PREVALENCE AND INTENSITY OF HELMINTH PARA SITOSIS FROM THE DIGESTIVE-TRACT OF ONCORHYNCHUS-MYKISS (PISCES, SALMONIDAE) FROM BAJA-CALIFORNIA, MEXICO

The prevalence and mean intensity of helminths in the digestive tract of San Pedro Martir rainbow trout (Oncorhynchus mykiss nelsoni) were s tudied in the Arroyo San Rafael, Baja California, Mexico, by examining 175 specimens (44-208 mm standard length and 0-4 years old) during on e year. The trematode Crepidostomum cooperi (Hopkins 1934) (Allocreadi idae) was the most prevalent (prevalence = 81%) and numerous (mean int ensity = 14.7) parasite, followed by the nematode Rhabdochona cascadil la Wigdor 1918 (Rhabdochonidae) (38% and 3.9, respectively). The mean intensity of C. cooperi increased with the length and age of the host, but it was similar between sexes. In addition, the mean intensity of R. cascadilla was similar regarding the length, age, and sex of the ho st.