Digestive enzymatic activity on Tropical gar (Atractosteus tropicus) larvae fed different diets Carlos Aguilera • Roberto Mendoza • Israel Iracheta • Gabriel Marquez Received: 2 March 2011 / Accepted: 8 August 2011 / Published online: 23 August 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Digestive enzymatic activity and growth performance on tropical gar (Atractosteus tropicus) larvae fed Artemia nauplii (LF), frozen adult Artemia (AB), an artificial diet (AF) with 46% protein and 16% lipids and a starvation group (SG) from first feeding (5 days after hatching—5 DAH) to 34 DAH were studied. All larvae under starvation (SG) died at 15 DAH. By the end of the experimental period, morpho- logical variables (total length, wet weight and specific growth rate) were significant in larvae fed AF compared to LF and AB. All enzymes studied in the experiment were present since the start of exogenous feeding (including pepsin) and the enzymatic activity varied with the diets. Low levels of enzymatic activity were observed until the 29 DAH; however, after this moment, there was a significant increase (eightfold), particularly for the AF treatment. In vitro protein digestibility tests performed with enzymatic extracts showed that artificial diets with 52% protein and 14% lipids were better digested by larvae before 30 DAH, while diets with 45% protein and 11% lipids were better digested after this age. Taking into account the better growth performance, higher enzymatic activity and better protein digestibility obtained, artificial diets can be used since the start of exogenous feeding on tropical gar larvae, as in other lepisosteids. Keywords Tropical gar Á Atractosteus tropicus Á Artificial diets Á Digestive enzymes Á Protein digestibility Introduction The family Lepisosteidae is represented by seven extant species of non-teleost bony fishes that are distributed in North America, Central America and Cuba. The southernmost limit is reached by tropical gar (Atractosteus tropicus). Many of the lepisosteid populations have declined due to factors such as high trophic position and relatively long life span of these fish, habitat loss, alteration and also overfishing (Mendoza et al. 2008a). In the state of Tabasco, Mexico, fisheries constitute one of the main eco- nomic activities, and 30% of the total catch corre- sponds to freshwater species. Among these species, the tropical gar outstands as one of the most popular, being captured in 32 official registered fisheries in the state (CONAPESCA 2008). Tropical gar capture peaked in 1996 attaining more than 500 tonnes; however, capture volumes, as well as the size of C. Aguilera Á R. Mendoza (&) Á I. Iracheta Laboratorio de Ecofisiologı ´a, Facultad de Ciencias Biolo ´gicas, Universidad Auto ´noma de Nuevo Leo ´n, Apartado Postal F-96, C. P. 66450 San Nicola ´s de los Garza, NL, Mexico e-mail: mendozar787@yahoo.com G. Marquez Laboratorio de Acuicultura Tropical-DACBIOL, Universidad Jua ´rez Auto ´noma de Tabasco, Villahermosa, Mexico 123 Fish Physiol Biochem (2012) 38:679–691 DOI 10.1007/s10695-011-9550-8