Larval Development of Rock Bass from the Susquehanna River

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Abstract
Eggs from the nest of a rock bass (Ambloplites rupestris) were collected by scuba divers in the Susquehanna River near Port Trevorton, Pennsylvania. At hatching, the mean total length (TL) and standard (notochord) length of three larvae were 5.6 and 5.5 mm, respectively. The newly hatched larvae were free of melanophores and had incomplete mouths, ovoid yolk sacs, straight urostyles, and pectoral fin buds. Melanophores began to appear in larvae by 6.8 mm TL. Caudal fin rays were visible by 6.9 mm; dorsal, anal, and pectoral fin rays by 8.6 mm; and pelvic fin rays by 13.5 mm. Rock bass larvae can be distinguished from Lepomis and Pomoxis by their larger size at hatching and larger body melanophores. Of the centrarchid larvae found in the Susquehanna River, rock bass can be easily confused only with smallmouth bass (Micropterus dolomieui); however, rock bass can be distinguished by the less dense arrangement of body melanophores, and by the larger numbers of preanal myomeres and anal spines.