Detection of anchoveta (Engraulis ringens Jenyns 1842) eggs in euphausiid diets using immunoassays (ELISA)

Employing the production of a polyclonal antibody and the use of indirect enzyme linked immuno sorbent assay (ELISA), we detect Engraulis ringens egg proteins in the guts of a natural predator Euphausia mucronata Sars 1883 in Chilean waters. With a dilution of 1:15,000, the immune serum allowed the detection of 0.1 μg of anchoveta egg protein. The immune serum showed low cross-reactions with eggs and larval proteins of other pelagic fishes. Laboratory feeding experiments showed a window of detection of the protein of 9 h (13 °C) in the digestive tract of E. mucronata. In field-collected euphausiids within the spawning area of the anchoveta in Northern Chile, we detected anchovy egg proteins in 18% of 155 euphausiids tested by ELISA. These results constitute the first field evidence of predation by the highly abundant euphausiid E. mucronata on the early life stages of the anchoveta E. ringens in the Humboldt Current.