Diapositiva 1

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Department of Ecology and HydrologyUniversity
of MurciaDoes polyculture of bivalve molluscs
and fin fish reduce environmental impact?
Francisco NAVARRETE-MIER, Carlos SANZ-LÁZARO
Arnaldo MARÍN 2009
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INTRODUCTION

• Intensive fish culture is a widely spread method
  around Europe, especially in the Mediterranean
  Sea
• Activity increasing
• since 1990 ?
• 5 annually

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• Water Enrichment ? Organic matter

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• Labile dissolved
• 
  material
• 
  influence

Non consumed pellets Excreta
Benthos
Benthic Organisms
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• Is polyculture systems an alternative?
• Integrated bivalve fish culture model is simple
• 
  Is It Really working?
• The use of stable isotopes of C and N could help
  to understand the food web structure

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• Objectives
• To valuate the growth of bivalves in a gradient
  of distance from floating fish cages.
• To determinate oysters and mussels approaching of
  wastes from non consumed food or fish faeces by
  stable isotopes measures.
• To analyse bivalves metals accumulation from feed
  or antifouling by its concentrations in a
  gradient of distance from the culture.

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Materials and Methods
37º 24 56 N 1º 32 04 W Águilas - Spain
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Cultured species
European sea bass Dicentrarchus labrax

• Gilthead seabream
• Sparus aurata

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Total depth 31 m Tº 21
26ºC Annual production 1000 ton 83 000 kg of
fish Daily feed input 994 kg (computer system
with underwater video cameras)
Two groups of 12 net cages Each cage 25 m
diameter 19 m deep
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Sites
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Bivalves
Mytillus galloprovincialis
Ostrea edulis
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n 112 / specie
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• 15 m depth
  90 days
• Biometry
• Dry weight
• 55 ºC 72 hours

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• Stable isotope ratio analyses
• d13C or d15N (Rsample / Rstandar
  1) 1000 (º/oo)
• Metal analyses
• Cu Cd Zn
  Pb
• Statistical analyses
• One way analyses of variance (ANOVA)
• Post-Hoc de Tukey HSD (a lt 0,05)

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• Results

a)
b)
Oysters growth after 90 days of experiment (mean
SE). a) Length of shell b) Meat dry weight
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a)
b)
Mussels growth after 90 days of experiment (mean
SE). a) Length of shell b) Meat dry weight
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Metals concentrations (mean SE) in oysters,
mussels and fish feed
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d15N
d15N
d13C
d13C
Mussels
Oysters
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Discussion

• Objetive of responsible aquaculture ? Minimize
  the possible impacts
  to the environment
• Efectiveness in open sea cultures ? Still
  discusing

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• Bivalves have significant growth ? adapted
• Size show no diferences between sites
• Stable Isotopes
• C N
• No differential
• accumulation of
• heavy metals

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• Mazzola et al (2001) and Peharda (2007) show
  diferences
• Cheshuk et al (2003) and Taylor et al (2006) no
  differences
• Comfirm ? Stable isotopes

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• Polyculture must be previusly analyzed
• Generate new impacts

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Thanks
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