An asymmetric index was developed to measure the competition relationships among fishing fleets (or gears or métiers) in a multispecies fishery. This index can be used to measure the degree of dominance of each fleet and its level of independence from competition. To illustrate the concepts, the index is applied to two case studies using two datasets, both from Catalonia, NW Mediterranean. The results show that in both case studies the dominance of bottom trawl over most other gears (especially small-scale ones) is evidenced and quantitatively measured. Bottom trawl is also highly independent of the others. Purse seine appears to be quite independent, but not dominant over the other gears. A practical use of these asymmetric indices is to assist fisheries managers in the decision-making process to optimize the allocation of fishing effort, including energy efficiency, and to reduce environmental impact.