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

ABSTRACT

Weight-length data were compiled from 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, log₁₀ Ws = −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, log₁₀Wg = −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.