Feeding Ecology of Juvenile (Age-0) Silver Hake (Merluccius bilinearis) on the Scotian Shelf

Abstract

Feeding patterns of juvenile silver hake (Merluccius bilinearis) (length range 19–90 mm) captured by midwater trawl were compared between seasons (fall and winter), years (1980 and 1981), fish lengths, and depth and time of capture. Prey selection shifted gradually with increasing fish length, from copepods at the smaller size ranges, to amphipods, euphausiids and silver hake at the larger sizes. An abrupt shift in the feeding pattern occurred as larvae metamorphosed into juveniles, but there were no similar "critical" changes during the juvenile phase itself. Cannibalism of juveniles by juveniles was pronounced and could be an important factor influencing year-class strength. Silver hake juveniles did not prey on the larvae or juveniles of other fish species, nor did they compete with them for available food, mainly because the juveniles of other species were rare during the period of greatest silver hake abundance in the pelagic zone. Evidence from abundance surveys and the feeding study suggests that increased size-at-date at the early juvenile stage, possibly due to more favourable growth and feeding conditions, resulted in increased survival. Differences in feeding patterns among fish in different size categories, and captured at different depths and times generally substantiate diet migration patterns inferred from previous vertical distribution experiments.