Ups and Downs of Burbot and Their Predator Lake Trout in Lake Superior, 1953–2011

Abstract

The fish community of Lake Superior has undergone a spectacular cycle of decline and recovery over the past 60 years. A combination of Sea Lamprey Petromyzon marinus depredation and commercial overfishing resulted in severe declines in Lake Trout Salvelinus namaycush, which served as the primary top predator of the community. Burbot Lota lota populations also declined as a result of Sea Lamprey depredation, largely owing to the loss of adult fish. After Sea Lamprey control measures were instituted in the early 1960s, Burbot populations rebounded rapidly but Lake Trout populations recovered more slowly and recovery was not fully evident until the mid-1980s. As Lake Trout populations recovered, Burbot populations began to decline, and predation on small Burbot was identified as the most likely cause. By 2000, Burbot densities had dropped below their nadir in the early 1960s and have continued to decline, with the densities of juveniles and small adults falling below that of large adults. Although Burbot populations are at record lows in Lake Superior, the density of large reproductive adults remains stable and a large reserve of adult Burbot is present in deep offshore waters. The combination of the Burbot's early maturation, long life span, and high fecundity provides the species with the resiliency to remain a viable member of the Lake Superior fish community into the foreseeable future.

Received October 1, 2012; accepted July 9, 2013

ACKNOWLEDGMENTS

This article would not have been possible without the help of many people dedicated to revealing the wonders of Lake Superior, including Lori Evrard for providing trawl-based data summaries, and numerous Northland College student interns for assisting with the entry of old field data records: Tyler Sikora, Jill Falck, Steve Whitlock, Kari Kudick, Becky Walters, and John “Logan” Tucker. Thanks also to Laura Graf for providing editorial assistance in preparing the manuscript. This work was supported by funds from the U.S. Geological Survey. This article is contribution 1783 of the U.S. Geological Survey, Great Lakes Science Center.