Feeding of lantern fish Benthosema glaciale off the Nova Scotia Shelf

Abstract

Benthosema glaciale populations on the slope of the Nova Scotia shelf were sampled at different months of the year on 8 occasions over 8 yr. Day/night vertical distributions are described in relation to distributions of their zooplankton prey. Feeding behavior was studied from stomach contents which showed feeding primarily on copepods during the night in the upper 200 m, but some daytime feeding at depths greater than 300 m. A modified Ivlev's electivity index showed B. glacjale positively selected certain species of copepods but not the most abundant Calanus finmarchicus, although this species was the most common species in its diet. B. glaciale tended to select copepod species whose body length was greater than 1 mm. Size range of prey increased with fish body length; however larger fish continued to feed on the same small prey as smaller fish. The estimated daily ration of B. glaciale decreased with body weight and ranged from 8 % of body weight for a 0.1 g fish to 2.5 % for a 3 g fish. The B. qlaciale population was estimated to consume between 0.2 and 0.1 % of the zooplankton biomass per day during spring but only 0.03 % in fall.