AGE AND GROWTH OF NELSON-TROUT, ONCORHYNCHUS-MYKISS-NELSONI, FROM ARROYO-SAN-RAFAEL, SIERRA-SAN-PEDRO-MARTIR, BAJA-CALIFORNIA, MEXICO

The age and growth characteristics of Nelson's trout (Oncorhynchus myk iss nelsoni), endemic to the western slope of the Sierra San Pedro Mar tir, Baja California, Mexico, were studied in the Arroyo San Rafael du ring January 1987 to August 1989. This trout is characterized by its s mall size (asymptotic length = 330.1 mm standard length [SL]), slow gr owth, and short life span (less than or equal to 4 years old). The wei ght-length (W-L) relationship was found to be W = (4.477 X 10(-5)) x S L2.810, indicating allometric growth. The slopes (b) of the W-L relati onship equations from males, females, and juveniles were not significa ntly different. Le Cren's mean relative condition factor (K-n) was 1.0 03 +/- 0.129 (SD). The mean K-n was similar between sexes and among ag e classes. Newly emerged trout entered the population from May to June .