No fish shall be furnished by the state for stocking any stream, river, pond or lake from which the taking of fish is prohibited by the owner or lessee; provided, if the state, in the opinion of the commissioner, has on hand at any time more fish than are required in any season for stocking streams, rivers, ponds or lakes from which the taking of fish is not prohibited, the commissioner may sell such surplus fish, or such fish as exceed hatchery rearing capacity, at the cost of such fish as estimated by him, to any person in the state for use for stocking any stream, river, pond or lake in the state, whether or not such water is open to public fishing. To encourage landowners to engage in fish management practices in waters over which they have control, the commissioner is authorized to sell to such landowners from stock on hand in the department, at a cost to be estimated by him, fish foods, chemicals and compounds used in fisheries management, lake and pond bottom contour maps and related incidental commodities. If the state, in the opinion of the commissioner, has on hand surplus, disease-free fish or fish eggs which exceed hatchery capacity, the commissioner may sell such surplus fish or fish eggs to commercial hatcheries, at a cost estimated by him to be competitive with the cost of such fish or fish eggs if purchased from commercial hatcheries. The proceeds of each such sale shall be remitted to the State Treasurer and shall be applied to the General Fund.