Egg and Larval Development of Spanish Sardine, Sardinella Aurita (Family Clupeidae), with a Synopsis of Characters to Identify Clupeid Larvae from the Northern Gulf of Mexico

Larvae of the Spanish sardine are poorly known and the taxonomy of Sardinella species are poorly understood. Despite high morphological variability in adults, recent evidence provides no clear indication of two sympatric species of Sardinella in the western Atlantic Ocean and all are considered S. aurita. Larval evidence supports the high morphological variability reported for adult Spanish sardine, but does little to augment the understanding of Sardinella taxonomy in the western Atlantic. Eggs and larvae of S. aurita are described in this paper. Spawning apparently occurs at night. Eggs average 1.08 mm in diameter, have a single oil globule, and are smaller than those of most other clupeids. Length-at-hatch is about 2.5 mm standard length and growth in the laboratory averaged about 1.2 mm˙day-1 at 26-27°C. Transformation begins at 16 mm and is complete at 23 mm. During transformation, full complements of fin rays develop, the gut shortens, and dorsal and anal fins move forward. Larval development of Spanish sardine off Brazil is delayed compared to that of northern Gulf of Mexico specimens. Larvae of S. aurita are recognized primarily by melanophores bilaterally situated on the nape. Pigment differences provide a more versatile taxonomic character than myomere counts alone for identifying clupeid larvae because myomere counts overlap among some species. Primary pigmentation characteristics that separate larval clupeids, including S. aurita, from the northern Gulf of Mexico are: 1) presence or absence of pigment at the notochord tip and on the nape; and, 2) the standard length at which pigment appears along the cleithrum both above and below the pectoral fin, dorsally along the hindgut, and along the caudal peduncle.