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

Abstract

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 from 1.0% to 12.7%, with lower stocking densities exhibiting higher survival. An exponential decay model 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 culture methods, this semi-intensive approach may represent a less labor-intensive and less costly method of efficiently producing Burbot for conservation or commercial production programs.

Received September 4, 2012; accepted March 14, 2013

ACKNOWLEDGMENTS

This project was funded in part by the U.S. Fish and Wildlife Service (grant 14330-7-H067); we offer special thanks to Ray Jones for program funding and coordination. This project was also supported by the Kootenai Tribe of Idaho (KTOI) and the Bonneville Power Administration (project 198806400, contracts 37267 and 46821). We extend our deepest gratitude to the KTOI, the British Columbia Ministry of Lands, Forests, and Natural Resource Operations, the Idaho Department of Fish and Game (IDFG), Cramer Fish Sciences, the U.S. Fish and Wildlife Service, and the University of Idaho Aquaculture Research Institute (UI–ARI), as this work would not have been possible without the valuable collaborations between these agencies. We thank UI–ARI staff and Scott Williams for installing the experimental in-ground tanks. Additional thanks to ARI staff members who assisted during this study, especially Chris Thornton. We also thank Vaughn Paragamian of the IDFG for his involvement in Burbot conservation. We also extend our gratitude to the anonymous reviewers and the associate editor whose thoughtful advice greatly improved this manuscript. Finally, we thank Bahman Shafii and William Price of the University of Idaho for statistical advice and guidance.