Vertical distribution and ecological significance of chaetognaths in the Arctic environment of Baffin Bay

Summary

The vertical distributions of species of chaetognaths are described to a depth of 1043 m in Baffin Bay during the summer. The dominant species in the southern region of the Bay were Eukrohnia hamata and Sagitta maxima and, in the northern region, E. hamata and S. elegans. The younger stages of all chaetognath species were found at depths above the older more mature stages. There was no evidence of any diurnal vertical migration by any species. The population structure of E. hamata was bimodal suggesting two sub-populations and a two year life cycle. Sagitta maxima showed a multimodal population suggesting a life cycle of four or more years. The population structure of E. elegans was unimodal. Gut contents showed that E. hamata fed at a higher rate than did S. maxima. E. hamata fed at a higher rate during the night but there was no significant difference between day/night feeding rates for S. maxima. It was estimated that E. hamata consumed up to 1.8 prey items day^-1 and S. maxima 0.5 prey items day^-1. The daily ration was influenced by the water temperature. Calculations showed chaetognaths are major predators on copepods consuming between 1.2 and 1.3% of the standing crop of copepods per day. Generally the maximum concentration of chaetognaths was found at a depth below the maximum concentration of copepods.