Proposed Standard Weight (W_s) Equation and Length Categories for Utah Chub

Abstract

Condition indices, such as relative weight (Wr), provide a simple method for comparing length–weight relationships among populations. However, no standard weight (Ws) equation has been developed for Utah Chub Gila atraria, a species of important management focus in the Intermountain West. We obtained length–weight data for 30,541 Utah Chub from 24 populations in Idaho, Montana, Utah, and Wyoming. We used the regression line percentile (RLP), linear empirical percentile (EmP), and quadratic EmP methods to develop average (50th percentile) and above average (75th percentile) Ws equations. Additionally, Froese’s method was used to develop another Ws equation for Utah Chub. Length‐related biases were detected in Ws equations developed using the RLP, 50th percentile quadratic EmP, and Froese methods. The linear EmP Ws equations did not exhibit length‐related biases for the 50th and 75th percentiles. We propose using the 75th percentile linear EmP Ws equation for Utah Chub between 90 and 410 mm TL. The EmP 75th percentile equation was log10(Ws) = −4.938 + 3.031·log10(TL), where Ws is weight in grams and TL is in millimeters. The English equivalent of this equation is log10(Ws) = −3.335 + 3.031·log10(TL), where Ws is weight in pounds and TL is in inches for 4–16‐in Utah Chub. Additionally, we propose that minimum TLs of 100 mm (4 in; stock), 200 mm (8 in; quality), 250 mm (10 in; preferred), 300 mm (12 in; memorable), and 380 mm (15 in; trophy) be used to calculate proportional size distribution (PSD) indices. Better understanding Utah Chub populations using Wr and PSDs will aid managers in assessing management strategies (e.g., biological controls) focused on Utah Chub.

Proposed standard weight (Ws) equation and standard length categories for Goldeye

“…Proportional size distribution is a convenient index for quantifying length-frequency distributions among populations for various species (Wege and Anderson 1978;Weithman 1978;Gabelhouse 1984). Gabelhouse (1984) used all-tackle world-record lengths listed by the International Game Fish Association to define minimum lengths for five size categories for many sport fish species, but recent studies have proposed accepted values for other species not initially included (Quist et al 1998;Bonvechio et al 2010;Dumont and Neely 2011;Bonvechio et al 2019;Kim et al 2019;Black et al 2021;Bonvechio and Bonvechio 2021;Bonvechio et al 2023). However, PSD categories have not been developed for Goldeye.…”

“…2011; Black et al. 2021; Bonvechio and Bonvechio 2021). The development of a W s equation for Goldeye is needed for size structure and condition evaluations across their range.…”

“…Relative weight is a common metric used to assess body condition in fishes (Wege and Anderson 1978;Murphy et al 1990;Neumann et al 2012) and is determined by dividing the individual weight of a fish by a W s for a given length for that species multiplied by 100 (Wege and Anderson 1978;Anderson and Neumann 1996). Several studies have developed W s equations for nongame native species to aid in their management (Bister et al 2000;Didenko et al 2004;Richter 2007;Neely et al 2008;Quist et al 2011;Black et al 2021;Bonvechio and Bonvechio 2021). The development of a W s equation for Goldeye is needed for size structure and condition evaluations across their range.…”