larval growth and mortality of japanese spanish mackerel (scomberomorus niphonius) in the central seto inland sea, japan

Abstract

Growth and mortality rates of larval Japanese Spanish mackerel (Scomberomorus niphonius) were estimated by using otolith daily increments in 1997 and 1998 in the Sea of Hiuchi, central Seto Inland Sea. There was no day^night di¡erence in the abundance and size-distribution of S. niphonius larvae in the 3^10 mm sizeclasses, indicating the larvae were e⁄ciently collected by the larva-net used for sampling (1.3 m mouth diameter, 0.5 mm mesh). Mean absolute growth rate (0.748 mm d 71 in 1997, 0.821mm d 71 in 1998), weight speci¢c growth coe⁄cient (G: 0.402 in 1997, 0.444 in 1998) and mortality coe⁄cient (M: 0.784 in 1997 and 0.625 in 1998) were among the highest reported for marine ¢sh larvae. Scomberomorus niphonius seems to have evolved survival strategies characterized by fast growth with strong piscivory that can reduce duration of the larval period with the high mortality. In 1997, spatial distribution of the larvae was not well corresponded to that of their prey, clupeid larvae, and the larval feeding incidence was lower than in 1998. Recruitment potential assessed by examining the ratio of G:M was lower in 1997 (0.513 in 1997, 0.711 in 1998) due to the lower G and higher M values. Prey ¢sh availability may be one of the important determinants for the recruitment potential by controlling the larval mortality due to starvation and/or starvation-related predation.

Growth-selective survival in piscivorous larvae of Japanese Spanish mackerel Scomberomorus niphonius: early selection and significance of ichthyoplankton prey supply

“…In previous studies, no significant relationship was observed between larval (<12 mm) and juvenile (>12 mm) abundance, whereas juvenile abundance was positively correlated with 1 yr old fish abundance in subsequent years in the 1980s (Kishida 1991) and 1990s (Shoji & Tanaka 2003). Strong year-classes occurred in years when larval growth rate was significantly high (Shoji & Tanaka 2003). Year-to-year fluctuation in mortality during the larval stage seems to be relatively large, but that between the juvenile and 1 yr old stage is small.…”

“…Young-of-the-year Japanese Spanish mackerel inhabit the Sea of Hiuchi until December, then migrate to oceanic waters . In previous studies, no significant relationship was observed between larval (<12 mm) and juvenile (>12 mm) abundance, whereas juvenile abundance was positively correlated with 1 yr old fish abundance in subsequent years in the 1980s (Kishida 1991) and 1990s (Shoji & Tanaka 2003). Strong year-classes occurred in years when larval growth rate was significantly high (Shoji & Tanaka 2003).…”

“…In order to establish otolith radius-fish length relationship throughout the larval and juvenile stages, larvae of Japanese Spanish mackerel <10 mm standard length (SL) were collected using a conical larvae-net with a 1.3 m mouth diameter and 0.5 mm mesh aperture in the Sea of Hiuchi in June from 1997 to 1999 (Shoji & Tanaka 2003). Ichthyoplankton samples collected by the larvae-net were preserved in 90% ethanol, and 15 larvae <10 mm were processed only for the analysis of otolith radius-fish length relationships and coefficient of variance of fish body length (not for growth back-calculation).…”

“…1) from April until August from 1997 to 1999 (Kagawa Prefecture Fisheries Experimental Station 1999, 2000, 2001 were used to calculate mean monthly temperature. Concentration of clupeiform larvae, the major prey of Japanese Spanish mackerel larvae and juveniles (Shoji & Tanaka 2005a), in the eastern part of the Sea of Hiuchi was used as an index of prey abundance. Ichthyoplankton was collected with a conical plankton-net at 6 stations ( Fig.…”

“…Among scombrids, particularly high growth (>1.0 mm d : Shoji & Tanaka 2005b) have been reported in Scomberomorus spp. larvae that are almost exclusively piscivorous from the first feeding (Jenkins et al 1984, Finucane et al 1990, Shoji & Tanaka 2001.…”