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Relative importance of predatory versus non-predatory mortality for dominant copepod species in the northern Chile (23° S) Humboldt Current Ecosystem

Sonia Yáñez, Pamela Hidalgo*, Kam W. Tang

*Corresponding author:

ABSTRACT: Copepods dominate the zooplankton communities and support large fisheries within the Humboldt Current System (HCS). Using detailed data of live/dead compositions, along with stage durations and molting rates, we derived for the first time both predatory and non-predatory mortality rates of the three main copepod species, Paracalanus cf. indicus, Acartia tonsa and Calanus chilensis, within HCS, and examined their relations with environmental factors. Predatory mortality rates of all three species increased linearly with developmental stages, hence body sizes, indicating top-down control by predators that prefer larger prey. Intrusion of oxygen-poor water via upwelling and low chlorophyll a concentration were linked to increased non-predatory mortality rates of P. cf. indicus and A. tonsa, whereas non-predatory mortality rate of C. chilensis was positively correlated with temperature. On average, non-predatory mortality accounted for 34.8 to 46.3% of the total mortality among the three species. Changes in upwelling intensity caused by climate change may alter the extents and patterns of predatory and non-predatory mortalities in the HCS copepod communities.