Life History and Fecundity of Mountain Whitefish from Utah Streams

Abstract

This paper describes aspects of the life history of mountain whitefish Prosopium williamsoni from a high-elevation stream, the West Fork of Blacks Fork River, Utah (2,835–2,926 m), and summarizes fecundity of mountain whitefish from five northeastern Utah streams (Blacks Fork, Blacksmith Fork, Logan, Provo, 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 fish/km. These fish attained a maximum age of 12 years and grew from a mean total length 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-October. All males were sexually mature by age 4 (181 mm or longer); females reached 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 body size (215–361 mm and 86–372 g, respectively). Fecundity of 190 mountain whitefish from the five streams was also positively correlated with fish size and was similar for fish of comparable sizes from all five streams. Variation in fecundity of individual fish increased with fish size. From size-grouped data, predicted fecundity for mountain whitefish increased by total length from 350 eggs for females averaging 217 mm to 11,844 eggs at 437 mm and 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 from other locations in western North America.