The implementation of an ecosystem based approach to fisheries management (EBFM) in multispecies fleets has the potential to increase fleet diversification strategies, which can reduce pressure on overexploited stocks. However, diversification may reduce the economic performance of individual vessels and lead to unforeseen outcomes. We studied the economic performance of different fleet segments and their fishing métiers in Wales (UK) to understand how the number of the métiers employed affects fishing income, operating costs and profit. For the small-scale segment more specialized fishers are more profitable and the diversity of métiers is limiting both the maximum expected income and profit but also on the operating costs. This last result may explain the propensity of fishers to increase the number of métiers for at least part of the studied fleet. Therefore, while for some vessels increasing the diversity of fishing métiers may be perceived to limit economic risk associated with the interannual variability of catches and prices and/or to reduce their operating costs, it can ultimately result in a less profitable activity than more specialised vessels.