Bio-economic modelling of the small pelagics fishery
in the Northern Adriatic Sea
Silvia Silvestri* and Francesc Maynou**
*Department Te.S.A.F, Faculty of Agriculture - Padua University,Viale dell'Università, 16, Agripolis, 35020 Legnaro, Padua, Italy (silvia.silvestri@unipd.it)
** Institut de Ciències del Mar (CMIMA-CSIC). Passeig Marítim de la Barceloneta, 37-49. 08003. Barcelona, Spain (maynouf@icm.csic.es)
Why apply a bioeconomic model to the Northern Adriatic Sea?
In the last years in the Northern Adriatic Sea we observe an increase of the captures of
the pelagic species, but, on the other hand, a gradual decline of the demersal resources
and a considerable reduction in the number of vessels, operators and hours of the
activity (1). The abandonment of the sector, is principally caused by the high costs
sustained to manage the activity and it is linked to the reduction both of the wholesale
and retail consumption, for excessive price, and of the net contribution margin for every
kilogram of captured and/or commercialized product. Another factor to consider is the
reduction of the competitiveness linked to the opening of larger markets.
Considering the economically most important pelagic species, we attempt to verify the
sustainability of the fishing activity in the Northern Adriatic Sea through a bio-economic
model called MEFISTO (Mediterranean Fishery Simulation Tool) (2).
Fishing systems and species to which we apply the model
The mid-water pair trawl (“volante”), towed by two fishing boats
Sardine (Sardina pilchardus Walb.) and anchovy (Engraulis encrasicolus L.)
Ad
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Bio-economic model: MEFISTO
Multispecies, multifleet and multigear
Output:
- biological indicators (biomass, number, catches)
- fleet indicators (number of boats, catch by boat)
- economic indicators (revenues, costs, profits)
- stochasticity
Simulation
We employed bio-economic simulation (1000 iterations,
10 years) analysis to assess the performance of
biological and economic indicators under different
management scenarios.
The simulations regard:
•Fuel price
•Number of days/year
Bio-economic model MEFISTO
Starting from an initial condition, the simulation model
incorporates the known trajectory of the resources and the
fishing fleet and allows to compute the most probable future
trajectory when some parameters in the model are changed.
Small pelagics fishery
in the Northern Adriatic Sea
We applied the MEFISTO model to the fishery of the small
pelagics that take place in the Veneto Region.
This kind of fishing is performed with a volante. The midwater pair trawl volante is towed by two fishing boats
working in pair and holding a tow-line, each one
tethered to the head rope, and the other one to the foot
rope. Volante vessels generally fish only by daylight, and
land their catches every evening: each fishing trip lasts
about 11-15 hours. The boats leave the harbour at 2.303.30 a.m. and come back between 11.00 a.m. to 7.00
p.m. depending on the success of the fishing day (3).
The working week is from Monday to Friday. 20 pairs of
volanti fishing vessels operate usually in the area, their
average engine power is 470 HP and the average size is
88 GRT, but there are wide variations in both size and
engine power.
In this study we divided the fleet in 4 classes according to
vessel size including vessels of 12 GRT as well as
vessels of 200 GRT.
The target species of the mid-water trawl are mainly
sardines and anchovies, even if also other species living
mid-water or in the proximity of the bottom could be
caught occasionally, as mackerel (Scomber scombrus)
and sprat (Sprattus sprattus).
In order to apply the model we estimated the growth
parameters and population numbers by the VIT (4)
program from catch data.
In 2004 the total catch of the small pelagic fishing for the
Veneto region amounted to 12,414 tons, of which, 1,300
are sardines and 11,130 are anchovies.
In terms of market price, sardines are considerably more
valuable than anchovies, and it is required above all for
the processing industry. The average price of sale for the
markets of the Veneto region amount to 0.852€ for
anchovy and 1.727€ for sardine.
The economic information was obtained from annual
statistics, interviews or hypothesis.
Analysis of the most probable future trajectory without management interventions
Biom ass
(x109 tons)
Biomass of anchovies and sardines
100
80
60
40
20
0
Profit
(x106 euro)
3,5
Max
3,0
2,5
Mean
2,0
1,5
Min
1,0
0,5
0,0
-0,5
-1,0
Max
Mean
2010 2011 2012 2013 2014 2015
year
year
Captures
(x109 tons)
In particular the biological parameters of biomass
and recruitment highlight a not important
reduction of the resource. This reduction can be
explained with an increase of the captures from
on the part of the fleet.
Min
2005 2006 2007 2008 2009
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
From the observation of the graphics that show
the most probable future trajectory for the next
10 years without management interventions we
can see a situation of substantial stability of the
conditions in which fishing is running.
Total profit of the fleet
Total catch
Revenues, costs and profit
Value
(x106 euro)
18
14
15
Max
12
Mean 10
— Revenues
12
9
Min
— Costs
8
6
6
4
3
— Profit
2
0
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
year
year
On the average the profit of the fleet will be
positive and show on the whole an increase. The
profit could be become negative beginning from
2009 with a probability of about 14% that could
attain at 21% in 2013. In the first years of the
simulation, all the vessels will be affected by a
decrease of the profit, while, the profit will be
substantially maintained positive for the vessel
with a GT> 135 tons, from 2013, to coincide with
extinction of the bank debt, that represents one
of the considerable fixed costs.
First simulation: analysis of the most probable future trajectory due to variation on the fuel price
Biomass
(x109 tons)
68,5
Total biomass of the fleet
0,40 euro
Profit
(x103 euro)
Total profit of the fleet
0,40 euro
1600
0,51 euro
68,0
0,51 euro
67,5
0,55 euro
1200
0,55 euro
67,0
0,60 euro
800
66,5
0,65 euro
0,60 euro
400
66,0
0,70 euro
0,65 euro
0
65,5
2005
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
2006
Total catch of the fleet
11,9
Value
(x106 euro)
0,40 euro
11,7
0,51 euro
11,5
0,55
11,3
0,60 euro
0,65 euro
11,1
0,70 euro
10,9
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
2008
2009
2010
2011
2012
2013
2014
0,70 euro
Re v e nue s, costs and profit
Revenues 0,40 euro
14000
Revenues 0,51 euro
12000
Revenues 0,60 euro
10000
Cost 0,40 euro
8000
Costs 0,51 euro
6000
Costs 0,60 euro
4000
Prof it 0,40 euro
Prof it 0,51 euro
2000
Prof its 0,60 euro
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
year
2015
year
year
Catch
(x109 tons)
2007
year
In red is highlighted the present cost
of the fuel. The simulation propose a
change of cost beginning from 2008.
The profit shows an inverse relation
with the price of fuel: when it
increases the profit decreases in a
proportional way. On the other hand,
generally, the more the price of fuel
increases, the worse the catch
decreases, according to the higher
costs that the fishermen could
support.
From a biological point of view a minor
cost of the fuel lead to an increase of
the fishing effort and to reduction of
the biomass.
The larger costs of the fuel imply,
indirectly, preservation of the
biomass.
Second simulation: analysis of the most probable future trajectory due to variation on the number of days/year
Biomass
(x109 tons)
Total biomass of the fleet
72
Profit
(x103 euro)
1400
___185
___ 205
70
__ 215
68
___ 225
___ 245
66
___ 225
1200
1000
___ 245
800
600
___ 235
__ 215
400
200
___ 235
64
Total profit of the fleet
___ 205
___185
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
year
year
Catch
(x109 tons)
12,5
Total catch of the fleet
Value
6
(x10 euro)
Revenues, costs and profit
___ Revenues225
___ Revenues 245
___ Costs 245
__ Costs 225
__ Revenues 185
__ Costs 185
__ Profit 225
__ Profit 245
__ Profit 185
14
___ 225 12
___ 245
12,0
11,5
10
11,0
___ 235 8
__ 215 6
10,5
10,0
___ 205 4
___185 2
9,5
9,0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
year
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
In red is highlighted the present
number of fishing days. The simulation
propose a change of number of days
beginning from 2008. We can observe
that, more time available to exercise
the fishing activity allows to obtain the
major catches. However, considering
the economic condition in which is
developing in the Veneto region the
fishing of anchovies and sardine, we
can arrive at a point in which a major
number of days do not guarantee
major profits.
In particular, this occur for the vessels
that present a small tonnage and have
a limited fishing power.
From a biological point of view the
biomass shows an inverse relation
with the number of days: when
this increase the biomass
decreases.
year
Conclusion
We analyzed the possible trajectory deriving from modifications of some parameters put in the model.
The employed model does not provides a point of balance, because it is not an optimization model but a simulation model. Therefore it allows to
verify the effects that can get in the sector some of the taken measures. In these terms this is a cause-effect model that can support policy maker on
the decisional processes. With this aim, for example, it shows that the adjustment should be done segmenting the fleet. The impact of each measure
produces different results depending on the size of the vessels to which it is applied.
Variation on the price of fuel: we can see that the profit shows an inverse relation with the price of fuel (when it increases the profit decreases in a
proportional way). On the other hand, generally, the more the price of fuel increases, the worse the catch decreases, according to the higher costs
that the fishermen could support. From a biological point of view a minor cost of the fuel leads to an increase of the fishing effort and to reduction of
the biomass. The price of fuel cannot be reduces by far with respect to the present price that is about 0,50 €/l.
Variation on the number of days: to preserve the biomass reducing the number of days can have a considerable negative effect on the profits of the
fleet. If we decrease the number of days to 215 the profit decreases about 20%, but, on the other hand if the number of days increases to 245, the
profit decrease anyway, although for about 6% only.
We could: apply a politic of differentiation on the basis of the dimension of the fleet:
- compensative policy for the smaller fleet
apply an import policy to support local products
References: (1) Cingolani, N. - Santojanni, A. - Arneri, E. - Berlardinelli, A. - Colella, S. - Donato, F. - Giannetti, G. - SinovEiF, G. - Zorica, B., 2004. Anchovy
(Engraulis encrasicolus, L.) stock assessment in the Adriatic Sea: 1975-2003. AdriaMed Occasional Papers n°14; (2) Lleonart J., Maynou F., Franquesa R., 1999. A bioeconomic model for Mediterranean fisheries. Fisheries Economics Newsletter, 48: 1-16; (3) Commission of the European Communities, 2004. European Union
Mediterranean Fisheries and exploited resources, Report n. 772, 488 pp.; (4) Lleonart J. and J. Salat, 1997. VIT: Software for fishery analysis. User's manual. FAO
Computerized Information Series, Fisheries. Vol. 11. 107 pp.