127 “naca” fish, Dormitator maculatus from the Alvarado lagoon, were analyzed, of which 1134 microplastics (MP) were obtained: 561 found in the digestive tract and 573 in gills. The predominant MP found in D. maculatus were fibers with 97.53%, the most abundant color was blue (62%), followed by transparent (12%) and of these the MP in the form of fibers predominated. Regarding the biological parameters, there was only a positive correlation with the weight of the intestine and the weight of the gills; However, this ratio is very low. The biological parameters analyzed: weight, height, condition index and intestinal fullness, lack a relationship between the amount of MP present in the intestines and gills. The type of PM obtained indicates that they come from urban areas, a product of daily activities such as washing clothes and fishing.