Early Development of the Yellow Perch, Perca flavescens

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Abstract
In this study, eggs and larvae of the yellow perch,Perca flavescens, were reared in the laboratory from fertilization to postlarval stages. Fish were sampled at intervals and changes in morphology, anatomy, and general characteristics were described and illustrated. Larvae raised in outdoor hatchery ponds were brought into the laboratory for comparison and to complete developmental descriptions up to the young stages. Eggs of the yellow perch are extruded in adhesive strands, and in the Chesapeake Bay these strands are found in the shallow, upper reaches of many major tributaries in March and April. Within the first few minutes after fertilization, the eggs “water harden” and expand. Eggs fertilized in this study reached a mean diameter of 2.26 mm; the mean diameter of the yolk was 1.28 mm and the oil droplet was 0.64 mm. Changes in the egg from fertilization through hatching do not deviate widely from known fish embryology. The most distinctive character of the egg is its thick, elastic case containing minute radial striations. Illustrations of important embryological stages allow easy understanding of the progression in development. Hatching occurs in 27 days at temperatures from 8.5–12.0C. This incubation period is long when compared to the hatching time of other common estuarine fish. In this study prolarvae were 5.5–6.0 mm T.L. at hatching. Early prolarvae have an undifferentiated continuous finfold, pigmented eyes, and a series of 15–20 pigment spots along the ventral surface of the tail. The mouth is fully developed at the end of the prolarval stage and although vestiges of yolk remain, active feeding is initiated. In postlarvae, pigmentation increases over the body, the head becomes more flattened, and a few teeth protrude from the maxillary. Fin formation starts at approximately 11 mm T.L. with differentiation of the basal portion of the caudal fin. The sequence of fin development is: pectorals (within the egg); caudal; anal, second dorsal, some spines of the first dorsal; pelvics; and, finally, the remaining first dorsal spines. Yellow perch are transformed from the larval stages at approximately 13 mm T.L. when all fins are formed. However, ray elements within the fins are incomplete until the fish reach 21 to 27 mm T.L. At this size the first soft ray of the anal transforms into a second spine, changing the formula from I, 8–9 to II, 7–8. The formation of distinct body bands begins when the young are about 20 mm T.L. and this pigmentation continues until the vertical bands become a distinct species characteristic. Morphometry, and meristics assume adult proportion near the end of the young stage. Morphometric changes in head length, body depth, and snout-to-vent length are compared. The ossification of a young specimen 17.0 mm T.L., which was cleared and stained with Alizarin red-S, is illustrated. Habits of cultured fish are briefly mentioned. There was an almost complete lack of feeding success in yellow perch larval stages. Comparison is made with other work on the yellow perch in the U.S.; excepting hatching size, head contours, and some pigmentation, little difference is noted. Comparison of this study with work from Europe encourages the theory thatPerca flavescens andPercafluviatilis may be conspecific.

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