Standard Weight ( W s) Equations for Four Rare Desert Fishes

Abstract

Standard weight (Ws) 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 Ws equation for flannelmouth suckers of 100–690 mm total length (TL) was developed from 17 populations: log10  Ws = −5.180 + 3.068 log10TL. The Ws equation for razorback suckers of 110–885 mm TL was developed from 12 populations: log10  Ws = −4.886 + 2.985 log10TL. The Ws equation for roundtail chub of 100–525 mm TL was developed from 20 populations: log10  Ws = −5.065 + 3.015 log10TL. The Ws equation for humpback chub of 120– 495 mm TL was developed from 9 populations: log10  Ws = −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.