Predator Stomachs as Sampling Tools for Prey Distribution: Atlantic Cod ( Gadus morhua) and Capelin ( Mallotus villosus)

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Fahrig, Lenore, Lilly, George R., Miller, Daniel S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1993
• Subjects: atlantic cod; Gadus morhua
• Online Access: http://dx.doi.org/10.1139/f93-175; http://www.nrcresearchpress.com/doi/pdf/10.1139/f93-175

We demonstrate a direct relationship between the amount of prey (capelin, Mallotus villosus) in its predators' stomachs (Atlantic cod, Gadus morhua) and the biomass of the prey in the same localities. The relationship at a local scale implies that predator stomach contents can be used to estimate prey distribution. There is no evidence for either (1) a negative effect of local predator abundance on stomach contents (expected if local prey depletion and/or feeding interference occurs when predator density is high) or (2) a negative effect of the amount of other food in cod stomachs on the amount of capelin in the stomachs (expected if prey switching occurs). There is a negative effect of bottom depth on amount of capelin in cod stomachs as expected, since capelin are pelagic and cod are primarily bottom-dwelling, resulting in less vertical overlap between the species in deep water. This type of analysis may be useful in other predator–prey systems. Simultaneous stomach samples and independent biomass estimates of the prey are required, but once the model is built, it permits estimation of prey distribution in places and times when no direct survey of the prey can be done.