Stability in Life History Characteristics among Burbot Populations across Environmental Gradients

We examined the variation in the growth, morphometry, life history, and reproductive traits of 24 lake-dwelling populations of Burbot Lota lota from across Canada with respect to latitude and lake characteristics as well as the differences in these traits between the sexes across populations. Overall, there was stability in most of the life history traits examined vis-a-vis the environmental gradients tested (latitude, Secchi depth, lake area, and maximum lake depth). Among populations, spawning dates ranged from the last week of January to mid-March (most commonly within the first three weeks of February), and date of spawning was not strongly related to latitude or lake characteristics. Liver size and gonad size did not vary significantly with latitude or other lake characteristics, and neither gonad size nor egg size were strongly related to maternal size. However, egg size decreased with latitude and increased with lake area. The proportion of females in nonspawning condition within populations was positively related to Secchi depth and lake area, whereas size at age decreased with Secchi depth. Both swim bladder mass and gas gland mass increased with maximum lake depth. With the exception of the relative liver size of fish in spawning condition, there were was no evidence of sexually dimorphic characteristics in Burbot across populations. The monomorphism of gonad size observed in Burbot across populations is unusual among boreal fishes. The geographic variation in Burbot reproductive ecology observed in this study provides insight into the potential impacts of a changing environment.