The income received and accruing from the investments of the wildlife management endowment fund, subject to limitations prescribed for funds received from the sale of lifetime sportsman licenses to holders under the age of sixteen (16) years, may only be spent in furthering the management, protection, propagation, and conservation of wildlife to assure perpetual protection and preservation for future generations of the heritage of hunting and fishing in this state and the efficient operation of the wildlife resources agency in accomplishing these objectives.