Geographic Distribution of Pelagic Copepods in the Mediterranean > Introduction
 
   


 

Introduction :

The knowledge we have on the identification of species in the Mediterranean is old (Giesbrecht, 1892; Giesbrecht & Schmeil, 1898). Thereafter Sars (1925) and Rose (1924-1954) complete information on the Mediterranean west side and the near Atlantic. More than 500 publications have been consulted on the Mediterranean on a total of 9059 for all global data that provide information on the biogeography of species.

With the increase in regional ecology work, and a fortiori digital ecology, the validity of fauna lists is not always sure at least for some reported species. For Böttger-Schnack (1999) forms without figures or characteristics morphological data specifying the validity of the species, are questionable. More serious is often the absence, by many authors, of bibliographic references on works and more recent changes behalf of taxonomists. We have of course taken into account when elaborating this work. It is obvious that no attempt at geographical synthesis would be possible without a minimum of confidence, and caution when using analysed publications. As Goetze & Bradford-Grieve (2005) indicate, genetic and morphological joint analysis of poorly differentiated species shows that some anatomical details appear when attention is drawn on controversial cases. Inversely, low genetic and morphological differences like between Calanus helgolandicus and C. euxinus (Unal & al. (2003, p.157, In : 3 rd International Zooplankton Production Symposium, 20-23 May, Gijon, Spain) maybe call into question the existence of their separation, until intercrossing tests have been carried out.

The knowledge of species' descriptive works, and their possible patches, require regular monitoring because of inter-oceanic exchanges and the specificity of pelagos. The mastery of world literature in this field is not easy but necessary.

Another difficulty also comes from the disparity between regions. Some have been more exploited than others, often close to major marine laboratories, or during shipment linked to a particular environmental theme. The modes of samples and the meshes sizes used are often very different from one author to another, generally valuing calanoids compared to podopleans (notably Oithonidae and Oncaeidae).

Finally, changes in the composition of copepods' populations have occurred either on a geological scale, or more recently, for example in the Gulf of Lion (Kouwenberg & Razouls, 1990), in Lebanese waters (Lakkis, 1990), in the NE Atlantic (Planque, 1996; Beare & al., 2002; Beaugrand & al., 2002), the North Sea (Corten, 1999), as in the NE Atlantic (Johns & al, 2001) and the north-east Pacific in British Columbia (Mackas & al., 2001).

The anthropogenic effects are now well known, like for examples in the bays of Toulon (Jamet & al., 2001), and Sevastopol (Gubanova & al., 2001), transports in ships' ballast that essentially concern brackish species (Orsi & Walter, 1991; Orsi & Ohtsuka, 1999; Sutherland & al., 2001) or presenting eggs in diapause or latency (like among Acartiidae, Centropagidae, Pontellidae), exchanges of aquaculture products.

A zoogeographic analysis of pelagic forms in the various Mediterranean basins was established by Furnestin (1979). The author shows the specificity of these for both hydrological and biological data. The circulation of surface and intermediary water is a broadly well known (Bethoux & Gentili, 1996; Bethoux & Gentili, 1999; Bethoux & al., 1999) and can only tend to a dispersion of planktonic forms to all Mediterranean, to the extent of the populations' adaptation to new hydro-biological conditions that they face. The climatic variations, changing over time in accordance with cycles bad determined yet, modify the structure of the ecosystem. These modifications in the case of pelagic copepods are difficult to apprehend unlike the benthic and ichtyological fauna (Laubier & al., 2003; Ben Souissi & al., 2004). Regardless well known species in the various Mediterranean regions that dominate in sub-sampling (Gaudy, 1985), a review of the fishery as a whole remains indispensable from the viewpoint of the zoogeography, of detection of indicator species as of the genetic variability of the species due to their dispersal because of pelagos.

The inventory is based on published data (Razouls, 1995, 1996; Razouls & De Bovée, 1998), updated until 2013/2014.

   

 Any use of this site for a publication will be mentioned with the following reference :

Razouls C., de Bovée F., Kouwenberg J. et Desreumaux N., 2005-2017. - Diversity and Geographic Distribution of Marine Planktonic Copepods. Available at http://copepodes.obs-banyuls.fr/en 
[Accessed November 18, 2017]

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