The Use of Winter Water Temperature and Food Composition by the Copepod <i>Cyclops vicinus</i> (Uljanin, 1875) to Provide a Temporal Refuge from Fish Predation
2021
Jong-Yun Choi | Seong-Ki Kim
Frequent predation induces various defense strategies in prey, including morphological changes or migration patterns in zooplankton. We hypothesized that the winter dominance of <i>Cyclops vicinus</i> in the Upo Wetlands, South Korea, is an evolved temporal defense mechanism to avoid fish predation. Long-term data (2014–2019) showed that fish consumed the most cyclopoid copepods from spring to autumn. <i>Lepomis macrochirus</i> preferentially consumed <i>C. vicinus</i>; thus, <i>C. vicinus</i> density was lower from spring to autumn. However, <i>C. vicinus</i> was abundant in winter when fish consumed fewer copepods. Nauplii density began to increase in late autumn (October–November), and their population growth was fueled through consumption of <i>Cyclotella</i> sp. and <i>Rhodomonas</i> sp. Culture experiments showed that <i>Cyclotella</i> sp. contributed more to the growth stage (copepodite or subadult) after nauplii than <i>Rhodomonas</i> sp. <i>C. vicinus</i> density was lower in the winters of 2013 and 2016 when the densities of these phytoplankton prey species were lower. In summary, although winter conditions were suitable for copepod survival and population growth, <i>C. vicinus</i> relied heavily on the diversity and species composition of its food sources. The winter dominance of <i>C. vicinus</i> could increase regional biodiversity and contribute significantly to the stability of the freshwater food web.
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