Feeding of the Chaetognath Sagitta elegans Verrill

Abstract

Gut contents of a total of 11 776 specimens of Sagitta elegans sampled monthly in the Irish Sea during 12 h at day and at night from February 1986 to October 1987 were analysed. Copepods were the main prey items in the diet. The Common and abundant calanoid copepods in the area Pseudocalanus elongatus, Oithona spp., Acartia clausi, and Temora longicornis were the main constituents in the diet. Calanus an abundant and ubiquitous copepod for the area, however, was preyed upon to a relatively smaller extent. In March 1987, cirripede larvae comprised up to 68% of the diet while tintinnids and dinoflagellates were mainly consumed in April 1986 (28·4%) and April 1987 (13%). Highest intrageneric predation ('cannibalism') was recorded in February 1986, when 10% of the diet consisted of Sagitta spp. Consumption of fish larvae was low and was mainly recorded at times of Clupea harengus spawning. Percentage of animals with gut contents was higher at night, and the daily feeding rate (FR) for this species ranged between 0·75 and 3·55 prey day -1 during the study period.