WSlit: All known standard weight equations.

In FSA: Simple Fisheries Stock Assessment Methods

All known standard weight equations.

Description

Parameters for all known standard weight equations.

Format

A data frame with observations on the following 13 variables:

species

Species name. Use wsVal() to see the list of available species.

units

Units of measurements. Metric uses lengths in mm and weight in grams. English uses lengths in inches and weight in pounds.

type

Type of equation (linear or quadratic).

ref

Reference quartile (75, 50, or 25).

measure

The type of length measurement used – total length (TL) or fork length (FL).

method

The type of method used to derive the equation (Regression Line Percentile (RLP; see Murphy et al. (1990) and Murphy et al. (1991)), Empirical Percentile (EmP; see Gerow et al. (2005)), or Other).

min.len

Minimum total length (mm or in, depending on units) for which the equation should be applied.

max.len

Maximum total length (mm or in, depending on units) for which the equation should be applied.

int

The intercept for the model.

slope

The slope for the linear equation or the linear coefficient for the quadratic equation.

quad

The quadratic coefficient in the quadratic equation.

source

Source of the equation. These match the sources given in Neumann et al. (2012).

comment

Comments about use of equation.

Details

The minimum TL for the English units were derived by rounding the converted minimum TL for the metric units to what seemed like common units (inches, half inches, or quarter inches).

Topic(s)

• Relative weight

• Standard weight

• Condition

IFAR Chapter

8-Condition.

Source

Most of these equations can be found in Neumann et al. (2012). Species not in Neumann et al. (2012) are noted as such in the comments variable.

References

Ogle, D.H. 2016. Introductory Fisheries Analyses with R. Chapman & Hall/CRC, Boca Raton, FL.

Gerow, K.G., R.C. Anderson-Sprecher, and W.A. Hubert. 2005. A new method to compute standard weight equations that reduces length-related bias. North American Journal of Fisheries Management 25:1288–1300.

Murphy, B.R., M.L. Brown, and T.A. Springer. 1990. Evaluation of the relative weight (Wr) index, with new applications to walleye. North American Journal of Fisheries Management 10:85–97.

Murphy, B. R., D. W. Willis, and T. A. Springer. 1991. The relative weight index in fisheries management: Status and needs. Fisheries (Bethesda) 16(2):30–38.

Neumann, R.M., C.S. Guy, and D.W. Willis. 2012. Length, Weight, and Associated Indices. Chapter 14 in Zale, A.V., D.L. Parrish, and T.M. Sutton, editors. Fisheries Techniques. American Fisheries Society, Bethesda, MD.

See Also

See wsVal and wrAdd for related functionality.

Examples

str(WSlit)
head(WSlit)

FSA documentation built on Aug. 27, 2023, 1:06 a.m.