Initial characterization of embryonic development in North American burbot

Declining wild populations and increasing commercial interest are encouraging development of aquaculture methods for the North American Burbot Lota lota maculosa. A current focus of Burbot aquaculture research is reducing high mortality that is typically associated with culture of Burbot embryos and larvae. However, no Burbot embryonic or larval staging systems are currently available to provide a comparative baseline for studies of these life stages. To help address this gap, we examined Burbot embryonic development from egg fertilization until the onset of the larval period at first feeding. Ontogeny was characterized using diagnostic morphological features visible with stereo microscopy. Six developmental periods were characterized (cleavage, blastula, gastrula, segmentation, swim bladder inflation, and first feeding), along with 15 developmental stages. Water temperature ranged from 3°C to 5°C for the duration of this study. Cleavage cycles were approximately 8 h/division. Segmentation began at 12 d postfertilization (DPF) and continued until first hatch at 33 DPF. First feeding was observed at 45 DPF, 12 d after first hatch. Results presented here are expected to help refine Burbot culture methodology and research efforts aimed at conservation, management, and commercial production. Future research should use additional cohorts and expose embryos to a range of culture conditions to better understand the factors governing embryonic survival and variability in the timing of events during development.