Prey composition and feeding rate of Sagitta elegans var. arctica (chaetognatha) in the Barents Sea in early summer

• Published in: Polar Research
• Main Author: Falkenhaug, Tone
• Format: Article in Journal/Newspaper
• Language: English
• Published: Norwegian Polar Institute 1991
• Subjects: Arctic; Barents Sea; Polar Research; Zooplankton; Copepods
• Online Access: https://polarresearch.net/index.php/polar/article/view/2332; https://doi.org/10.3402/polar.v10i2.6761

Sagitta elegans var. arctica, the dominant and locally abundant chaetognath in the Barents sea, was collected from the upper 50 m in Arctic water masses during an ice edge bloom in early summer 1983. In situ sampling was made along a transect at discrete depths with a 375 ?m mesh net mounted on a plankton pump. Prey composition and feeding rate were estimated from gut content analyses on preserved specimens combined with data on digestion times from previous studies. No diel variations were found in feeding activity. The diet reflected the composition of available prey in the zooplankton and consisted mainly of nauplii, small copepods (early stages of Calanus, Pseudocalanus, Oithona) and appendicularians. Prey usually occurred as a single item in the gut. Mean prey body width related to chaetognath head width yielded a power curve, with a large amount of scatter, showing that chaetognaths in the Barents Sea can use a wide spectrum of prey sizes. Similarly, maximum prey body width was related to chaetognath head width as a power curve, reflecting the existence of an upper prey size limitation due to the chaetognath mouth size. The highest abundance of S. elegans (5 specimens m?3), and the most intense feeding activity, were found within or beneath the maximum zooplankton biomass. Further, distribution and feeding were affected by light intensity, salinity, and the population structure of 5. elegans var. arctica. Estimated feeding rates ranged between 0.30 and 1.05 prey items per chaetognath day?1. This corresponds to an ingestion of 8-54 ?g AFDW day?1, and a consumption of 0.08–0.22% of the zooplankton standing stock day?1. From these rates, the calculated yearly ingestion by S. elegans var. arctica was 3% of the annually secondary production.