Fish condition calculator
Wr compares one fish to a species-wide standard. Judge a pond by the average of ten or more fish of the same size range, not one weighing.
Method and sources
log10 standard weight (g) = a + b × log10 total length (mm)
Standard weight (Ws) equations are the 75th percentile weight for the length across the species' range, from Anderson and Neumann, Fisheries Techniques (1996), and the papers it compiles. Each equation has a minimum length below which it is not valid. Length categories (stock, quality, preferred, memorable, trophy) follow Gabelhouse (1984).
A Wr of 90 to 110 is a fish in good condition. Under 80 across many fish points to too little food for the number of predators, or a crowded year class; over 110 is a well fed fish. Condition changes with season and spawning, so compare fish sampled at the same time of year.
Practitioner discussion: Pond Boss forum threads Relative Weight Charts and Fish Weight Calculator.