Identification of Eggs, Larvae, and Juveniles of the Rainbow Smelt, Osmerus mordax, with Comparisons to Larval Alewife, Alosa pseudoharengus, and Gizzard Shad, Dorosoma cepedianum

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Abstract Eggs and larvae of the rainbow smelt, Osmerus mordax, were reared in the laboratory to 7.4 mm total length. Larger sizes were collected by plankton net from Lake Erie, Lake Ontario, and Cayuga Lake, New York. Manually stripped eggs were adhesive and demersal with a granular, yellow yolk. Egg diameter after fertilization and water hardening was 1.0 mm. The majority of eggs hatched between 183 and 195 h after fertilization at an average water temperature of 16.5 C. Average length of larvae at 195 h was 5.6 mm. Yolk absorption was complete at 6.4 mm. Pectoral fin development began before hatching. The dorsal, anal, and caudal fin rays began development at approximately 14 mm. The pelvic fins budded between 17 and 20 mm. All fin rays were complete at 36 mm. The adipose fin was complete at 29 mm. Separation of rainbow smelt from alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) was accomplished using yolk sac position, preanal and postanal myomeres, and snout-to-vent length as a pe...