A STANDARD WEIGHT EQUATION TO ASSESS THE CONDITION OF NORTH-AMERICAN LAKE HERRING (COREGONUS-ARTEDI)

We developed a 75th-percentile standard weight (Ws) equation to aid in the analysis of lake herring (Coregonus artedi) body condition over t emporal periods and across populations. Weight-length data were obtain ed for 23,115 lake herring from 61 North American populations. The pro posed equation is log(10) Ws = -5.517 + 3.224 log(10) TL, where Ws is the standard weight in grams and TL is the maximum total length in mil limeters. The equation is valid for lake herring greater than or equal to 100 mm and allows calculation of the relative weight (Wr) index. S ignificantly lower (P<0.001) Wr values were present for Lake Superior lake herring populations than for the ''inland'' populations, suggesti ng that Lake Superior herring weigh less at a given length. Based on t he world record lake herring length (55.9 cm), we propose minimum stan dardized length categories of 13, 20, 28, 35, and 43 cm for stock, qua lity, preferred, memorable, and trophy lengths, respectively. The leng th categories facilitate analysis across length groups and the calcula tion of stock density indices.