Biomass and estimated production, and feeding pressure on zooplankton of chaetognaths in the Yellow Sea, China

Abstract

The biomass and estimated production, feeding rate of chaetognaths were studied in the Yellow Sea. Sagitta crassa, Sagitta enflata, Sagitta bedoti, and Sagitta nagae were found during the study period, and S. crassa and S. nagae were the dominant species. The mean chaetognath biomass was in the range of 2.56 - 5.57 mg DM m-3, and S. crassa and S. nagae comprised 49 - 90 and 10 - 33%, respectively. The geographical distribution pattern was differed between different species. The annual average estimated feeding rate and production of chaetognaths was evaluated as 55.24 mg C m-3 year-1 and 15.90 mg C m-3 year-1, respectively. The body length of Sagitta species less than 9 - 11 mm had relatively high feeding rate in August, September, and December because of their relatively high total biomass, while the body length with 8 - 16, 11 - 15, and 6 - 16 mm groups had relatively high feeding rate in March, May, and June, respectively. The average feeding pressure on zooplankton biomass and production by chaetognaths could be evaluated as 1.07 and 18.95%, respectively, and the biomass and production of small copepods, and nauplius and copepodite of large copepods would be seriously impacted during whole year.