Age, Growth, Reproduction, and Food of the Burbot, Lota lota (Linnaeus), in Southwestern Lake Superior

Abstract

This study was based on 1,285 burbot (Lota lota) collected in three southwestern Lake Superior in 1966-69. Age was determined from otoliths, the marginal zones of which were opaque from December to May and translucent from June to November. Average lengths of the age groups and annual increments were measured from a curve fitted by inspection to point estimates of lengths at capture. Burbot grew 5.7 inches during the first year ranged from 1.2 to 2.6 inches. Average total lengths calculated weights were 16.1 inches and 1.1 pounds at age V and 23.4 inches and 3.2 pounds at age X. First maturity was at age I, at a total length of 9.7 inches for males and 10.7 inches for females; all fish were mature at age V and at lengths greater than 16.4 inches (males) and 15.9 inches (females). Most burbot collected near shore in the Apostle Islands area in late January and February was spent, but none collected in offshore areas during January and March had spawned. The estimated number of eggs on the ovaries of eight burbot 14.7-21.3 inches long ranged from about 268,800 to 1,154,000 and averaged about 812,300. Burbot of all sizes fed on fish and crustaceans. Fish heavily predominated in the food of large burbot taken during winter (99.6% of the volume) but crustaceans (Mysis and Pontoporeia) became increasingly important during the summer and fall (when they contributed more than 73% of the volume). Due to the wide variety and large volume of food consumed, the burbot is probably a significant competitor of many other species.