Reproductive condition, oocyte maturation, and life history variation in Lake Superior burbot (Lota lota)

Burbot (Lota lota) are a cryophilic freshwater fish native to many cold-water systems in the Northern Hemisphere. Within the Laurentian Great Lakes, current fishing regulations and increasing popularity are leading to interest in population dynamics and the sustainability of current and future burbot populations. To understand population dynamics, it is important to better understand the reproductive ecology of burbot. Currently, little is known about the reproductive ecology and the variation within reproductive behavior of burbot. In this study, we evaluated the reproductive ecology of southern Lake Superior burbot by characterizing the timing of reproductively maturing adult burbot and assessing the final oocyte maturation process. Samples were collected during two sampling seasons, which spanned from December to April. Riverine-collected burbot had high proportions (>90 %) of reproductively maturing individuals matched with females in the final stages of oocyte development during a short (3–5 week) period. Alternatively, lacustrine-collected burbot had low proportions (24 %) of reproductively maturing individuals and low proportions of females within the final stages of oocyte development (16 %). Unlike riverine captures, lacustrine-captured individuals indicated a prolonged presence of reproductively maturing individuals that lasted from December to at least early April. These results suggest variation within the reproductive ecology of Lake Superior-residing burbot.