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

Abstract

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 EastAustralian Current over two cruises during the austral summer of 1998/1999. Compared to the nonupwelled 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. δ 15 N ratios were significantly correlated with larval length, indicating ontogeny in their diet. In November, slower growers in upwelled waters were enriched in δ 15 N and depleted in δ 13 C, 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.

Entrainment and retention of the coastal larval fish assemblage by a short‐lived, submesoscale, frontal eddy of the East Australian Current

“…T. novaezelandiae is more associated with EAC water than S. sagax and is likely to have a spring spawning distribution similar to S. australasicus (Syahailatua et al 2011a,b). Together these species occur as larvae during spring on the continental shelf and are observed in near-shore upwelling zones (Uehara et al 2005;Syahailatua et al 2011b) or 200 km offshore in the Tasman Front (Condie et al 2011;Mullaney et al 2011). The co-occurrence of these species within the eddy indicates mixing of shelf and EAC water prior to eddy formation.…”

“…RGI was calculated as the mean daily growth (mm) of the last three full days of life divided by the natural log of the standard length (Uehara et al 2005). This removed any relationship between growth and size.…”

“…152 (shelf) and the eddy were measured for standard length (SL) using a dissecting microscope and optical micrometer to the nearest 0.1 mm. The sagittae of S. sagax larvae were removed using a dissecting microscope and polarized light (Uehara et al 2005) and were fixed to microscope slides with Crystal BondH; then the total number of increments were counted. Since increment formation occurs 2-3 d post hatch (Hayashi et al 1989) we added 2 d to the total increment count to estimate larval age.…”

Combined study of daily growth variability and nitrogen-carbon isotopic signature analysis of schooling Sardina pilchardus larvae

“…10(a)], however, indicates an increasing δ 15 N trend, which demonstrates that larvae undergo ontogenetic development. δ 15 N enrichment linked to trophic shifts has been described in the Pacific sardine S. sagax and the Japanese anchovy Engraulis japonicus Temminck & Schlegel 1846 (Lindsay et al , 1998; Uehara et al , 2005). An increase in the variance of δ 15 N has been ascribed to a broader niche width in fish larvae (Malzahn & Boersma, 2009).…”

Temporal patterns of growth in larval cohorts of the Japanese sardine Sardinops melanostictus in a coastal nursery area

“…Likewise, Watanabe & Kuroki (1997) reported allometric R O and L T relationships for larvae collected offshore of the Kuroshio Current (range: 6–21 mm L T ) and in coastal waters (range: 18–34 mm L T ). In addition, Uehara et al , (2005) reported slightly allometric R O and L T relationships for larval Sardinops sagax (Jenyns) in pre‐upwelling and upwelling regions in the East Australian Current (range: 6–26 mm L T ). This evidence along with the results of the current study suggests that the otolith size–larval size relationship based on observed age‐on‐length data become asymptotic at the end of the larval stage.…”