Does It Vary the Feeding Selectivity of Larval Anchovy, Engraulis ringens in a Fjord-like Environment?

Diet and selectivity of Engraulis ringens larvae were studied during 4 consecutive days (austral spring) in Hornopirén inlet, a fjord-like environment of southern Chile. This environment was characterized by sharp halocline around 10 m depth, separating brackish and saltier waters. The potential prey field, microzooplankton, was collected at 4 depths (0, 5, 10 and 30 m), while the ichthyoplankton was collected at 2 strata, surface (0-10 m depth) and deep (10-45 m depth). Nauplii and copepodites were the major components of microzooplankton. The analysis of 487 gut contents of larval anchoveta indicates that similar volume of prey was ingested in both layers and during both tides. However, in the upper, brackish and warmer water, larval ingested significantly less prey but of larger size, selecting nauplii and copepodites as the main prey items. In the deep, saltier and colder water, larvae ingested more prey of smaller size, showing only selectivity for nauplii. The feeding incidence of E. ringens increased twice during the flood, when the abundance of copepodites in the field also increased. Therefore, complex biophysical interactions occur in Patagonian fjords during the feeding process of larval stages of this commercially important species in relationship with the spatio-temporal distribution of prey.