Effect of biotic and abiotic factors on the biochemical composition of wild eggs and larvae of several fish species

Abstract

he aim of this study is to establish possible associations between temperature, salinity and egg and larval abundance, and the biochemical composition of wild ferthsed eggs and larvae of marine fish species. Eggs and larvae of the most abundant species at each station at the time of sampling were collected during 2 surveys carried out from 25 March to 14 Apnl 1995 (MPH-95) for collecting eggs and from 30 May to 16 June (SEFOS-95) for collecting larvae. Both surveys were carried out on the N-NW coast of the Iberian Peninsula. Egg size, egg abundance, egg stage, temperature and salinity explained a small variance in the high variation observed within and between stations in protein, carbohydrate and lipid content of the eggs in both Trachurus trachurus and Scomber scombrus. Conversely, protein, carbohydrate and lipid content of larvae in Sardina pllchardus, Engraulis encrasicolus and T trachurus seemed to vary according to either larval body length, temperature, salinity andor larval abundance. Protein, carbohydrate and lipid content increased as larval body length increased for the 3 species. However, a percentage of lipid and protein in the larvae of the 3 species varied according to prevailing buoyancy conditions. An increment of larval lipid percentage and a reduction of larval protein percentage was observed as temperature increased and salinity decreased, the opposite case causing an increase in protein percentage and a decrease in lipid percentage of the larvae. This trade-off between protein and lipid production is interpreted as a mechanism to achieve optimal larval buoyancy.