Effects of salinity changes on hatching, hatching gene expression and hatching enzyme expression in Engraulis ringens eggs.

The Peruvian anchoveta (Engraulis ringens) is one of the most important commercial fishes along the Humboldt Current. Previous studies showed that egg quality (volume, protein and lipid content) and hatching rates decreases during the spawning season, from the rainy winter to late spring. In this study we assessed whether changes in atmospheric condition that led to an intense drought over a decade modified the freshwater river fluxes and seawater salinity at an E. ringens coastal spawning zone off Central Chile (36º30`S), and determined if changes in salinity affects the hatching gene expression, hatching enzyme, and hatching success in eggs incubated at a range of salinities (27-35psu) normally occurring during the reproductive season. Results show that the hatching enzyme expression increased as the embryo developed. The highest expression of the hatching enzyme gene and of the enzyme itself, along with hatching success were obtained in the lowest incubating salinity, 27psu. In the field, hatching success decreased from late winter to late spring, the start of the upwelling period at the end of the reproductive season. Thus, variations in salinity of the seawater during the spawning period are coincident with changes in gene expression of the hatching enzyme, protein expression, and hatching success. Spawning late in winter when rainfall is higher and seawater salinity in the coastal area is lower may increase hatching success, a reproductive strategy that might be affected by the observed climate changes and severe drought in central Chile.