Larval Development of the Redbreast Sunfish (Lepomis auritus) from the Susquehanna River

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Abstract
A redbreast sunfish (Lepomis auritus) nest with eggs was found in the Susquehanna River near Berwick, Pennsylvania. At hatching, the total length (TL) of the larvae ranged from 4.6 to 5.1 mm with a mean of 4.9 mm (standard or notochord length ranged from 4.5 to 5.0 mm with a mean of 4.8 mm). Newly hatched larvae had incomplete mouths, large ovoid yolk sacs, pectoral fin buds, and straight urostyles. Pigmentation appeared on the dorsal surface of the head in 7.8‐mm TL larvae. The caudal fin rays began to develop by 7.8 mm TL; dorsal, anal, and pectoral fin rays began to develop by 8.1 mm TL; and the pelvic fin rays by 15.0 mm TL. Transformation to mesolarval phase occurred by 7.8 mm TL, to metalarval phase by 11.8 mm TL, and to the juvenile period by 19.0 mm TL. Useful characteristics for distinguishing redbreast sunfish larvae in the Susquehanna River are their larger size at hatching and swim‐up, massively coiled guts, and the elongated patch of 20‐30 melanophores on the venter between the opercle and vent.