A buoyancy control system for a fish cage used in fish farming. The buoyancy system comprises spars having first and second sections separated by a bulkhead. The first section is filled with air and hermetically sealed from the second section and from the surrounding environment. The second section is sealable and may be filled with air or water to adjust the buoyancy of the spar. A fish cage having the buoyancy control system can be raised or lowered in accordance to the amount of air and water in the second sections of the spars. A segmented anchor can connected at each spar.