A revision on the use of multiple tools for trophic studies of fish communities

Fishes are among the most well-studied groups in papers aiming to analyze food webs and the trophic relations between their organisms. Their importance comes from the potential of the ichthyofauna to consume different types of prey, allowing the fishes to be representative at different trophic levels. However, the feeding plasticity showed by this group makes it difficult to reach a conclusive evaluation about their diets. The goal of this review is to describe the different tools used to evaluate fish diets, including their limitations and advantages. The stomach contents analysis describes and quantifies the diet, but it does not take into account the assimilation of food items. This information can be obtained through stable isotope analyses, influenced by turnover and fractionation rates. The bioaccumulation of mercury along a food web makes it a good indicator of the trophic level of organisms. These tools can provide complementary data, and thus studies including a multiple approach can give a better understanding of how different groups participate in the fish diets.