0.002 0.001 0.002 0.002 0.001 0.002
Refrigerant emissions in fishery 0 0 0 0 0 0.429 0.429 0.122
Fuel consumption in fishery 0.261 0.301 0.321 0.244 0.195 0.171 0.23 0.232
00.10.20.30.40.50.60.7
Ton
ne
CO
2eq
uiv
alle
nt
Vessel
2014
Fuel consumption in fishery Refrigerant emissions in fishery Materials: Vessel, fishing gear and maintenance
22
3.2 CF Individual Component Analysis
This section explored the individual components that were used to calculate the end carbon
footprint levels. The overall fuel consumption attributed to mackerel fishing per vessel per year
is shown in Figure 6. Inter-vessel fluctuations are seen quite clearly with Vessel 4 possessing the
highest fuel consumption in all but one year (2012), and Vessel 6 showing low emissions for all
three years. However, there are also clear intra-vessel fluctuations (e.g. Vessel 4), although for
some this is relatively minor (e.g. Vessel 1). While the similar averages in years 2012-2013 are
possibly evidence of natural fluctuations, the slightly higher average in 2014 suggests an overall
increase in fuel consumption in this year for the majority of vessels. There was no correlation
between fuel consumption and overall CF (P>0.05).
Figure 6 Fuel allocated by mass to the mackerel fishing 2012-2014 for the Shetland pelagic trawler fleet.
1 2 3 4 5 6 7 Average
2012 377,213 309,419 389,596 918,556 710,075 408,077 316,285 489,889
2013 383,633 427,644 649,451 642,954 871,741 339,426 348,160 523,287
2014 467,715 438,488 744,536 1,225,029 701,331 485,362 643,936 672,342
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
Fuel
in li
tres
Vessel
Fuel allocated to mackerel fishing for the Shetland Pelagic Trawler fleet
2012 2013 2014
23
Figure 7 shows the total weight of mackerel landed per vessel per year. The trends reflect the
same pattern seen with fuel consumption, with the exception of Vessel 5 in 2012 which shows a
lower landing than expected from the high fuel consumption. Overall there is little fluctuation
seen between the years 2012 and 2013 although a much higher average is evident in 2014. A
significant relationship is seen between total yearly landings and overall CF (P=0.02).
Figure 7 Total annual landings for the Shetland pelagic trawler fleet 2012-2014 by vessel.
Fuel spent per tonne of mackerel landed for each vessel per year is shown in Figure 8.
Fluctuations are seen between vessels and between years, with no clear trend overall between
years 2012 and 2013 (reflected in the similar averages). However, in 2014 the majority of
vessels spent less fuel per tonne of mackerel (the exceptions being Vessel 7 in 2013 and Vessel
3 in 2012). This was reflected in the lower fleet average value of 76.2 litres spent per tonne of
mackerel landed.
1 2 3 4 5 6 7 Average
2012 5,200 3,283 4,352 7,351 5,504 2,298 3,626 4,516
2013 5,282 3,162 4,785 7,332 5,091 3,321 6,090 5,009
2014 8,669 5,470 7,069 15,287 10,965 4,440 8,560 8,637
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
Mac
kere
l lan
din
gs in
to
nn
e
Vessel
Atlantic Mackerel landings 2012-2014 for Shetland Pelagic Trawler fleet
2012 2013 2014
24
A strong positive linear relationship is seen between litres spent per tonne of mackerel landed
and the overall CF for the year. In Figure 9 two distinct groups of results can be seen – those
that follow the main linear trend, and a smaller subset that follow a linear trend at more
elevated CF values. The elevated values represent figures from the two vessels with the
relatively high refrigeration leakage values. The overall relationship was not found to be
significant (P>0.05). However, the removal of the elevated outliers from the analysis resulted in
a highly significant correlation (P<0.01). The relationship between fuel spent and fish landed
was also explored. Again a significant positive relationship is seen between the two variables
(P<0.01).
Figure 8 Litres of fuel spent per tonne of Atlantic mackerel landed by individual vessels in the Shetland Pelagic trawler fleet from 2012-2014.
1 2 3 4 5 6 7 Average
2012 115 135 90 125 129 78 87 109
2013 121 129 136 88 171 64 57 106
2014 86 99 105 80 64 56 75 76
0
20
40
60
80
100
120
140
160
180
Litr
es p
er t
on
ne
Vessel
Litres of fuel spent by the Shetland Pelagic Trawler fleet per tonne of Atlantic mackerel landed
2012 2013 2014
25
Figure 9 Litres of fuel spent per tonne of Atlantic mackerel landed by the Shetland pelagic
trawler fleet against the resulting carbon footprint over the entire study period.
3.3 Seasonal Analysis
The effect of fishing season on overall CF values was explored by separating early season
landings from late season landings (Figure 10).
26
Figure 10 Total Atlantic mackerel landings over entire study period by season landed.
Generally, more fish are landed overall in the late season than in the early season. Despite this
there is considerable inter-vessel variation with a marked difference between seasons for some
vessels (e.g. 5 and 6) and little difference for others (e.g. Vessel 3).
Figure 11 shows the total fuel spent for each season. Overall there is an increase in the late
season, however there are some deviations from the trend seen in Vessel 7 and Vessel 2. There
was also considerable variation between vessels.
1 2 3 4 5 6 7
Early season landings total 5975 5821 9318 15264 10776 9087 10245
Late season landings total 8458 7141 9980 18738 15078 14691 12840
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
Fish
lan
ded
in t
on
nes
Vessel
Atlantic Mackerel Landings Total
Early season landings total Late season landings total
27
Figure 11 Total fuel consumption for Atlantic mackerel fishing over entire study period by season landed.
In order to put these figures into perspective, litres spent per tonne of fish landed (fuel
intensity) was calculated and is shown in Figure 12. There was no noticeable trend evident. For
some vessels fuel usage is higher in the late season, while with others the reverse is true, with
only one (Vessel 5) showing similar fuel usage between the two seasons.
1 2 3 4 5 6 7
Early season fuel consumption 358091 373879 539541 680566 1062383 501182 770691
Late season fuel consumption 682275 336523 701974 1143556 1391596 603899 548913
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
Tota
l fu
el c
on
sum
pti
on
in li
tres
Vessel
Total Fuel Consumption for Atlantic Mackerel fishing by Season
Early season fuel consumption Late season fuel consumption
28
Figure 12 Litres of fuel spent per tonne of Atlantic mackerel landed per season over the entire study period.
Table 2 shows the frequency of landings for each port used by the vessels. While Shetland was
one of the most frequently used ports (second equal with Selje, Norway, coming after Alesund,
Norway), Norway as a whole is frequented much more than the UK. This is true regardless of
season, though it is slightly more pronounced in the late season.
Table 2 Frequency of landings in each port for the entire study period.
Season
Total Early Late
Port: Killybegs 1 0 1
All Norway ports 24 68 92
Peterhead 7 2 9
Shetland 10 11 21
Total 42 81 123
1 2 3 4 5 6 7
Early total 65 133 122 90 82 99 80
Late total 116 51 76 119 79 169 56
0
20
40
60
80
100
120
140
160
180
Litr
es f
uel
sp
end
per
ton
ne
fish
lan
ded
Vessel
Fuel Consumption per Tonne of Atlantic Mackerel Landed by Season
Early total Late total
29
4 Discussion
4.1 Discussion of Study Results
The results of this study show that the majority of emissions in the CF for the Shetland pelagic
trawler fleet are caused by fuel combustion, as is in keeping with the findings of others
(summarised in Parker, 2012). Similarly, vessel maintenance and consumables are typically low.
Various studies (e.g. Irribarren, 2011; Vazquez-Rowe 2010) have also found refrigeration to
have a significant contribution to the overall figure, and indeed this is also seen in this study,
with refrigeration emissions raising the CF figure considerably. The variation in refrigerant
emissions is essentially due to the different refrigeration techniques. Vessels 1-5 in this study,
being more modern and built post 2000 and the implementation of the Ozone Regulations (IOR,
2007), use Ammonia as a refrigeration system, which is known to have little environmental
impact, while Vessels 6 and 7, being older and built before the 2000 regulations, still utilise R22
as a refrigerant. R22 is known to have a very high global warming potential and as a result was
banned by the 2000 regulations from being used in new build ships, with a view to phasing it
out completely from existing vessels by 2015. With this in mind the large contributions of the
refrigeration emissions for these two vessels are put into context.
Despite this, two key points should be borne in mind when interpreting these results; first, as
refrigeration could not be directly measured nor was leakage information known, estimated
refrigeration values are based on the likely reference range offered by Seafish in their GHG
Emissions Profiling tool (Detailed – V2: Seafish, n.d.). Also, following basic guidelines given by
the PAS (BSI, 2012), a worst case scenario was assumed and the uppermost of the suggested
range calculated for all vessels. This may or may not be reflective of true leakage values,
however, the vessel engineers were not aware of any significant leakage from their vessels.
Zeigler et al (2013) noted that modern vessels typically had only low levels of leakage
suggesting that the value estimated in this study might be higher than the true value. Another
important issue to consider is the date of the out-phasing of R22 as a refrigerant. While the
profile presented here is considered to be representative of the study period, correspondence
with the skippers of the vessels in question has confirmed that they will now be using the
30
ammonia method. As such, the contribution of refrigerants from their individual and overall
fleet CF would be considerably reduced from 2015 onwards.
No correlation was seen between vessel size and fuel emissions, suggesting that vessel size
does not play any significant effect on a vessels’ overall CF. The overall decrease in CF in 2014 is
almost certainly due to the increased quota that was awarded in 2014 following the
agreements between the Faeroe Islands, Norway and the EU (MSC, 2014). While an increase in
fuel consumption was also seen, the resulting litres of fuel spent per tonne of fish landed was
overall reduced.
Due to the small dataset, significant trends should be interpreted with caution. Despite this, a
number of conclusions can be considered. While total fuel spent had no clear bearing
individually on the overall CF, fuel intensity shows a clear significant relationship with it. This
supports Parker’s (2012) assertion that fuel use can be used as a proxy indicator for CF, at least
for the Shetland pelagic trawler fleet, providing that the landing rate is known and ammonia is
the refrigerant used. This enables consideration of seasonal differences to simply focus on litres
spent per tonne of fish landed, as all other contributions (consumables, fuel used in non-fishing
periods, refrigeration leakage) would be allocated either as a 50/50 split or by mass of landings
per species.
A partial positive correlation was found between fuel spent and quantity of fish landed with
more variation than in litres per tonne and CF. This may be expected as an increase in fuel
spent suggests more time at sea with the potential to catch more fish. However additional
external factors would also have an affect here because fluctuation in the size of catches and
the ease of locating fish.
In keeping with the expected, the larger catch was seen to be taken in the late season when the
fish are passing nearby to Shetland and thus easier to access. A higher fuel consumption was
also seen. Despite this no clear tread is seen in fuel intensity, with prominent inter- vessel
fluctuations seen, some vessels favouring the early season while others favoured the late.
Although it may be expected that catches of mackerel closer to Shetland would result in lower
fuel intensity, this discrepancy is possibly explained by the tendency of the Shetland fleet to
31
land their catch outside of Britain. While Shetland is one of the most commonly used ports in
Europe, UK ports collectively are notably less used than the collective ports of Norway. Landing
outside the UK would remove any potential fuel savings from catching the fish close to
Shetland.
Caution must be taken when considering the results for this stage of the analysis as accuracy of
fuel purchased cannot be guaranteed to be representative of fuel spent. For the study as a
whole this was not felt to be an issue as any discrepancy between fuel used and fuel bought
would very likely even out over the study period. However when looking at such small and
exact timescales as is seen when splitting by season, this becomes a possibility for inaccuracy.
4.2 Comparison of Results with Other Aquatic Meat Studies
On the whole the findings of this study are in keeping with the trends found in similar studies.
As illustrated in Table 3, the results of this study indicate that the Shetland mid-water mackerel
fishery has a considerably lower CF than that of demersal fish such as haddock, cod and farmed
salmon. This is in keeping with the general trend for small pelagics to have one of the lowest
CFs of all fish in general, and for pelagic trawling to have a lower footprint than demersal
trawling.
Table 3 Carbon footprint values for tonne of live fish caught or produced at farm gate expressed in tonne carbon dioxide equivalent (t CO2e) over a 100 year period.
Meat type Place of
study
Authors Year of
publication
Fishing
method
Carbon
Footprint
Atlantic Mackerel Shetland This Study 2015 Pelagic trawl 0.41
Atlantic Mackerel Galicia Irribaren et al 2011 Pelagic trawl 0.88
Atlantic Mackerel Galicia Irribaren et al 2011 Purse seine 0.61
Farmed salmon UK Pelletier et al 2009 Farmed 3.27
Farmed Salmon Norway Winther et al 2009 Farmed 2.00
Cod Norway Winther et al 2009 Mixed 1.60
Haddock Norway Winther et al 2009 Mixed 1.75
32
Due to the deficit of publically available UK based research, comparisons had to be made
looking at general European fisheries as a whole despite the differences noted from fishery-
fishery and region-region (illustrated in Table 3). Additionally while mass allocation (where
allocation was required) was favoured to allow for the most accurate comparisons, an
exception was made for Pelletier et al (2009) to allow for the inclusion of another UK fishery
based study. However despite these concessions it was felt that the comparisons still highlight
the general differences between fish species and gear types.
The results of this study suggest that, in comparison with a similar fishery (Atlantic mackerel in
Galicia caught by pelagic trawl) (Irribarren, et al, 2011), the Shetland fishery has a lower CF for
the initial stage of its supply chain. However, the fishing fleet in the Galician study was relatively
old and outdated and refrigeration leakage contributed significantly to the end figure. Despite
this, the CF of the current study is still considerably lower, even when refrigeration leakage in
the Galician fishery is taken into consideration. In contrast with the Galician fleet, the Scottish
pelagic trawler fleet are highly modernised vessels, most of which (5/7) were build post 2000,
the remaining two having been built 1996. This almost certainly has an effect on the efficiency
of the vessels, with the more modern technology presumably aiding in fuel efficiency as well as
dealing with the issue of refrigeration leakage (the two main contributors to the CF). While the
current study’s findings were considered low in comparison both to other fisheries and to other
European Atlantic mackerel fisheries, there are other fisheries that have considerably lower
footprints still. Ramos et al (2011) showed quite a variation over their study period in CF
(ranging from around 0.45 t CO2e at its highest to under 0.1 t CO2e at its lowest), however the
highest value in their findings (in line with this study’s value of 0.41 CO2e) was caused by a
single year peak, with the other years showing values closer to the lower end of their range
(from 0.2 CO2e and below). This study noted an extremely low fuel usage for the fishery for
which they credited the low CF values. As with their CF values the fuel showed a great degree of
fluctuation in values over the study period from approx. 16.5 litres per live tonne (lpt) to 85.8lpt
(assuming a fuel density of 0.885kg per litre). The Basque study’s highest average fuel
consumption of 85.8lpt is similar to the lowest average fuel consumption of 76.2lpt reported
for this study. The Basque study does note that it is considerably lower than other North East
33
Atlantic mackerel (NEAM) fishing regions, including those within the same country (e.g.
Irribarren et al, 2011 - Ramos et al concluded that the environmental impacts in general are up
to 88% lower in the Basque fleet, showing the dangers of extrapolating regional figures from
specific fisheries) and Norway (with the Norwegian fishery coming in at 101.7 litres per tonne).
They claim this is because of the specialised fishing season in the region with the fish being
caught close to port at the exclusion of any other target species.
The results of the present study are similar to those reported in Norway. The Norwegian fleet,
like the Shetland fleet, consists of large, modern vessels and has been reported as having a CF
lower than most (Winther et al, 2009), suggesting that, while there are examples of more fuel
efficient mackerel fisheries, Shetland’s figures for fuel combustion are still considered relatively
low. Furthermore, if the assertion of Ramos et al (2011) about the reasons for the low fuel
impact of the Basque region are correct, it suggests that the Shetland fleet could conceivably
lower its emissions further by landing its catch to the nearest port – especially during the late
season when the fish are passing closer to Shetland. However, it is acknowledged that there
may be economic or other practical reasons preventing this from happening. To provide a
comprehensive and more detailed view of the carbon footprint of the whole mackerel fishery,
additional research into the various fishing methods utilised (e.g. Scottish seine and inshore
mackerel handlining) is required along with a consideration of other national fleets utilising the
same stock.
4.3 Comparison of Results with Terrestrial Meat Studies
The CF of terrestrial food systems has long been explored in both the media, with growing
consumer awareness, and in scientific literature. There are difficulties in direct comparison of
aquatic systems with that of terrestrial systems due to vastly different methods involved in the
production of them. It can be argued that the only fair comparison would be in end of life CF or
LCA studies to ensure all contributions are accounted for. Nonetheless, as with aquatic systems,
terrestrial systems have typically found that the single largest contribution to most product
chains is that of the initial stage (to farm gate/slaughter).
34
Because of regional variation, and to avoid the complication of post farm gate emissions, only
studies considered the most relevant to the results of this study’s focus are shown in Table 4.
The criteria for this was that it was a UK based study, ending at ‘farm gate’ or just prior to
slaughter (measured in live weight), with preference given to the most recent study available.
The variation shown in the table is reflective of the different farming methods investigated in
the studies. It should be noted that the chosen allocation method typically used for terrestrial
meat studies differs from that of the aquatic, with economic allocation or by protein/energy
content preferred over general mass, as the difference in allocation methods has been shown
to have an effect on the overall LCA of a product (Svanes et al, 2011). As such, caution should
be used when comparing figures. However, a general theme is evident, with even the lowest
values (pork and chicken) showing a figure distinctly higher than those reported for the Atlantic
mackerel in this study. This conclusion is supported by additional research by Scarborough et al
(2013) who noted a positive relationship between personal CF (the carbon footprint created by
a specific individual in a year) and the quantity of meat eaten, with fish eaters found to have a
lower CF in general than full meat eaters, very closely followed by vegetarians and then vegans.
This study does not however list the typical diet of a ‘fish eater’ so it is unclear if it consists
more of the higher CF value species (often the more commercial ones such as cod and prawns)
or not. There is debate however as to whether the difference in personal CF is actually
connected to the chosen protein source or if awareness of sustainable produce is the key factor
(Risku-Norja et al, 2009).
Whether reflective of fish eaters having a lower CF diet than that of traditional meat eaters or
simply the result of more informed consumer choice, it is in keeping with the findings of this
study. Mackerel, as has been demonstrated in this study and many others, has a very low CF in
comparison to other fish species and under current guidelines is accepted as being sustainably
harvested (currently in the process of MSC assessment for recertification). Therefore an
increase of mackerel in the diet (assuming it is in replacement of other high emission meats and
within safe harvesting limits) could be beneficial both in increasing omega three oils in the diet
but also in lowering the consumer’s personal footprint. Additionally as only around 30.6 % of
people eat the government advised 2 portions of fish a week (Clonan, et al 2012), mackerel
35
promotion could help both achieve this goal while promoting sustainable protein choices in
general and promoting fish in particular.
Table 4 Carbon footprint values for UK based meat systems expressed in tonnes of carbon dioxide equivalent per tonne of live weight.
Meat type Place of study Authors Year of
publication
Carbon Footprint
Atlantic mackerel Shetland This study 2015 0.41
Beef UK EBLEX as per
APPG on Beef and
Lamb
2013 10.60-19.20
Sheep UK EBLEX as per
APPG on Beef and
Lamb
2013 11.00-13.60
Pork England Kool, et al 2009 3.50 – 4.40
Chicken UK Williams et al 2006 4.57 - 6.68
5 Conclusion
This study has found the Shetland Atlantic mackerel pelagic trawl fishery to have a comparably
low CF at the point of landing in comparison both to other fisheries and terrestrial meat
systems to a similar end point. This was found to be in keeping with other studies that show
small pelagic species and pelagic trawl fisheries in general to have a low CF value. Though
refrigerants do play a large part in the current estimation of CF for the Shetland fleet, this is
caused by a minority of vessels and will no longer be the case as of 2015 and the
implementation of new regulations regarding systems. Once refrigeration leakage has been
omitted, fuel consumption is the single main contributor to the CF, both for the fleet as a whole
36
and for individual vessels. As a result, any steps to further reduce fuel consumption will have a
positive effect on the fleet’s CF.
Although larger quantities of fish were landed in the later season, there was no noticeable
trend in fuel intensity between the two. This is most likely due to the fleet’s preference for
landing fish out-with the UK, removing any advantage of fishing close to Shetland as the fish
pass during migration. Although there are undoubtedly economic reasons for this preference, if
mackerel was landed locally more frequently, fuel consumption and subsequent CF would
almost certainly be reduced.
Unfortunately it was concluded at an early stage that a CF for the inshore mackerel fishery of
Shetland was not feasible as part of this study, but it is recommended that this be considered
for future study to allow for a comparison between the two methods and a more complete
figure for the Atlantic mackerel fishery of Shetland as a whole.
37
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