Morphometric variation of wild trout populations from northwestern Mexico (Pisces: Salmonidae)

Morphometric variation of 17 wild trout populations of the genus Oncorhynchus from northwestern Mexico was analyzed. We used 25 standardized morphometric characters following a box truss protocol. In the discriminant function analysis (DFA) of the examined specimens (n=214), grouped by drainage, the canonical root 1 explained 88.1% of the total variation. Sixteen linear characters allow distinguishing O. mykiss nelsoni (Sierra San Pedro Martir [SSPM]) from O. chrysogaster and O. mykiss sspp. (Sierra Madre Occidental [SMO]). Two distinctive groups of populations were recognized on the basis of the squared Mahalanobis' distances, one for the SSPM (O. m. nelsoni) and the other for the SMO. The latter group is divided into four subgroups: (1) O. chrysogaster (Rio Fuerte and Rio Culiacan) and O. mykiss ssp. (Rio Piaxtla); (2) O. mykiss sspp. (Rio San Lorenzo, Rio Baluarte, and Rio Acaponeta); (3) O. mykiss sspp. (Rio Yaqui and Rio Mayo); and (4) O. chrysogaster (Rio Sinaloa). In the DFA among populations within each taxon, the canonical variable 1 accounted for 41.8% of the total variation for O. m. nelsoni, 59.4% for O. chrysogaster, and 43.8% for O. m. sspp.