The Brook Trout of the Nipigon River, Lake Nipigon and indeed the Coasters of Lake Superior defy the usual trout weight formulas with their stout "girth-to-length" proportions. A special formula was developed by Nipigon angler Kurt Melancon from Minneapolis. While I re-created the Nipigon Brook Trout Weight Table listed below, the true credit goes to Kurt and fellow anglers Bill Boote and  Scott E. Smith, along with others who gathered the actual measurements of girth, length and weight as first displayed in Scott's book:
Ontario Blue Ribbon Fly Fishing Guide. 

While the chart above was specifically designed for Nipigon Brook Trout based on actual Length/Girth/Weight measurements. The traditional weight formula that is often used is: weight (lbs) = length(inches) * girth(inches)^2 / 800.  Research out of British Columbia based on Steelhead and Salmon species challenges this formula with new data. A site called: Fly Fishing Research has this mission statement: "Enhance fly fishing enjoyment, learning, and effectiveness through science, research and publication". Based on actual Length/Girth/Weight measurements, they revised the formula to be multiplied by 690, stating it is a more accurate representation. Here is a link to their research and chart.

        I could not resist the challenge to test this new formula against the Nipigon Brook Trout which are known to exceed the traditional formula. Since I had actual Length/Girth/Weight measurements for Nipigon Brookies, I applied their revised formula to see how accurate it was compared to the actual weight of each fish. Using the 690 number, the weights came out accurate within a few ounces for each fish and better represented the true estimate of weight. When I have more time, (non fishing season) I'll post my data and see if I come up with the same 690 number.

Length-weight relationship of brook trout captured within Cameron Falls, Jessie Lake, and Lake Nipigon from Co-operative angler program.

The predicted weight of Nipigon area brook trout of a given lengths.

A conservationists approach to fishing the Nipigon

Nipigon Brook Trout Weight Chart