Use of Scale Circuli Pattern Analysis to Differentiate between Hatchery and Wild Red Drum

Abstract

Abstract In 1983, the Texas Parks and Wildlife Department initiated a stock enhancement program that released up to 20 million red drum Sciaenops ocellatus annually. To evaluate the contribution of hatchery production to the fishery, scale pattern analysis was used to differentiate between hatchery-reared and wild fish. Scale patterns from 30–150-d-old hatchery-reared red drum fingerlings (13–35 mm total length, TL) from two hatcheries and wild red drum juveniles (<121 mm TL) were analyzed to establish a linear discriminant function. Accurate identification of 30-d-old hatchery-reared red drum ranged from 61–64%, but decreased to 35% for 60–150-d-old fish; classification rates for wild fish ranged from 63% to 70%. Correct classification of 30-d-old hatchery fish was significantly better than chance, but correct classification of wild fish was only significantly better than chance at one hatchery. Linear discriminant functions were used to evaluate variation between spring and fall hatchery-reared red drum and wild red drum. Correct identification ranged from 41% to 77% for spring fish, from 43% to 63% for fall fish, and from 38% to 54% for wild fish. Classification of spring and fall fish were significantly better than chance at both hatcheries, but classification of wild fish was significantly better than chance at only one hatchery. Scale pattern analysis was effective at differentiating between hatchery and wild fish but was not as effective at separating seasonally produced hatchery-reared fish and wild fish.