Evaluation of methods for the collection and fertilization of burbot eggs from a wild stock for conservation aquaculture operations

In the Kootenay River, British Columbia, Canada, burbot (Lota lota maculosa) numbers have diminished to near extirpation due to factors including physical changes to habitat and overfishing. Habitat restoration is currently underway but short-term recovery measures include the release of hatchery-reared burbot. Moyie Lake has been identified as a suitable brood source for a conservation aquaculture program but uncertainties remain regarding current population size, the feasibility of capturing broodstock and the ability to collect eggs from wild spawners. Specific objectives of our study were to: (i) develop a length at age key to provide a non-destructive means of population age structure identification, (ii) determine the location and general habitat characteristics of burbot spawning locations on Moyie Lake, (iii) provide a marked sample for future population estimation, and (iv) investigate the feasibility of collecting gametes for use in a conservation aquaculture program. A total of 181, 554, and 370 burbot were captured in 2009, 2010 and 2011, respectively. No significant relationship was established between length and age for burbot on Moyie Lake. Spawning burbot were observed over a number of different habitats, but high use areas consisted of steep banks dominated by a mix of gravel / boulder / cobble substrates. Mature burbot were reliably collected each year, and eggs from females were fertilized and transported to the hatchery. Egg survival was highly variable (range 0-98%) and resulted in an estimated 353 429, 3 032 143, and 3 970 283 eggs for use in the aquaculture program in 2009, 2010 and 2011, respectively. Results of this study demonstrate that gametes can be collected from adult burbot during spawning and eggs can be successfully fertilized in the field. Further methodological refinement aimed at improving egg fertilization and subsequent survival to the hatchery will be important as recovery moves forward.