EFFECT OF BIOTIC AND ABIOTIC FACTORS ON THE BIOCHEMICAL-COMPOSITION OF WILD EGGS AND LARVAE OF SEVERAL FISH SPECIES

The aim of this study is to establish possible associations between te mperature, salinity and egg and larval abundance, and the biochemical composition of wild fertilised eggs and larvae of marine fish species. Eggs and larvae of the most abundant species at each station at the t ime of sampling were collected during 2 surveys carried out from 25 Ma rch to 14 April 1995 (MPH-95) for collecting eggs and from 30 May to 1 6 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, carboh ydrate and lipid content of the eggs in both Trachurus trachurus and S comber scombrus. Conversely, protein, carbohydrate and lipid content o f larvae in Sardina pilchardus, Engraulis encrasicolus and T. trachuru s seemed to vary according to either larval body length, temperature, salinity and/or larval abundance. Protein, carbohydrate and Lipid cont ent increased as larval body length increased for the 3 species. Howev er, a percentage of lipid and protein in the larvae of the 3 species v aried according to prevailing buoyancy conditions. An increment of lar val 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 lipi d percentage of the larvae. This trade-off between protein and lipid p roduction is interpreted as a mechanism to achieve optimal larval buoy ancy.