An Assessment of Weight-Length Relationships for Muskellunge,Northern Pike, and Chain Pickerel In Carlander's Handbook of Freshwater Fishery Biology

Carlander's Handbook of Freshwater Fishery Biology (1969) contains life history data from many species of freshwater fish found in North America. It has been cited over 1200 times and used to produce standard-weight curves for some species. Recent work (Cole-Fletcher et al. 2011) suggests Carlander (1969) contains numerous errors in listed weight-length equations. This paper assesses the weight-length relationships listed in Carlander for muskellunge, northern pike, and chain pickerel by comparing graphs of the weight vs. length equations with other data listed and with standard weight curves published by independent sources. A number of discrepancies are identified through this analysis and new weight-length relationships are produced from listed data. Introduction Weight-length relationships are a cornerstone of fishery research and management, (Anderson and Neumann 1996) because of their importance in assessing body condition and estimating biomass from length class surveys. (Froese 2006) Carlander's “Handbook of Freshwater Fishery Biology” (1969) includes key life history information on species in the pike genus (Esox) and many other important freshwater species. Pike are of considerable economic and ecological importance. (Doyon et al. 1988) Owing to some combination of compilation and unit conversion errors, the weight-length parameters tabulated in Carlander (1969) are not generally reliable and numerous errors have been propagated in the popular on-line database FishBase. (Cole-Fletcher et al. 2011) This paper assesses the Carlander length-weight data in muskellunge (E. masquinongy), northern pike (E. lucius), and chain pickerel (E. niger) by graphing the weight-length relationships and comparing to the main data table also found in Carlander as well as the published standard weight curves (Anderson and Neumann 1996). New weight-length relationships are generated in cases where Carlander (1969) includes applicable data, in the form W(L) = 1000 (l/l1) and in the traditional form W(l) = al, where W is the weight in grams and l is the total length in mm. The relationship W(l) = 1000 (l/l1) is preferred, because l1 is easily interpreted as the typical length of a fish weighing 1 kg, and because this relationship usually yields smaller uncertainties and covariances in the parameter values that result from regression analysis. (Dexter et al. 2011) Muskellunge (Esox masquinongy) Figure 1a was created using the equations given on p. 355 of Carlander’s “Handbook of Freshwater Fishery Biology” (1969). Note the variation between the curves; H138 (East & Central Canada) suggests that 1000 mm long fish typically weigh over 16 kg, which is unrealistic for species with a long, narrow body type such as the muskellunge, and 198% of the standard weight. The group of curves clustered near the standard weight curve seem reasonable, but the lowest curve, M329 ON central Canada muskies seems questionable at 74% of the standard weight curve. Data in the table on pp. 356-358 of Carlander (1969) allows for a new weight-length relationship to be computed for muskellunge from the H138 data in east and central Canada. This data is compared with both the new and errant weight-length relationship in Figure 1b. The error bars in the figure were estimated as 20% of the mean weight divided by the square root of the number of samples. Figure 1b makes it unmistakable that the weight-length relationship given