Shinji Uehara

Recent growth rate of larval pilchards Sardinops sagax in relation to their stable isotope composition, in an upwelling zone of the East Australian Current

The recent growth rate and stable isotope composition of larval pilchards, (Sardinops sagax, 6–29 mm standard length), captured in surface and near-surface waters, were examined in coastal upwelling and non-upwelling regions of the East Australian Current over two cruises during the austral summer of 1998/1999. Compared to the non-upwelled regions, larvae were larger in the upwelling regions, and yet the back-calculated recent growth over 2 days before capture was significantly less on both cruises. This surprising result is consistent with slower larval growth of this species near coastal Japan and California, where strong year classes may form in offshore waters. δ15N ratios were significantly correlated with larval length, indicating ontogeny in their diet. In November, slower growers in upwelled waters were enriched in δ15N and depleted in δ13C, consistent with expected ratios from diets derived from deeper water. The pilchard’s early life history off eastern Australia is proposed and compared with that off eastern Japan.

The occurrence of two species of Macroramphosus (Gasterosteiformes : Macroramphosidae) in Japan : morphological and ecological observations on larvae, juveniles, and adults

Earlier opinions that Macroramphosus is monotypic are refuted, with two species apparently occurring in Japan (tentatively identified as M. gracilis and M. scolopax). In postsettlement young and adults, the former is characterized by a dark slender body (vs. red-orange and deep) and short second dorsal fin spine with a smooth posterior margin (vs. long spine with a serrated margin). Food habits also differ between the two species, which are either plankton or benthos feeders. Two types of Macroramphosus larvae and juveniles occurring at the surface were recognized, one having a straight ventral body profile of the body (identified here as M. gracilis) and the other having a notch in the anal region. The dark body of postsettlement M. gracilis is considered to be a retention of the character suited to the neustonic distribution of the larval and juvenile stages, the species remaining to ca. 40 mm in standard length (SL) in that habitat (vs. to ca. 12 mm SL in M. scolopax).