Out-Of-Season Spawning Of Burbot (Lota Lota) Through Temperature And Photoperiod Manipulation.

Intensive commercial production of burbot fingerlings will depend on consistent supply of eggs and larvae at multiple times during the year; however, no information on out-of-season spawning of burbot exists. The current study was designed to shift sexual maturation of burbot broodstock by six months from the natural spawning season through temperature and photoperiod manipulation. Results demonstrated that out-of-season spawning of burbot was successful. Broodstock, egg quality, and larval condition data were compared between out-of-season and in-season groups. For both production regimes, broodstock were sampled for condition factor and egg production, and embryos were monitored for development, viability, and survival. Larvae were reared to 35 days post hatch (dph) for growth and survival comparison. There was no significant difference in pre-spawn condition factor between in-season and out-of-season males or females. Post-spawn condition factor for out-of-season females was not statistically different from in-season females, 0.83 (+/- 0.06) and 0.66 (+/- 0.07) respectively. However, post-spawn condition factor for out-of-season male broodstock was significantly higher, 0.82 (+/- 0.04), than in-season fish, 0.64 (+/- 0.02). Eggs produced relative to weight of pre-spawn female did not differ significantly between in-season and out-of-season production, 328.5 (+/- 22.95) and 213 (+/- 38.04) eggs/g, respectively. Fertilization did not differ significantly between treatments, averaging 90% for both in and out-of-season production. Egg survival was higher, 61.18% (+/- 9.3), in the final week of incubation for out-of-season groups compare to eggs from in-season broodstock, 20.59% (+/- 10.6). However, no difference in larval growth or survival was observed out to the 35dph termination point. Overall, egg quality and larval survival was not negatively impacted for broodstock spawned out-of-season. This is the first report demonstrating that burbot eggs can be produced outside the natural spawning season by altering photoperiod and temperature. As commercial production of this species develops, this will be an important tool to mitigate the risk of relying on a single annual spawning season and can ensure a consistent supply of burbot fingerlings throughout the year.