d5bbf9d190ce73155c2ba82c817f308eSymposium 2 : « Le Poisson »

Cette quatrième et dernière partie du compte rendu de la 3ème Conférence GID-Parmenides regroupe les interventions et les travaux des participants du symposium et des ateliers consacrés au Poisson .



SYMPOSIUM 2 – Le Poisson



Président :

  • Giorgio Bernardi (Italie)

Rapporteurs :

  • Nadia Ounaïs (Monaco)
  • Denis Lacroix (France)

Introduction :
– Gilles Boeuf (Président, Muséum national d’histoire naturelle, France)

1. Aquaculture en Méditerranée :

  • Ivan Katavic (Croatie)
  • Denis Lacroix (Ifremer, Agropolis International)
  • François René (CGPM / Comité de l’aquaculture) – Sherif Sadek (Égypte)

2. Pêche, évolution des écosystèmes et « aliens » (espèces invasives) en Méditerranée :

  • Giorgio Bernardi (Italie) : Environmental genomics : a tale of two fishes
  • Bastien Mérigot (IRD, France) : Overview of fisheries in the Mediterranean : status and prospectives
  • Ricardo J. Haroun Tabraue (Espagne, Canaries) : Interactions of Aquaculture with the Environment
  • John Siontas (Grèce)

3. Bio- et chimio-diversité marines :

  • Gilles Boeuf (France)

Conclusion :

  • Nadia Ounaïs (Directeur, Institut Océanographique de Monaco)
  • Michel Petit (Académie des sciences et IOM) : Rôle des musées océanographiques

L’avenir du poisson en Méditerranée :

Président :

  • Giorgio Bernardi (Italie)

Rapporteurs :

  • Nadia Ounaïs,
  • Denis Lacroix

Atelier 1 : Gestion et exploitation des ressources marines
Atelier 2 : Environnement et préservation des ressources marines

Participants :

  • Institut de Naples (Italie)
  • Michel Petit : Les Grands prédateurs ; les grands fonds
  • Nureddin Esarbout (Libye)
  • Amir Ibrahim (Syrie)
  • Denis Lacroix (Ifremer-Agropolis)
  • Omar El-Magsodi (Libye)
  • Ridha Mrabet (Tunisie)
  • Chafika Rebzani Zahaf (Algérie)





Gilles Boeuf (Président, Muséum national d’histoire naturelle, France)

« The Mediterranean Sea : not only a piece of the Atlantic Ocean , much more ! »

1. Aquaculture en Méditerranée

Ivan Katavic (Institute of Oceanography and Fisheries, Split, Croatie)

Integrated coastal zones management : a case study with the Croatian aquaculture

  • COAST – area of conflict ; characterized by complexities and uncertainties
  • MARINE AQUACULTURE – most fasting development and environmental concerns
  • HUMANS AND NATURE – enemies or friends ?
  • Some potentially conflicting uses of coastal resources
  • Voir toutes les diapositives accompagnant cette intervention.

Denis Lacroix (Ifremer, Agropolis International)

Aquaculture in the Mediterranean : a Foresight Analysis

Main data on the Mediterranean :

  • Production for Fisheries # 1 100 000 T. (# 1% world capture)
  • 60% coming from EU countries, ie, 20% in weight and 35% in value of EU total
  • Fishing Mediterranean fleeet # 100 000 boats, 90% for small coastal fisheries
  • Med. Aquaculture (watershed) # 1.000 000 T.
  • Annual growth rate from 1990 to 2005 : + 7 % (+ 25 % for fish)
  • Coastal Population : 133 Millions in 1985, 200 Millions anticipated in 2025
  • Tourism : 1% oceans surface and 30% world tourism (1st spot) – 135 Millions in 1990 ; 230-350 Millions anticipated in 2025

Start point of the issue : 2 Key questions

  1. What is the most likely evolution of Aquaculture (& Fisheries) in the Mediterranean (objective : 2030) ?
  2. In this frame, is it possible to manage a sustainable aquaculture ?

2. Pêche, évolution des écosystèmes et « aliens » (espèces invasives) en Méditerranée

Giorgio Bernardi (Italie)

Environmental genomics : a tale of two fishes

Authors : Giuseppe Bucciarelli, Miriam Di Filippo, Domenico Costagliola, Fernando Alvarez-Valin, Giacomo Bernardi, and Giorgio Bernardi

The influence of the environment on two congeneric fishes, Gillichthys mirabilis and Gillichthys seta, that live in the Gulf of Mexico at temperatures of 10°- 25°, and up to 42°- 44°, respectively, was addressed by analyzing their genomes. Compared to G. mirabilis, G. seta showed some striking features : (i) extremely fast substitution rates in mitochondrial genes, indicating a divergence time of less than 0.66-0.75 million years ago ; (ii) an expansion of a GC-rich minisatellite in the gene-rich regions of the nuclear genome ; (iii) a decrease in DNA methylation ; (iv) ratios of non-synonymous/synonymous changes (Ka/Ks) suggesting that some genes may be under positive selection ; (v) high ratios of transversions over transitions and of AT to GC over GC to AT. These observations (i) indicate that the environment can rapidly mould the genome through natural selection and (ii) provide a model for the genome changes that accompany body temperature increases, as found after the emergence of homeothermy.


Classically, sequence changes in the genome were visualized as resulting from point mutations and recombination. We found, however, that the vertebrate genomes underwent massive regional GC increases at the emergence of homeothermy (Thiery et al. 1976 ; Macaya et al. 1976), and proposed that these changes were due to the need of maintaining the thermodynamic stability of DNA, RNA and proteins (GC-rich codons preferentially encoding aminoacids that stabilize proteins) at the higher body temperature of warm-blooded vertebrates (Bernardi and Bernardi 1986 ; Bernardi 2004, 2007). This “thermodynamic stability hypothesis” was supported by finding that compositional changes affected only the gene-rich and not the gene-poor regions of the genome. Indeed, the gene-rich regions (the “genome core” see Bernardi 1993) are characterized by an open chromatin structure (Bernardi 2000 ; Saccone et al. 2002 ; Di Filippo and Bernardi 2008) and need an increased GC level to be stable at 37°- 40°, whereas the gene-poor regions (the “empty space”, or ”the genome desert” Bernardi 2004) are embedded in a closed chromatin structure (Saccone et al. 2008) which can by itself stabilize DNA.

A critical test to demonstrate that an environmental factor, such as temperature, can affect the structure of the genome is provided here by comparing the compositional patterns, the DNA methylation, and the nucleotide substitutions in the nuclear and the mitochondrial genomes of two congeneric goby fishes that live at very different temperatures (Huang et al. 2001 ; Fields et al. 2002). The sister relationship of these two species solves the problem we were confronted with in our initial work (Bernardi and Bernardi 1986) on the Death Valley pupfish, Cyprinodon salinus, and the Lake Magadi tilapia, Oreochromis alcalicus grahami, which showed regional GC increases in their genomes, but could only be compared with evolutionarily distant species.

The long-jawed mudsucker G. mirabilis inhabits salt water creeks in coastal California, Baja California, and the northern Gulf of California. The short-jawed mudsucker G. seta, a paedomorphic variant of G. mirabilis (Barlow 1961), is restricted to the uppermost tide pools, that are reached by sea water only rarely at the highest spring tides, in the northern Gulf of California. While G. mirabilis lives at 10°- 25°C, G. seta experiences temperatures that may reach 42°- 44°C, among the highest temperatures encountered by any fish (Nelson 2006) and hypoxia. G. mirabilis was previously studied in its hypoxia-induced gene expression (Gracey et al., 2001) and its response to heat stress (Buckley at al. 2006 ; Hochachka and Somero 2002 ; Cossins and Crawford 2005).

In this study, we used two experimental approaches, working at the genome level and at the level of orthologous genes, respectively.