The distribution of copepods in the gulf of Gabes

Abstract EN

The present study is based on plankton samples collected at intervals during three cruises organized during 1972-1974 at the Gulf of Gabes.

Collection of samples was carried out by types of standared plankton nets (i.e.

dossing and Mediterranean) at 0-50 m.

depth and at 0-200 m.

depth during different times of the day.

The number of species (20 species) identified shows that the copepod population inhabiting the surface water of the area is a quite heterogenous one.

Of the total populations, few species had markedly wde distribution, and are recorded, almost, from all stations, eg., Oithona spp.

Acartia spp.

and Paraculanus sp.

Copepodite has markedly wide distribution, and it is recorded from all stations.

The majority of species, however, were of rather irregular distribution being found in some stations and not4n others; eg Microcalanus sp., Calanus sp .

Eucalnus sp., Calocalanus sp., Temora sp.

and Cent-ropages.

The extent of this discontinuous distribution in the area investigated varied considerably from one species to another.

The presence of some was even limited to only one or two stations such as Microsetella and Copilia sp.

This distribution irregularity reduced considerably the variety of species records from any station; but inspite of this, the population was still variable.

The copepod species follow the vertical diurnal migration phenomena, for example Acartia spp.

were completelly absent at noon at a depth of 0-20m.

Copepods showed a marked seasonal fluctuations showing an increase in autumn and decrease in spring.

The highest concentration of copepods was recorde near the Island of Djerba.

The copopod count gradually decrease eastward to Sidra