SETTING UP AN EGG-DENSITY MODEL FOR EUROPEAN ANCHOVY, ENGRAULIS ENCRASICOLUS

Abstract The vertical distribution of pelagic fish eggs is an important issue in modeling and fisheries science. Knowledge on the influence of egg-density is a key aspect in IBM's where satisfactory equations to simulate realistic spatial variation are required. The egg-density of European anchovy is poorly known and only some studies on Atlantic provide information about it. An equation was fitted to describe changes in egg-density across development time. We found that the egg-density of anchovy in the Mediterranean is higher than in Atlantic waters. A functional model suitable for Mediterranean and Atlantic waters was established. Keywords: Fishes, Density, Ichthyoplankton, Models, Spawning 1 1 1 Introduction Small pelagic fish populations have a reproductive strategy resulting from past natural selection pressure, which make them adapted to the constant structural instability where they persist Materials & Methods Ichthyoplankton samples from the Gulf of Lions were collected in May-June 2008 survey. The samples were immediately taken to the laboratory onboard. We identified anchovy eggs and their stages; only early stages (I-II) were selected for the experiment. Egg-density measurements were carried out in a Density Gradient Column (DGC) Results We found that the egg-density of anchovy in the Mediterranean is higher than in Atlantic waters. However, the curve shape describing the egg-density trough development is the sam