FOOD AND FEEDING OF PACIFIC HAKE LARVAE, MERLUCCIUS PRODUCTUS, OFF SOUTHERN CALIFORNIA AND NORTHERN BAJA CALIFORNIA

Abstract

The diet of larval Pacific hake, Merlucciusproductus. consisted primarily of copepod eggs and calanoid copepod adults, copepodites, and nauplii, based on an examination of material collected in March 1975 off southern California and northern Baja Califomia. In spite of a large mouth, Pacific hake larvae ingested a broad size range of prey, with a concentration of food particles 70200 pm in width. First-feeding Pacific hake larvae fed upon a wide range of prey (50 to about 400 pm prey width), and the range in prey sizes changed little with larval length from 3.0-10.7 mm. Although copepod eggs, nauplii, and copepodites were a significant portion of the diet in numbers of prey, adult copepods contributed about 74% of prey volume. Observations of feeding incidence in relation to time of capture revealed a slow rate of gut evacuation. Larvae began feeding at about lo00 hours, and the number of prey items found in the gut increased during the day, reached a maximum after sunset, and thereafter decreased gradually. The comparatively large mouth, slow evacuation rate, and ability to feed on cope@ stages from eggto adult seem to form an adaptive strategy for success in the relatively deep and cold strata inhabited by Pacific hake larvae. RESUMEN