Larval morphology of North American burbot (Lota lota maculosa) from two spatially separated populations

Abstract

Burbot (Lota lota) are a freshwater fish that exhibits a circumpolar distribution and is considered an indicator species for climate change. Adult burbot were artificially fertilized from the Sturgeon River, Michigan and eggs were incubated until hatch. For 10 weeks following hatch larvae were photographed, along with comparable samples from the Kootenai River, Idaho. Geometric morphology was used to quantify significant morphological differences between groups (n = 510). During the yolk sac stages, body shape near yolk sacs varied, likely linked to absorption differences. In preflexion and flexion stages, variable body shape in the mid-body region coincided to head and tail positions. Mean linear morphological measurement (n = 919) showed significant differences, indicating variability of size at stage between groups. Sturgeon River preflexion larvae growth patterns were variable and exhibited allometric growth in comparison to Kootenai River larvae. This suggests that development of critical structures occurs at different rates allowing for flexibility in habitat settlement or environmental conditions. Both groups showed isometric growth patterns in the flexion stage, indicating that critical structures have developed, marking an important ontogenetic shift. Variability in larval burbot hatching, morphology, and developmental rates is important to their persistence throughout North America.