Development of eggs, larvae and juveniles of laboratory-reared blue whiting, Sillago parvisquamis (Percoidei : Sillaginidae)

The embryonic, larval and juvenile development of blue whiting, Sillago par visquamis Gill, are described from a series of laboratory-reared specimens. Mean egg diameter and mean total length (TL) of newly-hatched larvae were 0.71 mm and 1.58 mm, respectively. The eggs were non-adhesive, buoyant and spherical with an oil globule (mean diameter 0.18 mm). Hatching occurred ab out 20 hours after fertilization at a temperature of 24.0-25.0 degrees C, n ewly-hatched larvae having 38-40 myomeres. The yolk and oil globule were co mpletely absorbed 3 days after hatching at 2.8-3.2 (mean 3.0) mm TL. Notoch ord flexion was completed by 7.2-8.2 (7.7) mm TL, and pectoral and caudal f in rays fully developed by approximately 10 mm and 8.5 mm TL, respectively. Completion of fin development occurred in the following sequence: caudal, pectoral, anal and second dorsal, first dorsal and pelvic, the last-mention ed by approximately 11 mm TL. The larvae of S. parvisquamis and S. japonica , which closely resemble each other in general morphology and pigmentation, could be distinguished as follows. Newly-hatched S. parvisquamis larvae ha d more myomeres than S. japonica (38-40 vs. 32-34) and more melanophores on the dorsal surface of the body (19-28 vs, about 40). Sillago japonica had a vertical band of melanophores on the caudal peduncle, which was lacking i n post-flexion S. parvisquamis larvae. In addition, juveniles of S. parvisq uamis (larger than 23 mm TL) had melanophores on the body extending anterio rly to below the lateral line to form a midlateral band, whereas no obvious band occurred on similarly-sized S. japonica juveniles.