Rossella Boscolo

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Venice 12-13 June 2008
Could fishing activity be sustainable in Venice
lagoon?

• Rossella Boscolo
• C. Antonini, A. Bonometto, F. Cacciatore, M.
  Cornello, A. Feola, E. Ponis,

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Fishery in Venice Lagoon
Artisanal fishery in the Venice lagoon is a
MULTI-TARGET activity with a LONG TRADITION.
FISHERY and CULTIVATION of soft crab MOECHE
EXTENSIVE AQUACULTURE in the VALLI DA PESCA
640 t/year
37 t/year
480 t/year
FISHERY with BILANCIONI
FIXED NETS
Drift net
Codend nets Cogolli
Nassino or cheba
12 t/year
t/year mean 1998-2003 (M.A.V. 99 03)
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Extensive aquaculture in the Valli da pesca
Extensive aquaculture has been traditionally
practised in the "Valli da pesca of the northern
and south-western sectors of the Venice Lagoon.
In these areas fish are raised and then caught in
traps as they try to return to the open sea. The
number of marsh fish farms are estimated in 9,500
hectares for an annual production about 640 tons
(132 Kg/ha).
mean catches 1998-2003 (M.A.V. 99 03)
Fry fishing is a residual activity (60 people in
Veneto lagoons) which acts a major role for the
annual re-supply of juveniles in the valli da
pesca.
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FIXED NETS
There are several types of fixed nets which
differ in their size, shape and mesh size used
for almost all of the year. This type of gear is
located in specific areas and management by a
group of people, while the catch haul requires
the presence of one or two fishermen.
Target species
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Traditional fishery and cultivation of soft crab
moeche
The production of moeche is a traditional
activity of fishermen (about an hundred) in the
southern part of the Venice Lagoon. These are a
type of crab that sheds its shell as its grows
and is gathered when it is soft and more
palatable for consumers.
production chain
most important phase is sorting out the crabs
which are ready to shed their shells after a few
days
catch the crabs with fixed nets during the
fishing season (autumn and spring)
80/Kg
vieri
Annual production is estimated in 37 t/year by
this artisanal fishery of the Venice lagoon
average of period 2002-2004.
Ref MAV, 03 04 Photos Varagnolo, 04
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Mussel culture

• For about the last 10 years this practice in the
  open lagoon has diminished significantly,
• only about 42 hectares of the lagoon surface area
  are used,
• it is estimated that about 220 workers are
  currently employed.

Currently the abandoned structures could be
reconverted for the clams pre fatten
Most of the sector operators have established new
plantations in the sea (off-shore) the duration
of the productive cycle in the lagoon is about 18
months versus the 9 months in the sea
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Fishery in Venice Lagoon Early 1900s Vs Today
mean 548 t
mean 1,713 t
Today
Ref Levi Morenos, 1920 M.A.V. C.V.N., 2003
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Clams Tapes philippinarumlove and hate
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• In 1983 the introduction of the clam T.
  philippinarum to improve the period of crisis due
  to the pollution of lagoon waters changed the
  organization of fishery in the lagoon more
  fishermen left traditional fishing activities to
  harvest the T. philippinarum which also
  guarantees high incomes.

Tapes decussatus native species
Tapes philippinarum non-native species

• In a few years natural banks of the clam T.
  philippinarum replaces the native species (Tapes
  decussatus) that is less resistant to variability
  in temperature and salinity, shortly adaptable to
  many substrates, and lower growth rate.

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Estimated annual production by artisanal fishery
of the Venice Lagoon averaged on 1998-2003 period
The harvesting of the invasive clam, Tapes
philippinarum, is the main exploitative activity
the clam collection involves 1150 shellfishermen
with a total profit of 100 milions of euros while
the traditional fishing activity involves 500
fishermen with a gross profit of 25 milions of
euros.
Ref M.A.V., 99 03 04, Pellizzato et al, 06
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Fishermen with licence of type A - Distribution
in the Lagoon
Jesolo (n 35)
Only 200 of the 1000 licenses for the fishery in
Venice Lagoon are used for artisanal fishery.
(MAV, 1999)
Cavallino Treporti (n 76)
Venice (n 405)
Chioggia (n 515)
Data Provincia di Venezia 2007
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Total catches Artisanal fishery VS Clam
Production
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CLAM TAPES PHILIPPINARUM
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HOW MANAGEMENT CLAM FISHING ???

• In order to minimize the impacts arisen from
  clam fishing the different Administrations
  decided to convert from free fishing into clam
  farming three-year cycles sowing, fattening and
  managed fisheries) (Advice of the prefecture
  meeting 31/07/06).
• Today the breeding areas are 3241.44 ha but
  during this period of transition (18 months)
  Administrations give a series of prescription in
  order to give environmental sustainability to
  clam fishing out of breeding areas.

• Spat collecting in SIN area allowed only with
  use of appropriate systems for silt limitation
• Fishing prohibition (even in case of spat
  collecting) in areas in which sediment is
  labelled in C and gtC classes, according to
  Protocollo fanghi
• Limited number of boats and fixed harvesting
  quotas per boat
• Fishing allowed only during neap tides or during
  incoming tides in order to limit silt dispersion
• Use of silt limitation systems during the
  fishing activity in areas characterised by strong
  erosion
• Appropriate monitoring to evaluate the effects
  of the scheduled activities and to assess the
  suitability of the adopted procedures for silt
  limitation.

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Areas for breeding of clams
581.42 ha
1240.25 ha
775.88 ha
643.89 ha
TOT. 3241.44 ha
Data GRAL 2007
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ICRAM Venice 29th February
Some numbers about the fishing activities out of
the breeding areas
The time table and the areas of fishing changes
Tot ha 442
Tot days 38
tons 338.5
Data GRAL 2007
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ICRAM Venice 29th February
Fishing activities out the breeding areas
Tot ha 1182
Tot days 23
tons 370.8
Data GRAL 2007
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ICRAM Venice 29th February
Some numbers about the fishing activities out to
breeding areas
Tot ha 522
Tot days 22
tons 168.3
Data GRAL 2007
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ICRAM Venice 29th February
Some numbers about the fishing activities out to
breeding areas
Tot ha 133
Tot days 23
tons 28.95
Data GRAL 2007
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ICRAM Venice 29th February
Some numbers about the fishing activities out to
breeding areas
Tot ha 451
Tot days 28
tons 216
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 406.3
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 257
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 3.6
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 327.8
Brenta river
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 79.5
Brenta river
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 49.65
Adige river
Data GRAL 2007
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ICRAM Venice 29th February
Spat fishing
Tot tons 314.
Data GRAL 2007
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ICRAM Venice 29th February
Adult clams collected out of breeding areas in
the years 2006-2007 1122.5 tons
Seed of clams collected out of breeding areas in
the years 2006-2007 1127.3 tons
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The equipment usedfor the harvest Manila clams
the 'rasca' a mechanical crate armed with a rake
which penetrates 5 to 15 cm into the sediment
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The rusca
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The vibrating rake (draga vibrante)
It consists of a crate mounted onto a sleigh,
which prevents it from sinking. It is equipped
with an electrical vibrating mechanism which
results in the breaking-up of the collected
sediment and its cleaning by the water flowing
into the crate.
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• The well known negative effects
• change the morphology and composition of the
  sea-beds
• modified the granular gradients and the texture
  of the sediments,
• resuspended large amounts of sediment, rendering
  the water turbid,

The morphological impact in the lagoon is
therefore considerable. At low tide, it is
possible to observe the furrows left behind by
the fishing equipment. The furrows reach depths
of 15 to 20 cm and form micro-environments which
later become stagnation zones where it is
possible to observe dystrophy. The continuous
ploughing up of the sediment, its re-suspension,
and the continuous resettling, results in a
gradual impoverishment at several levels and a
simplification of both the flora and the fauna.
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Clam fishing in not authorized zone as in front
of Porto Marghera

• ILLEGAL FISHING of clam is a current problem in
  not authorized zone as in front of Porto Marghera
  (an important nursery area for the clams) for
• re-suspension of the fine sediment fraction
  carrying away with it both nutrients and
  pollutants
• sanitary-toxicological problems due to the
  consumption of molluscs.

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• ESSENTIAL QUESTIONS ON FISHING SUSTAINABLE IN
  VENICE LAGOON
• How can fishing sustainability be controlled?
• In which areas should this activity be carried
  out?
• Which is the sustainable effort in those areas?
• Is the clam farming sustainable over the whole
  3241.44 ha area?
• Are the areas currently licensed the more
  suitable according to ecological, productive and
  sanitary requirements?
• Should the use of spat produced in hatchery, in
  addition to wild spat, should be considered as a
  sustainable opportunity? In which amount?
• Should further mitigation activities be adopted?
  
• Can morphological restoration be finalized to
  favour traditional fishing activities?
• Is it possible to create new breeding areas
  giving back ecologically important areas?
• Can phanerogams transplantation be used as
  natural barrier into clam culture area?
• How to couple traditional fishing with clam
  farming?

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Thank you
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