Effects of Stocking Density on Survival and Yield of North American Burbot Reared under Semi-Intensive Conditions

The effects of six stocking densities on the survival and yield of larval Burbot Lota lota in a semi-intensive culture setting were investigated over a 3-year period. A stocking initiation trial indicated that a stocking date of at least 45 d after the first exogenous feeding (DPEF) would yield surviving juveniles after a 108-d semi-intensive culture period. Following this, stocking density was investigated, and larval Burbot were stocked into in-ground outdoor tanks 45 DPEF at densities of 50, 100, 150, 200, 250, and 300 larvae/m2. Tanks were harvested after 65 d, and the trials were repeated over two consecutive years. At harvest, the mean TL of fish ranged from 41 to 68 mm and the mean weight from 0.5 to 2.1 g over both years. Survival ranged from1.0% to 12.7%, with lower stocking densities exhibiting higher survival. An exponential decaymodel revealed a significant influence of stocking density on survival, with 50 larvae/m2 being predicted to provide the highest survival and the maximum yield being predicted to occur at 100/m2. These results indicate that a stocking density of 100 larvae/m2 should not be exceeded under the conditions described in this study. This experiment demonstrated that semi-intensive culture strategies can be successfully adapted for North American Burbot. Relative to other culturemethods, this semi-intensive approachmay represent a less labor-intensive and less costly method of efficiently producing Burbot for conservation or commercial production programs.