The district attorney for the Fifteenth Judicial District of this state shall receive as compensation for his services, in addition to the annual salary paid him by the state, an annual salary of seventeen thousand four hundred dollars, payable monthly on his own warrant, by the parishes comprising the Fifteenth Judicial District, apportioned as follows:
By the parish of Acadia, the sum of five thousand eight hundred dollars per annum;
By the parish of Lafayette, the sum of five thousand eight hundred dollars per annum;
By the parish of Vermilion, the sum of five thousand eight hundred dollars per annum.
La. R.S. § 16:321