MEPS 630:13-23 (2019)  -  DOI: https://doi.org/10.3354/meps13130

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 3 dominant copepod species—Paracalanus cf. indicus, Acartia tonsa and Calanus chilensis—within the HCS and examined their relationships with environmental factors. Predatory mortality rates of all 3 species increased linearly with developmental stage, and hence body size, 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 rates of C. chilensis were positively correlated with temperature. On average, non-predatory mortality accounted for 34.8-46.3% of the total mortality among the 3 species. Changes in upwelling intensity caused by climate change may alter the extent and patterns of predatory and non-predatory mortalities in the HCS copepod communities.

KEY WORDS: Copepod mortality · Neutral red stain · Copepod carcasses · Vertical life table