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Vertical distribution and feeding of chaetognaths in the South Adriatic Pit

The vertical distribution and feeding of pelagic chatognaths were studied in the northern part of the south Adriatic Pit at three stations (0-1000 m depth) during five cruises from April 1993 to February 1994. Higher numerical differences between stations and cruises were noted only in the 0-100 m layer. A maximum number of chaetognaths (406 ind/10 m3) was registered in the surface layer at the inshore station in September 1993. The lowest total number (< 50 ind./10 m3) was recorded in April 1993 at all stations. Sagitta inflata, S. minima and S. setosa were the most abundant species in the surface layer accounted for more than 80% of the total number of chaetognaths. S. decipiens and S. lyra dominated in the layers below the 100 m depth. Gut contet analysis of the dominant species showed that S. inflata and S. lyra consumed a wider variety of prey than other. Copepods were the predominant food organisms, but canibalism was also significant in all five species. Food contain ratio (FCR) and Number of prey pre chatognath (NPC) of S. inflata were highest in the intensive reproduction period. Higher FCR and NPC for S. decipiens and S. lyra occured in deeper layers where older developmental stages dominated.

chaetognath; vertical distribution; South Adriatic Pit

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