My main line of research focuses on the digestive biochemistry of aquaculture species, using the determinations of digestive enzyme activities as an applied tool for evaluating the bioavailability of macronutrients as well as their value as indicators of adaptation of the species to a nutritional regime. In 1993, I established a Research Group for which I am still responsible, which among other works has carried out the characterization of digestive enzyme ontogeny in different native and foreign aquaculture species, becoming an international benchmark in terms of applied methodologies. Currently, we have increased the sensitivity and precision of the determinations by using fluorimetric substrates that allow the quantification of different activities in a single fish larva. In the mid-1990s we started the first in vitro modeling tests of fish digestion in the Group using the pH-stat technique. Our modifications and contributions were a novelty in this area and were included in the corresponding publications. However, given my interest in developing a somewhat more complex digestive model usable in the evaluation of not only the bioavailability of proteins, but also of other nutrients, I made a stay at Laval University (Québec) to familiarize myself with the use of bioreactors of membrane and its possible application in nutrition in aquaculture. The result has been the launch of a very productive line whose applications have led to collaborations with researchers from Cuba, Argentina, Mexico, Chile, Norway and Australia, as well as different research contracts with companies. The in vitro simulation system of fish digestion has been used to date for the comparative evaluation of commercial ingredients, the comparison of the digestive efficiency between species or the evaluation of the effects of antinutritive factors present in vegetable ingredients. It should be noted that we are currently the only group in Spain that develops and applies these techniques both for research purposes and from a perspective applied through contracts with companies, and one of the few worldwide that works on in vitro modeling of the digestive system.