Proposed Revision of the Standard Weight (Ws) Equation for Redear Sunfish

Authors

Kevin L. Pope, South Dakota State UniversityFollow
Michael L. Brown, South Dakota State UniversityFollow
David W. Willis, South Dakota State UniversityFollow

Date of this Version

1995

Citation

Journal of Freshwater Ecology, Volume 10, Number 2

Abstract

Weight-length data were compiled trom 289 redear sunfish Lepomis

microlophus populations. We applied the regression· line-percentile (RLP)

technique to weight-length data for 150 redear sunfish populations to develop

a new 75th-percentile standard weight (Ws) equation. The proposed RLP Ws

equation, log₁₀Ws = -4.968 + 3.119log₁₀TL where Ws is the standard weight

In grams and TL is the total length in millimeters, is valid for fish ≥70 mm TL

The English-unit equivalent, log₁₀Ws = -3.263 + 3.119log₁₀TL where Ws is the

standard weight In pounds and TL is the total length in inches, Is valid for fish

~3 in TL. We used the remaining 139 independent populations to evaluate the

current [log₁₀ Ws = -5.164 + 3.227(log₁₀TL)] and RLP Ws equations for any

length-related biases. We confirmed that the current Ws equation is length-biased.

That is, relative weight (Wr) values significantly decreased with

increasing fish length for far more populations (N=45) than they increased

(N=7). We tested the proposed RLP Ws equation with the same 139

populations, and found no consistent length-related bias in Wr values

calculated with the proposed RLP Ws equation (N=38, 29). Thus, we

recommend the use of the proposed RLP Ws equation for redear sunfish.