Standard Weight (W_s) Equations for Four Rare Desert Fishes

Abstract

Standard weight (W _s) equations have been used extensively to examine body condition in sport fishes. However, development of these equations for nongame fishes has only recently been emphasized. We used the regression-line-percentile technique to develop standard weight equations for four rare desert fishes: flannelmouth sucker Catostomus latipinnis, razorback sucker Xyrauchen texanus, roundtail chub Gila robusta, and humpback chub G. cypha. The W _s equation for flannelmouth suckers of 100–690 mm total length (TL) was developed from 17 populations: log₁₀ W _s = −5.180 + 3.068 log₁₀TL. The W _s equation for razorback suckers of 110–885 mm TL was developed from 12 populations: log₁₀ W _s = −4.886 + 2.985 log₁₀TL. The W _s equation for roundtail chub of 100–525 mm TL was developed from 20 populations: log₁₀ W _s = −5.065 + 3.015 log₁₀TL. The W _s equation for humpback chub of 120– 495 mm TL was developed from 9 populations: log₁₀ W _s = −5.278 + 3.096 log₁₀TL. These equations meet criteria for acceptable standard weight indexes and can be used to calculate relative weight, an index of body condition.