Biochemical composition and condition in anchovy larvae Engraulis encrasicolus during growth

Abstract

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.

Impacts of climate change on the complex life cycles of fish

“…The larvae feed on microzooplankton and mesozooplankton in the size range 50-500 lm (Tudela et al, 2002), with prey size increasing with increasing larval size. Although the nutritional condition of larvae has been related to carbohydrate assimilated from feeding on mesozooplankton (Bergeron, 2009), food-limited growth has not been reported during the larval stage (Diaz et al, 2008). However the vertical structure of larval habitats has been correlated with larval condition and ultimately recruitment.…”

RNA:DNA Ratio and Other Nucleic Acid Derived Indices in Marine Ecology

“…Besides the usually pattern of increasing RNA:DNA ratio with size is registered [ 7 , 34 , 42 ], eg. for early life stages of sardine [ 41 ] or the asymptotic value of RNA:DNA ratio, after obtaining a threshold larval size for anchovy (4–15 mm) [ 43 ]. By the opposite a pattern of decreasing RNA:DNA ratio with fish length was observed by [ 44 , 45 ] for soleid juveniles and also for late larvae of clupeids [ 46 ].…”

Lipids as a proxy for larval starvation and feeding condition in small pelagic fish: a field approach on match-mismatch effects on Baltic sprat

“…Experimentally derived starvation thresholds for the point of no return (Håkanson 1989b) were applied to identify proportions of severely starving clupeid larvae in the field (Håkanson et al 1994). Lipid content (determined either as content of total fatty acid [FA], TL or triacylglycerols, or as a ratio of triacylglycerols to sterols) was positively (Coombs & Håkanson 1991cited in Håkanson 1993, Håkanson et al 1994) but also negatively related to larval and juvenile growth rates or its proxies (RNA:DNA) (Su thers et al 1992, Díaz et al 2008, making it an ambiguous tool for predicting condition. Moreover, most field studies lack information about the consequences of larval condition on survival or even recruitment, making it difficult to validate the meaning of a low lipid-derived condition factor.…”