By Erich Luening
By Erich Luening
As wild North American burbot populations continue to fall some industry observers are encouraging development of commercial aquaculture production for the species. And one of the keys to burbot’s success in a commercial setting will inevitably require a reduction in larval mortality rates during the hatchery phase.
With this in mind a recently published study, “Initial Characterization of Embryonic Development in North American Burbot,” looks at curtailing the mortality rate of burbot embryos and larvae in culture systems.
For the study biologists at the University of Idaho examined burbot embryonic development from egg fertilization until onset of the larval period at first feeding.
“We have pioneered much of the culture work being done in the US and this has paralleled some of the work being done in Europe,” lead researcher Kenneth Cain, of the Aquaculture Institute at the University of Idaho, told Hatchery International.
“Here in the US, research was driven by the need to develop conservation aquaculture methods for recovery of at-risk populations in Idaho and British Columbia. However, we hope to move forward and prove that this “freshwater” cod could be an ideal commercial food-fish and would expand opportunities for freshwater systems and may be an alternative for some “trout” facilities in the future.”
Cain said that burbot is often referred to as the “poor man’s lobster” and in Europe its flesh is prized but also sought after for caviar and liver which is also considered a delicacy.
Reducing the mortality rates of embryo and larvae requires establishment of rearing protocols that account for differences in favorable environmental conditions through early development, as has been done for more widely cultured fish species, Cain explained.
Initial embryo survival
Cain’s team found that timing of embryonic cell cleavage within burbot eggs appeared to be synchronous and generally occurred in about twice the time it takes Atlantic Cod, a comparable species used by the researchers.
“The application for this particular study would be in understanding the various stages of embryo development and increasing incubation and hatching success for this species,” Cain said.
The first group of wild-collected eggs were sampled every three hours to determine this embryonic staging period. A cleavage period of approximately eight hours was observed, so embryos were then sampled every eight hours until the end of the cleavage period. After the cleavage stage, embryos were sampled daily, according to the study.
For each sample, 10 embryos were randomly pipetted from the incubators, euthanized and photographed with a stereo microscope to evaluate health variations in each sample.
“Some of the challenges for rearing burbot relate to the cold temperatures and long
timeframe’s for incubation and early rearing,” explained Cain. “Eggs take about 40 days to hatch at temperatures from 2-4°C and then there is an extended period of Artemia feeding before weaning fish onto a dry diet. However, once they are weaned they can grow quite fast at temperatures of 10-20°C making them a potential polyculture species at trout facilities with temperatures in that range.”
Results of the study are expected to further develop and refine burbot culture methods for conservation and commercial applications, and guide additional research needed to inform burbot conservation and management, the study authors wrote.
– Erich Luening