Asymptotic growth trajectories of larval sardine ( Sardinops melanostictus ) in the coastal waters off western Japan

Growth and condition of larval Engraulis encrasicolus larvae in the Bay of Biscay were analysed relative to their biochemical composition. Protein, carbohydrate, lipid, DNA and RNA contents of larvae were quantified during larval ontogeny to analyse changes associated with growth. Proteins were the main organic component of E. encrasicolus at every larval stage, followed by lipids and carbohydrates. The increase in relative protein content in terms of protein percentage (P%) and the decrease in lipid relative content (L%) of the total organic matter (OM) with size observed are consistent with the definition of Type 1 larvae. Protein relative content increased until the P% in larvae reached ~71%, whereas L% and carbohydrate relative content (CH%) declined, exhibiting minimum values of ~20, and ~6%, respectively. In general terms, the feeding condition of larvae, as defined by their RNA/DNA ratio, was good. Food did not seem to be a major factor limiting larval growth in the study area throughout late spring and early summer. The RNA/DNA ratio was size-related and increased during larval growth up to an asymptotic optimal value of ~3.6 in postflexion larvae in relative protein content, in terms of protein percentage (P%). The 'actual' RNA/DNA ratios found in a given larval population when compared with the 'starving' RNA/DNA ratio, and using an 'absolutely optimal' value as complementary information, could be used to determine the overall status of the population. Parental effect of low egg quality is a possible explanation of delayed ontogenetical development of larvae from July 2000.

Section: Condition Of Larvaesupporting

confidence: 90%

Biochemical composition and condition in anchovy larvae Engraulis encrasicolus during growth

Dı́az¹,

Txurruka²,

Villate³

2008

“…Allometric parameters were determined for each fish using the biological intercept method (Campana 1990, Campana & Jones 1992, Watanabe & Kuroki 1997. Otolith daily rings start to be deposited at the first feeding stage (Day 5 at 19°C) in Japanese Spanish mackerel (Shoji & Tanaka 2004).…”

Section: Methodsmentioning

confidence: 99%

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

Shoji

Tanaka²

2006

Scombrid fishes are considered to have adopted a survival strategy characterized by fast growth and the ability to consume large prey at an early age. Variability in feeding condition can significantly affect larval growth as early as the post first-feeding stage and may control growth-related survival during the early larval stage. Through otolith microstructure analysis, growth-selective survival was demonstrated for post first-feeding larvae of Japanese Spanish mackerel Scomberomorus niphonius, which exhibit exclusive piscivory, a high growth rate, and low tolerance to starvation. Larvae and juveniles were repeatedly collected in the Seto Inland Sea in June and July from 1997 to 1999. Growth trajectory back-calculated using otolith microanalysis was compared between the survivors (SV) captured in July and the presumed original population (OP) captured in June. Selection for fast-growing larvae was evident during the 5 d after first feeding (Days 5 to 10). More than 90% of the SV had a mean growth rate during Days 5 to 10 (G 5 -10 ) > 0.8 mm d -1, and those with G 5 -10 < 0.8 mm d -1 rarely survived the period. Intensity of selection differed among 3 years. A less intense selection was observed in 1999 when the larval cohort experienced higher prey concentrations and G 5 -10 . Laboratory experiments demonstrated that 1 to 2 d starvation retarded the larval growth during the following larval period, and supported the conclusion that fluctuation in ichthyoplankton prey abundance alters larval survival probability by affecting the larval growth rate within a short period subsequent to first feeding.

“…Hatching date was determined according to age and date of capture. SL and daily growth rate at each age were back-calculated by the biological intercept method (Campana 1990, Campana & Jones 1992, Watanabe & Kuroki 1997, Oozeki & Watanabe 2000 in order to obtain the growth trajectories and histories of individual larvae. Since the relationship between OR and SL was well expressed as an allometric relationship (data not shown), the back-calculation procedure used an allometric formula that was separately determined for individual larvae, with SL at the first ring deposition fixed at 5.6 mm (Fukuhara 1983).…”

Section: Methodsmentioning

confidence: 99%

Three synergistic growth-related mechanisms in the short-term survival of larval Japanese anchovy Engraulis japonicus in Sagami Bay

Takasuka

Aoki²,

Mitani³

2004

The 'growth-mortality' hypothesis, which holds that larger and/or faster growing individuals will have a higher probability of survival, currently includes 3 functional mechanisms (hypotheses) in its theoretical framework: 'bigger is better', 'stage duration' and the recently proposed 'growth-selective predation', which are based on size, time and per se growth rate, respectively. Through otolith microstructure analysis, we tested these 3 synergistic growth-related mechanisms according to growth characteristics of the survivors vs the original population in the short-term (ca. 2 wk) survival process of larval Japanese anchovy Engraulis japonicus in the 'shirasu' (larval anchovy) fishing ground in Sagami Bay, Japan. Back-calculated standard length (growth trajectory) and growth rate (growth history) were compared between the survivors (SV) captured on 18 July 2001 and the presumed original population (OP) captured on 1 and 5 July 2001. The larvae from SV were consistently smaller than the larvae from OP until at least the start of the ca. 2 wk survival process (1 July). Daily growth rates, however, were higher for SV than for OP at least at the start of the survival period. Therefore, faster growing individuals survived even if they were smaller than slowergrowing conspecifics. This was probably mediated by predation. Growth histories were generally similar between the metamorphosing larvae and non-metamorphosing larvae older than 40 d, the minimum age for metamorphosis, except for the period immediately after hatching. As such, we failed to detect a clear relationship between growth rates and the timing of metamorphosis (stage duration) as a whole. The results supported and extended the 'growth-selective predation' hypothesis but not the 'bigger is better' hypothesis. The 'stage duration' hypothesis was not unequivocally supported by the present findings.KEY WORDS: Growth rate · Otolith microstructure analysis · Short-term survival · Growth-selective predation hypothesis · Larval Japanese anchovyResale or republication not permitted without written consent of the publisher