Ecosystem interactions such as competition and predation, are not taken into consideration in the current method of single species assessments. A multispecies, ecosystem-based approach incorporates species interactions using diet composition to assess the effects predator-prey dynamics can cause on fish stocks. Stomach content analysis offers insight into the feeding strategy of the species in terms of abundance and diversity of the prey groups identified. The diet composition of boarfish (Capros aper) in its northern distribution is unknown, therefore stomach content analysis is used to assess spatial, size and sex-related variation within the diet. Carbon conversions are calculated for the two major prey groups to determine the energy contributed. Diet composition of herring is compared to boarfish diet to assess niche overlap and therefore interspecific competition. The relationship between boarfish abundance in the northeast Atlantic from 2002 in relation to continuous plankton recorder (CPR) data of the zooplankton abundances in that area, are compared to analyse any potential correlation. A one-year time lag was included to correlate surplus biomass of boarfish with the relative abundance of copepods in the previous year. Understanding the ecological processes impacting both boarfish and herring and the interactions between the two species and their feeding strategies, will offer a new basis on which future decisions on the management of fisheries can be addressed.
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