Abstract
BackgroundPredatory copepods of the family Euchaetidae are widely distributed in polar, temperate, subtropical and tropical oceans. Paraeuchaeta concinna is the most abundant Euchaetidae in the subtropical coastal seas of Hong Kong and southern China. However, compared to Euchaetidae species in temperate and polar regions, relatively little information is available on the ecology of P. concinna and other Euchaetidae species in the subtropical oceans. This paper provides information on the seasonal abundance of P. concinna in the coastal seas of eastern Hong Kong. The diel vertical distribution of P. concinna, feeding behavior, and predation impact on mesozooplankton in eastern Hong Kong were also investigated.ResultsP. concinna is most abundant in winter and spring. Their abundance decreases shoreward, and densities are generally higher in the open waters of eastern Hong Kong than in the inner parts of Mirs Bay and Tolo Harbour. P. concinna exhibits both diel vertical migration and diel feeding rhythms in Mirs Bay. P. concinna females show strong preference for the copepods of the genera Acrocalanus, Paracalanus, and Parvocalanus, and remove ~4% of their standing stocks daily.ConclusionsThe low abundance of P. concinna during most of the year suggests it is not indigenous to coastal seas of eastern Hong Kong. P. concinna performs diel vertical migration, most likely as a strategy to avoid visual predation. Gut content analysis showed that Acrocalanus, Paracalanus, and Parvocalanus are highly preferred prey of P. concinna. A daily predation impact of ~4% of the standing stocks of Acrocalanus, Paracalanus, and Parvocalanus suggests that P. concinna may play an important role in regulating the populations of these small copepods in Mirs Bay, especially during winter and spring.
Highlights
Predatory copepods of the family Euchaetidae are widely distributed in polar, temperate, subtropical and tropical oceans
Seasonal abundance and spatial distribution The density of adult P. concinna was lowest at S1 in the inner part of Tolo Harbour and highest at S5 and S6 in the open seas of southeastern Hong Kong (Figure 3)
P. concinna is common in the coastal waters of eastern Hong Kong only during winter and spring
Summary
Predatory copepods of the family Euchaetidae are widely distributed in polar, temperate, subtropical and tropical oceans. Paraeuchaeta concinna is the most abundant Euchaetidae in the subtropical coastal seas of Hong Kong and southern China. This paper provides information on the seasonal abundance of P. concinna in the coastal seas of eastern Hong Kong. Marine calanoid copepods of the family Euchaetidae are widely distributed in polar, temperate, subtropical and tropical oceans, typically large in size (2–12 mm), and primarily predaceous [1]. Euchaetidae is one of the most abundant groups of large predatory copepods in the coastal waters of Hong Kong and southern China [20,21,22,23].
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