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Several copepods are part of the diet of large paralarvae and juveniles of cephalopods, but during the short time that early stages of cephalopods overlap spatio-temporally with adult stages of the nominal preys, the predator-prey roles can reverse. A total of 14 oceanographic cruises were made along the Baja California Peninsula and in the Gulf of California, México, during 1997-2006. However, evidence of copepod predation on ommastrephid paralarvae was registered only in two cruises made during November 2004 and 2006 in the mouth of the Gulf of California. Zooplankton samples where predatory activity was detected were collected with a Meter net towed obliquely and with a Neuston net (335 µm). Although other carnivore copepod species were present in the plankton samples, we found the warm-water cosmopolitan copepod Oncaea venusta was the only predator attacking paralarvae. In 2004, predation activity was observed in 10% of the total sampling stations, while in 2006, copepod predation was as high as 46%. The frequency of predation was higher near Bahía de La Paz during 2006, and most attacks were associated with a high abundance of paralarvae collected at surface. Mean mantle lengths of paralarvae was 1.2 mm, and were morphologically identified as Complex SD (Sthenoteuthis oualaniensis or Dosidicus gigas paralarvae). Paralarvae were analyzed by amplification of the COI gene for genetic identification. Proportion of O. venusta predatory activity by station (1 to 30%), supports the hypothesis that this copepod species accounts for a high proportion of recently hatched paralarvae mortality.

Palabras clave: Predator-prey; Cephalopod paralarvae; Oncaea venusta

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