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

Morphometric variation of 17 wild troutpopulations of the genus Oncorhynchusfrom northwestern Mexico was analyzed.We used 25 standardized morphometric characters following a box truss protocol. In thediscriminant function analysis (DFA) of theexamined specimens (n = 214), grouped bydrainage, the canonical root 1 explained 88.1%of the total variation. Sixteen linearcharacters allow distinguishing O. mykissnelsoni (Sierra San Pedro Mártir [SSPM])from O. chrysogaster and O. mykisssspp. (Sierra Madre Occidental [SMO]). Twodistinctive groups of populations wererecognized on the basis of the squaredMahalanobis' distances, one for the SSPM (O. m. nelsoni) and the other for the SMO. Thelatter group is divided into four subgroups:(1) O. chrysogaster (Río Fuerte andRío Culiacán) and O. mykiss ssp.(Río Piaxtla); (2) O. mykiss sspp.(Río San Lorenzo, Río Baluarte, andRío Acaponeta); (3) O. mykiss sspp.(Río Yaqui and Río Mayo); and (4) O. chrysogaster (Río Sinaloa). In the DFAamong populations within each taxon, thecanonical variable 1 accounted for 41.8% ofthe total variation for O. m. nelsoni,59.4% for O. chrysogaster, and 43.8%for O. m. sspp.