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AQUACULTURE ENVIRONMENT INTERACTIONS
Aquacult Environ Interact
Vol. 12: 485– 494, 2020
https://doi.org/10.3354/aei00378 Published November 5
1. INTRODUCTION
The European lobster Homarus gammarus (Lin-
naeus, 1758) is an important economic decapod
crusta cean, with a natural distribution ranging from
Morocco to northern Norway (Wilson 2008). Global
demand for lobster is increasing, but over the past few
decades wild stocks have been decreasing (Drengstig
& Bergheim 2013, Ellis et al. 2015, Nillos Kleiven et
al. 2019), prompting research into commercial hatch-
ery production of larvae for restocking purposes
(Addison et al. 1994, Schmalenbach et al. 2011).
However, lobsters grown in land-based hatcheries
and then directly released into the environment are
known to be vulnerable to immediate predation as
they have limited exposure to environmental stimuli
(Agnalt et al. 2017). To improve survivability, sea-
based containers have been used successfully to ac -
climatise juvenile lobsters to environmental condi-
tions before final release (Beal et al. 2002, Perez
Benavente et al. 2010, Beal & Protopopescu 2012,
Daniels et al. 2015, Halswell et al. 2016). At the
release stage, juvenile lobsters form small burrows in
sediment and feed on zooplankton and organic mat-
ter particles suspended in the water column, using
currents created by their pleopods (swimmerets).
The particle sizes consumed at this stage are nor-
mally between 60 and 100 µm (Lavalli & Barshaw
1989), suggesting that they are able to consume fine
particulate wastes from fish farms.
Atlantic salmon Salmo salar cage farms are gener-
ally sited in coastal environments and release nutrient-
© The authors 2020. Open Access under Creative Commons by
Attribution Licence. Use, distribution and reproduction are un -
restricted. Authors and original publication must be credited.
Publisher: Inter-Research · www.int-res.com
*Corresponding author: tasosbaltak@gmail.com
European lobsters utilise Atlantic salmon wastes
in coastal integrated multi-trophic aquaculture
systems
A. Baltadakis1,*, J. Casserly2, L. Falconer1, M. Sprague1, T. C. Telfer1
1Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
2Marine Institute, Rinville, Oranmore H91 R673, Ireland
ABSTRACT: In this study, we investigated if juvenile European lobsters Homarus gammarus would
eat waste from Atlantic salmon Salmo salar cages in a coastal integrated multi-trophic aquacul-
ture (IMTA) setup and if there were any impacts on growth. Trophic interactions between salmon
and lobsters were assessed using δ15N and δ13C stable isotope analysis and fatty acid profiling
from fish feed as indicators of nutrient flow. Analysis revealed that lobsters directly utilised partic-
ulate waste from salmon production, as levels of indicator fatty acids from salmon feed were sig-
nificantly higher in lobster tissues near the fish cages compared to the control site. Route of uptake
may have been direct consumption of waste feed or faecal material or indirectly through fouling
organisms. Stable isotope analysis did not indicate nutrient transfer to lobsters, suggesting that
the duration of the study and/or the amount of waste consumed was not sufficient for stable isotope
analysis. Lobsters grew significantly over the trial period at both sites, but there was no significant
difference in lobster growth between the sites. Our results show a trophic relationship between
salmon and lobsters within this IMTA system, with no apparent advantage or disadvantage to
growth.
KEY WORDS: Integrated multi-trophic aquaculture · IMTA · Lobster · Salmon · Fatty acids ·
Stable isotopes · Ecosystem services
O
PEN
PEN
A
CCESS
CCESS
486 Aquacult Environ Interact 12: 485–494, 2020
rich particulate and dissolved wastes such organic
carbon and nitrogen from uneaten food and faecal
wastes and excreted soluble nitrogen into the sur-
rounding environment (Wang et al. 2012). The con-
cept of integrated multi-trophic aquaculture (IMTA)
endeavours to utilise these wastes, thereby increasing
the resource efficiency of trophically linked co-cultured
species to improve nutrient uti lisation for environ-
mental mitigation while producing additional organ-
isms (Chopin et al. 2012). Placing lobsters in sea-
based containers next to fish cages may provide a
regular food supply, together with other potentially
beneficial conditions (e.g. shelter, co-location for effi-
ciency improvements), for improved growth and
management. This may also function as an ecosystem
service from salmon aquaculture and provide positive
societal benefits; for example, if there is improve-
ment of growth and better survival when released, it
could aid enhancement of local lobster populations
and any re sulting fishery.
Performance of IMTA can be measured empirically
by comparing growth or nutrient uptake by the con-
sumer species between the culture site and a refer-
ence location. This approach has been used to assess
shellfish growth (Sarà et al. 2009, Lander et al. 2013)
and nutrient uptake and growth of seaweeds (Blouin
et al. 2007, Abreu et al. 2009). Direct nutrient transfer
between species is commonly in vestigated using bio-
chemical tracers, such as fatty acids (FAs) and stable
isotopes (Redmond et al. 2010, Colombo et al. 2016,
White et al. 2019, Sardenne et al. 2020).
FAs have been used to assess the dispersal of par-
ticulate-derived waste, both spatially and through
food webs, with studies assessing the level of influ-
ence aquaculture has on wild fish and benthic com-
munities (e.g. Fernandez-Jover et al. 2009, 2011,
White et al. 2017, 2019, Woodcock et al. 2018). How-
ever, assessing the performance of an IMTA system
with FAs is dependent on the target species, as there
have been variable results using blue mussels Mytilus
edulis (Redmond et al. 2010, Irisarri et al. 2015),
although more consistency has been found for zoo-
plankton (Fernandez-Jover et al. 2009), shrimp (Olsen
et al. 2012) and sea urchins (George & Parrish 2015).
Stable isotopes of carbon and nitrogen have been
used widely to assess the flow of nutrients through
food webs, and more recently, to trace waste products
from aquaculture (Marín Leal et al. 2008, Deudero et
al. 2012). Stable isotopes assimilate within the tissues
of consumers, with heavier isotopes, 13C and 15N, re-
maining longer in animal tissues than lighter ones, 12C
and 14N, which are rapidly utilised during metabolism
(Marín Leal et al. 2008). Consequently, the tissues of
organisms tend to adopt the same stable isotopic signa-
ture as their food source (Paulet et al. 2006). δ13C
and δ15N ratios have been applied for nutrient tracking
within IMTA systems with fish and mussels in the
Bay of Fundy, Canada (Irisarri et al. 2015), fish with
oysters and mussels (Navarrete-Mier et al. 2010) and
in multiple farms with fish and mussels in the Western
Mediterranean (Sanz-Lazaro & Sanchez-Jerez 2017).
The aim of this study was to investigate if juvenile
European lobsters would consume wastes from salmon
cages by assessing the nutrient transfer between
salmon waste and lobsters within a pilot-scale coastal
site and whether there were any positive or negative
effects on growth. FA analysis and stable isotopes were
used as tracers of nutrient transfer, and growth was
determined as an increase in carapace length (CL).
2. MATERIALS AND METHODS
2.1. Experimental site and data collection
The study was conducted at the Lehanagh Pool
marine research site, a small-scale experimental IMTA
site in Bertraghboy Bay, Connemara, County Galway,
Ireland (Fig. 1), between January 2018 and March
2019. The site comprised 2 polar circle cages (50 m
circumference and 8 m deep) at a water depth of 21 m.
These were stocked in April 2018 with 7660 Atlantic
salmon post-smolts (5360 and 2300 in the 2 cages), aver-
aging 90 to 100 g. In addition, 400 lumpfish Cyclopetrus
lumpus, averaging 40−50 g, were also stocked into
each cage as a preventative method for controlling
sea lice as per commercial standards. The fish were
hand-fed a maintenance diet according to the manu-
facturer’s feeding tables. The site was managed ac-
cording to organic farm standards, with no prescrip-
tion medicines or antifoulants used. A control site for
the study was set up approximately 300 m west of the
cages. European lobsters (Stage IV juveniles, n = 204)
were deployed in May 2018 (108 at the cage site, 96 at
the control site) within sea-based container culture
(SBCC) structures (see Daniels et al. 2015). Lobsters (n
= 36) were housed individually and labelled in each
stack suspended from the cages at 2 m depth and
from a longline at the control site at the same depth.
Particulate organic matter loading from the salmon
cages was modelled with a spreadsheet-based partic-
ulate dispersion model (Telfer et al. 2006) to assess the
organic load dispersal and deposition around the cages
and ensure that the SBCC structures were situated
in locations where the lobsters would be ex posed to
salmon waste and that the control site was far enough
487
Baltadakis et al.: Lobsters and integrated multi-trophic aquaculture
away not to be influenced by particu-
late wastes. The model was run using
data from fish production and measured
current speeds and directions collected
using a MIDAS ECM self-re cording
electromagnetic current meter (Vale-
port) deployed at 2 depths (9 and 14 m)
within 50 m of the cages between 1 and
15 July 2018.
During this time, 3 sediment traps
were positioned to assess the numerical
and distributional accuracy of the model.
Two sediment traps were placed at a
depth of 19 m, one 0 m and one 5 m from
the south-west cage; the latter was be-
tween the 2 cages. The third sediment
trap was deployed at the control site at
5 m depth. Each sediment trap had 4
cylinders with a height:diameter ratio
7.5:1 (60:8 cm) secured vertically on a
gimballed stainless steel frame. A clear
container (plastic fixed pot) was
screwed onto the bottom of every cylinder. The design
of the sediment traps was based on specifications in
Blomqvist & Hakanson (1981). Total sedimentation
rate per m2over 15 d was calculated by dry weight
(DW). Model outputs were compared to amount of
waste material collected in deployed sediment traps
next to the cages to assess model accuracy.
2.2. Lobster growth
Lobsters were deployed in SBCCs at the cage site
at the beginning of April 2018, and growth measure-
ments commenced after a period of 1 mo. Growth of
lobsters was as sessed by measuring CL (mm) on 9
occasions over a 319 d period, between May 2018 and
March 2019. Due to variable weather conditions, be -
tween 20 and 60 lobsters were randomly subsampled
from the cage and control sites, at each sampling
event. Each lobster was re moved from the SBCC unit
and placed on gridded paper. A digital image was
taken at 90 degrees to each specimen. The lobster
was then returned to its container and to the water.
CL was measured from the images using Digi mizer
image analysis software (MedCalc Software).
CL gain (CLG) was used as an indicator of growth
at the cage and control sites and was calculated as:
CLG = CLt− CL0(1)
where CLtis final CL and CL0is initial CL.
A von Bertalanffy growth curve (von Bertalanffy
1938) was fitted to the mean CL measurements during
the trial:
(2)
where L(t) is CL (mm) as a function of time (t), L∞is the
largest lobster CL, and Kis the growth coefficient
(yr−1).
2.3. Lipid and FA analysis
At the end of the trial (March 2019), 20 juvenile
lobsters were sampled and stored in a freezer (−20°C)
overnight. The next day, samples were shipped on
ice to the University of Stirling for analysis. Ten indi-
vidual juvenile lobsters from the control and 10 from
the cage location, and a sample of the salmon aqua -
feed used at the cage site were individually homo -
genised and subjected to lipid extraction.
Total lipids were extracted from 0.5−1.0 g of feed
and lobster tissue in ice-cold chloroform:methanol
solution (ratio 2:1, v/v). Extraction of lobster tissue
was achieved using 20 ml of solution and feed using
36 ml of solution. The samples were homogenised in
an Ultra-Turrax tissue disruptor (Fisher Scientific).
Lipid content was determined gravimetrically (Folch
et al. 1957).
FA methyl esters (FAMEs) were separated from
total lipids by acid-catalysed transmethylation at 50°C
( ) {1 exp[– ( – )]}
0
Lt L Kt t=∞−
Fig. 1. Bertraghboy Bay, Ireland, and the location of the marine research site.
The photograph shows the cage site and the sea-based container culture
(SBCC) structures. The black circle indicates the location of the experimental
site in relation to the Irish West Coast
Aquacult Environ Interact 12: 485–494, 2020
for 16 h using 2 ml of 1% (v/v) sulphuric acid (95%,
Aristar®, BDH Chemicals) in methanol and 1 ml
toluene (Christie 1993). FAMEs (6 ml) were extracted
and purified by adsorption chromatography using
500 mg sorbent acid washed solid-phase extraction
cartridges (Clean-up® silica extraction columns; UCT).
Cartridges were pre-conditioned with 5 ml of iso-
hexane before the sample was added and the FAMEs
eluted with 10 ml isohexane:diethyl ether (95:5, v/v)
and separated and quantified by gas-liquid chromato -
graphy using a Fisons GC-8160 (Thermo Scientific)
equipped with a 30 m × 0.32 mm i.d. × 0.25 µm ZB-wax
column (Phenomenex). Hydrogen was used as the
carrier gas with an initial oven gradient of 50 to 150°C at
40°C min−1 to a final temperature of 230°C at 2°C min−1.
Individual FAMEs were identified by comparison to
standards (SupelcoTM 37- FAME mix; Sigma-Aldrich).
All data were collected and processed using Chrom-
CardTM for Windows (Version 1.19; Thermoquest Italia)
software. 17:0 heptadecanoic acid was used as inter-
nal standard to calculate FA content per g of tissue.
Predominant FAs measured within the salmon feed
were used as tracers. A total of 5 FAs were selected.
Three FAs, oleic acid (OA, 18:1n-9), linoleic acid (LA,
18:2n-6) and α-linolenic acid (ALA, 18:3n-3), were
based on the in creased ‘terrestrial’ FAs derived from
an increasing inclusion level of vegetable oil used
within salmon feed (Sprague et al. 2016). Cetoleic acid
(22:1n-11) and eicosenoic acid (20:1n-9) were also cho-
sen, as they tend to be typically found in higher quan-
tities within salmon feed and have consequently been
observed in fish farm waste (Henderson et al. 1997).
2.4. Stable isotope analysis
Five samples of lobster leg muscle from each site
(n = 5 control site, n = 5 cage site) and 2 samples of
salmon feed were subjected to stable isotope analysis.
Each sample was frozen at −20°C prior to lyophilisa-
tion in a Christ Alpha 1-4 LSC freeze-drier (Martin
Christ Gefriertrocknungsanlagen). For the analysis,
0.7 mg of lobster leg muscle and 1.5 mg of feed were
weighted into 3 × 5 mm tin capsules and loaded onto
an Elementar Procure analyser, which converted
organic N and C in the samples to N2and CO2for
measurement of δ15N and δ13C, respectively, on a
Thermo-Fisher-Scientific Delta XP Plus isotope ratio
mass spectrometer.
Units of isotope ratios were expressed in δ15N
and δ13C:
(3)
where Xis 13C or 15N, and Ris either the 13C:12C ratio
or the 15N:14N ratio. In-house reference materials
used were: gelatine solution, alanine-gelatine solu-
tion spiked with 13C-alanine, and glycine-gelatine
solution, each dried for 2 h at 70°C. Four USGS 40
glutamic acid standards (Qi et al. 2003, Coplen et al.
2006) were used as independent checks of accuracy.
2.5. Statistical analyses
FA percentages for each sample were arcsine
transformed prior to statistical analysis to correct for
the binomial distribution of proportional data (Sokal
& Rohlf 1995). FAs occupying more than 0.1% of the
feed FA profile were compared between the cage
and the control site, using a 2-sample Student’s t-test.
Statistical tests were performed using MinitabTM sta-
tistical software. Principal component analysis (PCA)
was used to classify and discriminate between the FA
profiles of the lobster samples at different locations.
PCA creates 2 orthogonal values (principal compo-
nents, PCs) which are representative of the original
variables. The higher the PC value is, the more re -
presentative of the data set it is. PCA was per-
formed using MVSP statistical software (KCS). A
non-parametric multivariate ANOSIM was performed
with PRIMER 5 (Clark & Gorley 2001) to detect sig-
nificant differences be tween a priori sources of vari-
ation for the cage site and control site results (as
defined factors) using a Bray-Curtis similarity matrix.
Stable isotopes (δ13C and δ15N) for lobster leg mus-
cle were compared between the 2 locations using a
2-sample Student’s t-test, using Minitab software.
Growth was compared between the 2 locations
over time with a repeated-measures ANOVA, using
SPSS Ver 26 software (IBM). As sphericity is an im -
portant assumption of a repeated-measures ANOVA
(where the variances of the differences between all
possible pairs of within-subject conditions are equal),
the growth data were tested using Mauchly’s test of
sphericity.
3. RESULTS
3.1. Waste dispersion and current flow at
the cage site
The hydrographic data collected by the current
meter showed that the cage site was characterised by
moderate to slow average current speeds of 0.040 m
s−1 in mid-water and 0.028 m s−1 near the seabed. The
1 1000
sample
standard
XR
R
()
δ=−
⎡
⎣
⎢⎤
⎦
⎥×
488
Baltadakis et al.: Lobsters and integrated multi-trophic aquaculture 489
residual current flow showed a very slow movement
in a southerly direction over time. Distribution of par-
ticulate waste from the cages over the trial period
was very local to the fish cages, with only low
amounts of particulate waste travelling beyond 20 m
from the cage edge (Fig. 2).
Model predictions of sedimentation for suspended
solids near the SBCC deployment locations (100−
200 g m−2 15 d–1) showed broad agreement with aver-
age sediment trap-collected material (252 g m−2 15 d–1).
However, the model underestimated the distribu-
tion of solid waste between the cages, with modelled
values of 50 and 100 g vs. an average measured value
of 368 g m−2 15 d–1. Both model and sediment traps
illustrated that the SBCCs near the cages were placed
in areas of high particulate waste distribution of
between 100 and 200 g m−2 15 d–1. The models also
showed little possibility that much particulate waste
from the cages would reach the control lobster site
approximately 300 m to the west.
3.2. FAs
The FA profile of lobster tissues varied with loca-
tion, as the amount of FA tracers (given as % of total
lipid) showed significant differences (p < 0.05) be -
tween the cages and control stations (Table 1). Lob-
sters located near the cages had a significantly higher
total lipid content (1.22 ± 0.34 mg g−1 DW; mean ± SD)
than those at the control site (0.93 ± 0.19 mg g−1 DW)
(p < 0.05). The FA profile of the supplemented sal -
mon feed was largely characterised by OA (18:1n-9;
24.4%), eicosenoic acid (20:1n-9; 7.2%), cetoleic acid
(22:1n-11; 12.8%), LA (18:2n-6; 11.6 %) and ALA
(18:3n-3; 4%), confirming that these FAs are indica-
tive and appropriate for use as tracers. The relative
percentages of these FAs were significantly higher
(p < 0.05) in lobsters located near the cage site (Fig. 3)
than in those at the control site. Additionally, n-6
polyunsaturated FA (PUFA) levels were found to be
significantly higher at the cage site (12.24 ± 0.77%)
compared to the control (10.27 ± 0.65 %) (p < 0.05),
with LA (18:2n-6) being higher in the cage (6.3 ±1.4%)
Fig. 2. Contour plot of suspended solids settlement (g m−2
15 d–1) around cages 1 and 2, presented as output from a
spreadsheet-based dispersion model
Feed Lobsters Signifi-
Cages Control cance
Total lipid (%) 24.16 1.22 ± 0.34 0.93 ± 0.18
Fatty acids
14:0 4.6 1.2 ± 0.3 0.5 ± 0.1 ***
16:0 10.6 12.1 ± 0.5 11.8 ± 0.5 NA
18:0 1.5 4.6 ± 0.6 6.8 ± 0.4 ***
20:0 0.3 0.4 ± 0.0 0.5 ± 0.1 ***
Total saturated 17.4 19.3 ± 0.8 20.8 ± 0.5 ***
16:1n-7 3.4 3.1 ± 0.5 2.7 ± 0.4 *
18:1n-9 24.0 14.6 ± 1.6 8.4 ± 0.8 ***
18:1n-7 2.0 5.2 ± 0.4 6.3 ± 0.6 ***
20:1n-9 7.2 3.4 ± 0.5 1.5 ± 0.2 ***
22:1n-11 12.7 3.9 ± 1.2 0.1 ± 0.1 ***
24:1n-9 0.7 0.4 ± 0.1 0.1 ± 0.1 ***
Total monoenes 51.9 33.8 ± 3.6 21.6 ± 1.3 ***
18:2n-6 11.5 6.4 ± 1.4 0.9 ± 0.1 ***
20:2n-6 0.2 1.2 ± 0.2 1.4 ± 0.1 *
20:4n-6 0.3 3.6 ± 0.7 6.6 ± 0.9 ***
Total n-6 PUFAs 12.0 12.2 ± 0.8 10.3 ± 0.7 ***
18:3n-3 4.0 0.8 ± 0.1 0.5 ± 0.1 ***
18:4n-3 2.0 0.6 ± 0.2 0.4 ± 0.1 **
20:3n-3 0.1 0.4 ± 0.0 0.5 ± 0.0 ***
20:4n-3 0.3 0.5 ± 0.1 0.5 ± 0.1 NA
20:5n-3 5.0 14.9 ± 2.0 22.8 ± 1.0 ***
22:5n-3 0.6 1.2 ± 0.2 1.4 ± 0.8 NA
22:6n-3 5.5 13.8 ± 1.5 17.3 ± 1.5 ***
Total n-3 PUFAs 17.8 32.3 ± 3.0 43.3 ± 1.4 ***
Total PUFAs 30.7 44.7 ± 2.6 54.1 ± 1.4 ***
Total DMA 0.0 2.2 ± 0.5 3.4 ± 0.5 ***
Table 1. Fatty acid (FA) profile (% FA of total lipid) of lobster
muscle. Values are means (±SD). Last column indicates
level of significance between the 2 locations (***p < 0.001,
**p < 0.01, *p < 0.05). PUFA: polyunsaturated FA; DMA: di-
methyl acetal. Total saturated FAs also include 15:0, iso17:0,
anteiso17:0, iso18:0, anteiso18:0, 22:0 and 24:0; total mono -
enes also include 16:1n-9, 17:1, 20:1n-11, 20:1n-7 and 22:1n-9;
total n-6 PUFAs also include 18:3n-6, 20:3n-6, 22:4n-6 and
22:5n-6; total n-3 PUFAs also include 21:5n-3; total PUFAs
also include 16:2, 16:3 and 16:4; total DMA includes 16:0
DMA, 18:0 DMA, 18:1 DMA and 20:0 DMA. NA: not appli-
cable
Aquacult Environ Interact 12: 485–494, 2020
490
compared to the control (0.9 ± 0.1 %) (p < 0.05) (see
Table 1). Overall, tracer FAs accounted for 29.08% of
the total lipid content of the cage station, which was
significantly higher when compared to the control
station (11.36%). Conversely, total n-3 PUFA levels
were significantly higher (p < 0.05) at the control site
(43.27 ± 1.38%) compared to the cage site (32.3± 3%).
FA s contributing to the difference between the con-
trol and the cage site were eicosapentaenoic acid
(EPA, 22.8 ± 1% and 14.9 ± 0.9 %) and docosa-
hexaenoic acid (DHA, 17.2 ± 1.46% and 13.8 ±1.4%),
respectively.
The PCA plot (Fig. 4) indicated clear differences
between FA profiles of lobster leg muscle from the
cage site and from the control site along PC-1, which
accounted for 92.8% of the total variance in the data.
Post hoc ANOSIM confirmed the groups from control
and cage sites were significantly different (p < 0.05, R =
0.994). The FAs primarily driving this difference at
the cage site were OA (18:1n-9) and LA (18:2n-6) of
terrestrial origin, along with eicosenoic acid (20:1n-9)
and cetoleic acid (22:1n-11). These are marine oil-
based, and both were incorporated at high levels
within the salmon feed. On the other hand, EPA and
DHA together with arachidonic acid (20:4n-6) were
more dominant in defining the FA profile at the con-
trol site, making it likely that the diet of the lobsters
was primarily influenced by naturally derived marine
oils, accounting for 40.4% of total FAs compared to
28.7% for lobsters at the cages (Table 1).
3.3. Stable isotopes
The δ13C and δ15N signatures for lobster tissue at
the control and cage sites were similar, as shown by
their similar positions in the plot (Fig. 5). However,
the signature for salmon feed differed from those
found for lobsters (Fig. 5). A 2-sample Student’s t-test
Fig. 3. Contribution of selected fatty acids (% of total lipid,
mean ± SD) to the total fatty acid content in the lobster tissue
at the end of the experiment (March 2019) at the control and
cage sites. Feed levels are included for reference
Cage
Control
PC-2
PC-1
–0.01
–0.02
–0.04
0.01
–0.05
0.02
0.04
0.05
0.06
–0.01–0.02–0.04–0.05 0.01 0.02 0.04 0.05 0.06
16:1n-7
18:1n-9
18:1n-7
20:1n-9
22:1n-11
24:1n-9
18:2n-6
20:4n-6
20:5n-3
22:5n-3
22:6n-3
Vector scaling: 0.07
Fig. 4. Principal component analysis for fatty acid profiles
(over 0.1%) from the leg muscle of lobsters taken from the
cage and control sites. Vectors for key fatty acids responsible
for the grouping pattern are displayed
Baltadakis et al.: Lobsters and integrated multi-trophic aquaculture
indicated no significant differences for δ13C or δ15N
between cage and control sites for lobsters (t = 1.33,
df = 5, p = 0.240), and neither showed any similarity
to the signatures for the salmon feed.
3.4. Growth of lobsters
An increase in CL was observed over the trial
period at both cages and control sites. These were fit-
ted to von Bertalanffy growth curves (Fig. 6) using
calculated values of K= 0.0048, t0= −32.08 for the
cage site and K= 0.0044, t0= −0.4318 for the control
site. After Mauchly’s test showing that the data con-
formed to sphericity (W = 0.0224, p = 0.150), the
repeated-measures ANOVA indicated significant
growth in lobsters over the trial period (F = 77.5, p <
0.001) at both sites, although there was no significant
difference in lobster growth between the sites (F =
20.9, p = 0.149).
4. DISCUSSION
The aim of this study was to determine if juvenile
European lobsters would feed on waste from salmon
cages in a coastal IMTA setup and assess if there
was a subsequent impact on growth of the lobsters.
Other studies have shown that the flow of wastes
from coastal finfish aquaculture could potentially be
used for aquaculture-based production of extractive
species such as kelp (Fossberg et al. 2018) and
bivalves (Lander et al. 2012). In this study, we eval-
uated a novel combination of co-cultured species
wherein the juvenile lobsters would be used for re -
stocking purposes rather than as an additional eco-
nomic crop.
The results from the FA analysis showed that the
content of OA (18:1n-9), LA (18:2n-6), ALA (18:3n-3),
cetoleic acid (22:1n-11) and eicosenoic acid (20:1n-9),
which were characteristic of the salmon feed used,
were each significantly higher in the tissues of the
lobsters located near the cages than in those at the
control location. The PCA further confirmed these
results, as the lobsters at the cage and control sites
showed distinctly different FA profiles, which sug-
gests different food sources. The FA profile of lob-
sters at the cage site was clearly influenced by the
salmon feed, whereas at the control site, lobster
nutrition was dominated by natural marine oils.
In contrast, stable isotope analysis of lobster leg
muscle taken at the cage and control sites showed lit-
tle difference in the δ15N ratio between locations, nor
was there a similarity between the signature ratio for
lobster tissue and salmon feed. There may be several
reasons for the differences between the FA tracers
and the stable isotope analysis. Bethoney et al. (2011)
demonstrated that δ15N values in lobster tissue
reflect their long-term diet, so the time-period of our
study may not have been long enough. Another con-
sideration is that there may have been an insufficient
amount of waste consumed to establish an isotopic
signal, as lobsters are slow and periodic feeders (Bor-
dner & Conklin 1981).
491
Fig. 5. Biplot of δ15N and δ13C (mean ± SD) stable isotopes
of lobster leg muscle and supplemented feed between
cage and control stations at the end of the trial in
March 2019
Fig. 6. Growth curves of lobsters between control and cage
stations, based on measured values (mean ± SD). Von Berta-
lanffy growth functions plotted by trial day and increases in
carapace length for 319 d of the trial. Parameters estimated
for the cage site were L∞= 9.43, K= 0.0044, t0= −0.4318, and
control site L∞= 8.44, K= 0.0048, t0= −0.3208
Aquacult Environ Interact 12: 485–494, 2020
Based on their FA profiles, juvenile lobsters at
the cage site consumed fish farm nutrient waste,
although it was not clear if this was direct or indirect.
The sizes of waste feed and faecal particles in the
water column from the salmon cages were not meas-
ured in this experiment, but other studies have
shown that suspended particulate organic matter
originating from cages is often between 1 and 10 µm
(Lander et al. 2013) and up to 300 µm (Law et al.
2014). As the internal mesh size of the SBCC struc-
tures was 2.5 × 2.5 mm (Daniels et al. 2015), particles
of waste this size could have entered the SBCC and
been within the size range eaten directly by juvenile
lobsters (Lavalli & Barshaw 1989). Studies have
demonstrated direct uptake of waste particles by
consumer IMTA species (Handå et al. 2012, Bergvik
et al. 2019). However, in the marine environment
there will be a wider dietary choice and a complex
food web. An in situ study showed that mussels did
not directly assimilate wastes and had a selective
diet, preferring other sources of food (Sanz-Lazaro &
Sanchez-Jerez 2017). Even within the SBCC system,
there would be a dietary choice (Daniels et al. 2015),
and the uptake of wastes by lobsters could have been
indirect via fouling organisms.
Despite the differences in the FA profiles of the
juvenile lobsters at the cage site and the reference
site, there was no significant difference in growth.
Information on growth rates of wild juvenile Euro-
pean lobsters is scarce (Mercer et al. 2001, Wahle et
al. 2013), which prevents comparison to natural con-
ditions. Stage IV is the first postlarval stage of the
life cycle, and juvenile lobsters are transitioning to
benthic organisms (Charmantier et al. 1991). There-
fore, the position of the SBCC may not have been
deep enough in the water column for their feeding
behaviour and could have influenced the results, as
other studies have shown that depth can be an
important factor in IMTA systems (Sanz-Lazaro et
al. 2018). There will always be multiple factors to
consider in designing the optimal setup and there
will often be trade-offs (Halswell et al. 2018). In this
case, the scale of the experimental site meant there
were limited options to position the SBCC within the
waste stream of the fish cage. This study focussed
on 1 cage site and 1 control site, but the dispersal of
wastes around fish cages varies depending on site
characteristics, and other locations may have had
different results. Furthermore, this research used a
pilot-scale experimental site, but the results may be
different if the research was repeated at a full-
scale commercial farm, as there would be higher
volumes of waste.
Previous studies have demonstrated the advantage
of acclimatising juvenile lobsters using in situ containers
as a way of improving survivability (Beal et al. 2002,
Perez Benavente et al. 2010, Beal & Proto po pescu 2012,
Daniels et al. 2015, Halswell et al. 2016), and locating
an SBCC next to salmon cages might offer additional
shelter from storm events. However, it is also impor-
tant to note that fish medication can be harmful to ju-
venile lobsters, and is often used to treat fish diseases
(Burridge et al. 2014, Cresci et al. 2018). The effect of
routine operations, such as disease treatment, on the
different components of an IMTA system is not only an
issue for lobsters and salmon, but is an essential con-
sideration for any combination of species in an IMTA
system. For example, lobsters could only be deployed
at sites which use non-medicinal treatments.
The interaction between salmon cages and wild
lobsters is an important area of research, especially
in Canada where studies have explored the conflict
over use of space between salmon farms and lobster
fisheries (Walters 2007, Grant et al. 2019). In Canada
and Norway, research has also focussed on the
potential impact of medicinal treatments used for
salmon aquaculture on lobsters (Burridge et al. 2014,
Cresci et al. 2018). This present study focussed on
potential benefits of having lobsters in an IMTA sys-
tem alongside salmon cages prior to release into the
wild for restocking purposes. The results clearly
demonstrated utilisation of wastes from the salmon
cages, but this had no obvious impact on growth.
Other potential implications for lobster physiology,
metabolic processes and behaviour were not ex -
plored. Sardenne et al. (2020) suggested that a diet
shift toward waste fish feed may have an influence
on reproductive success in some wild crustaceans.
Therefore, although a trophic connection has been
established within this system, further research and
trials will be required to determine if a coastal
salmon−lobster IMTA setup would be appropriate as
a stage in lobster restocking programmes.
Acknowledgements. This work received funding from the
European Union’s Horizon 2020 research and innovation
programme under Grant Agreement No. 678396 (Tools for
Assessment and Planning of Aquaculture Sustainability,
TAPAS). We are grateful to Dr. Ronan Browne, Bord Ias-
caigh Mhara and to the staff of the Marine Institute, par-
ticularly Frank Kane, for kindly providing administrative
management and practical support through the sampling
campaign. We also thank Dr. Carly Daniels and the staff
of the National Lobster Hatchery for their support; the
Nutritional Analytical Services, University of Stirling, for
providing analytical facilities; and Maria Scolamacchia
and Jessica Di Toro for providing training support on FA
analysis.
492
Baltadakis et al.: Lobsters and integrated multi-trophic aquaculture
LITERATURE CITED
Abreu M, Varela D, Henríquez L, Villarroel A, Yarish C,
Sousa-Pinto I, Buschmann A (2009) Traditional vs. inte-
grated multi-trophic aquaculture of Gracilaria chilensis
C. J. Bird, J. McLachlan & E. C. Oliveira: productivity
and physiological performance. Aquaculture 293:
211−220
Addison J, Lovewell S, Bannister R (1994) Growth, move-
ment, recapture rate and survival of hatchery-reared
lobsters (Homarus gammarus (Linnaeus, 1758)) released
into the wild on the English east coast. Crustaceana 67:
156−172
Agnalt A, Grefsrud E, Farestveit E, Jørstad K (2017) Training
camp — a way to improve survival in European lobster
juveniles? Fish Res 186: 531−537
Beal B, Protopopescu G (2012) Ocean-based nurseries for
cultured lobster (Homarus americanus Milne Edwards)
postlarvae: field experiments off the coast of eastern
Maine to examine effects of flow and container size on
growth and survival. J Shellfish Res 31: 167−176
Beal B, Mercer JP, Conghaile AO (2002) Survival and
growth of hatchery-reared individuals of the European
lobster Homarus gammarus (L.), in field-based nursery
cages on the Irish west coast. Aquaculture 210: 137−157
Bergvik M, Stensås L, Handå A, Reitan K, Strand Ø, Olsen Y
(2019) Incorporation of feed and fecal waste from salmon
aquaculture in great scallops (Pecten maximus) co-fed by
different algal concentrations. Front Mar Sci 5: 524
Bethoney ND, Stokesbury KDE, Stevens BG, Altabet MA
(2011) Bait and the susceptibility of American lobsters
Homarus americanus to epizootic shell disease. Dis
Aquat Org 95: 1−8
Blomqvist S, Hakanson L (1981) A review on sediment traps
in aquatic environments. Arch Hydrobiol 91: 101−132
Blouin N, Xiugeng F, Peng J, Yarish C, Brawley S (2007)
Seeding nets with neutral spores of the red alga Por-
phyra umbilicalis (L.) Kützing for use in integrated
multi-trophic aquaculture (IMTA). Aquaculture 270:
77−91
Bordner CE, Conklin DE (1981) Food consumption and
growth of juvenile lobsters. Aquaculture 24: 285−300
Burridge LE, Lyons MC, Wong DKH, MacKeigan K, VanGeest
JL (2014) The acute lethality of three anti-sea lice
formulations: AlphaMax®, Salmosan®, and Interox®
Para move™50 to lobster and shrimp. Aquaculture 420-
421: 180−186
Charmantier G, Charmantier-Daures M, Aiken DE (1991)
Metamorphosis in the lobster Homarus (Decapoda): a
review. J Crustac Biol 11: 481−495
Chopin T, Cooper J, Reid G, Cross S, Moore C (2012) Open-
water integrated multi-trophic aquaculture: environ-
mental biomitigation and economic diversification of fed
aquaculture by extractive aquaculture. Rev Aquacult 4:
209−220
Christie WW (1993) Preparation of derivatives of fatty acids
for chromatograpgic analysis. In: Christie WW (ed) Ad -
vances in lipid methodology—two. Oily Press, Dundee,
p 69– 111
Clark KR, Gorley RN (2001) PRIMER v5: user manual/
tutorial. PRIMER_E, Plymouth
Colombo SM, Parrish CC, Whiticar MJ (2016) Fatty acid sta-
ble isotope signatures of molluscs exposed to finfish
farming outputs. Aquacult Environ Interact 8: 611−617
Coplen TB, Brand WA, Gehre M, Gröning M, Meijer HAJ,
Toman B, Verkouteren MR (2006) New guidelines for
δ13C measurements. Anal Chem 78: 2439−2441
Cresci A, Samuelsen OB, Durif CMF, Bjelland RM, Skiftes -
vik AB, Browman HI, Agnalt AL (2018) Exposure to
teflubenzuron negatively impacts exploratory behaviour,
leaning and activity of juvenile European lobster
(Homarus gammarus). Ecotoxicol Environ Saf 160:
216−221
Daniels C, Wills B, Ruiz-Perez M, Miles E, Wilson R,
Boothroyd D (2015) Development of sea-based container
culture for rearing European lobster (Homarus gam-
marus) around South West England. Aquaculture 448:
186−195
Deudero S, Díaz D, Tor A, Mallol S, Goñi R (2012) Isotopic
fractionation in wild and captive European spiny lobsters
(Palinurus elephas). J Crustac Biol 32: 421−424
Drengstig A, Bergheim A (2013) Commercial land-based
farming of European lobster (Homarus gammarus (L.)) in
recirculating aquaculture system (RAS) using a single
cage approach. Aquacult Eng 53: 14−18
Ellis CD, Hodgson DJ, Daniels CL, Boothroyd DP, Bannister
RCA, Griffiths AGF (2015) European lobster stocking
requires comprehensive impact assessment to determine
fishery benefits. ICES J Mar Sci 72(Suppl 1): i35−i48
Fernandez-Jover D, Sanchez-Jerez P, Bayle-Sempere J,
Arechavala-Lopez P, Martinez-Rubio L, Jimenez JAL,
Lopez FJM (2009) Coastal fish farms are settlement sites
for juvenile fish. Mar Environ Res 68: 89−96
Fernandez-Jover D, Arechavala-Lopez P, Martinez-Rubio L,
Tocher DR and others (2011) Monitoring the influence of
marine aquaculture on wild fish communities: benefits
and limitations of fatty acid profiles. Aquacult Environ
Interact 2: 39−47
Folch J, Lees M, Sloane Stanley GH (1957) A simple method
for the isolation and purification of total lipids from ani-
mal tissues. J Biol Chem 226: 497−509
Fossberg J, Forbord S, Broch OJ, Malzahn AM and others
(2018) The potential for upscaling kelp (Saccharina latis-
sima) cultivation in salmon-driven integrated multi-
trophic aquaculture (IMTA). Front Mar Sci 5: 418
George EM, Parrish CC (2015) Invertebrate uptake of lipids
in the vicinity of Atlantic salmon (Salmo salar) aqua-
culture sites in British Columbia. Aquacult Res 46:
1044−1065
Grant J, Simone M, Daggett T (2019) Long-term studies of
lobster abundance at a salmon aquaculture site, eastern
Canada. Can J Fish Aquat Sci 76: 1096−1102
Halswell P, Daniels CL, Johanning L (2016) Sea based con-
tainer culture (SBCC) hydrodynamic design assessment
for European lobsters (Homarus gammarus). Aquacult
Eng 74: 157−173
Halswell P, Daniels C, Johanning L (2018) Framework for
evaluating external and internal parameters associated
with Sea Based Container Culture (SBCC): towards
understanding rearing success in European lobsters
(Homarus gammarus). Aquacult Eng 83: 109−119
Handå A, Ranheim A, Olsen AJ, Altin D, Reitan KT, Olsen Y,
Reinertsen H (2012) Incorporation of salmon fish feed
and feces components in mussels (Mytilus edulis): impli-
cations for integrated multi-tropic aquaculture in cool-
temperature North Atlantic waters. Aquaculture 370-
371: 40−53
Henderson RJ, Forest DAM, Black KD, Park MT (1997) The
lipid composition of sealoch sediments underlying
salmon cages. Aquaculture 158: 69−83
493
Aquacult Environ Interact 12: 485–494, 2020
Irisarri J, Fernandez-Reiriz MJ, Labarta U, Cranford PJ,
Robinson MC (2015) Availability and utilization of waste
fish feed by mussels Mytilus edulis in a commercial inte-
grated multi-trophic aquaculture (IMTA) system: a
multi-indicator assessment approach. Ecol Indic 48:
673−686
Lander TR, Robinson SMC, MacDonald BA, Martin JD
(2012) Enhanced growth rates and condition index of
blue mussels (Mytilus edulis) held at integrated multi-
trophic aquaculture sites in the Bay of Fundy. J Shellfish
Res 31: 997−1007
Lander TR, Robinson SMC, MacDonald BA, Martin JD
(2013) Characterization of the suspended organic parti-
cles released from salmon farms and their potential as a
food supply for the suspension feeder, Mytilus edulis in
integrated multi-trophic aquaculture (IMTA) systems.
Aquaculture 406-407: 160−171
Lavalli KL, Barshaw DE (1989) Post-larval American lobsters
(Homarus americanus) living in burrows may be suspen-
sion feeding. Mar Behav Physiol 15: 255−264
Law BA, Hill PS, Maier I, Milligan TG, Page F (2014) Size,
settling velocity and density of small suspended particles
at an active salmon aquaculture site. Aquacult Environ
Interact 6: 29−42
Marín Leal JCM, Dubois S, Orvain F, Galois R and others
(2008) Stable isotopes (δ13C, δ15N) and modelling as
tools to estimate the trophic ecology of cultivated oys-
ters in two contrasting environments. Mar Biol 153:
673−688
Mercer JP, Bannister RCA, van der Meeren GI, Debuse V
and others (2001) An overview of the LEAR (Lobster
Ecology and Recruitment) project: results of field and
experimental studies on the juvenile ecology of Homarus
gammarus in cobble. Mar Freshw Res 52: 1291−1301
Navarrete-Mier F, Sanz-Lázaro C, Marín A (2010) Does
bivalve mollusc polyculture reduce marine fin fish farm-
ing environmental impact? Aquaculture 306: 101−107
Nillos Kleiven P, Espeland S, Olsen E, Abesamis R, Moland
E, Kleiven A (2019) Fishing pressure impacts the abun-
dance gradient of European lobsters across the borders
of a newly established marine protected area. Proc R Soc
B 286: 20182455
Olsen SA, Ervik A, Grahl-Nielsen O (2012) Tracing fish farm
waste in the northern shrimp Pandalus borealis (Krøyer,
1838) using lipid biomarkers. Aquacult Environ Interact
2: 133−144
Paulet Y, Lorrain A, Richard J, Pouvreau S (2006) Experi-
mental shift in diet δ13C: a potential tool for ecophysio-
logical studies in marine bivalves. Org Geochem 37:
1359−1370
Perez Benavente G, Uglem I, Browne R, Marino Balsa C
(2010) Culture of juvenile European lobster (Homarus
gammarus (L.)) in submerged cages. Aquacult Int 18:
1177−1189
Qi H, Coplen T, Geilmann H, Brand W, Böhlke J (2003) Two
new organic reference materials for δ13C and δ15N meas-
urements and a new value for the δ13C of NBS 22 oil.
Rapid Commun Mass Spectrom 17: 2483−2487
Redmond K, Magnesen T, Hansen P, Strand Ø, Meier S
(2010) Stable isotopes and fatty acids as tracers of the
assimilation of salmon fish feed in blue mussels (Mytilus
edulis). Aquaculture 298: 202−210
Sanz-Lazaro C, Sanchez-Jerez P (2017) Mussels do not
directly assimilate fish farm wastes: shifting the rationale
of integrated multi-trophic aquaculture to a broader
scale. J Environ Manag 201: 82−88
Sanz-Lazaro C, Fernandez-Gonzalez V, Arechavala-Lopez
P, Izquierdo-Gomez D, Martinez-Garcia E, Sanchez-
Jerez P (2018) Depth matters for bivalve culture in inte-
grated multitrophic aquaculture (IMTA) and other poly-
culture strategies under non-eutrophic conditions.
Aquacult Int 26: 1161−1170
Sarà G, Zenone A, Tomasello A (2009) Growth of Mytilus
galloprovincialis (Mollusca, Bivalvia) close to fish farms:
a case of integrated multi-trophic aquaculture within the
Tyrrhenian Sea. Hydrobiologia 636: 129−136
Sardenne F, Simard M, Robinson SMC, McKindsey CW
(2020) Consumption of organic wastes from coastal
salmon aquaculture by wild decapods. Sci Total Environ
711: 134863
Schmalenbach I, Mehrtens F, Janke M, Buchholz F (2011) A
mark−recapture study of hatchery-reared juvenile Euro-
pean lobsters, Homarus gammarus, released at the rocky
island of Helgoland (German Bight, North Sea) from
2000 to 2009. Fish Res 108: 22−30
Sokal RR, Rohlf FJ (1995) Biometry. Freeman, New York, NY
Sprague M, Dick J, Tocher D (2016) Impact of sustainable
feeds on omega-3 long-chain fatty acid levels in farmed
Atlantic salmon, 2006−2015. Sci Rep 6: 21892
Telfer TC, Baird DJ, McHenery JG, Stone J, Sutherland I,
Wislocki P (2006) Environmental effects of the anti-sea
lice (Copepoda: Caligidae) therapeutant emamectin
benzoate under commercial use conditions in the marine
environment. Aquaculture 260: 163−180
Von Bertalanffy L (1938) A quantitative theory of organic
growth (inquiries on growth laws. II). Human Biol 10:
181–213
Wahle RA, Castro KM, Tully O, Cobb JS (2013) Homarus. In:
Phillips BF (ed) Lobsters: biology, management, aquacul-
ture and fisheries, 2nd edn. John Wiley & Sons, New
York, NY, p 221−258
Walters BB (2007) Competing use of marine space in a mod-
ernizing fishery: salmon farming meets lobster fishing on
the Bay of Fundy. Can Geogr 51: 139−159
Wang X, Olsen LM, Reitan KI, Olsen Y (2012) Discharge of
nutrient wastes from salmon farms: environmental
effects, and potential for integrated multi-trophic aqua-
culture. Aquacult Environ Interact 2: 267−283
White CA, Bannister RJ, Dworjanyn SA, Husa V, Nichols
PD, Kutti T, Dempster T (2017) Consumption of aquacul-
ture waste affects the fatty acid metabolism of a benthic
invertebrate. Sci Total Environ 586: 1170−1181
White C, Woodcock S, Bannister R, Nichols P (2019) Terres-
trial fatty acids as tracers of finfish aquaculture waste in
the marine environment. Rev Aquacult 11: 133−148
Wilson E (2008) Homarus gammarus. Common lobster. In:
Tyler-Walters H, Hiscock K (eds) Marine Life Information
Network. Marine Biological Association of the United
Kingdom. https://www.marlin.ac.uk/species/detail/1171
(accessed June 8)
Woodcock SH, Strohmeier T, Strand Ø, Olsen SA, Bannister
RJ (2018) Mobile epibenthic fauna consume organic
waste from coastal fin-fish aquaculture. Mar Environ Res
137: 16−23
494
Editorial responsibility: Philippe Archambault,
Rimouski, Québec, Canada
Submitted: January 27, 2020; Accepted: September 7, 2020
Proofs received from author(s): October 30, 2020
