This document discusses methodological support for exploring the properties of the Large Fish Indicator (LFI) for interpreting changes in the fish community of the South Adriatic Sea. It analyzes time series data from 1996-2003 using three size thresholds (20, 30, 40 cm) and two metrics (number of individuals, weight). The results show that a threshold of 30 cm accounts for a higher proportion of biomass compared to 40 cm, with lower variability than 20 cm. For both thresholds, hake is the most important species. Future steps proposed include expanding the analysis to other areas and exploring relationships between LFI and other indicators.

1. METHODOLOGICAL SUPPORT FOR EXPLORING THE LFI:
“PROPORTION OF LARGE FISH - INDICATOR” PROPERTIES FOR
INTERPRETING THE CHANGES IN THE FISH COMMUNITY OF THE
SOUTH ADRIATIC AREA (GSA18)
Maria Teresa Spedicato1, I. Bitetto1, P. Carbonara1,
J. Kolitari2, A. Joksimovic3 and G. Lembo1
1COISPA Tecnologia & Ricerca, Bari, Italy
2University of Agriculture, Tirana, Albania,
3Institute of Marine Biology, Kotor, Montenegro
First MedSuit Regional Workshop on
indicators and targets to ensure GES of
commercially exploited marine populations
in the GFCM area
FAO HQs, Rome, Italy, 6-7 November 2014

2. Study of marine size spectra which basic models assume a
stringent relationship between the trophic level and the size of
species, implying that the species at the top of the foodweb
are the largest ones.
(WGECO, 2001)
Changes in the proportion of top predators within fish
communities might therefore be inferred from changes in the
LFI, although high trophic level predators with larger body can
be replaced by smaller predators feeding at the same trophic
level.
(Jennings et al. 2002)
THE LARGE FISH INDICATOR (LFI)

3. LFI is also considered a metric of the impact of fishing on marine
foodwebs.
Such impact is related to the loss of top predators within the fish
community which size structure is sensitive to fishing
(Myers and Worm, 2003; Jennings and Blanchard, 2004).
The adoption of LFI as indicator at Regional or Sub-regional level
can raise some problems.
Indeed, it is known that the LFI can be more or less effective if a
proper threshold is selected to separate “small” and “large”
categories for a given assessment area.
(Greenstreet et al., 2011; Shephard et al., 2011).
THE LARGE FISH INDICATOR (LFI)

4. • developed by ICES to support an Ecological Quality Objective (EcoQO)
for the North Sea
• included in the monitoring program of the Data Collection Framework
(EU Reg. 199/2008; Commission Decision of 18 December 2009,
2010/93/EU, Appendix XIII )
• associated to the Criterion 4.2 of the Marine Strategy Framework
Directive (MSFD)
• Included in the UNEP-MAP Ecosystem Approach Process (EcAP)
proposal prepared with GFCM
• Problems with implementation given to:
• the responsiveness of the indicator (rather long time response),
• variability
• difficulties in setting thresholds valid at wide geographical scale
• setting targets
(ICES Advice 2013, Book 1; Shephard et al., 2011; ICES, WGECO 2012)
OVERVIEW ON THE LARGE FISH INDICATOR (LFI)
WITHIN MONITORING PROGRAMS

5. to carry out an exploratory analysis on the performance and properties of
the LFI in the case of the south Adriatic sea GSA18
OBJECTIVE OF THIS EXERCISE
considering four different aspects:
• different thresholds of the indicator;
• differences between metrics (i.e. number of individuals per square km or
weight of individuals per square km);
• which information on the fish community the indicator is conveying;
• understanding the relationships with other commonly used indices.

6. METHODS
time series 1996-2003
Standardised indices
• fish and elasmobranchs which were target since the beginning of the
time series were retained
• crustaceans and cephalopods were excluded
• rare species were excluded
Three thresholds:
20, 30 and 40 cm
defined as lbig.
two metrics:
number of individuals
weight
Citharus linguatula Lophius piscatorius Pagellus acarne Spicara flexuosa
Eutrigla gurnardus Merluccius merluccius Pagellus bogaraveo Trachurus mediterraneus
Helicolenus dactylopterus Micromesistius potassou Pagellus erythinus Trachurus trachurus
Lepidorhombus bosci Mullus barbatus Phycis blennoides Trisopterus m. capelanus
Lophius budegassa Mullus surmuletus Raja clavata Zeus faber
20 target species
with 3 benthopelagic
L-W relationships
estimated in the area

7. RESULTS
Biomass fish GSA18
0
20
40
60
80
100
120
140
160
180
200
1996 1998 2000 2002 2004 2006 2008 2010 2012
B all lengths without benthopelagic B all lengths
The two time series related to biomass indices including and
excluding the benthopelagic species had generally a similar shape
except for the period from 2002 to 2006

8. LFI in number of individuals all species
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
>20 cm
>30 cm
>40 cm
CV of LFI in number of individuals all species
0.000
0.100
0.200
0.300
0.400
0.500
0.600
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
>20 cm
>30 cm
>40 cm
LFI in weight all species
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
>20 cm
>30 cm
>40 cm
CV of LFI in weight all species
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
> 20 cm
> 30 cm
> 40 cm
RESULTS
Threshold >30 cm accounts on average 0.9% of the number of individuals
and 23% of weight
Threshold >40 cm accounts for 0.2% of individuals and about 14% of weight.

9. LFI in weight all species
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
>30 cm >40 cm
LFI in weight without bentho-pelagic
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
>30 cm >40 cm
LFI in number of individuals and weight
without bentho-pelagic
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
1996
1998
2000
2002
2004
2006
2008
2010
2012
n.ofindividuals
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
weight
>30 cm n. of individuals >30 cm in weight
LFI in number of individuals and weight all species
0.000
0.005
0.010
0.015
0.020
1996
1998
2000
2002
2004
2006
2008
2010
2012
n.ofindividuals
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
weight
>30 cm n. of individuals >30 cm in weight
the influence of benthopelagic species was not much important especially
if the metric weight was used
RESULTS

10. kg/km2 > 30 cm GSA 18 all species and LFI
0
5
10
15
20
25
30
35
40
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
ZEUS FAB
TRIS CAP
TRAC TRA
TRAC MED
SPIC FLE
SOLE VUL
RAJA CLA
PHYI BLE
PAGE ERY
PAGE BOG
PAGE ACA
MULL SUR
MULL BAR
MICM POU
MERL MER
LOPH PIS
LOPH BUD
LEPM BOS
HELI DAC
CITH MAC
LFI in weight
RESULTS

11. RESULTS
kg/km2 > 40 cm - GSA 18 all species
0
5
10
15
20
25
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
0.00
0.05
0.10
0.15
0.20
0.25
ZEUS FAB
TRIS CAP
TRAC TRA
TRAC MED
SPIC FLE
RAJA CLA
PHYI BLE
PAGE ERY
PAGE BOG
PAGE ACA
MULL SUR
MULL BAR
MICM POU
MERL MER
LOPH PIS
LOPH BUD
LEPM BOS
HELI DAC
CITH MAC
LFI in weight

12. >30 cm >40 cm
Species kg/km2 % Species kg/km2 %
MERL MER 8.89 37.29597 MERL MER 5.23 36.42163
LOPH BUD 3.81 15.97921 LOPH PIS 2.40 16.72699
PHYI BLE 3.31 13.87256 LOPH BUD 2.40 16.70339
LOPH PIS 2.46 10.33855 PHYI BLE 1.54 10.72448
ZEUS FAB 1.51 6.333472 RAJA CLA 1.25 8.681293
RAJA CLA 1.31 5.506177 ZEUS FAB 1.11 7.7408
TRAC TRA 0.74 3.102727 TRAC TRA 0.16 1.117356
MICM POU 0.46 1.940151 MICM POU 0.15 1.060597
TRAC MED 0.39 1.617512 TRAC MED 0.12 0.82345
LEPM BOS 0.34 1.412958 CITH MAC 0
CITH MAC 0.16 0.671982 HELI DAC 0
PAGE BOG 0.15 0.641825 LEPM BOS 0
HELI DAC 0.10 0.407209 MULL BAR 0
PAGE ERY 0.09 0.371884 MULL SUR 0
MULL SUR 0.07 0.293624 PAGE ACA 0
MULL BAR 0.05 0.214177 PAGE BOG 0
PAGE ACA 0 PAGE ERY 0
SPIC FLE 0 SPIC FLE 0
TRIS CAP 0 TRIS CAP 0
89%89% 97%97%
RESULTS
The same species
composition was
observed for the
two thresholds,
though with a
different ranking
Hake is the
dominant species
This indicator
would be
coincident with
the Proportion of
predatory fish in
the catch (and in
the community)
(GFCM
SAC16/2014/Inf.25)

13. y = 3E-05x6 - 0.0017x5 + 0.0307x4 - 0.2181x3 + 0.3825x2 + 1.1918x - 1.9469
R2 = 0.76
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
> 30 cm > 40 cm
It seems that the indicator experienced a cycle with a sharp decrease from
2000 to 2004, followed by a remarkable increase, from 2004 to 2009.
This cycle was fitted by a 6th degree polynomial smoother to the time-series
of LFI >30 and >40 cm, giving a good fit (r2=0.76)
…..To be validated along the time and in other areas…
RESULTS

14. CONCLUDING REMARKS
From this first analysis the threshold of 30 cm seems more suitable for
both metrics, weight and number of individuals.
It accounts for a higher proportion of biomass (compared to >40 cm
threshold) with a lower CV compared to the threshold > 20 cm.
The LFI is relying upon a few number of species (about 6).
The most relevant species, regardless of the threshold is hake
Can be the LFI so considered well representative of the fish
community?

15. CONCLUDING REMARKS
Would the reference direction of the observed trend be a suitable
criterion for the judgement of the environmental status?
Are there possible alternatives? For example and as first approximation,
bounds of the percentile distribution of time series (already used in the
GFCM assessment framework).

16. Results so far suggest future steps of investigation that can be
based inter alia on:
• expand the analysis to other areas (e.g. GSA17)
• analyse the relationships between community averaged fishing
mortality index (Fcom,y) and the LFI time-series;
• make an exploratory analysis and comparison of LFI with
Typical Length (TyL) indicator (TyL is defined as the geometric
mean length of fish, weighted by body mass; WGECO, 2014),
which does not require pre-defined thresholds.
• explore relationships between LFI and guild biomass indices as
proxies of functional groups.
FUTURE STEPS