Patterns of vertical distribution of Pseudocalanidae and Paracalanidae (Copepoda) in pelagic waters (0 to 300 m) of the eastern Mediterranean Sea

The vertical distribution (0-300 m) of a numerically important group of small and morphologically similar calanoid copepods (Clausocalanus, Ctenucalanus, and Paracalanus) of the families Pseudocalanidae and Paracalanidae is described from a series of hauls taken in six areas of the eastern Mediterranean Sea during a synoptic survey in October/November 1991. A niche separation by partial depth segregation of the species has been observed. The median depth in the total sampling area of the adult females of the species was: Clausocalanus furcatus (26 m), Paracalanus denudatus (30 m), Clausocalanus masligophorus (41 m), Clausucalanus arcuicornis (67 m), Clausocalanus paululus (72 m), Clausocalanus pergens (95 m), Ctenocalanus vanus (98 m) and Clausocalanus parapergens (113 m). Adults were found in the same depth layer or slightly deeper in the water column than the corresponding copepodid stages. No statistically significant difference (ANOVA, P > 0.05) was detected among the median depths of the species in the six areas sampled, i.e., Sicily Channel, Ionian Sea, Cretan Sea, Levantine Sea, Rhodes area, and Cretan Passage.