Predation by omnivorous copepods on early developmental stages of Calanus finmarchicus and Pseudocalanus spp.

Abstract

Predation is thought to be an important source of mortality in the early life stages of fish and copepods on Georges Bank. Omnivorous copepods may be predators on copepod eggs and nauplii, but data on feeding rates or selectivity are scarce. As part of the GLOBEC Georges Bank program, we generated functional response curves for the omnivorous copepods Metridia lucens, Centropages typicus, and Temora longicornis feeding on the eggs and nauplii of Calanus finmarchicus or Pseudocalanus spp. in shipboard predation trials. Neither C. typicus nor M. lucens reached saturation feeding on Calanus eggs until prey concentration was >400 L−1. Individual M. lucens and C. typicus ingested up to 34 ± 9 (mean ± SD, n = 3) and 24 ± 14 eggs d−1, respectively (68C). T. longicornis was more abundant in late spring, when they ingested Calanus eggs at rates similar to those of C. typicus. At ambient prey concentrations, ingestion rates of Calanus nauplii were higher than rates of Calanus eggs for the predator M. lucens but were similar for C. typicus. Advanced naupliar stages were less susceptible to predation than young stages. Pseudocalanus nauplii moved faster and were ingested at lower rates than similarly sized Calanus nauplii. Predation rates increased with increasing temperature for the warm‐water species C. typicus but decreased for the cold‐water species M. lucens. These results may contribute to models predicting the development of copepod populations and their availability to larval fish.