Life history and fecundity of mountain whitefish from Utah streams

This paper describes aspects of the life history of mountain whitefish Pros opium williamsoni from a high-elevation stream. the West Fork of Blacks For k River. Utah (2.835-2.926 m), and summarizes fecundity of mountain whitefi sh from five northeastern Utah streams (Blacks Fork. Blacksmith Fork, Logan , Prove, and Weber rivers). The standing crop of mountain whitefish in a 0. 14-ha reach of the: Blacks Fork River was 224.5 kg/ha or 2.375 fishlkm. The se fish attained a maximum age of 12 years and grew from a mean total lengt h of 72 mm at age 1 to 347 mm at age 12, growing more slowly than fish from other stream populations. Spawning in Blacks Fork River began in mid-Octob er. All males were sexually mature by age 4 (181 mm or longer); females rea ched sexual maturity at 201-251 mm (ages 5-7). The ratio of mature males to females was 1.6:1. Fecundity (772-4,860 eggs) was correlated to female bod y size (215-361 mm and 86-372 g, respectively). Fecundity of 190 mountain w hitefish from the five streams was also positively correlated with fish siz e and was similar for fish of comparable sizes from all five streams. Varia tion in fecundity of individual fish increased with fish size. From size-gr ouped data, predicted fecundity for mountain whitefish increased by total l ength from 350 eggs for females averaging 217 mm to 11,844 eggs at 437 mm a nd by weight from 1,171 eggs for females averaging 86 g to 17,083 eggs at 1 .1 kg. These results were consistent with fecundity of mountain whitefish f rom other locations in western North America.