NOT TO BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHORS

INTERNATIONAL COUNCIL FOR THE EXPLORATION OF THE SEA

DEMERSAL FISH COMMITTEE C.M. 1993/G:37

Spatial, Temporal and Predator-Prey Size Patterns of Cannibalism by Silver Hake.

R.A. Rountree and M.J. Fogarty

National Oceanic and Atmospheric Administration National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, MA 02543 USA

Abstract

Silver Hake (Merluccius bilinearis) is an important piscivore in Northwest Atlantic fish community dynamics. This species is known to exert significant predation pressure on other fish populations in this region. Intraspecific predation has been shown in previous studies to account for a substantial component of the diet of this species. The objective of the present study is to document the relative importance of cannibalism in the diet of silver hake in two populations off the northeastern United States during 1981-90 and to examine the role of size-related and spatial processes in the occurrence and importance of intraspecific predation. Stomach samples for selected species have been routinely collected in conjunction with standardized research vessel surveys off the northeastern United States during spring and autumn. The stomach samples are collected according to a stratified cluster sample design.

Cannibalism represented an important fraction of the diet of silver hake for both populations and seasonal periods. We noted a general trend for increasing cannibalism with increasing size; however evidence for intracohort cannibalism was also found. The occurrence of cannibalism was highly localized, predominately in regions of high overlap between small (< 20 cm) and larger (>20 cm) silver hake and in areas adjacent to high overlap sites. The prevalence of intraspecific predation in this species and the spatial dynamics of this process has important implications for both population regulation and the form of the stock recruitment relationship.

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